Posts by: "Marine Mammal Research Unit"

New study shows loss of sea ice will require walruses to swim more and eat more to survive climate change

Balzak, one of two walruses that participated in the study at the Vancouver Aquarium to determine how much energy walruses spend swimming and resting in water.

Estimating how much food individual animals need, and understanding how their behaviours alter their food requirements, are necessary to predict how species will respond to climate change. In the simplest sense, an animal must obtain enough food to power all of the things it must accomplish in life—growing, staying warm, reproducing, travelling, foraging for food, etc. These individual expenses make up an animal’s total energy budget. 

Scientists can build mathematical computer models to predict the cost of these individual activities, and how they might change under different environmental conditions, such as altered prey distribution, warming oceans, or deteriorating ice conditions.   However, these models are only as good as the data that goes into them—and that requires detailed studies with real, live animals.

In a recent study, MMRU’s Dr. David Rosen measured energy expenditure in a pair of young walruses that were on loan to the Vancouver Aquarium from the Aquarium du Quebec. The results of the study were recently published in the journal Marine Mammal Science, and presented at the Alaska Marine Science Symposium:

While at the Vancouver Aquarium, the two walruses, Balzak and Lakina, were trained to measure two important costs—resting at the water’s surface and swimming under water. The cost of resting was measured while the walruses floated calmly in the water with their head in a floating respirometry dome, where the amount of oxygen they used could be accurately measured. To measure the cost of swimming, the walruses were trained to swim several laps of the pool—all the while remaining underwater— and then surfacing in the floating dome. 

For many marine mammals, the cost of resting is much higher than for terrestrial mammals of the same size.  This cost forms the foundation of many food requirement models, so inaccuracies can have a major impact on overall food estimates. However, David’s study found that the resting energy expenditure of the walruses was much lower than expected. Unfortunately for the walruses though, it turns out that any cost savings from resting are overshadowed by the cost of swimming. This is because walruses have to expend more energy while swimming than other, more streamlined, marine mammals. 

Walrus at MMRU
Everyone who participates in research likes nothing better than a good meal at the end of a successful set of trials — even if it is just raw clams!

The aim of the study was to improve existing mathematical models of how much food walruses might need in the wild, particularly in a changing Arctic environment. More specifically, the study determined how much more energy is expended—and food required—for walruses to adapt to this changing environment. Walruses depend on hauling out onto the ice edge to rest and raise their young, which are traditionally located over top of prime clam beds. Unfortunately, a loss of ice cover due to global warming means that walruses have to spend more time in the water and travel further to reach these food sources. And, as this study demonstrates, these changes in behaviour can be very expensive. 

PublicationsPublication


2021
 
Resting and swimming metabolic rates in juvenile walruses (Odobenus rosmarus).
Rosen, D.A.S. 2021.
Marine Mammal Science 37:162-172.
abstract
Changes in Arctic ice conditions have raised concerns regarding potential impacts on energy expenditure and food requirements of walruses. Modelling the repercussions of environmental changes requires accurate species-specific measures of bioenergetic expenditures. This is particularly true for walruses, who have a unique anatomy and foraging ecology from other pinnipeds. This study measured resting metabolic rate (RMR) and subsurface swimming metabolism in two juvenile walruses over a 13-month period. The walruses had relatively low RMR compared to studies of other young pinnipeds. RMR was greater for the male than the female, as expected given his larger size; the reverse was true on a mass-specific basis. There was also considerable variability in RMR for each walrus during the year that could not be accounted for by changes in body mass. Metabolism while swimming was about twice RMR, and locomotor costs were higher than generally predicted for other marine mammals. The lower calculated swimming efficiency may reflect the fact that walruses are not “high velocity” pursuit predators. The estimates of metabolic expenditure obtained in this study for young walruses are invaluable for quantifying the energetic consequences of behavioral changes induced by environmental shifts in the wild.

keywords     bioenergetics, metabolism, swimming, walrus
show/hide abstract View Reference Learn more about what was found

Biologging data from foraging harbour seals shows less impact on outmigrating salmon than expected. A few seals in the study population targetted juvenile coho, and exerted less pressure on chinook—appearing instead to target larger fish preying on juvenile chinook

Predation by harbour seals is believed to significantly impact juvenile coho and Chinook salmon as they enter the ocean — and are thought by some to be responsible for the poor return of spawning adults. Researchers from the University of British Columbia set out to determine who was eating juvenile salmon, and when and where it was occurring by capturing and tracking harbour seals that carried cell-phone-like devices that recorded everything and everywhere the seals went.   
Harbour Seal MMRU

Harbour seals tend to haulout to rest as the tide falls and intertidal areas are exposed. 

In a recently published paper in the journal, Marine Ecology Progress Series, Hassen Allegue and colleagues report that only a few of the seals they followed targetted outmigrating coho salmon. They were equally surprised when they discovered that the seals did not seem to take the smaller-bodied chinook, but appeared instead to target fish preying on juvenile chinook. Most of the feeding-type behaviours occurred as tide height rose (which were higher at dusk and night), especially during full moonlight. 
Harbour Seal 2 MMRU

Resting harbour seals showing one of the study animals wearing the tracking device.

These findings bring new insight into the complexity of the interactions between harbour seals and out-migrating coho and Chinook smolts. As the authors note, “they show the highly individualistic nature of seal predation, and suggest that there may be complex indirect effects associated with seals consuming fish that also prey on juvenile salmon.”  “Such confounding factors need to be addressed when considering broad conservation measures that might be taken against harbour seals to enhance the marine survival of salmonids.”

Publications PUBLICATION


2020
 
Harbour seals responded differently to pulses of out-migrating coho and Chinook smolts.
Allegue, H., A.C. Thomas, Y. Liu, and A.W. Trites. 2020.
Marine Ecology Progress Series 647:21-227.
abstract
There is increasing evidence that predation by harbour seals on out-migrating salmon smolts may be responsible for the low return of adult coho and Chinook salmon in the Salish Sea. However, little attention has been given to understanding where and when this predation occurs, and the extent to which it might be conducted by few or many seals in the population. We equipped 17 harbour seals with data-loggers to track seal movements, and used accelerometry to infer prey encounter events (PEE) following the release of ~384,000 coho (May 4th) and ~3 million Chinook smolts (May 14th) into the Big Qualicum River. We found a small proportion (5.7%) of all PEE occurred in the estuary where salmon smolts entered the ocean-and that only one-quarter of the seals actively fed there. PEE counts increased in the estuary after both species of smolts were released. However, the response of the seals was less synchronous and occurred over a greater range of depths following the release of the smaller-bodied and more abundant Chinook smolts. Harbour seals feeding in the estuary appeared to target coho smolts at the beginning of May, but appeared to pursue predators of Chinook smolts in mid-May. PEE counts in the estuary increased as tide height rose, and were higher at dusk and night-especially during full moonlight. Such fine-scale behavioural information about harbour seals in relation to pulses of out-migrating smolts can be used to design mitigation strategies to reduce predation pressure by seals on salmon populations.

keywords     predation, salmon, harbour seals, coho, Chinook, data-loggers, biologging, accelerometry, accelerometers, prey encounters, estuary, size selection, mitigation, PIT tags
show/hide abstract View Reference

2020 B.C. Marine Mammal Symposium – Cancelled

We have made the difficult decision to cancel the 2020 symposium.

Plans had been developed to hold a hybrid symposium at the end of the month that would have had some presentations pre-recorded and other live-streamed from BC.  Unfortunately, the increased restrictions on social gatherings announced this week by the BC Government to restrict the spread of COVID-19 make this impossible.

For 27 years, the BC Marine Mammal Symposium has been a forum and gathering place for those interested in the research, conservation and welfare of marine mammal. It has been a community event to reconnect with friends and acquaintances — and to meet new people that share the same passions.  

The BC Marine Mammal Symposium is an event that many eagerly look forward to each year.  We therefore regret having to cancel this year’s symposium, but look forward to coming back in November 2021, when we hope the world will look more normal.

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Sneak peak into the lives of killer whales

For the past two weeks, UBC Researchers led by Dr. Andrew Trites have been studying the feeding behaviours of northern resident killer whales. They are using hydroacoustics to assess prey abundance, and are placing suction-cup camera tags onto whales to record what they see and hear, as well as their three-dimensional movements, diving depths and feeding behaviours.

The video is a sneak peak into some of the things they are recording.  The video was taken by D26 (a 10 year old member of the D1 pod) from its orca-cam.  Each frame of the video has corresponding data on depth, speed, vocalizations and 3D-movement.  The video shows D26 interacting with other family members as they travel together through Queen Charlotte Strait.

The researchers were surprised to see how different the skin of a killer whale looks underwater.  The skin appears completely black above water, but appears quite different underwater most likely due to lighting.

They shared the images with a pathologist and a veterinarian who thought we are seeing edema (spongiosus) based on dead orcas that they have examined.  Edema is a skin condition that should resolve with time, and may be associated with nutritional and health condition, or a change in the environment.

This is the most marked up whale the researchers have seen so far, but all have shown unexpected skin colourations and lesions such as in this video from D26.

The research team are making daily posts on the MMRU Facebook page www.facebook.com/marinemammal should you wish to follow.

Satellite telemetry and time-depth recorders are providing new and surprising insights into the secret lives of bowhead whales

Bowhead whales for MMRU on the move

Bowhead whales traveling along the shore in Cumberland Sound, Nunavut during summer 2016. Image captured by unmanned aerial system (VDOS Global LLC) with support from World Wildlife Fund Canada. 

Bowhead Whales live year-round in Arctic and sub-Arctic waters and are split into different geographic populations. One of these populations—the Eastern Canada – West Greenland population—generally summers in western Baffin Bay, the Canadian High Arctic, northern Foxe Basin, northwestern Hudson Bay and Cumberland Sound. Wintering is thought to occur in areas with less ice such as Hudson Strait.  

However, new research shows that at least one of these areas—Cumberland Sound (Nunavut, Canada)—is an important year-round feeding ground for bowhead whales.

Map of research for Bowhead whales

Map of the known range of Eastern Canada-West Greenland bowhead whales with important areas identified (FB=Frobisher Bay, DB=Disko Bay, A=Admiralty Inlet, PRI=Prince Regent Inlet and GB=Gulf of Boothia).

In a recently published paper in the journal Marine Ecology Progress Series, University of British Columbia (UBC) Post-Doctoral Fellow Sarah Fortune reported the results of a 4-year study on the seasonal diving and foraging behaviors of Eastern Canada – West Greenland bowhead whales in Cumberland Sound.

Dr. Fortune and her team from Fisheries and Oceans Canada (Steve Ferguson, Justine Hudson and Bernard LeBlanc), Woods Hole Oceanographic Institution (Mark Baumgartner), and UBC (Valery LeMay and Andrew Trites) tracked 25 bowheads with satellite-linked time-depth telemetry tags to determine movements and dive behaviors. They also collected zooplankton samples in Cumberland Sound to determine prey species and biomass.

Prey sampling data suggested that the bowheads in Cumberland Sound were eating energy-rich Arctic copepods such as Calanus glacialis during summer. Dive depths were substantially shallower during spring and summer compared to fall and winter, and appear to correspond with seasonal changes in the vertical distribution of the copepods—which suspend development and overwinter at depth during fall and winter. 

Bowhead whale for MMRU

An individual bowhead whale resting near the surface in Cumberland Sound, Nunavut during summer 2016. Image captured by unmanned aerial system (VDOS Global LLC) with support from World Wildlife Fund Canada. 

The researchers also found that bowhead dive depths changed with time of day—providing evidence that their prey are migrating each day up and down the water column. Zooplankton avoid predation from visual predators by staying away from the sunlight surface waters during daylight, and move to the surface waters to eat phytoplankton at night. 

One of the big surprises of Dr. Fortune’s research was finding that bowhead whales resided in Cumberland Sound during all four seasons, with one animal remaining all year. Some of the whales she followed were infrequent visitors to Cumberland Sound, spending only a day to several weeks, while others had considerably longer residency times, spending several consecutive months in the area that occasionally included overwintering. However, peak bowhead occupancy occurred during summer and fall. 

The satellite telemetry locations also showed movement patterns indicative of feeding—suggesting that Cumberland Sound is a year-round feeding area. 

These findings provide a new understanding of the feeding behavior of bowhead whales, and the biological significance of Cumberland Sound to the Eastern Canada – West Greenland population.


Dr Sarah Fortune is a Post-Doctoral Fellow at the Marine Mammal Research Unit at the University of British Columbia


This research was made possible through the support of our community partners, Levi Qaunaq and Natalino Piugattak from Igloolik, and Noah Ishulutaq and Timeosie Akpalialuk from Pangnirtung, who were responsible for vessel operations. Logistical support was provided by the Igloolik and the Pangnirtung Hunters and Trappers Organizations and the Government of Nunavut. Bowhead whale data were collected under UBC ACC A14-0064 and Department of Fisheries and Oceans License to Fish for Scientific Purposes S-12/13-1014-NU and S-13/14-1009-NU and Animal Use Protocol FWI-ACC-2012-034 and FWI-ACC-2013-018.

Publications PUBLICATION


2020
 
Seasonal diving and foraging behaviour of Eastern Canada-West Greenland bowhead whales.
Fortune, S. M. E., S. H. Ferguson, A. W. Trites, B. LeBlanc, V. LeMay, J. M. Hudson and M. F. Baumgartner. 2020.
Marine Ecology Progress Series 643:197-217.
abstract
Climate change may affect the foraging success of bowhead whales Balaena mysticetus by altering the diversity and abundance of zooplankton species available as food. However, assessing climate-induced impacts first requires documenting feeding conditions under current environmental conditions. We collected seasonal movement and dive-behaviour data from 25 Eastern Canada-West Greenland bowheads instrumented with time-depth telemetry tags and used state-space models to examine whale movements and dive behaviours. Zooplankton samples were also collected in Cumberland Sound (CS) to determine species composition and biomass. We found that CS was used seasonally by 14 of the 25 tagged whales. Area-restricted movement was the dominant behaviour in CS, suggesting that the tagged whales allocated considerable time to feeding. Prey sampling data suggested that bowheads were exploiting energy-rich Arctic copepods such as Calanus glacialis and C. hyperboreus during summer. Dive behaviour changed seasonally in CS. Most notably, probable feeding dives were substantially shallower during spring and summer compared to fall and winter. These seasonal changes in dive depths likely reflect changes in the vertical distribution of calanoid copepods, which are known to suspend development and overwinter at depth during fall and winter when availability of their phytoplankton prey is presumed to be lower. Overall, CS appears to be an important year-round foraging habitat for bowheads, but is particularly important during the late summer and fall. Whether CS will remain a reliable feeding area for bowhead whales under climate change is not yet known.

keywords     Climate change, zooplankton, prey availability, foraging behavior, biologging, state-space model, bowhead whale, copepods, Calanus
show/hide abstract View Reference

It’s a Drag Wearing a Tag

What impacts do tracking tags have on the behavior and swimming costs of marine mammals?

Electronic devices affixed to individual animals are invaluable tools for researchers studying the lives of wild marine mammals. These data logging “tags” can record the animal’s behavior, physiology, and physical and auditory environment — data that would be unobtainable by other means.

Developments in microcomputer technology have increased the capacity of these devices, but the size of these electronic tags has not decreased as rapidly. This led Dr. David Rosen (UBC) to ask whether the relatively large sizes of electronic tags affects the behavior and swimming costs of individuals being tracked at sea? Surprisingly few studies have quantified the behavioral or energetic effects of tag attachment on marine mammals despite the widespread use of this technology.

Dr. Rosen tested the potential short-term impact of tag attachment with a group of trained northern fur seals held as part of a long-term research program at the Vancouver Aquarium.

Aquarium trainers trained four fur seals to swim between a respirometry dome floating at the surface of a large research pool, down to the opposite bottom of the pool where they were rewarded with a fish, and then to immediately return to the dome where scientists could measure how much oxygen they had consumed (energy they used).

For each trial, the fur seals had to complete this 18.6 m course a total of 5 times in quick succession. By timing the laps, Dr. Rosen’s team could also measure their swimming speed.

To test the effects of wearing a tag, the fur seals had to complete these trials while wearing one of two models of data loggers typically used in field research. Normally, tags are glued directly to the animals’ fur. For this study, the fur seals were outfitted with a Velcro patch that allowed trainers to easily switch between tags for different trials, as well as undertake matching trials without tags.

The results of the study were recently published in the journal Marine Mammal Science. They show that the tags significantly affected both the short-term behavior and energetics of the fur seals, despite the fact that tag mass was <1% of body mass. The animals swam slower and used more energy to swim. As a result, the total cost of swimming the prescribed circuit increased by 12-19%.

As noted in the published paper, the study specifically measured the effects of short-term placement of tags on northern fur seals. Care must be taken when extrapolating the results to long-term deployments in the wild.

However, if the persistence of these short-term effects would potentially bias data sets obtained from wild animals and could even lead to long-term impacts on life history traits.

Dr. Rosen is also quick to note that this study is not a denunciation of using external data loggers. Rather, scientists must consider these potential effects to interpret their data, and guide ethical and scientific designs of future studies.

Dr. David Rosen is a Research Associate at UBC’s Marine Mammal Research Unit.

The two visiting walruses, Balzak and Lakina

Dr. David Rosen, an Assistant Professor at UBC’s Marine Mammal Research Unit, has often contended that walrus should be the poster child for climate change, particularly for sea ice loss in the Arctic. After all, walruses are an “ice-dependent species” that require stable ice to raise their calves. They also need the ice to be in a specific location in order to forage efficiently. When the ice isn’t where it is supposed to be, walruses have to swim farther from their ice floes to find food, which takes more energy (meaning they need even more food). In very poor ice years they may be forced to haul out on land, which not only raises costs to reach foraging grounds, but also where the threats of disease and trampling dramatically increase. 

In December 2017, two young walruses — Balzak and Lakina — arrived at the Vancouver Aquarium. They were born in the Spring of 2016 at the Aquarium du Quebec, and were on temporary loan. For Dr. Rosen, these large, exciting toddlers soon became the focus of an exciting research program to answer the question “how much does it take to power a walrus?”.

As Dr. Rosen explains, “One of the central questions that scientists face is trying to figure out how much food a walrus normally needs and how much more it needs if it has to be more active or spend more time in the water”. Although scientists have built mathematical models to try and answer this question, there are no real data on the energy expenditure of walruses. This means scientists have had to base their models on information from other species, despite the fact walruses seem pretty different than most other marine mammals.

Food intake measured

The research program had five related studies. The first was to keep careful track of the food intake and growth of the animals. These data provided insight into their growth patterns and how efficiently they converted food into body mass. 

A second study carefully tracked how their body changed as they grew. Training staff taught the walruses to lie on measuring ropes to track how different parts of their body grew as they got older. It also provided data for evaluating the “condition” of young walruses in the wild. 

A third project tracked the growth of their tusks. Both male and female walruses have tusks, although they are often removed in Aquariums. Scientists took fine-scale measurements of the width, length, and thickness of their tusks as they got older. Given “you are what you eat”, tusks provide a permanent chemical record of the feeding ecology of walruses over their lifetime. In order to use tusk samples — either from wild animals or museum specimens — scientists need to know exactly what life stage the parts of the tusk represent.

The final two studies measured two types of energy expenditure: resting metabolic rate and swimming metabolism. Resting metabolic rate is the amount of energy a walrus uses while resting calmly in water, and is the foundation of mathematical models used to estimate total food requirements. 

 “These types of energetic studies had never previously been done with young walruses”, says Dr. Rosen. “The walruses had to be trained to sit quietly underneath a floating dome, while we measured how much oxygen they consumed and carbon dioxide they produced.  Remember, this required a rambunctious toddler walrus weighing several hundred kilograms to sit still for 7-10 minutes floating in a dome with minimal food reinforcement.” 

Surprisingly (and with credit to the Aquarium training staff) it only took a few months for the walruses to learn this behavior. Dr. Rosen and his team were then able to measure resting metabolism every few weeks over an entire year, allowing them to track changes as the animals grew and as the seasons changed (which is very important for determining the food requirements of almost all marine mammals). 

Walruses swimming
Walruses swimming

The final project was perhaps the most exciting from both a science and training perspective. The amount of energy walruses use swimming is perhaps their greatest energy expenditure in the wild, and the cost most likely to be affected by climate change. To measure this, the training staff taught the walruses to swim multiple lengths of their pool completely underwater (~110m), only surfacing within the floating dome at the end of their task! The results represent the first direct measurements of the cost of swimming in young walruses. Even Dr. Rosen was “totally amazed it worked out so well.”

Unfortunately, both Dr. Rosen and the Aquarium training staff said a tearful goodbye in November when Balzak and Lakina returned to Quebec City. Yet the information they provided during their stay in Vancouver, together with data from older walruses at other institutions, will be instrumental in enabling scientists to better predict how the loss of sea ice will affect the health of individual walruses and, ultimately, how climate change will impact walrus populations in the Arctic.

This summer, a team of researchers from the University of British Columbia, together with the Hakai Institute, set out to determine how fish-eating killer whales find their food, and whether there is a shortage of Chinook salmon available to killer whales in the Salish Sea.  Here is a peek into what the researchers saw.

Saturday November 23, 2019

27th Annual
B.C. MARINE MAMMAL SYMPOSIUM
Saturday, November 23, 2019 – 9:30 am – 5:00 pm

UNIVERSITY OF BRITISH COLUMBIA
AQUATIC ECOSYSTEM RESEARCH LABORATORY
GROUND FLOOR, AERL, 2202 MAIN MALL
VANCOUVER, B.C.   CANADA   V6T 1Z4

Registration Fee: 

  • Advanced: $0 (pre-register by Noon on Thursday November 21, 2019)
  • Late: $5 (cash only at the door)

Join us for presentations as well as discussion on issues that concern us all. This meeting is open to students, researchers, educators, businesses and others involved with marine mammals. Anyone in one or more of these categories is welcome to attend. 

Please register on EVENTBRITE   

https://www.eventbrite.ca/e/27th-annual-bc-marine-mammal-symposium-tickets-73468727943     OR email  bc.symposium@oceans.ubc.ca  before Noon November 21, 2019 to indicate that you plan to attend. Lunch and refreshments will be provided, but we need to know how many people to plan for.  There will also be a social evening (6:00-8:00 pm) where beer and pizza can be purchased. 

The Agenda will be distributed at the meeting. Please email bc.symposium@oceans.ubc.ca  before Noon November 18, 2019 if you would like to make a five minute presentation about your research. Longer presentations on topics of general interest are welcomed.  We would also like to know if there are any issues that should be discussed by the group at large.  

This year we are planning to stream live to the general public via YouTube.  All presentations will be recorded for posting on the internet. Presenters can decline to have their talks posted after previewing them.

We look forward to hearing from you and seeing you at: 

9:30 am on Saturday, November 23, 2019

Email: bc.symposium@oceans.ubc.ca

WE WILL BE STREAMING THE EVENT LIVE HERE:

SPONSORS:

Is seal predation driving salmon declines in the Strait of Georgia?

To many people, the sight of a harbor seal feasting on a salmon is an iconic west coast moment. For thousands of years, harbor seals and Pacific salmon have coexisted in a complex relationship between predator and prey.  

Harbor seal

Yet some salmon populations in the Strait of Georgia have declined steadily amidst increased human activity, a changing ocean climate, and predatory pressure from marine mammals. One theory suggests that predation by harbor seals may be driving the salmon decline—but scientists have yet to find enough evidence to assign culpability.

A new study led by quantitative ecologist Benjamin Nelson (The University of British Columbia) sought to understand how predation by seals might impact the number of juvenile salmon from the Strait of Georgia that survive to adulthood and enter the fishery each year. The research was recently published in the Canadian Journal of Fisheries and Aquatic Sciences.

AN ECOSYSTEM VIEW

“People often see harbor seals eating adult salmon, but we wanted to know how many juvenile fish were being eaten,” says Nelson. “This is the point in the salmon’s life cycle that has been attributed to the recent declines in their populations.”

Chinook Salmon

Following three years of analyzing seal diets, Nelson and colleagues concluded that in some areas of the Strait of Georgia, harbor seals are indeed eating a significant number of juvenile salmon each year. On the strength of this discovery, Nelson wanted to take an ecosystem view to see if the same trend extends elsewhere.

Using several decades of salmon population data, Nelson and colleagues constructed a statistical model of 20 populations of Chinook salmon in British Columbia and Washington State. They combined that with aerial survey data on harbor seal populations at the same times and places. 

“We found that in 14 of the 20 salmon populations we studied, there was a strong association between the abundance of harbor seals and large declines in salmon productivity,” Nelson says. Surprisingly, he found no evidence of “local” effects in the Strait of Georgia, noting that the association between seal abundance and salmon productivity seemed to apply uniformly over the entire Salish Sea.

“People may believe harbor seals are a problem in certain areas with unique issues, but they don’t believe this is happening everywhere,” Nelson says. “Our results suggest this is a common theme among wild Chinook salmon populations. It’s happening not only on the inside waters of the Salish Sea, where seals are exploiting a degraded environment near urban areas, but also on the coastal areas of Washington State where relatively pristine habitat for salmon still exists.”

HATCHERIES RULED OUT

Nelson and colleagues also used their models to consider another potential factor in seal predation: salmon hatcheries. 

“Since the 1970s, we’ve seen a lot more hatchery fish released into the system as wild stocks declined,” says Nelson. “Because of the sheer number of hatchery fish released into the ocean, it’s led to a lot of speculation that an overproduction of hatchery fish may have also influenced the wild decline as well. Could it not just be seals but also hatchery fish, or hatchery fish instead of seals, that are driving the declines in wild salmon?”  

Upon investigating this hypothesis, Nelson and colleagues found no statistically significant negative association between hatchery productivity and wild productivity. Hatchery fish may be impacting wild fish on some level, he says, but the increases in hatchery productivity probably aren’t driving the declines in wild fish. He believes the seal populations have greater explanatory power in those declines. 

“With all the alarm over the plight of killer whales and wanting to mitigate their risk of extinction, people are wondering whether we can use hatcheries to supplement their prey populations,” Nelson says. “If we did that what would the impact be on wild populations? Our models suggest that if we were to increase hatchery abundance, it probably wouldn’t significantly affect wild productivity.”

NO SMOKING GUN

With hatchery effects ruled out, Nelson is quick to point out that his study is a correlational analysis, not a “smoking gun” that incriminates seals in the decline of salmon stocks. While he acknowledges that conservation arguments can be polarizing in favor of one species or the other, he cautions against drawing conclusions about causation without evidence.

“Our study is one piece of evidence towards establishing causality between seal predation and salmon declines,” he says. “If this were a courtroom you couldn’t convict the seals, but you’d be looking at the evidence and be pretty suspicious about the seals at this point.”

“The novelty of this study is that — if there is a causal link between harbor seals and salmon — over how many areas could this be more widely occurring?” he says. “If there’s a causal link, it probably occurs over a very wide part of the ecosystem, which could explain declines in British Columbia, Washington State, and possibly beyond.”

Publications PUBLICATION

Wild Chinook salmon productivity is negatively related to seal density, and not related to hatchery releases in the Pacific Northwest.
Nelson, B.W., C.J. Walters, A.W. Trites, and M.K. McAllister. 2019.
Canadian Journal of Fisheries and Aquatic Sciences 76:447-462.
abstract
Predation risk and competition among conspecifics significantly affect survival of juvenile salmon, but are rarely incorporated into models that predict recruitment in salmon populations. Using densities of harbour seals (Phoca vitulina) and numbers of hatchery-released smolts as covariates in spatially-structured Bayesian hierarchical stock-recruitment models, we found significant negative correlations between seal densities and productivity of Chinook salmon (Oncorhynchus tshawytscha) for 14 of 20 wild Chinook populations in the Pacific Northwest. Changes in numbers of seals since the 1970s were associated with a 74% decrease (95% CI: -85%, -64%) in maximum sustainable yield in Chinook stocks. In contrast, hatchery releases were significantly correlated with Chinook productivity in only one of 20 populations. Our findings are consistent with recent research on predator diets and bioenergetics modeling that suggest there is a relationship between harbour seal predation on juvenile Chinook and reduced marine survival in parts of the eastern Pacific. Forecasting, assessment, and recovery efforts for salmon populations of high conservation concern should thus consider including biotic factors, particularly predator-prey interactions.

keywords     salmon, seal density, hatchery
show/hide abstract View Reference Learn more about what was found


Are female northern fur seals finding enough food to help their pups survive?

The first few months at sea are a precarious time in the life of a young northern fur seal. After spending its first four months onshore, sustained by its mother’s milk, a juvenile fur seal must carry enough fat reserves to survive while it learns to catch fish—or it may starve.
New Consortium research highlights the important role of the mother’s foraging habits in preparing the young for weaning. Led by Dr Tiphaine Jeanniard du Dot (The University of British Columbia), the researchers studied the foraging strategies of lactating female northern fur seals. The results were published in the journal Marine Ecology Progress Series.

ONSHORE VS. OFFSHORE

“The northern fur seal population has been declining by six percent per year for the last 20 years,” says Jeanniard du Dot. “During the breeding season, the mothers are challenged to capture enough food to sustain themselves and to feed their pups. Lactation is very expensive energetically. I wanted to understand where the mothers forage and how efficient they are at finding and capturing prey.”
The researchers equipped 20 lactating female fur seals from St Paul Island with biologgers that tracked their location and their diving behavior. Using a variety of methods, the researchers calculated the amount of energy each seal gained and expended during a foraging trip.
“We discovered that the females on these rookeries displayed two different foraging strategies,” says Jeanniard du Dot. “One group made frequent short trips to a shallow shelf near the shore, where they fed on low-quality prey like walleye pollock and squid. The second group foraged in the deep Bering Sea basin further from shore, where they found energy-rich prey like northern smoothtounge, but were spending longer time at sea.”

“The females that foraged offshore in the deep basin had a higher foraging efficiency,” says Jeanniard du Dot, meaning they consumed more energy per unit of time than they spent; however, they spent much more time away from their pups, which were forced to fast in their absence. The onshore group nursed their pups more frequently but consumed lower quality prey, and therefore gained less energy per feeding trip than they spent.
“It’s a bit like the dilemma faced by many working parents,” explains Jeanniard du Dot. “If you spend more time working you get less time with your kids, but you get more money to put food on the table. It’s the same trade-off with seals: females who spent more time at sea came back with milk that was likely higher in energy content than females that stayed onshore and fed on lower energy fish. We’re not sure whether the higher quality milk is enough to compensate for the fact that the pups are not fed as often.”

ENVIRONMENTAL CONDITIONS

Each strategy required the female to compromise on either time or energy, but neither strategy maximized efficiency on both, says Jeanniard du Dot. The results did not indicate whether one strategy might give some juveniles an advantage under certain conditions during their first year at sea, or whether both strategies would lead to a similar survival rate amongst juveniles.
“Under the current environmental changes in the North Pacific Ocean,” she says, “it’s difficult to tell which foraging strategy will be more successful. Conditions may change that could favor one strategy over the other, which is probably why both strategies still exist in the population, as females tend not to change behavior from year to year.”

Jeanniard du Dot says that while the results of her study do not provide clear-cut links between foraging strategies and the northern fur seal population decline, it provides strong clues as to why first-year pups might not return in as many numbers.
“The decline in northern fur seals is not due to one factor,” she explains. “Environmental changes affect the population by impacting the weakest part: the lactating females and growing pups who require the most energy.” Consequently, she believes that conservation efforts should focus on two key periods: the reproductive season for females, and the first year at sea for pups.
“An increase in ocean temperature means fish will be found deeper, making it harder for both females and pups to access those fish,” she says. “The pups need to have really good energy reserves to survive while they are learning to dive and developing diving capacity to reach the deep fish.”

PublicationsPUBLICATION

Trade-off between foraging efficiency and pup feeding rate of lactating northern fur seals in a declining population.
Jeanniard-du-Dot, T., A.W. Trites, J.P.Y. Arnould, J.R. Speakman, and C. Guinet. 2018.
Marine Ecology Progress Series 600:207-222.
abstract
Foraging strategies and their resulting efficiency (energy gain to cost ratio) affect animals' survival and reproductive success and can be linked to population dynamics. However, they have rarely been studied quantitatively in free-ranging animals. We investigated foraging strategies and efficiencies of wild northern fur seals Callorhinus ursinus during their breeding season to understand potential links to the observed population decline in the Bering Sea. We equipped 20 lactating females with biologgers to determine at-sea foraging behaviors. We measured energy expenditure while foraging using the doubly labeled water method, and energy gained using (1) the types and energy densities of prey consumed, and (2) the number of prey capture attempts (from acceleration data). Our results show that seals employed 2 foraging strategies. One group (40%) fed mostly in oceanic waters on small high energy-density prey, while the other (60%) stayed over the shallow continental shelf feeding mostly on larger, lower quality fish. Females foraging in oceanic waters captured 3 times more prey, and had double the foraging efficiencies of females that foraged on-shelf in neritic waters. However, neritic seals made comparatively shorter trips, and likely fed their pups ~20-25% more frequently. The presence of these strategies which either favor foraging efficiency (energy) or frequency of nursing (time) might be maintained in the population because they have similar net fitness outcomes. However, neither strategy appears to simultaneously maximise time and energy allocated to nursing, with potential impacts on the survival of pups during their first year at sea.
show/hide abstract View Reference

Mei Sato on board the Fishing Vessel Nordic Pearl in Johnstone Strait, Canada.


by Leslie Smith on September 26, 2018 in News, Science Highlights
Mei Sato grew up surrounded by the ocean in Japan. It permeated every aspect of her life from swimming to fishing to the cultural importance of eating seafood as well as learning to prepare for tsunamis.
In high school Sato had a chance to meet with a local fisherman, Mr. Shigeatsu Hatakeyama, and that started her interest in a career in ocean sciences. The fisherman had an aquaculture farm and was planting trees upstream to protect ‘his’ ocean by providing clean nutrient-rich water that keep his oysters healthy. “His efforts made me realize how different ecosystems are interconnected to each other,” says Sato. “I became very interested in what is going on in marine ecosystems and how connected they are to land ecosystems.”

Monitoring data collection of the mini-cabled observatory located on the dock of the Darling Marine Center. Credit: Mei Sato


To pursue this new passion, Sato enrolled in the Tokyo University of Fisheries (now Tokyo University of Marine Science and Technology) and began a major in Aquaculture. One of the unique requirements of this school was that each student had to take a course for five days to learn how to swim in the ocean. The location for the course was Tokyo Bay, complete with floating garbage and tanker traffic. “It was a very intense class,” says Sato, “the school took it very seriously that everyone needs to swim. For our final we had to swim for 2-3 hours straight. There was a small boat nearby in case you needed to be pulled on board.”
Additionally, while at college, Sato was able to take advantage of an exchange program with the University of Victoria (UVic) in British Columbia, Canada. During that year at UVic, Sato was able to take oceanography courses and shortly after changed her major to Biological Oceanography. “I am excited about the interaction between biology and physics,” says Sato. “They are tightly coupled together but it is so complicated.”

Frame to deploy hydroacoustics underwater, made of PVC pipes, at the dock of Darling Marine Center. Credit: Mei Sato


After completing her undergraduate degree, Sato applied for a master’s program at the Darling Marine Center in the University of Maine. There she began to work with bio-acoustics systems and explore how biological and physical interactions impact animal behavior. To do this, she created her own tiny cabled observatory off the dock of the marine station. Her observatory consisted of a laptop in a waterproof box on the dock connected by cable to deployed sensors (bio-acoustic sonar, ADCP, fluorometer, and CTD) on the bottom, 10 meters deep. These sensors were deployed for three months at a time across two summers.
“It is fun to think that I was working with a much much smaller version of the OOI Cabled Array,” says Sato. “I know just how much work it is for you all to run the OOI because my small thing was so hard. I had to SCUBA dive 3 times a week to clean the instruments, even recovery and deployment were challenging with the small PVC frames. And once there was a thunderstorm and the acoustic sensor died due to lightning strike.”
After her master’s, Sato decided to explore the world outside of academia and went back to Japan to work in the engineering department of a company that makes fish finders. Sato worked with universities and government fishery institutions to create a novel fish finder for fishermen using similar technologies to the bio-acoustic systems she used in her research. After two years, Sato realized that she was being held back professionally because she was a woman. With superstitions about women onboard fishing vessels she was not able to get the same field opportunities as her male counterparts. So, she decided to leave the industry in Japan and head back across the Pacific to UVic and began her PhD.

Preparing to set sail on the F/V Nordic Pearl.


During her PhD, Sato worked with acoustics on another cabled observatory, the Ocean Networks Canada (ONC).  “At the time, no one was really using the acoustic data because they were not calibrated yet,” says Sato. Not one to be so easily deterred, Sato decided to take matters into her own hands and calibrated the sensors with the ONC team. “I learned a lot through the calibration process,” says Sato. “It was a really good experience to learn how everything works. The ONC team and the sensor manufacturer were both very helpful and patient throughout the process.” The calibration values are now applied to the ONC data and freely accessible online. She then used the newly calibrated acoustic data to examine seasonal variations in diel vertical migration of krill in Saanich Inlet, British Columbia.
After her PhD, Sato hopped across the Juan de Fuca Strait and began a post-doctoral fellowship at the University of Washington. During her post doc, Sato moved higher up in the food chain to look at fish, specifically how hypoxia in Puget Sound impacts herring and hake distributions.
Continuing her move south, Sato did a second post doc at Oregon State University with Drs. Kelly Benoit-Bird and Jack Barth. She was very excited about getting a chance to dive into the OOI data, but at the time the OOI bio-acoustic sonar data were not calibrated. So once again Sato climbing onboard to help calibrate the bio-acoustic sensors. Sato and Benoit-Bird worked with the OOI team from OSU on these calibrations and they currently have a paper about their work under review. “We are hoping that the product we are developing can be used on the echosounders throughout the OOI,” says Sato. “This calibration was very challenging because the echosounders are deployed so deep.”

Making field observations while following a killer whale and simultaneously recording the presence of fish (shown on the monitor).


Calibrating bio-acoustic sensors is much more involved than physical sensors where one could simply apply calibration values provided by the manufacturers. With the bio-acoustic sensor you need to position a small sphere, about the size of a golf ball, over the transducer while it is deployed, which for the OOI is 200 meters below the sea surface. The solution the OOI team came up with was to attach the sphere to the sensor via a fishing line with a float on it so that it could hover above the transducer. Since you only want the sphere there during calibration, the OOI team employed a “sacrificial link” at the attachment point with the float so that after the link dissolved, the float would be released and the sphere would disappeared from the sampling area. Though a very clever design, it was met with its share of challenges, like tangled fishing line. For instances when sphere deployment is not possible, the team investigated cross calibration with acoustic sensors on the ship.
“Now we have the calibration, I am starting to look at the actual data,” says Sato. “Calibration is a really hard step, but without the calibration no one will use the data. To ensure the wide usage of acoustic data by the community, calibration is critical.”
Sato is using these bio-acoustic data collected at the Coastal Endurance Array Oregon Line to explore the links between upwelling strength and zooplankton diel vertical migration in the California Current System. “We used to not be able to measure such small-scale changes because we only had a snap shot from the ship-based surveys,” says Sato. “But now with the OOI’s continuous, high-resolution data, we can now answer questions that we couldn’t have tackled before. It is exciting because usually with cabled observatories, we only have one site in an area, but with the OOI we have three sites going across the shelf so we can see the spatial changes too.”

Knowing what hydroacoustic signals correspond with what types of fish requires catching some fish with trawl gear deployed from the stern of the ship.


Sato is now a researcher at the University of British Columbia in Vancouver where she continues to move up the food chain, this time studying the interactions between Chinook salmon and killer whales by collaborating with Dr. Andrew Trites. As part of her research Sato is trying to determine if you can detect Chinook using a portable hydro-acoustic system on the boat. Because Chinook are strong swimmers, Sato cannot trawl for them to see if they are present, she has to bring a fisherman onboard to catch them to validate acoustic signals. And so, it appears Sato has come full circle from struggling to be invited to work on fishing vessels in Japan, to inviting fishermen aboard her own boat.
In terms of her next step, she has already reached the zenith of the food chain, so it will be interesting to see what new organisms Sato tries to capture with her echosounders. Regardless, one thing is clear, Sato wants to stay connected to her observatories. “I want to keep my ONC and OOI connection as a continuation of my research to understand biological-physical interactions,” says Sato. She did, after all, spend a lot of effort calibrating those sensors.
“The OOI is great opportunity for early career scientists,” says Sato. “They don’t have a lot of money or equipment or ship time. With the OOI we can explore a lot of questions that we want to answer.” Because Sato’s research is so interdisciplinary, she requires biological and physical data in addition to the acoustics. Purchasing and deploying all of those sensors would be beyond the scope of something she could do by herself, or any other early career scientist for that matter. But she does not have to, the OOI has these sensors available to her. “Having all of those sensors available at the same time as bioacoustics data is a huge opportunity for me and other scientists,” says Sato. “It is not just biology or physics, it is the coupling that is so critical. I think the OOI will provide a big opportunity for us to answer questions in this gap.”
Sato is still in touch with the fisherman and he has been planting trees for the last 30 years. Many of his colleagues are planting trees now too and they conduct outreach events with local elementary school students to share their story and help plant trees to develop the forest too. In addition to planting trees that day, he planted a seed in Sato that drew her to ocean research. And just like her old friend, Sato thinks beyond her immediate research and is planting trees for others too, by making the echosounder data more accessible.


 

Female northern fur seals with data logging tags on their backs.

It’s a Drag Wearing a Tag

What impacts do tracking tags have on the behavior and swimming costs of marine mammals?

Electronic devices affixed to individual animals are invaluable tools for researchers studying the lives of wild marine mammals. These data logging “tags” can record the animal’s behavior, physiology, and physical and auditory environment — data that would be unobtainable by other means.

Developments in microcomputer technology have increased the capacity of these devices, but the size of these electronic tags has not decreased as rapidly. This led Dr. David Rosen (UBC) to ask whether the relatively large sizes of electronic tags affects the behavior and swimming costs of individuals being tracked at sea? Surprisingly few studies have quantified the behavioral or energetic effects of tag attachment on marine mammals despite the widespread use of this technology.

Dr. Rosen tested the potential short-term impact of tag attachment with a group of trained northern fur seals held as part of a long-term research program at the Vancouver Aquarium.

Aquarium trainers trained four fur seals to swim between a respirometry dome floating at the surface of a large research pool, down to the opposite bottom of the pool where they were rewarded with a fish, and then to immediately return to the dome where scientists could measure how much oxygen they had consumed (energy they used).

For each trial, the fur seals had to complete this 18.6 m course a total of 5 times in quick succession. By timing the laps, Dr. Rosen’s team could also measure their swimming speed.

To test the effects of wearing a tag, the fur seals had to complete these trials while wearing one of two models of data loggers typically used in field research. Normally, tags are glued directly to the animals’ fur. For this study, the fur seals were outfitted with a Velcro patch that allowed trainers to easily switch between tags for different trials, as well as undertake matching trials without tags.

The results of the study were recently published in the journal Marine Mammal Science. They show that the tags significantly affected both the short-term behavior and energetics of the fur seals, despite the fact that tag mass was <1% of body mass. The animals swam slower and used more energy to swim. As a result, the total cost of swimming the prescribed circuit increased by 12-19%.

As noted in the published paper, the study specifically measured the effects of short-term placement of tags on northern fur seals. Care must be taken when extrapolating the results to long-term deployments in the wild.

However, if the persistence of these short-term effects would potentially bias data sets obtained from wild animals and could even lead to long-term impacts on life history traits.

Dr. Rosen is also quick to note that this study is not a denunciation of using external data loggers. Rather, scientists must consider these potential effects to interpret their data, and guide ethical and scientific designs of future studies.

Dr. David Rosen is a Research Associate at UBC’s Marine Mammal Research Unit.


Saturday November 24, 2018

Join us for presentations as well as discussion on issues that concern us all. This meeting is open to students, researchers, educators, businesses and others involved with marine mammals. Anyone in one or more of these categories is welcome to attend.

9:30am – 5:00pm 

Eventbrite Invitations will be sent out in late October

 

You can see the symposium video below.

 

 

 

Researchers publish first reference ranges for Steller sea lions

Over the past 15 years, a small group of Steller sea lion pups has been raised to adulthood at the Vancouver Aquarium. In an effort to better understand their physiology, researchers and veterinary staff have kept precise records of their nutritional status and overall health.
Today, these records from Aquarium-raised animals provide a valuable biological library for studying the health of their wild counterparts.
Consortium researchers recently analyzed hundreds of blood samples to compile the first reference ranges for blood health in Steller sea lions. Their results were recently published in the Journal of Zoo and Wildlife Medicine

A Rare Opportunity

“You can learn a lot from a blood sample,” says Carling Gerlinsky (The University of British Columbia) who led the study. “The molecules in blood have been extensively studied in humans, and we can apply a lot of what we know to wildlife.”

Carling Gerlinsky with one of the female Steller sea lions at the Open Water Research Station. The sea lions wear a harness in the open ocean to carry scientific instruments.


When studying wild populations, it can be difficult to tell whether an animal is nutritionally healthy, or whether it is diseased. Analyzing a blood sample can provide these answers, but Gerlinsky acknowledges that obtaining blood samples in the wild is difficult.
It’s even more difficult to gather enough blood samples to know what is normal or abnormal across an entire population or species, she says.
“We had a unique opportunity at the Vancouver Aquarium,” she added. “We had access to a very large dataset of blood samples that were taken over 15 years. It’s rare to have data at our fingertips that spans that long, and we could see how the values change with age.”
Gerlinsky and her colleagues analyzed the data to establish the first baseline levels for blood health in Steller sea lions. These can be immediately useful as reference ranges for both wild and captive animals, she says.
“For example, rescue and rehabilitation groups often need to assess the health of an animal they are caring for,” she notes. “They can now compare our reference ranges with the levels they see in the animal they are treating, and determine whether that animal is healthy or not.”

Age and Exercise Matter

Gerlinsky and her colleagues analyzed samples from animals ranging from 3 weeks to 16 years in age. They found that nearly all of the 40+ blood parameters they studied either increased or decreased with age.

Each of the Steller sea lions cared for by the Vancouver Aquarium receives a daily physical checkup.


“Many of the changes in their blood chemistry reflected changes in their life history,” Gerlinsky says. “For example, their diet changes during weaning, their diving capacity improves as they grow, and their immune system matures over time. These changes are all reflected in the blood, so it’s important to know how old the animal is that you’re comparing to a reference range.”
The researchers also found differences in two key blood parameters among diving and non-diving animals. Some of the animals dove regularly at the Open Water Research Station, while others didn’t.
“I found it interesting that the act of diving and exercising caused a difference in some of those blood parameters,” Gerlinsky says. “This tells us that the blood parameters are responding to changes in the animals’ environment, and they’re not simply innate or genetically driven.”
Gerlinsky notes there are opportunities to further develop the reference ranges, especially by including more data from animals that dive regularly, and from male Steller sea lions.

PublicationsPUBLICATION

Reference ranges and age-related and diving exercise effects on hematology and serum chemistry of female Steller sea lions (Eumetopias jubatus).
Gerlinsky, C. D., M. Haulena, A. W. Trites and D. A. S. Rosen. 2018.
Journal of Zoo and Wildlife Medicine 49(1):18-29.
abstract
Decreased health may have lowered the birth and survival rates of Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska and Aleutian Islands over the past 30 yr. Reference ranges for clinical hematology and serum chemistry parameters needed to assess the health of wild sea lion populations are limited. Here, blood parameters were serially measured in 12 captive female Steller sea lions ranging in age from 3 wk to 16 yr to establish baseline values and investigate age-related changes. Whether diving activity affects hematology parameters in animals swimming in the ocean compared with animals in a traditional aquarium setting was also examined. Almost all blood parameters measured exhibited significant changes with age. Many of the age-related changes reflected developmental life history changes, including a change in diet during weaning, an improvement of diving capacity, and the maturity of the immune system. Mean corpuscular hemoglobin and mean corpuscular volume were also higher in the ocean diving group compared with the aquarium group, likely reflecting responses to increased exercise regimes. These data provide ranges of hematology and serum chemistry values needed to evaluate and compare the health and nutritional status of captive and wild Steller sea lions.

keywords     Diving, Eumetopias jubatus, hematology, marine mammal, serum chemistry, Steller sea lion
show/hide abstract View Reference Learn more about what was found

.

Climate contributions to hard times in US West Coast salmon fisheries

SPEAKER: Nate Mantua

NOAA NMFS    Southwest Fisheries Science Center

The “warm blob” of 2014-2016 was the latest, and perhaps most dramatic, case of climate extremes that had severe negative impacts on west coast salmon fisheries. U.S. west coast Chinook salmon catches in 2016 were the 5th lowest since 1971, harvest quotas were not met, and spawning escapements to the Klam­ath and Sacramento River basins were very low.  Salmon fisheries were sharply restricted from southern Oregon to southern California in 2017, and salmon fisheries are again sharply restricted in 2018.  Sustained hard times for modern US west coast salmon fisheries arguably began in the early 1990s, with 11 of the past 25 years marked by federal disaster declarations. In this talk, I use an integrated framework to link nature, law, and economy to evaluate the role that climate extremes, resource management policies, and the evolving salmon production system played in federal fishery disaster determinations for US west coast Chinook salmon fisheries since the early 1980s. I also evaluate the role of climate change in recent Northeast Pacific climate trends and extremes, and what future climate projections suggest for the future of the west coast salmon fisheries.

Tuesday, September 18, 2018 @ 5:00pm 


Please Register at EVENTBRITE OR EMAIL larkinlecture@oceans.ubc.ca

UNIVERSITY OF BRITISH COLUMBIA

AQUATIC ECOSYSTEM RESEARCH LABORATORY

GROUND FLOOR, AERL, 2202 MAIN MALL

VANCOUVER, B.C.  V6T 1Z4


 

Reception to Follow the Lecture

Dr. Andrew W. Trites (on left) – receives award from Andrew Stewart who represented DFO.

Congratulations to our very own Dr. Andrew Trites, professor in the Institute for the Oceans and Fisheries, who has been awarded the Timothy R. Parsons Medal from Fisheries and Oceans Canada!

This award is awarded for distinguished achievement in ocean sciences, leadership through teaching or mentoring, and significant contributions to multidisciplinary facets of ocean sciences.

Dr. Andrew Trites has been studying marine mammals (primarily Steller sea lions, harbor seals, northern fur seals, and killer whales), in the North Pacific for over 30 years.

In 1993 he, with Dr. Peter Larkin, created the North Pacific Universities Marine Mammal Research Consortium to bring together the very best research talents from west coast universities (Universities of Alaska, British Columbia, Washington and Oregon State) to collectively resolve critical research problems pertaining to marine mammals. He also established the UBC Open Water Research Station to undertake open-ocean diving and foraging studies with free-swimming trained sea lions, and oversees field programs in Alaska and British Columbia. He leads the UBC Marine Mammal Research Unit (MMRU), a research program that furthers the conservation and understanding of marine mammals and resolves conflicts between people and marine mammals.

Dr. Trites was given the medal 12 June 2018, at a gala luncheon in Halifax, NS.

Bowhead rubbing

Sometimes the coolest things happen, when you least expect it.

These four bowhead whales with mottled skin were filmed rubbing their bodies against boulders. Animal A is seen rubbing the right side of its head on a boulder, and Animal D is using the rocks to exfoliate its chin. The long, thin lines running length and width-wise across the body of Animal C were caused by rubbing against rocks. Images captured by VDOS Global LLC

Since grade school, we’ve been taught the importance of applying the scientific method while observing and answering questions about the world around us. This means having clear hypotheses to test—and employing rigorous methods to collect, analyze and interpret data.

But, what happens when things don’t go quite to plan and you stumble upon something that falls completely outside your research scope?

This is what happened during Sarah Fortune’s PhD fieldwork in the remote waters of Cumberland Sound, Nunavut. Sarah and her colleagues had traveled there to study the diet and feeding behavior of Eastern Canada-West Greenland bowhead whales by recording their underwater movements using archival tags and collecting co-located prey data using a suite of oceanographic sampling equipment.

To their amazement, the team found that bowheads don’t just feed in Cumberland Sound, but they also exfoliate here with help of large rocks along the shoreline.

This unexpected observation of whales rubbing their bodies against large rocks gives new insight into the biological significance of Cumberland Sound to the whales — and shows how the coolest things can sometimes happen when you least expect them!

 

Sarah Fortune is a PhD Student at UBC’s Marine Mammal Research Unit.


Project Partners: Fisheries and Oceans Canada (Steven Ferguson), World Wildlife Fund Canada (Brandon Laforest), LGL Limited (Bill Koski), VDOS Global LLC (Thomas Seitz), Higdon Wildlife Consulting (Jeff Higdon), Woods Hole Oceanographic Institution (Mark Baumgartner), Pangnirtung Hunter and Trappers Association and Peter’s Expediting & Outfitting Services. 

 


See the rest of the Marine Mammal Research Newsletter from March 2018

Contents | Into the Field | From the Lab | Science Outreach |  Science InreachThis Just In |

Into the Field

Bowhead rubbing

Sometimes the coolest things happen, when you least expect it. <see full story>


From the Lab

It’s a drag wearing a tag

What impacts do tracking tags have on the behavior and swimming costs of marine mammals?  <see full story>


Science Outreach

Marine mammalogists share their latest findings

A full house gathered in a hockey rink in eastern Canada as the pinniped scientists took on the cetacean scientists.<see full story>


Science Inreach

Workshop held on the availability of prey for southern resident killer whales

What can be done to make more salmon available to southern resident killer whales? <see full story>


This Just In

7 new publications…

Molting bowhead whales, northern fur seal diets, killer whale foraging behavior, measuring stroke rates of sea lions and fur seals, and more … <see full story>

7 new publications…

Molting bowhead whales, northern fur seal diets, killer whale foraging behavior, measuring stroke rates of sea lions and fur seals, and more …


2018
 
Availability of prey for southern resident killer whales. Technical workshop proceedings. November 15 - 17, 2017.
Trites, A.W. and D.A.S. Rosen (Eds.). 2018.
Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, B.C. pp. 64
abstract
This workshop assembled scientists and managers with technical expertise on killer whales and Chinook salmon to identify and evaluate short-term management actions that might increase the immediate abundance and accessibility of Chinook salmon for southern resident killer whales, given the current size of Chinook salmon stocks. The workshop did not consider ways of producing more Chinook salmon (which will be the subject of a subsequent workshop), but rather considered ways of making more of the fish that are presently in the ocean available to southern resident killer whales (SRKW). Workshop participants presented and discussed technical information on the prey requirements of SRKW, the availability of Chinook salmon, and current protections for SRKW. Participants then split into four groups with an even distribution of expertise to evaluate three potential non- exclusive Management Actions: 1) Increase the abundance of Chinook for SRKW by reducing coast-wide fishery removals; 2) Increase the abundance of Chinook for SRKW by adjusting fishery removals at specific times and in specific areas of SRWK habitat; and 3) Increase the accessibility of Chinook by decreasing underwater noise and the physical presence of vessels where SRKW forage.

keywords     killer whales, southern resident, prey, availability, abundance, accessibility, noise, disturbance, fishing, commercial, recreational, Chinook, salmon
show/hide abstract View Reference

2017
 
Evidence of molting and the function of rock-nosing behavior in bowhead whales in the eastern Canadian Arctic.
Fortune, S. M. E., W. R. Koski, J. W. Higdon, A. W. Trites, M. F. Baumgartner and S. H. Ferguson. 2017.
PLoS ONE, pages: e0186156 Vol 12(1)
abstract
Bowhead whales (Balaena mysticetus) have a nearly circumpolar distribution, and occasionally occupy warmer shallow coastal areas during summertime that may facilitate molting. However, relatively little is known about the occurrence of molting and associated behaviors in bowhead whales. We opportunistically observed whales in Cumberland Sound, Nunavut, Canada with skin irregularities consistent with molting during August 2014, and collected a skin sample from a biopsied whale that revealed loose epidermis and sloughing. During August 2016, we flew a small unmanned aerial system (sUAS) over whales to take video and still images to: 1) determine unique individuals; 2) estimate the proportion of the body of unique individuals that exhibited sloughing skin; 3) determine the presence or absence of superficial lines representative of rock-rubbing behavior; and 4) measure body lengths to infer age-class. The still images revealed that all individuals (n = 81 whales) were sloughing skin, and that nearly 40% of them had mottled skin over more than two-thirds of their bodies. The video images captured bowhead whales rubbing on large rocks in shallow, coastal areas --likely to facilitate molting. Molting and rock rubbing appears to be pervasive during late summer for whales in the eastern Canadian Arctic.
show/hide abstract View Reference

2017
 
Combining hard-part and DNA analyses in scats with biologging and stable isotopes can reveal different diet compositions and feeding strategies within a population.
Jeanniard-du-Dot, T., A. C. Thomas, Y. Cherel, A. W. Trites and C. Guinet. 2017.
Marine Ecology Progress Series 584:1-16.
abstract
Accurately estimating predators' diets at relevant spatial and temporal scales is key to understanding animals' energetics and fitness, particularly in populations whose decline might be related to their diet such as northern fur seals Callorhinus ursinus. Our goals were to improve the accuracy of diet estimates and extend understanding of feeding ecology by combining 2 scat-based methods of diet determination (hard-part identification and DNA-metabarcoding) with stable isotope measurements and individual behavioural data. We collected 98 scats on a northern fur seal breeding colony. We also tracked 20 females with biologgers, and took blood samples to determine δ13C and δ15N values as proxies for seal foraging habitat and diet. Results show that diet composition from hard-parts analysis corresponded well with DNA results, with DNA yielding a greater diversity of prey species at a finer taxonomic level. Overall, scat-based methods showed that seals mostly fed on neritic shelf-associated prey. Cluster analyses of combined hard-parts and DNA results however identified 2 diet groups, one mostly neritic and the other mostly pelagic. Stable isotopes and behavioural data revealed that 40% of seals fed in oceanic waters on pelagic prey. This is more than indicated by scat-based analyses, which are likely biased towards animals foraging closest to the colony and underestimate some dietary specializations within the population. Consequently, the combination of multiple methods for diet identification with at-sea tracking of individuals can help identify and quantify specialist groups within a population and provide a wider spatial and temporal ecological context for dietary analysis.
show/hide abstract View Reference

2017
 
Proxies of energy expenditure for marine mammals: an experimental test of the time trap.
Ladds, M. A., D. A. S. Rosen, D. J. Slip and R. G. Harcourt. 2017.
Scientific Reports 7:11815
abstract
Direct measures of energy expenditure are difficult to obtain in marine mammals, and accelerometry may be a useful proxy. Recently its utility has been questioned as some analyses derived their measure of activity level by calculating the sum of accelerometry-based values and then comparing this summation to summed (total) energy expenditure (the so-called 'time trap'). To test this hypothesis, we measured oxygen consumption of captive fur seals and sea lions wearing accelerometers during submerged swimming and calculated total and rate of energy expenditure. We compared these values with two potential proxies of energy expenditure derived from accelerometry data: flipper strokes and dynamic body acceleration (DBA). Total number of strokes, total DBA, and submergence time all predicted total oxygen consumption (sVO2 ml kg−1). However, both total DBA and total number of strokes were correlated with submergence time. Neither stroke rate nor mean DBA could predict the rate of oxygen consumption (sV.O2 ml min−1 kg−1). The relationship of total DBA and total strokes with total oxygen consumption is apparently a result of introducing a constant (time) into both sides of the relationship. This experimental evidence supports the conclusion that proxies derived from accelerometers cannot estimate the energy expenditure of marine mammals.

keywords     energy expenditure, accelerometers, Steller sea lions
show/hide abstract View Reference

2017
 
On the utility of accelerometers to predict stroke rate using captive fur seals and sea lions.
Ladds, M. A., D. A. S. Rosen, D. J. Slip and R. G. Harcourt. 2017.
Biology Open 6:1396-1400.
abstract
Energy expenditure of free-living fur seals and sea lions is difficult to measure directly, but may be indirectly derived from flipper stroke rate. We filmed 10 captive otariids swimming with accelerometers either attached to a harness (Daily Diary: sampling frequency 32Hz, N = 4) or taped to the fur (G6a+: 25Hz, N = 6). We used down sampling to derive four recording rates from each accelerometer (Daily Diary: 32, 16, 8, 4Hz; G6a+: 25, 20, 10, 5Hz). For each of these sampling frequencies we derived 20 combinations of two parameters (RMW - the window size used to calculate the running mean, and m – the minimum number of points smaller than the local maxima used to detect a peak), from the dynamic acceleration of x, z and x+z, to estimate stroke rate from the accelerometers. These estimates differed by up to ~20% in comparison to the actual number of foreflipper strokes counted from videos. RMW had little effect on the overall differences, nor did the choice of axis used to make the calculations (x, z or x+z), though the variability was reduced when using x+z. The best m varied depending on the axis used and the sampling frequency, where a larger m was needed for higher sampling frequencies. This study demonstrates that when parameters are appropriately tuned, accelerometers are a simple yet valid tool for estimating the stroke rates of swimming otariids.

keywords     otariid, swim mechanics, stroke rate, accelerometer, energetics, biologger
show/hide abstract View Reference

2017
 
Marine mammals exploring the oceans pole to pole: a review of the MEOP consortium.
Treasure, A. M., F. Roquet, I. J. Ansorge, M. N. Bester, L. Boehme, H. Bornemann, J.-B. Charrassin, D. Chevallier, D. P. Costa, M. A. Fedak, C. Guinet, M. O. Hammill, R. G. Harcourt, M. A. Hindell, K. M. Kovacs, M.-A. Lea, P. Lovell, A. D. Lowther, C. Lydersen, T. McIntyre, C. R. McMahon, M. M. C. Muelbert, K. Nicholls, B. Picard, G. Reverdin, A. W. Trites, G. D. Williams and P.J. Nico de Bruyn. 2017.
Oceanography 30:132-138.
abstract
Polar oceans are poorly monitored despite the important role they play in regulating Earth's climate system. Marine mammals equipped with biologging devices are now being used to fill the data gaps in these logistically difficult to sample regions. Since 2002, instrumented animals have been generating exceptionally large data sets of oceanographic CTD casts (>500,000 profiles), which are now freely available to the scientific community through the MEOP data portal (http://meop.net). MEOP (Marine Mammals Exploring the Oceans Pole to Pole) is a consortium of international researchers dedicated to sharing animal-derived data and knowledge about the polar oceans. Collectively, MEOP demonstrates the power and cost-effectiveness of using marine mammals as data-collection platforms that can dramatically improve the ocean observing system for biological and physical oceanographers. Here, we review the MEOP program and database to bring it to the attention of the international community.
show/hide abstract View Reference

2017
 
Fine-scale foraging movements by fish-eating killer whales (Orcinus orca) relate to the vertical distributions and escape responses of salmonid prey (Oncorhynchus spp.).
Wright, B. M., J. K. B. Ford, G. M. Ellis, V. B. Deecke, A. D. Shapiro, B. C. Battaile and A. W. Trites. 2017.
Movement Ecology 5:1-18.
abstract
Background: We sought to quantitatively describe the fine-scale foraging behavior of northern resident killer whales (Orcinus orcas), a population of fish-eating killer whales that feeds almost exclusively on Pacific salmon (Oncorhynchus spp.). To reconstruct the underwater movements of these specialist predators, we deployed 34 biologging Dtags on 32 individuals and collected high-resolution, three-dimensional accelerometry and acoustic data. We used the resulting dive paths to compare killer whale foraging behavior to the distributions of different salmonid prey species. Understanding the foraging movements of these threatened predators is important from a conservation standpoint, since prey availability has been identified as a limiting factor in their population dynamics and recovery. Results: Three-dimensional dive tracks indicated that foraging (N = 701) and non-foraging dives (N = 10,618) were kinematically distinct (Wilks

keywords     Foraging, Movement, Diving behavior, Biologging, Dtag, Accelerometry, Killer whale, Orcinus orca, Pacific salmon
show/hide abstract View Reference

Oil painting “Hide and Seek” by Bruce Muir (2017) showing a southern resident killer whale pursuing Chinook salmon.

Workshop held on the availability of prey for southern resident killer whales

What can be done to make more salmon available to southern resident killer whales?

In November 2017, the UBC Marine Mammal Research Unit hosted a workshop with Canadian and US scientists and managers with technical expertise on killer whales and Chinook salmon.

The goal of the workshop was to identify and evaluate short-term management actions that might increase the immediate abundance and accessibility of Chinook salmon for southern resident killer whales (SRKW), given the current size of Chinook salmon stocks.

The workshop did not consider ways of producing more Chinook salmon (which will be the subject of a subsequent workshop), but rather considered ways of making more of the fish that are presently in the ocean available to southern resident killer whales.

Workshop participants presented and discussed technical information on the prey requirements of SRKW, the availability of Chinook salmon, and current protections for SRKW. Participants then split into four groups with an even distribution of expertise to evaluate three potential non- exclusive Management Actions:

A. Increase the abundance of Chinook for SRKW by reducing coast-wide fishery removals;
B. Increase the abundance of Chinook for SRKW by adjusting fishery removals at specific times and in specific areas of SRWK habitat; and
C. Increase the accessibility of Chinook by decreasing underwater noise and the physical presence of vessels where SRKW forage.

Based on the current state of knowledge and best available data, workshop participants had higher confidence in the effectiveness of Action C (limiting vessel disturbances to make the Chinook that are already present easier for SRKW to catch) than they did in increasing the abundance of Chinook by closing or adjusting fisheries (Actions A & B).

With >900 stocks of Chinook salmon migrating through BC waters at different times and strengths, there is currently insufficient evidence to support being able to surgically manage fisheries to avoid catching the stocks destined for SRKW habitat. Nor is there evidence that fishery reductions would add significant numbers to the estimated 600,000 Chinook thought to currently move through inside waters to Puget Sound and the Fraser River.


2018
 
Availability of prey for southern resident killer whales. Technical workshop proceedings. November 15 – 17, 2017.Trites, A.W. and D.A.S. Rosen (Eds.). 2018.Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, B.C. pp. 64 

Contents | Into the Field | From the Lab | Science Outreach |  Science Inreach | This Just In |

SMM and AMSS Conferences

A full house gathered in a hockey rink in eastern Canada as the pinniped scientists took on the cetacean scientists.

Poster sessions for the international conference on marine mammals were held at center ice in this hockey arena in Nova Scotia

Halifax, Nova Scotia, opened its arms to almost 2,000 marine mammal scientists, managers, and educators in October 2018. The 22nd Biennial Conference on the Biology of Marine Mammalsallowed researchers to attend specialized workshops, discover and debate the latest developments in marine mammal science and conservation, and set up future collaborative research projects.

Members of the UBC Marine Mammal Research Unit gave a number of presentations on their research, including:

  • Selina Agbayani: Bioenergetics of migrating grey whales in the face of climate change
  • Sarah Fortune: Combining data from drones, multi-scale time-depth-recorders and prey sampling reveals complex foraging behavior of bowhead whales.
  • Aaron Purdy: Switch vs Slide: Rethinking the aerobic dive limit.
  • Rhea Storlund: The aortic bulb: an adaptation for diving?
  • Andrew Trites: Pre-historic insights into northern fur seals and fishing territories in the Pacific Northwest

Posters were grouped in bays by themes, where researchers could explain their studies and findings to conference delegates one-on-one.

In addition, David Rosen won a People’s Choice Award for his presentation “Dive Steller dive: A decade of shedding light on the energetic consequences of foraging behaviour”, which reviewed the work carried out at the Open Water Research Station.

Anchorage, Alaska, also opened it arms in January to participants attending the annual Alaska Marine Science Symposium. This year, Dr. Rosen presented the findings on his NPRB project, “The efficacy of fecal hormones to detect nutritional status in northern fur seals.”

Scientists have been finding it increasingly difficult to attend scientific meetings due to budgetary cutbacks. This is regretful given the important role these meetings play in disseminating findings to managers, stakeholders and scientists prior to publication. These meetings also provide scientists with early feedback on their research—allowing them to develop, clarify, and refine their work before formal publication. Perhaps most importantly for those holding the research-purse strings, scientific conferences are where new research approaches and tools are first revealed, which can ultimately save researchers time (and money), and accelerate progress.

Contents | Into the Field | From the Lab | Off the Bench | Science Outreach | This Just In | Crunching the Numbers |

Brianna Cairns with one of the sea lions at the Open Water Research Station that participated in her study.

How fat is that sea lion?

Estimating the body condition of Steller sea lions may be as simple as pushing a button

Unlike humans, the more body fat a Steller sea lion has, the better off it is. Scientists working to understand the reasons for the decline of Steller sea lions in the wild have long recognized that body condition is an important measure of overall health and food intake. However, there is no simple means to assess the condition of Steller sea lions in the field—but a simple solution might be at hand.

Brianna Cairns, an undergraduate at UBC, has been testing whether a commercially available FatMeter can accurately determine the body condition of Steller sea lions.

The FatMeter is a small, hand-held device that uses the attenuation of low-level microwaves to instantaneously measure the fat content of commercial fish and meats. The method is somewhat akin to how a bathroom scale estimates your percentage fat. Brianna wanted to know whether this same sort of technology could be repurposed to predict the total body fat of Steller sea lions.

Brianna conducted a pilot study with the Consortium’s sea lions at the Vancouver Aquarium and the Open Water Research Station. Initial results are promising, and suggest that the FatMeter can provide a quick, inexpensive way of measuring the body fat of sea lions in the field. Brianna hopes to expand the project after she completes her undergraduate B.Sc. degree this winter.

The FatMeter experiment was not Brianna’s first encounter with Steller sea lions. In fact, she was first introduced to them when her high school class came to visit UBC’s Open Water Research Station. She credits this experience with encouraging her to pursue an undergraduate degree in marine sciences at UBC. This in turn led to a summer NSERC scholarship working at the Open Water Station in 2016 — and an opportunity to undertake her own research with the Consortium sea lions for her Honors project under the supervision of Dr. David Rosen.

Brianna Cairns is a Undergraduate Student at UBC

Studying Acceleration and Energetics… in 3-D

A fur seal “fitness tracker” called a Daily Diary Tag records three-dimensional acceleration, depth, water temperature, and many other variables while the fur seals are at sea.


How many calories did you burn today? If you wear a fitness tracker, the answer is easy. You can see how many steps you took, and estimate how much energy you expended. You can even plan your meals to replace those calories.
For scientists studying energetics in wild fur seals, the answers are not so straightforward. Seals move in three dimensions through the water, and they expend different amounts of energy while diving, swimming, grooming, and even sleeping. How much energy does each activity consume, and how to accurately measure this? Can this information ultimately help to conserve fur seal populations?
A new Consortium study, led by Dr. Tiphaine Jeanniard-du-Dot (University of British Columbia), tracked the movements of 40 wild fur seals over extended foraging trips in the northern and southern hemispheres. Using the data from the tracking devices, the authors developed a novel way to estimate energy expenditure in fur seals.
The new study was published in the journal Functional Ecology, and extends from Jeanniard-du-Dot’s previous work measuring flipper strokes in fur seals.

Female northern fur seals nurse their pups for about a day between week-long foraging trips.


Dynamic Body Acceleration
“In the flipper stroke study, I measured forward acceleration,” says Jeanniard-du-Dot. “This new study focuses on Dynamic Body Acceleration [DBA], which measures acceleration in three dimensions—for example, when the animals roll, twist, turn, or swim up or down. Our results give us a more complete estimate of how much energy they expend when hunting for food.”
The study involved temporarily fitting 20 lactating northern fur seals and 20 lactating Antarctic fur seals with tracking devices to measure their position, acceleration, and movements in three dimensions.
The scientists wanted to know whether DBA could accurately predict the energy expended over a full foraging trip that can last up to 15 days. At the same time, they wanted to know whether it was more accurate to measure the energy expended over the entire trip, or by partitioning the trip into periods of different types of activity, such as traveling, diving, grooming and resting.
“Different activities have different energy costs,” says Jeanniard-du-Dot. “Our goal was to see whether 3-D accelerometers could be used to estimate how much energy an animal burns each day while swimming, diving and resting at sea.”

Relationships between dynamic-body acceleration and energy expenditure in lactating northern fur seals (triangles, n=16 seals) and Antarctic fur seals (squares, n=17 seals) while diving, transiting, and grooming and resting on the surface. The graphs show fur seals spend more energy diving compared to transiting and engaging in surface activities.  They also show northern fur seals spend more energy to swim (transiting) compared with Antarctic fur seals.


It might seem logical to expect faster activities to require more energy. But the relationship between acceleration and energy expenditure isn’t linear, she says. For example, fur seals foraging at depth spend more energy overcoming drag, which reduces acceleration but increases energy expenditure. At the surface there is less drag, making porpoising a faster and more energy efficient activity.
From Individuals to Populations
The study concludes that measuring Dynamic Body Acceleration is a promising way to estimate energy expenditures of free-ranging fur seals at a fine scale never attained before. The methodology can be applied to other species by linking time-activity budgets to acceleration, says Jeanniard-du-Dot.
However, she adds that the results also underscore the importance of measuring expenditure based on the individual activities that make up foraging trips, rather than as a single measure applied to entire foraging trips. In all, the study provides valuable baseline data for both species of fur seal.
“As an energetics researcher, I think having estimates of energy expenditures for a wild species is paramount to understanding everything that is happening in their environment,” she says. “These animals can only use whatever energy they can capture in the form of food. If we know how much energy they need to survive, then we know how much they extract from their environment. We can then extrapolate from the individual animal to an entire population.”
“This is particularly important in a changing marine environment,” she notes. “At the individual level, if animals can’t capture enough prey, they will begin to have problems with their health, reproduction, and survival. This can be an indicator of a declining population.”

A female Antarctic fur seal with her pup in the Sub Antarctic.


“Climate change is coming, and more quickly in polar regions,” notes Jeanniard-du-Dot. “Prey will potentially be less available, accessible and abundant. This means that fur seals might have to work harder to get their prey—go further from their colony, dive deeper for longer, and so on. They will probably have to increase the time spent in the two most energetically expensive activities, which are transiting and diving.”
When time-activity budgets of marine mammals change due to fishing or environmental conditions, scientists will be able to use the methods developed by Jeanniard-du-Dot and colleagues to determine what is happening, and anticipate the consequences at the population level.

PublicationsPUBLICATION

Accelerometers can measure total and activity-specific energy expenditure in free-ranging marine mammals only if linked to time-activity budgets.
Jeanniard du Dot, T., C. Guinet, J. P. Y. Arnould, J. R. Speakman and A. W. Trites. 2017.
Functional Ecology 31:377-386.
abstract
1-Energy expenditure is an important component of foraging ecology, but is extremely difficult to estimate in free-ranging animals and depends on how animals partition their time between different activities during foraging. Acceleration data has emerged as a new way to determine energy expenditure at a fine scale but needs to be tested and validated in wild animals. 2-This study investigated whether vectorial dynamic body acceleration (VeDBA) could accurately predict the energy expended by marine predators during a full foraging trip. We also aimed to determine whether the accuracy of predictions of energy expenditure derived from acceleration increased when partitioned by different types of at-sea activities (i.e., diving, transiting, resting and surface activities) vs calculated activity-specific metabolic rates. 3-To do so, we equipped 20 lactating northern (Callorhinus ursinus) and 20 Antarctic fur seals (Arctocephalus gazella) with GPS, time-depth recorders and tri-axial accelerometers, and obtained estimates of field metabolic rates using the doubly-labelled water (DLW) method. VeDBA was derived from tri-axial acceleration, and at-sea activities (diving, transiting, resting and surface activities) were determined using dive depth, tri-axial acceleration and traveling speed. 4-We found that VeDBA did not accurately predict the total energy expended by fur seals during their full foraging trips (R2 = 0.36). However, the accuracy of VeDBA as a predictor of total energy expenditure increased significantly when foraging trips were partitioned by activity and used activity-specific VeDBA paired with time activity budgets (R2 = 0.70). Activity-specific VeDBA also accurately predicted the energy expenditures of each activity independent of each other (R2 > 0.85). 5-Our study confirms that acceleration is a promising way to estimate energy expenditures of free-ranging marine mammals at a fine scale never attained before. However, it shows that it needs to be based on the time-activity budget that make up foraging trips rather than being derived as a single measure of VeDBA applied to entire foraging trips. Our activity-based method provides a cost-effective means to accurately calculate energy expenditures of fur seals using acceleration and time-activity budgets, a stepping stone for numerous other research fields.

keywords     Antarctic fur seal, Arctocephalus gazella, Callorhinus ursinus, diving, energy expenditure, foraging, metabolic rate, northern fur seal, time-activity budget
show/hide abstract View Reference

Watch the Symposium from November 25, 2017:

Join us for presentations as well as discussion on issues that concern us all. This meeting is open to students, researchers, educators, businesses and others involved with marine mammals. Anyone in one or more of these categories is welcome to attend.


Our next Symposium will be on November 24, 2018

Email: bc.symposium@oceans.ubc.ca

 

 

 

 

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Hassen Allegue uses his laptop computer to program one of the biologging tags before deploying it on a harbor seal.

Biologging tags reveal specialist-feeding behaviors by seals that have implications for conservation of salmon

Large numbers of juvenile salmon (smolts)–whether from a river or hatchery raised—leave their natal streams each spring to enter the ocean. Harbor seals often gather in river mouths at this time, presumably to take advantage of this predictable food source. However, it is not clear whether predation on this early life-stage of is a significant source of mortality for coho and Chinook salmon populations.

Hassen Allegue, a UBC MSc student, investigated where, when and how this predation occurs in relation to the release of smolts from a Vancouver Island hatchery. He wanted to know the extent to which this predation might be opportunistic, or whether it represents a specialist feeding behavior. Is it a common strategy or something practiced by only a few highly visible individuals? Does seal predation differ with different types of salmon smolts?

To answer these questions, Hassen equipped 17 harbor seals with GPS loggers and Daily Diary tags to track the seals before and after the release of thousands of coho and Chinook smolts from the Big Qualicum hatchery. The data recorded by the tags carried by the seals allowed Hassen to reconstruct the high-resolution movements of the seals, and quantify the number of times they encountered prey.

Allegue and his team prepare to glue the tracking tags to the fur of a harbor seal. The tags will fall off when the animals molt. The tag that records the fine-scale behaviors of the seals floats, and is recovered after molting to download the data.

Hassen found that the harbor seals present during spring in the Big Qualicum Estuary could be grouped into 4 types of foragers. While about half of the seals fed in the estuary where smolts were present, only a small portion (18%) of these seals were actually salmon smolt specialists. While these “smolt-specialist” seals appeared to target the coho smolts in the river mouth, they apparently ignored the Chinook smolts, which left the river just a few days later. However, there was a second group of seals (18%) that seemed to target larger species of fish preying on the out-migrating Chinook smolts. The two other seal groups did not feed at the river mouth in association with the concentrated numbers of smolts, but either fed near their main haul-out sites away from the river (52%), or were transient and left the estuary area all together (12%).

A well dressed harbor seal returns to sea carrying the data loggers that will record every second of the seal’s life for the next month.

Hassen’s results suggest there is a high degree of individual foraging and diet specializations among harbor seals. They also show that a small number of seals specialize in consuming coho smolts, but do not appear to respond to the large pulse of the smaller bodied Chinook smolts at the river mouth.

Such information concerning the fine-scale foraging behavior of harbor seals in relation to pulses of out-migrating smolts can be used to design mitigation strategies to enhance coho and Chinook populations.

Further details about Hassen’s study can be found in:

Variability of harbour seal (Phoca vitulina) foraging behaviour during out-migrations of salmon smolts.
Allegue, H. 2017.
M.Sc. Thesis, University of British Columbia, Vancouver BC. 107 pages

Hassen Allegue is a MSc Student at UBC’s Marine Mammal Research Unit.

 

Crunching the Numbers

A female Antarctic fur seal on the Kergulen Islands, southern Indian Ocean.

Stroke Signals: Studying flipper strokes in fur seals gives insights into their energetics

Thanks to small sensors in popular new activity tracking devices like the FitBit, people can now answer questions about their daily lives that used to require a great deal of guesswork. How many steps did I walk or run today? How many calories did I burn given my daily activities? It’s handy information if you’re trying to stay healthy.

Consortium scientists are asking similar questions about marine mammals, and are using devices with similar sensors to find the answers. For example, it is now possible to track the detailed movements of fur seals at sea, and calculate how much energy they expend while diving and swimming using tri-dimensional accelerometers. This information helps to understand how much energy they spend during their daily lives and consequently how much food they need to meet their energetic needs.

Without such devices, it would be impossible to obtain important biometric information about these marine mammals, who range freely over hundreds of kilometers in some of the most remote parts of the oceans. Some of these populations have declined suddenly, and  research on energetics helps to understand why.

In a new Consortium study, researchers tracked the movements at sea of two species of fur seals: northern fur seals living in the northern hemisphere, and Antarctic fur seals living in the southern hemisphere. They analyzed flipper strokes to estimate the amount of energy expended during various activities. The study, led by Dr Tiphaine Jeanniard-du-Dot, was published in Nature Scientific Reports.

Different Strokes

“We set out to answer two questions,” says Jeanniard-du-Dot, who completed the study as part of her PhD research. “First, can we identify flipper strokes in the acceleration signals recorded by the devices? And second, can we predict energy expenditures by counting the flipper strokes in both species of fur seal, over a wide range of behaviors at sea?”

Northern fur seals returning to shore on the Pribilof Islands, Alaska.

Fur seals at sea spend most of their time diving, swimming slightly below the surface, or resting at the surface, says Jeanniard-du-Dot. Each flipper stroke causes a momentary acceleration that is detected and stored in the tracking device. In their analysis, the researchers worked to isolate the animal’s own movements from the background “noise” generated by waves, currents and wind.

“It was easy to detect flipper strokes when the seals were underwater and diving, because there was less noise from wind or waves,” she says. “The signals were less clear when the animals were swimming at or slightly below the surface, but we could still detect them. When the fur seals were moving slowly at the surface, grooming or resting, it was difficult to detect anything at all.”

The scientists were surprised to find some consistency between flipper strokes among the northern fur seals in the Alaskan Bering Sea, and the Antarctic fur seals in the Southern Ocean and Antarctic peninsula. Each species used a similar number of flipper strokes to travel the same distance, had the same swimming rhythm, and expended the same amount of energy. However, while diving the smaller Antarctic fur seals expended slightly more energy to accelerate, likely due to their smaller flipper size.

Analyzing Amplitude

In addition to counting the number of strokes, the scientists also assessed the relative power of each stroke by measuring its amplitude, or intensity.

Fur seals regularly porpoise as they travel in search of food.

“A big flipper stroke generates more acceleration, and requires more energy, than a small flipper stroke,” says Jeanniard-du-Dot. “We found that measuring amplitude was a better predictor of energy expenditure over the whole range of behaviors during an entire foraging trip. If we want to get a better estimate of what is going on overall, we should take amplitude into account and not simply measure the number of flipper strokes.”

As a field biologist, Jeanniard-du-Dot believes that understanding basic energetics is fundamental to estimating what fur seals need to survive and reproduce successfully.

“Just as a person couldn’t run a marathon on a diet of two salads per day, we can’t expect fur seals to thrive in the wild if they aren’t getting the calories they need,” she says. “By using acceleration data to estimate the energy they expend, we are a step closer to understanding how much food they need, and eventually, how best to manage and share the ocean’s resources.”

PublicationsPUBLICATION

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Tiphaine Jeanniard-du-Dot  is an alumni PhD Student at UBC’s Marine Mammal Research Unit.


7 new publications…


2017
 
Accelerometers can measure total and activity-specific energy expenditure in free-ranging marine mammals only if linked to time-activity budgets.
Jeanniard du Dot, T., C. Guinet, J. P. Y. Arnould, J. R. Speakman and A. W. Trites. 2017.
Functional Ecology 31:377-386.
abstract
1-Energy expenditure is an important component of foraging ecology, but is extremely difficult to estimate in free-ranging animals and depends on how animals partition their time between different activities during foraging. Acceleration data has emerged as a new way to determine energy expenditure at a fine scale but needs to be tested and validated in wild animals. 2-This study investigated whether vectorial dynamic body acceleration (VeDBA) could accurately predict the energy expended by marine predators during a full foraging trip. We also aimed to determine whether the accuracy of predictions of energy expenditure derived from acceleration increased when partitioned by different types of at-sea activities (i.e., diving, transiting, resting and surface activities) vs calculated activity-specific metabolic rates. 3-To do so, we equipped 20 lactating northern (Callorhinus ursinus) and 20 Antarctic fur seals (Arctocephalus gazella) with GPS, time-depth recorders and tri-axial accelerometers, and obtained estimates of field metabolic rates using the doubly-labelled water (DLW) method. VeDBA was derived from tri-axial acceleration, and at-sea activities (diving, transiting, resting and surface activities) were determined using dive depth, tri-axial acceleration and traveling speed. 4-We found that VeDBA did not accurately predict the total energy expended by fur seals during their full foraging trips (R2 = 0.36). However, the accuracy of VeDBA as a predictor of total energy expenditure increased significantly when foraging trips were partitioned by activity and used activity-specific VeDBA paired with time activity budgets (R2 = 0.70). Activity-specific VeDBA also accurately predicted the energy expenditures of each activity independent of each other (R2 > 0.85). 5-Our study confirms that acceleration is a promising way to estimate energy expenditures of free-ranging marine mammals at a fine scale never attained before. However, it shows that it needs to be based on the time-activity budget that make up foraging trips rather than being derived as a single measure of VeDBA applied to entire foraging trips. Our activity-based method provides a cost-effective means to accurately calculate energy expenditures of fur seals using acceleration and time-activity budgets, a stepping stone for numerous other research fields.

keywords     Antarctic fur seal, Arctocephalus gazella, Callorhinus ursinus, diving, energy expenditure, foraging, metabolic rate, northern fur seal, time-activity budget
show/hide abstract View Reference

2017
 
Reproductive success is energetically linked to foraging efficiency in Antarctic fur seals.
Jeanniard-du-Dot, T., A.W. Trites, J.P. Arnould, and C. Guinet. 2017.
PLoS ONE. 12:e0174001
abstract
The efficiency with which individuals extract energy from their environment defines their survival and reproductive success, and thus their selective contribution to the population. Individuals that forage more efficiently (i.e., when energy gained exceeds energy expended) are likely to be more successful at raising viable offspring than individuals that forage less efficiently. Our goal was to test this prediction in large long-lived mammals under free-ranging conditions. To do so, we equipped 20 lactating Antarctic fur seals (Arctocephalus gazella) breeding on Kerguelen Island in the Southern Ocean with tags that recorded GPS locations, depth and tri-axial acceleration to determine at-sea behaviours and detailed time-activity budgets during their foraging trips. We also simultaneously measured energy spent at sea using the doubly-labeled water (DLW) method, and estimated the energy acquired while foraging from 1) type and energy content of prey species present in scat remains, and 2) numbers of prey capture attempts determined from head acceleration. Finally, we followed the growth of 36 pups from birth until weaning (of which 20 were the offspring of our 20 tracked mothers), and used the relative differences in body mass of pups at weaning as an index of first year survival and thus the reproductive success of their mothers. Our results show that females with greater foraging efficiencies produced relatively bigger pups at weaning. These mothers achieved greater foraging efficiency by extracting more energy per minute of diving rather than by reducing energy expenditure. This strategy also resulted in the females spending less time diving and less time overall at sea, which allowed them to deliver higher quality milk to their pups, or allowed their pups to suckle more frequently, or both. The linkage we demonstrate between reproductive success and the quality of individuals as foragers provides an individual-based quantitative framework to investigate how changes in the availability and accessibility of prey can affect fitness of animals.

keywords     foraging, energetics, pups, growth, biologging, doubly-labeled water, Antarctic fur seal, Arctocephalus gazella
show/hide abstract View Reference

2017
 
Activity-specific metabolic rates for diving, transiting and resting at sea can be estimated from time-activity budgets in free-ranging marine mammals.
Jeanniard-du-Dot, T., A.W. Trites, J.P.Y. Arnould, and C. Guinet. 2017.
Ecology and Evolution 2017:1-8.
abstract
Time and energy are the two most important currencies in animal bioenergetics. How much time animals spend engaged in different activities with specific energetic costs ultimately defines their likelihood of surviving and successfully reproducing. However, it is extremely difficult to determine the energetic costs of independent activities for free-ranging animals. In this study, we developed a new method to calculate activity-specific metabolic rates, and applied it to female fur seals. We attached biologgers (that recorded GPS locations, depth profiles, and triaxial acceleration) to 12 northern (Callorhinus ursinus) and 13 Antarctic fur seals (Arctocephalus gazella), and used a hierarchical decision tree algorithm to determine time allocation between diving, transiting, resting, and performing slow movements at the surface (grooming, etc.). We concomitantly measured the total energy expenditure using the doubly-labelled water method. We used a general least-square model to establish the relationship between time-activity budgets and the total energy spent by each individual during their foraging trip to predict activity-specific metabolic rates. Results show that both species allocated similar time to diving (~29%), transiting to and from their foraging grounds (~26-30%), and resting (~8-11%). However, Antarctic fur seals spent significantly more time grooming and moving slowly at the surface than northern fur seals (36% vs. 29%). Diving was the most expensive activity (~30 MJ/day if done non-stop for 24 hr), followed by transiting at the surface (~21 MJ/day). Interestingly, metabolic rates were similar between species while on land or while slowly moving at the surface (~13 MJ/day). Overall, the average field metabolic rate was ~20 MJ/day (for all activities combined). The method we developed to calculate activity-specific metabolic rates can be applied to terrestrial and marine species to determine the energetic costs of daily activities, as well as to predict the energetic consequences for animals forced to change their time allocations in response to environmental shifts.

keywords     Antarctic fur seal, Arctocephalus gazella, Callorhinus ursinus, diving, energy expenditure, foraging, metabolic rate, northern fur seal, time-activity budget
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2017
 
Physiological constraints and energetic costs of diving behaviour in marine mammals: a review of studies using trained Steller sea lions diving in the open ocean.
Rosen, D.A.S., A.G. Hindle, C. Gerlinsky, E. Goundie, G.D. Hastie and A.W. Trites. 2017.
Journal of Comparative Physiology B 187:29-50.
abstract
Marine mammals are characterized as having physiological specializations that maximize the use of oxygen stores to prolong time spent under water. However, it has been difficult to undertake the requisite controlled studies to determine the physiological limitations and trade-offs that marine mammals face while diving in the wild under varying environmental and nutritional conditions. For the past decade, Steller sea lions (Eumetopias jubatus) trained to swim and dive in the open ocean away from the physical confines of pools participated in studies that investigated the interactions between diving behaviour, energetic costs, physiological constraints, and prey availability. Many of these studies measured the cost of diving to understand how it varies with behaviour and environmental and physiological conditions. Collectively, these studies show that the type of diving (dive bouts or single dives), the level of underwater activity, the depth and duration of dives, and the n utritional status and physical condition of the animal affect the cost of diving and foraging. They show that dive depth, dive and surface duration, and the type of dive result in physiological adjustments (heart rate, gas exchange) that may be independent of energy expenditure. They also demonstrate that changes in prey abundance and nutritional status cause sea lions to alter the balance between time spent at the surface acquiring oxygen (and offloading CO2 and other metabolic by-products) and time spent at depth acquiring prey. These new insights into the physiological basis of diving behaviour further our understanding of the potential scope for behavioural responses of marine mammals to environmental changes, the energetic significance of these adjustments, and the consequences of approaching physiological limits.
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2016
 
Bayesian data fusion approaches to predicting spatial tracks: application to marine mammals.
Liu, Y., J. V. Zidek, A. W. Trites and B. C. Battaile. 2016.
Annals of Applied Statistics 10:1517-1546.
abstract
Bayesian Melding (BM) and downscaling are two Bayesian approaches commonly used to combine data from different sources for statistical inference. We extend these two approaches to combine accurate but sparse direct observations with another set of high-resolution but biased calculated observations. We use our methods to estimate the path of a moving or evolving object and apply them in a case study of tracking northern fur seals. To make the BM approach computationally feasible for high dimensional (big) data, we exploit the properties of the processes along with approximations to the likelihood to break the high dimensional problem into a series of lower dimensional problems. To implement the alternative, downscaling approach, we use R-INLA to connect the two sources of observations via a linear mixed effect model. We compare the predictions of the two approaches by cross-validation as well as simulations. Our results show that both approaches yield similar results— both provide accurate, high resolution estimates of the atea locations of the northern fur seals, as well as Bayesian credible intervals to characterize the uncertainty about the estimated movement paths.

keywords     Bayesian Melding, Downscaling, Bio-logging, Conditional independence, INLA, Dead-Reckoning, Tracking, Marine mammals
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2016
 
Transiting to depth disrupts the relationship between overall dynamic body acceleration and oxygen consumption in freely diving Steller sea lions.
Volpov, B.L., E.T. Goundie, D.A.S. Rosen, A.W. Trites and J.P.Y. Arnould. 2016.
Marine Ecology Progress Series 562:221-236.
abstract
Previous research has presented contradictory evidence on the ability of overall dynamic body acceleration (ODBA) to predict oxygen consumption (sV̇O2) in air-breathing diving vertebrates. We investigated a potential source of these discrepancies by partitioning the ODBA: sV̇O2 relationship over 3 phases of the dive cycle (transiting to and from depth, bottom time, and post-dive surface interval). Trained Steller sea lions (Eumetopias jubatus) executed 4 types of dives to 40 m (single dives, long-duration dive bouts of 4-6 dives, short-duration dive bouts of 10 or 12 dives, and transit dives with minimal bottom duration). Partitioning single dives by dive phase showed differing patterns in the ODBA: sV̇O2 relationship among dive phases, but no significant linear relationships were observed. The proportion of the dive cycle spent transiting to and from the surface was a significant predictive factor in the ODBA: sV̇O2 relationship, while bottom duration or post-dive surface interval had no effect. ODBA only predicted sV̇O2 for dives when the proportion of time spent transiting was small. The apparent inability of ODBA to reliably predict sV̇O2 reflects differences in the inherent relationships between ODBA and sV̇O2 during different phases of the dive. These results support the growing body of evidence that ODBA on its own is not a reliable field predictor of energy expenditure at the level of the single dive or dive bout in air-breathing diving vertebrates likely because ODBA (a physical measure) cannot account for physiological changes in sV̇O2 that occur during the different phases of a dive cycle.

keywords     diving behaviour, metabolic rate, ODBA, dive phase, pinniped
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2016
 
Bottom time does not always predict prey encounter rate in Antarctic fur seals.
Viviant, M., T. Jeanniard du Dot, P. Monestiez, M. Authier and C. Guinet. 2016.
Functional Ecology 30:1834-1844.
abstract
1. Optimal foraging models applied to breath-holding divers predict that diving predators should optimize the time spent foraging at the bottom of dives depending on prey encounter rate, distance to prey patch (depth) and physiological constraints. 2. We tested this hypothesis on a free-ranging diving marine predator, the Antarctic fur seal Arctocephalus gazella, equipped with accelerometers or Hall sensors (n=11) that recorded mouth-opening events, a proxy for prey capture attempts and thus feeding events. Over the 5896 dives analyzed (>15m depth), the mean number of mouth-opening events per dive was 1.21 ą 1.69 (mean ą sd). Overall, 82% of mouth-openings occurred at the bottom of dives. 3. As predicted, fur seals increased their inferred foraging time at the bottom of dives with increasing patch distance (depth), irrespective of the number of mouth-openings. 4. For dives shallower than 55m, the mean bottom duration of dives without mouth-openings was shorter than for dives with mouth-opening events. However, this difference was only due to the occurrence of V-shaped dives with short bottom durations (0 or 1s). When removing those V-shaped dives, bottom duration was not related to the presence of mouth openings anymore. Thus, the decision to abandon foraging is likely related to other information about prey availability than prey capture attempts (i.e. sensory cues) that seals collect during the descent phase. We did not observe V-shaped dives for dives deeper than 55m, threshold beyond which the mean dive duration exceeded the apparent aerobic dive limit. For dives deeper than 55m seals kept on foraging at bottom irrespective of the number of mouth-openings performed. 5. Most dives occurred at shallower depths (30-55m) than the 60m depth of highest foraging efficiency (i.e. of greatest number of mouth-opening events per dive). This is likely related to physiological constraints during deeper dives. 6. We suggest that foraging decisions are more complex than predicted by current theory and highlight the importance of the information collected by the predator during the descent as well as its physiological constraints. Ultimately, this will help establishing reliable predictive foraging models for marine predators based on diving patterns only.

keywords     aerobic diving limit, diving behaviour, foraging strategies, foraging depth, Antarctic fur seals
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Science Outreach

21st Annual meeting of the Northwest Student Chapter of Marine Mammalogy

Nearly 60 people from BC, Washington and Oregon came to discuss their marine mammal research and latest findings

The 21st annual meeting of the Northwest Student Chapter of Marine Mammalogy (NWSSMM) brought university students from Canada and the United States to the University of British Columbia to connect and share their research on marine mammals.

The symposium drew about 60 people from universities and colleges in British Columbia, Washington and Oregon to hear oral and poster presentations from university students, as well as young researchers from NOAA Fisheries, and the Cascadia Research Collective. Topics discussed ranged from foraging ecology and conservation, to physiology and functional anatomy.

Dr. John Ford, the outgoing head of DFO’s Cetacean Research Program, gave the plenary address—a fascinating look into the history of killer whales along BC’s coast, and anecdotes of his own experience studying these incredible animals. Another highlight of the daylong symposium was the Philosopher’s Café, where groups of students met and spoke with marine mammal experts from DFO, NMFS, Universities, and NGOs in a more intimate and casual setting.

Some groups discussed the nitty gritty of olfaction and gustation, bio-logging, ecophysiology, eco-toxicology and conservation, while others tackled broader questions related to the use of science to influence policy, and how to approach a science career in today’s political climate.

MSc student Aaron Purdy (UBC) won Best Talk, while fellow MSc student Rhea Storlund (UBC) received the People’s Choice for Best Poster. Other award winners were Michelle Fournet (Oregon State University, Best Poster) and Erica Escajeda (UW, People’s Choice Oral Presentation).

In addition to the day of science, the students held a group dinner and a visited the MMRU lab at the Vancouver Aquarium to learn firsthand about the research conducted on Steller sea lions and northern fur seals.

This is an annual event, and plans are underway to meet next year at Oregon State University for the 22nd meeting. Students feel that these meetings are an incredibly rewarding opportunity to share their research and stories of studying marine mammals—and they encourage other students to attend.

Off the Bench

Nattan Telmer shows some of the equipment he used to test the ability of sea lions to generate power from their body heat.

Steller sea lions as power generators

High school student finds heat given off by Steller sea lions can be used to recharge data loggers

Consortium scientists have always believed in the value of outreach. Each year, scientists and staff give lectures to community groups and schools, and accommodate tours of the research areas at the Vancouver Aquarium and the Open Water Research Station. It is all part of the mission to raise awareness of the importance of the marine environment, and the role that science can play in safeguarding its future. Sometimes this outreach pays off in surprisingly direct ways.

Grade 9 student Nattan Telmer contacted Dr. David Rosen for input on a study he wanted to undertake for the 56th Vancouver Island Regional Science Fair. Nattan had an idea that could revolutionize the tracking of marine mammals at sea by extending the battery life of biologging tags.

Nattan Telmer places a base plate on the back of a Steller sea lion at the Vancouver Aquarium while David Rosen pours water over it.

Nattan proposed charging data tags attached to seals and sea lions by incorporating a baseplate that generates electricity from the temperature difference between the warm skin of the animal and the cold ocean water.

While the idea seemed sound from an engineering perspective, Nattan needed to try it on a living sea lion.

Nattan came to the UBC Marine Mammal Energetics and Nutrition Lab at the Vancouver Aquarium to test his tag on one of our trained Steller sea lions.

The test was a complete success, generating even more power than originally predicted. The idea was a success too—for Nattan not only won the Regional Science Fair competition in April, but also took home a Silver Excellence Award in the Canada-Wide Science Fair in May.


Into the Field

Harbour seals prey on salmon smolts

Biologging tags reveal specialist-feeding behaviors by seals that have implications for conservation of salmon
<see full story>


From the Lab

How fat is that sea lion?

Estimating the body condition of Steller sea lions may be as simple as pushing a button
<see full story>


Off the Bench

Steller sea lions as power generators

High school student finds heat given off by Steller sea lions can be used to recharge data loggers
 <see full story>


Science Outreach

21st Annual meeting of the Northwest Student Chapter of Marine Mammalogy

Nearly 60 people from BC, Washington and Oregon came to discuss their marine mammal research and latest findings
<see full story>


This Just In

7 new publications…

Energy expenditure & reproductive success of fur seals, physiological constraints faced by Steller sea lions, reconstructing swimming paths of seals, Dynamic Body Acceleration to estimate cost of swimming, and determining prey encounter rates.
<see full story>


Crunching the Numbers

Stroke Signals

Counting flipper strokes to estimate numbers of calories burned
<see full story>

Steller sea lion research at the Vancouver Aquarium is undergoing a major overhaul!  

The sea lions at the Aquarium moved this past week into “Steller’s Bay”— a stylized west coast fishing village where visitors can come nose to snout with Steller sea lions and marine biologists. The new exhibit is designed to bring the valuable research conducted by Consortium scientists front and center into the public’s eye.
The new exhibit created by the Vancouver Aquarium gives the Stellers a larger pool and haul out space, and allows the public to watch trainers and scientists care for the sea lions and collect valuable information for ongoing studies.
For almost 25 years, researchers with the North Pacific Universities Marine Mammal Research Consortium have been working with the Vancouver Aquarium to determine why Steller sea lions declined throughout most of Alaska. Their research has resulted in over 100 publications that address all the major hypotheses to explain the decline, and validates new technologies developed for use in fieldwork. Current studies are focusing on how sea lions find their food, and what limits their abilities to dive for extended periods. Additional studies are being designed to make the most of their habitat and its huge pool with large underwater viewing areas.

Science is crucial for the conservation of wild animals, and studies with trained sea lions provide critical data that scientists cannot collect in the field. The Steller’s Bay Research Station connects Vancouver Aquarium visitors to ongoing scientific studies, illustrating the research that happens daily and how that information contributes to the overall understanding of Steller sea lions.

A female Antarctic fur seal on the Kergulen Islands, southern Indian Ocean.

Studying flipper strokes in fur seals gives insights into their energetics

Thanks to small sensors in popular new activity tracking devices like the FitBit, people can now answer questions about their daily lives that used to require a great deal of guesswork. How many steps did I walk or run today? How many calories did I burn given my daily activities? It’s handy information if you’re trying to stay healthy.
Consortium scientists are asking similar questions about marine mammals, and are using devices with similar sensors to find the answers. For example, it is now possible to track the detailed movements of fur seals at sea, and calculate how much energy they expend while diving and swimming using tri-dimensional accelerometers. This information helps to understand how much energy they spend during their daily lives and consequently how much food they need to meet their energetic needs.
Without such devices, it would be impossible to obtain important biometric information about these marine mammals, who range freely over hundreds of kilometers in some of the most remote parts of the oceans. Some of these populations have declined suddenly, and  research on energetics helps to understand why.
In a new Consortium study, researchers tracked the movements at sea of two species of fur seals: northern fur seals living in the northern hemisphere, and Antarctic fur seals living in the southern hemisphere. They analyzed flipper strokes to estimate the amount of energy expended during various activities. The study, led by Dr Tiphaine Jeanniard-du-Dot, was published in Nature Scientific Reports.
Different Strokes
“We set out to answer two questions,” says Jeanniard-du-Dot, who completed the study as part of her PhD research. “First, can we identify flipper strokes in the acceleration signals recorded by the devices? And second, can we predict energy expenditures by counting the flipper strokes in both species of fur seal, over a wide range of behaviors at sea?”

Northern fur seals returning to shore on the Pribilof Islands, Alaska.


Fur seals at sea spend most of their time diving, swimming slightly below the surface, or resting at the surface, says Jeanniard-du-Dot. Each flipper stroke causes a momentary acceleration that is detected and stored in the tracking device. In their analysis, the researchers worked to isolate the animal’s own movements from the background “noise” generated by waves, currents and wind.
“It was easy to detect flipper strokes when the seals were underwater and diving, because there was less noise from wind or waves,” she says. “The signals were less clear when the animals were swimming at or slightly below the surface, but we could still detect them. When the fur seals were moving slowly at the surface, grooming or resting, it was difficult to detect anything at all.”
The scientists were surprised to find some consistency between flipper strokes among the northern fur seals in the Alaskan Bering Sea, and the Antarctic fur seals in the Southern Ocean and Antarctic peninsula. Each species used a similar number of flipper strokes to travel the same distance, had the same swimming rhythm, and expended the same amount of energy. However, while diving the smaller Antarctic fur seals expended slightly more energy to accelerate, likely due to their smaller flipper size.
Analyzing Amplitude
In addition to counting the number of strokes, the scientists also assessed the relative power of each stroke by measuring its amplitude, or intensity.

Fur seals regularly porpoise as they travel in search of food.


“A big flipper stroke generates more acceleration, and requires more energy, than a small flipper stroke,” says Jeanniard-du-Dot. “We found that measuring amplitude was a better predictor of energy expenditure over the whole range of behaviors during an entire foraging trip. If we want to get a better estimate of what is going on overall, we should take amplitude into account and not simply measure the number of flipper strokes.”
As a field biologist, Jeanniard-du-Dot believes that understanding basic energetics is fundamental to estimating what fur seals need to survive and reproduce successfully.
“Just as a person couldn’t run a marathon on a diet of two salads per day, we can’t expect fur seals to thrive in the wild if they aren’t getting the calories they need,” she says. “By using acceleration data to estimate the energy they expend, we are a step closer to understanding how much food they need, and eventually, how best to manage and share the ocean’s resources.”

PublicationsPUBLICATION

Flipper strokes can predict energy expenditure and locomotion costs in free-ranging northern and Antarctic fur seals.
Jeanniard du Dot, T., A.W. Trites J.P.Y. Arnould, and C. Guinet. 2016.
Scientific Reports. 6:33912
abstract
Flipper strokes have been proposed as proxies to estimate the energy expended by marine vertebrates while foraging at sea, but this has not been validated on free-ranging otariids (fur seals and sea lions). Our goal was to investigate how well flipper strokes correlate with energy expenditure in 33 foraging northern and Antarctic fur seals equipped with accelerometers, GPS, and time-depth recorders. We concomitantly measured field metabolic rates with the doubly-labeled water method and derived activity-specific energy expenditures using fine-scale time-activity budgets for each seal. Flipper strokes were detected while diving or surface transiting using dynamic acceleration. Despite some inter-species differences in flipper stroke dynamics or frequencies, both species of fur seals spent 3.79 ± 0.39 J/kg per stroke and had a cost of transport of ~1.6-1.9 J/kg/m while diving. Also, flipper stroke counts were good predictors of energy spent while diving (R2 = 0.76) and to a lesser extent while transiting (R2 = 0.63). However, flipper stroke count was a poor predictor overall of total energy spent during a full foraging trip (R2 = 0.50). Amplitude of flipper strokes (i.e., acceleration amplitude x number of strokes) predicted total energy expenditure (R2 = 0.63) better than flipper stroke counts, but was not as accurate as other acceleration-based proxies, i.e. Overall Dynamic Body Acceleration.

keywords     accelerometer, energy expenditure, field metabolic rate, doubly-labelled-water, flipper strokes, cost of transport, ODBA, VeDBA, northern fur seal, Antarctic fur seal
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Statistics brings fur seal foraging trips into focus

For northern fur seals, a foraging trip in the Bering Sea can span hundreds of miles and last a week or more. This extraordinary journey offers scientists a unique opportunity to track the seals using high-tech devices that measure their location, position, and speed in the water.

Two feeding trips made in late July by two female northern fur seals tagged on Bogoslof Island. The dots and triangles are GPS observations, and the lines joining them are the reconstructed swimming paths calculated using the Bayesian Melding approach. The trip on the left was 7 days, and the one on the right lasted 7.6 days.


The devices record an enormous amount of data that enables researchers to reconstruct the seals’ routes using a calculation called ‘dead reckoning.’ However, this method does not account for sources of uncertainty in the data, and it can yield inaccurate results.
New Consortium research led by Yang (Seagle) Liu (University of British Columbia) and his supervisor Prof. James V. Zidek has produced a new statistical method that provides a more accurate picture of the actual routes taken. The study was published in the journal Animal Biotelemetry.

After a week-long feeding trip, a female fur seal that has just returned to the rookery verifies by smell whether the hungry pup that called out to her is hers.

Understanding Uncertainty

“We were presented with a huge data set from two northern fur seals who each undertook a very long foraging trip,” explains Liu. “Generally, statisticians like to work with as much data as possible—but the seals collected more data than what our computers could process all at once.”
“The data was also ‘biased’, or heavily influenced, by environmental variables like ocean currents and gravity, and by the limitations of the devices themselves,” Liu advises. When reconstructing the path, he needed to consider these factors and make the appropriate course corrections.

Females often ‘porpoise’ when traveling, and sleep very little during their long foraging trips.


“Fur seals nursing pups always return to the same place they began their foraging trip to reunite with their pups,” says Liu. “From a statistical perspective, this inspired me to use a Brownian Bridge model, in which two ends are fixed and the middle part is random.”
Liu’s statistical method attacked two inherent problems in reconstructing the foraging path: the unknown biases (i.e., from ocean currents, gravity, or equipment) and the accumulation of that bias over time, which produces ever-larger errors in distance.

Correcting Convention

“Our next problem was how to make an inference to predict where the animal would go next,” Liu says. “The huge amount of data required more computing power than most scientists have available, so we found a way to chop the whole trip into small sequences and try to control the chopping points”
When Liu’s results were cross-validated, he discovered his method was able to reconstruct the animals’ movements more accurately than the conventional dead-reckoning calculation, correcting the overall distance traveled by more than 100 kilometers (62 miles).

Daily-Diary biologging tag manufactured by Wildlife Computers. The tag recorded depth, light levels, motion (3 dimensional acceleration), attitude (3 dimensional magnetometry), and water temperature.  Data downloaded from the tag were used to reconstruct the swimming paths and locations of northern fur seals feeding in the Bering Sea.


“This study presented a unique opportunity to make accurate predictions of an animal’s location based on the combination of large, high-resolution data sets and good statistical methods,” Liu says. “Our model corrected the uncertainty in conventional methods, and demonstrated that the animal’s path is lengthier using conventional analysis than it actually is.”
The new statistical technique developed by Lui and colleagues is a significant advancement in animal tracking. Their method calculates confidence limits for animal tracks, and provides a means to assess the accuracy of satellite-reported locations of animals at sea.
 

PublicationsPUBLICATIONS

Bayesian data fusion approaches to predicting spatial tracks: application to marine mammals.
Liu, Y., J. V. Zidek, A. W. Trites and B. C. Battaile. 2016.
Annals of Applied Statistics 10:1517-1546.
abstract
Bayesian Melding (BM) and downscaling are two Bayesian approaches commonly used to combine data from different sources for statistical inference. We extend these two approaches to combine accurate but sparse direct observations with another set of high-resolution but biased calculated observations. We use our methods to estimate the path of a moving or evolving object and apply them in a case study of tracking northern fur seals. To make the BM approach computationally feasible for high dimensional (big) data, we exploit the properties of the processes along with approximations to the likelihood to break the high dimensional problem into a series of lower dimensional problems. To implement the alternative, downscaling approach, we use R-INLA to connect the two sources of observations via a linear mixed effect model. We compare the predictions of the two approaches by cross-validation as well as simulations. Our results show that both approaches yield similar results— both provide accurate, high resolution estimates of the atea locations of the northern fur seals, as well as Bayesian credible intervals to characterize the uncertainty about the estimated movement paths.

keywords     Bayesian Melding, Downscaling, Bio-logging, Conditional independence, INLA, Dead-Reckoning, Tracking, Marine mammals
show/hide abstract View Reference Learn more about what was found

Bias correction and uncertainty characterization of dead-reckoned paths of marine mammals.
Liu, Y., B.C. Battaile, A.W. Trites and J.V. Zidek. 2015.
Animal Biotelemetry 3(51):1-11.
abstract
Biologgers incorporating triaxial magnetometers and accelerometers can record animal movements at infra-second frequencies. Such data allow the Dead-Reckoned (DR) path of an animal to be reconstructed at high-resolution. However, poor measures of speed,undocumented movements caused by ocean currents, confounding between movement and gravitational acceleration and measurement error in the sensors, limits the accuracy and precision of DR paths. The conventional method for calculating DR paths attempts to reduce random errors and systematic biases using GPS observations without rigorous statistical justification or quantification of uncertainty in the derived swimming paths. Methods: We developed a Bayesian Melding (BM) approach to characterize uncertainty and correct for bias of DR paths. Our method used a Brownian Bridge process to combine the fine-resolution (but seriously biased) DR path and the sparse (but precise and accurate) GPS measurements in a statistically rigorous way. We also exploited the properties of underlying processes and some approximations to the likelihood to dramatically reduce the computational burden of handling large, high-resolution data sets. We implemented this approach in an R package "BayesianAnimalTracker", and applied it to biologging data obtained from northern fur seals (Callorhinus ursinus) foraging in the Bering Sea. We also tested the accuracy of our method using cross-validation analysis and compared it to the conventional bias correction of DR and linear interpolation between GPS observations (connecting two consecutive GPS observations by a straight line). Results: Our BM approach yielded accurate, high-resolution estimated paths with uncertainty quantified as credible intervals. Cross-validation analysis demonstrated the greater prediction accuracy of the BM method to reconstruct movements versus the conventional and linear interpolation methods. Moreover, the credible intervals covered the true path points albeit with probabilities somewhat higher than 95%. The GPS corrected high-resolution path also revealed that the total distance traveled by the northern fur seals we tracked was 40% - 50% further than that calculated by linear interpolation of the GPS observations.

keywords     Biologging; Dead-Reckoning; High-resolution animal tracking; Bayesian melding; energy expenditure; Global Positioning System; uncertainty statement; Brownian Bridge
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Open Water Research Station Contributes a Decade of Discoveries

This year marks the ten-year anniversary of the Open Water Research Station, a floating laboratory at the center of a ground-breaking scientific collaboration that has significantly advanced understanding of how nutritionally stressed Steller sea lions forage in the wild.

The harness worn by Sitka carries scientific instruments, a GoPro camera, and satellite tracking tag.


To mark this anniversary, Consortium researchers have published a comprehensive review of their key discoveries and insights on marine mammal diving physiology, contributed through dozens of studies and publications. The review was recently published in the Journal of Comparative Physiology B.
“Our success as a community of researchers is very reflective of the way good science works,” says David Rosen, lead author of the review article. “Ten years ago, we asked some very basic questions about the diving abilities of Steller sea lions. This led us down different scientific pathways and allowed us to uncover some surprising insights that have only been achieved for a very few species.”

Immense Gamble

The Open Water Research Station launched without fanfare in 2006, in a quiet harbor near Vancouver. A small cohort of Steller sea lions, once considered untrainable, had been taught to take part in research at the Vancouver Aquarium. But they were now faced with the daunting task of performing in the open ocean, without any physical restraints or barriers.
“This program was an immense gamble because nobody had tried working with Steller sea lions in the open water before,” says Rosen. “A lot of people said we were crazy. Just getting it going was a huge milestone.”
The research program led by Rosen and Andrew Trites seeks to understand how wild Steller sea lions survive in a dramatically changing ocean.

The Steller Shuttle is used to transport sea lions up the fjord, as well to conduct swimming studies testing biologging tags and the effects of ocean currents and tide changes on swimming performance.  The Steller Shuttle uses a jet propulsion engine (that has no propeller) when the sea lions are swimming near the boat.


“When we change a variable in our experiments, like the amount of fish available at a certain depth, we’re ultimately trying to find out what would happen if something similar occurred in the wild,” says Rosen. “For example, what if their prey has moved or become less concentrated, or changed in composition? What if the animals are nutritionally stressed before they try to forage? How do these factors affect behavior in the wild?”
Because Steller sea lions are divers, the unique setting at the Open Water Research Station allowed Rosen and his colleagues to observe behaviors they would not have seen in an aquarium.
“There’s simply no other way of getting this information,” he says. “Monitoring wild animals doesn’t tell us why they’re making these choices at depth, and an aquarium has too many physical restrictions. No other research facility in the world has the capacity for doing this type of research with these animals.”

Unique Collaboration

Through a long-term partnership with the Vancouver Aquarium, the Open Water Research Station is staffed with full-time animal care professionals who are primarily concerned with the health and welfare of the animals. This allows the scientific teams to stay focused on experimental design and analysis, and to make the best use of their time with the animals.
“We work together as a team, understanding that none of us could succeed alone,” says Rosen. “The staff we’ve had over the decade — including researchers, postdoctoral fellows, graduate students, trainers and veterinarians — have been tremendously dedicated to the program.”
Collectively, this group has published 25 scientific papers and trained 5 graduate students from the University of British Columbia and other institutions.

Carling Gerlinsky is one of the graduate students who made new discoveries at the Open Water Research Station about the foraging abilities of Steller sea lions.


One of the graduate students, Carling Gerlinsky, studied how nutritional stress affects the ability of Steller sea lions to dive. She predicted that a sea lion that looses body mass due to eating less would store less oxygen in its tissue and blood when diving, and would ultimately have more difficulty foraging. Surprisingly, her measurements showed an increase in blood volume and red blood cells when nutritionally stressed, which allowed the sea lions to work harder to get the fish they needed. Her discovery has generated considerable interest in the research community. Another surprising finding was the realization that Steller sea lions are poor divers — their aerobic dive limit is only 3 minutes!
Another graduate student, Liz Goundie, studied diving behavior, and how the sea lions responded to changes in fish density at different depths. She found that when the sea lions were fed more fish at depth, they stayed underwater for longer. Although this meant they had to recover longer at the surface after a dive, Goundie concluded that the strategy of making one long, deep dive was much more energetically efficient than making several short dives to the same depth. “This type of knowledge about the foraging ecology of Steller sea lions cannot be obtained in the wild, but can only be found by running carefully controlled experiments”, says Rosen.

 Critical Research

“We began this research program with a single question: What is the energetic cost of diving?” says Rosen. “We quickly realized that there is no single cost of diving—rather, there are a whole bunch of inter-related questions about what things affect the various costs of diving.”

Although our sea lions are free to leave at any time, none has ever chosen this option over staying with the trainers and research scientists.  However, there have been occasions when the sea lions opted to swim back to the lab from the remote dive site rather than accept a free lift aboard their Steller Shuttle.


Rosen says one of his team’s big insights is that the sea lions employ different diving tactics in different situations. For example, they may choose to make one long dive or a series of short dives depending on the circumstances. Each choice produces a vastly different physiological response and prompts different behaviors at depth, which in turn influences foraging success.
The ten-year research program led by Rosen and Trites has provided an unprecedented window into Steller sea lion physiology and behavior. As wild populations decline sharply in Western Alaska, there has never been a more critical time for this research.
Rosen admits that the funding for the Open Water Research Station is uncertain beyond next year. He hopes that the scientific milestones summarized in the recent review will underscore the importance of renewed funding and action on behalf of dwindling Steller sea lion populations in the North Pacific.
“It would be a huge shame to stop now, given the incredible progress we’ve made,” he says.

PublicationsPUBLICATION

Physiological constraints and energetic costs of diving behaviour in marine mammals: a review of studies using trained Steller sea lions diving in the open ocean.
Rosen, D.A.S., A.G. Hindle, C. Gerlinsky, E. Goundie, G.D. Hastie and A.W. Trites. 2017.
Journal of Comparative Physiology B 187:29-50.
abstract
Marine mammals are characterized as having physiological specializations that maximize the use of oxygen stores to prolong time spent under water. However, it has been difficult to undertake the requisite controlled studies to determine the physiological limitations and trade-offs that marine mammals face while diving in the wild under varying environmental and nutritional conditions. For the past decade, Steller sea lions (Eumetopias jubatus) trained to swim and dive in the open ocean away from the physical confines of pools participated in studies that investigated the interactions between diving behaviour, energetic costs, physiological constraints, and prey availability. Many of these studies measured the cost of diving to understand how it varies with behaviour and environmental and physiological conditions. Collectively, these studies show that the type of diving (dive bouts or single dives), the level of underwater activity, the depth and duration of dives, and the n utritional status and physical condition of the animal affect the cost of diving and foraging. They show that dive depth, dive and surface duration, and the type of dive result in physiological adjustments (heart rate, gas exchange) that may be independent of energy expenditure. They also demonstrate that changes in prey abundance and nutritional status cause sea lions to alter the balance between time spent at the surface acquiring oxygen (and offloading CO2 and other metabolic by-products) and time spent at depth acquiring prey. These new insights into the physiological basis of diving behaviour further our understanding of the potential scope for behavioural responses of marine mammals to environmental changes, the energetic significance of these adjustments, and the consequences of approaching physiological limits.
show/hide abstract View Reference Learn more about what was found

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The 24th Annual BC Marine Mammal Symposium was streamed on YouTube Live, Saturday, November 26 2016.

About 230 people attended in person, and over, 2,100 people from 26 countries participated on line to hear and discuss short presentations on issues pertaining to killer whales, porpoise, sea lions and other marine mammals. This all-day event was open to students, researchers, educators, businesses and others involved with marine mammals.

The Symposium was recorded and is archived below for those that missed it, or would like to see it again.

We hope you will join us on line!

UBC Marine Mammal Research Unit
The Pacific Wildlife Foundation
Pacific Whale Watching Association

Diving Hard at It

Sitka the Steller sea lion

Sitka, one of four Steller sea lions, has participated in many research studies over the past 12 years.

As with all animals, Steller sea lions must eat enough food to meet their basic needs to ensure survival. When prey is scarce or of low quality, an animal must work harder to find prey or capture enough prey to meet their daily energy requirements. This can be particularly troublesome for breath-holding divers whose foraging time is limited by how long they can dive.

For sea lions and other air-breathing animals, swimming harder while diving usually means using up oxygen faster, which means having to wait longer on the surface to recover and catch their breath before diving again. So what does it cost a Steller sea lion to dive harder, and how does sea lion behavior change when they exert more effort to dive and find food?

These are the questions Aaron Purdy aims to answer with his MSc research. Aaron has been working at the Open Water Research Station to determine the costs and benefits of increased foraging effort.

student Aaron Purdy

Graduate student Aaron Purdy has spent alot of time on the ocean with Sitka and 3 other sea lions.

The four adult female Steller sea lions housed at this facility are trained to dive in the open ocean. Using respirometry equipment, Aaron can use measurements of oxygen and carbon dioxide to determine the energetic cost of different dives they make. He can also determine how long it takes them to recover.

To challenge the diving ability of the sea lions and give them a harder workout, Aaron has been attaching strips of artificial grass (like AstroTurf) to the sea lions’ harnesses. This light fluffy material has no effect on the sea lions when out of water, but causes significant drag in the water and makes it more difficult for the sea lions to swim without using more energy.

Aaron plans to use the data he has collected to determine what happens when sea lions in the wild exceed their physiological comfort zone. One such physiological limit is the “aerobic dive limit,” the amount of time an animal can remain submerged using only the oxygen stored in their lungs and blood. Diving past this point forces the animal to use anaerobic metabolism, a much less efficient process that results in lactate accumulating in the body that must eventually be cleared. Sea lions that use more anaerobic metabolism will produce more lactate acid and will have to spend more time recovering at the surface instead of feeding.

Steller sea lion at the open water research station getting ready to dive

Diving platform and scientific instruments used to study the sea lions in the open ocean.

To determine the aerobic dive limit in sea lions, Aaron took voluntary blood samples from the animals after varying dive lengths to measure lactic acid in their blood. He then compared lactic acid levels to post-dive recovery times, to assess the costs of increased foraging effort.

Aaron’s study is providing valuable insights into the diving abilities of Steller sea lions and the extent to which sea lions can push their limited diving abilities to contend with ecosystem changes and reductions in prey abundance. Aaron’s diving studies are also providing data needed to interpret the diving behaviors of sea lions in Alaska and assess whether they are consistent with changes in the quantity and quality of available prey. Understanding how sea lions are affected by such changes can help to better manage and protect them and their ecosystem.

Aaron Purdy is a MSc Student at UBC’s Marine Mammal Research Unit.


Saturday, November 26, 2016 – 9:30am – 5:00pm

UNIVERSITY OF BRITISH COLUMBIA
AQUATIC ECOSYSTEM RESEARCH LABORATORY
GROUND FLOOR, AERL, 2202 MAIN MALL
VANCOUVER, B.C. V6T 1Z4

Copyright © 2016 Andrew Trites

Registration Fee:

  • Advanced: $0 (pre-register by Friday November 21)
  • Late: $5 (cash only at the door)

Join us for presentations as well as discussion on issues that concern us all. This meeting is open to students, researchers, educators, businesses and others involved with marine mammals. Anyone in one or more of these categories is welcome to attend.

Please register on Eventbrite or email bc.symposium@oceans.ubc.ca before November 21, 2016, to indicate that you plan to attend. Lunch and refreshments will be provided, but we need to know how many people to plan for. There will also be a social evening (6:00-9:00 pm) where beer and pizza can be purchased.

The Agenda will be distributed at the meeting. Please email bc.symposium@oceans.ubc.ca before November 21, 2016 if you would like to make a five minute presentation about your research. Longer presentations on topics of general interest are welcomed. We would also like to know if there are any issues that should be discussed by the group at large.

This year we are planning to stream live to the general public via YouTube. All presentations will be recorded for posting on the internet. Presenters can decline to have their talks posted after previewing them.

We look forward to hearing from you and seeing you at:

9:30 am on Saturday, November 26, 2016

 

Registration: Eventbrite

Email: bc.symposium@oceans.ubc.ca

 

SPONSORED BY:

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New Behaviors Observed in Northern Fur Seals

Thanks to the emergence of new technologies in tagging, scientists are able to gain an unprecedented level of insight into the movements of marine mammals in the wild. These data offer an important window into the daily habits of northern fur seals, and provide possible explanations for the population decline occurring in the central Bering Sea.

Northern fur seals

A pup suckles while others frolic around exhausted adult northern fur seals. The pups shown here on St. Paul Island fasted for an average of 7 days while their mothers foraged far from the rookery.


A new Consortium study led by Brian Battaile (University of British Columbia) used data loggers to identify several previously undocumented behaviors amongst northern fur seals, and to gain new insights into their activity at sea.
Using data loggers that were temporarily affixed to 82 female northern fur seals, the researchers gathered valuable data about how each animal behaved at sea, including its orientation in the water, the depth of its dives, and its rate of movement through the water. By analyzing the combined data, the researchers were able to describe how the animals moved through the water.

Shaking & Rolling

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Brian Bataille observing northern fur seals on Bogoslof Island.


“We were interested in recording fur seal behaviors, and discovering how much time fur seals from a declining and an increasing population in Alaska spent grooming, travelling, sleeping and diving,” says Battaile. “Some of the shaking and grooming behaviors we saw had been described before, but the things that were really new, were two types of rolling behaviors and a prone position.”
The researchers identified the new rolling behaviors as a revolving 300-degree ‘w-spin’ and a 360-degree ‘sine spin’. To confirm these behaviors, the scientists observed tagged northern fur seals they are studying at the Vancouver Aquarium, and matched those same behaviors to the recorded wild data.
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Swimming behaviors of female northern fur seals observed at the Vancouver Aquarium.


The data from the wild fur seals enabled the researchers to construct an at-sea activity budget, which describes how the seals typically spend their time at sea.
“The at-sea activity budget tells what percentage of the time they spent travelling, diving, shaking, or grooming,” says Battaile. “We were surprised to see that they spent as much as 30 percent of their time doing the two new rolling behaviors, primarily at the surface. We are not sure what the point of it is, but suspect it may allow the seals to search and scan an area while swimming at high speeds.”

Island Insights

The mystery deepened when the researchers compared data from animals in two distinct but nearby populations—St. Paul Island and Bogoslof Island. From an earlier study, the researchers knew that animals from the increasing Bogoslof population were travelling shorter distances to their feeding grounds than the animals from the declining St. Paul population. They wondered whether this may translate into different behaviors at sea—but this was not the case when they looked at the data.

Study sites in the eastern Bering Sea. Northern fur seals were tagged for this study on St. Paul Island and Bogoslof Island. Also shown are the 50, 100 and 200m depth contours.

Study sites in the eastern Bering Sea. Northern fur seals were tagged for this study on St. Paul Island and Bogoslof Island. Also shown are the 50, 100 and 200m depth contours.


“We were surprised to find that there weren’t any differences in the proportion of behaviors between the two populations,” says Battaile. “We expected to see more travelling-type behaviors in the St. Paul animals because they travel so much further. Similarly, we expected to see more resting-type behaviors and less diving time in the Bogoslof animals because we assumed they were getting into denser foraging areas and wouldn’t need to dive as much.”
Battaile says that their behaviors might be “hardwired” by other factors, such as the time of day. “An animal could be travelling around at the surface during daytime trying to find suitable foraging habitat,” he says, “but may be more likely to just dive at night when their prey are closer to the surface.”
Having a ‘daily diary’ for northern fur seals at sea will help energetics researchers construct an energy budget, which estimates how much energy the animals need to perform these basic activities. From this, researchers can calculate the amount of food needed to produce this energy, which could ultimately help determine why the St. Paul population is declining, as well as help make management decisions on fisheries quotas in the Bering Sea.
 
 

PublicationsPUBLICATION

Accelerometers identify new behaviors and show little difference in the activity budgets of lactating northern fur seals (Callorhinus ursinus) between breeding islands and foraging habitats in the eastern Bering Sea.
Battaile, B.C., K.Q. Sakamoto, C.A. Nordstrom, D.A.S. Rosen and A.W. Trites. 2015.
PLoS ONE Vol 10(3):e0118761
abstract
We tagged 82 lactating northern fur seals (Callorhinus ursinus) with tri-axial accelerometers and magnetometers on two eastern Bering Sea islands (Bogoslof and St. Paul) with contrasting population trajectories. Using depth data, accelerometer data and spectral analysis we classified time spent diving (30%), resting (~7%), shaking and grooming their pelage (9%), swimming in the prone position (~10%) and two types of previously undocumented rolling behavior (29%), with the remaining time (~15%) unspecified. The reason for the extensive rolling behavior is not known. We ground-truthed the accelerometry signals for shaking and grooming and rolling behaviors—and identified the acceleration signal for porpoising—by filming tagged northern fur seals in captivity. Speeds from GPS interpolated data indicated that animals traveled fastest while in the prone position, suggesting that this behavior is indicative of destination-based swimming. Very little difference was found in the percentages of time spent in the categorical behaviors with respect to breeding islands (Bogoslof or St. Paul Island), forager type (cathemeral or nocturnal), and the region where the animals foraged (primarily on-shelf <200m, or off-shelf > 200m). The lack of significant differences between islands, regions and forager type may indicate that behaviors summarized over a trip are somewhat hardwired even though foraging trip length and when and where animals dive are known to vary with island, forager type and region.

keywords     seals, accelerometers, animal behavior, foraging, biological locomotion, sine wave, fur seal
show/hide abstract View Reference

New DNA technique offers dietary insights

Of all the species that share the North Pacific Ocean with humans, among the most visible are harbor seals. Some 40,000 harbor seals make their home in the Strait of Georgia, near Vancouver, and they prey on the same types of fish we do.

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One of 40,000 harbor seals living in the Strait of Georgia.


Fisheries managers need to balance the dietary needs of these important predators with the needs of human fisheries. But how much fish do harbor seals need to consume in order to survive?
The precise answer to this question is notoriously elusive, but a new study led by Austen Thomas (The University of British Columbia) has provided scientists with a promising new technique to analyze both the composition and quantity of prey in a harbor seal’s diet.
“Up until now, the tools we have used to quantify the diets of seals have been inadequate for certain types of questions,” says Thomas. “They rely primarily on identifying the bones in the droppings of seals, and the resulting calculations produce only a rough estimate of what they’ve eaten. We’re using a tool that does a much better job of characterizing the prey species in a seal’s diet and—for the first time—gives us an idea of the quantity of each prey species present.”
Fig. 2. Austen Thomas collecting harbor seal scats.

Austen Thomas collecting harbor seal scats in the Fraser River estuary.

Sophisticated Technique

Thomas and colleagues have refined a promising new technique called DNA metabarcoding, which is used to identify specific marker genes in a sample of soil or water—or seal droppings. This sophisticated technique indicates whether the gene for a certain fish species is present or absent in a given sample, and its quantity relative to other species.
“We wanted to go further—to establish a link between the amount of prey DNA in a predator diet sample and the biomass of what they consumed,” Thomas says. “To do this, we prepared and analyzed fish samples of known biomass composition. This gave us a series of controls, which we compared against samples of seal droppings that contained an unknown prey composition.”

Fig. 3. Vials of harbour seal scats soaking in ethanol to obtain prey DNA.

Vials of harbor seal scats soaking in ethanol to obtain prey DNA.


Thomas and colleagues developed a series of correction factors—a number unique to each fish species that helped to determine how much of each species-specific DNA marker occurred in the unknown samples.

Micro to Macro

After proving and replicating their technique, the researchers were able to establish an entire library of correction factors for different fish species. They then applied the correction factors to identify any interactions between species—for example, whether herring produced the same correction factor when mixed with pollock as it did when mixed with salmon. “The consistency of the individual correction factors across mixed samples was encouraging,” Thomas says.
“Our study aims to improve the overall accuracy of seal diet data,” says Thomas. “Small changes in how we measure an individual seal’s diet at the DNA level can lead to profoundly different estimates of fish consumed by the population. From a fisheries management perspective, it’s important to know what the 40,000 seals in the Straight of Georgia are eating because it has a potential impact on the things people like to consume. They’re an important predator.”
 

PublicationsPUBLICATION

Quantitative DNA metabarcoding: improved estimates of species proportional biomass using correction factors derived from control material.
Thomas, A. C., B. E. Deagle, P. J. Eveson, C. H. Harsch and A. W. Trites. 2016.
Molecular Ecology Resources 16:714-726.
abstract
DNA metabarcoding is a powerful new tool allowing characterization of species assemblages using high-throughput amplicon sequencing. The utility of DNA metabarcoding for quantifying relative species abundances is currently limited by both biological and technical biases which influence sequence read counts. We tested the idea of sequencing 50/50 mixtures of target species and a control species in order to generate relative correction factors (RCFs) that account for multiple sources of bias and are applicable to field studies. RCFs will be most effective if they are not affected by input mass ratio or co-occurring species. In a model experiment involving three target fish species and a fixed control, we found RCFs did vary with input ratio but in a consistent fashion, and that 50/50 RCFs applied to DNA sequence counts from various mixtures of the target species still greatly improved relative abundance estimates (e.g., average per species error of 19 ± 8% for uncorrected versu s 3 ± 1% for corrected estimates). To demonstrate the use of correction factors in a field setting, we calculated 50/50 RCFs for 18 harbour seal (Phoca vitulina) prey species (RCFs ranging from 0.68 to 3.68). Applying these corrections to field-collected seal scats affected species percentages from individual samples (Δ 6.7 ± 6.6%) more than population level species estimates (Δ 1.7 ± 1.2%). Our results indicate that the 50/50 RCF approach is an effective tool for evaluating and correcting biases in DNA metabarcoding studies. The decision to apply correction factors will be influenced by the feasibility of creating tissue mixtures for the target species, and the level of accuracy needed to meet research objectives.

keywords     DNA metabarcoding, high-throughput amplicon sequencing, harbor seal, Phoca vitulina, diets, prey consumption, diet reconstruction, scats, fecal samples
show/hide abstract View Reference Learn more about what was found

Which prey offer the greatest energetic return?

In the remote reaches of the Bering Sea, the Pribilof Islands were once home to the world’s largest population of northern fur seals. However, the population has been declining for over 4 decades and scientists do not know why.

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Northern fur seals have declined on the Pribilof Islands by over 80%.


One theory suggests that the types of prey available to northern fur seals have shifted, from an abundance of fatty fish to more protein-rich fish. Could this change in diet make it more difficult for fur seals to obtain the energy they need?

Mariana Diaz Gomez with Tikva.


In a new Consortium study led by Mariana Diaz Gomez (The University of British Columbia), scientists measured the effects of different diets in six female northern fur seals housed at the Vancouver Aquarium. The results showed that some types of prey were significantly easier to digest and offered far greater energetic returns.
“We were able to quantify and test something that has only been hypothesized, but not measured, for over two decades,” says Diaz Gomez. “We measured what went in, measured what it cost to digest, and then measured what came out. This allowed us to calculate how much energy the fur seals gained from eating different diets.”

Crash diet

“Imagine you are at a party that offers only celery sticks, candy and popcorn,” explains Diaz Gomez. “That low-quality food won’t sustain you, even if there’s plenty of it. You’ll be hungry by the time you get home.”
Similarly, northern fur seals in the Bering Sea—who have relatively little control over their diet—may be forced to rely on their own junk food: young pollock. Diaz Gomez found that although these high-protein fishes are abundant, they offer little energetic return when eaten because of digestive costs.
“Prey with a lot of protein and little fat require a huge amount of energy to break down and absorb,” she says. “When our fur seals ate a lot of these types of fish, they absorbed as much of it as possible and didn’t produce much feces. There was almost nothing left over.”

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The energetic cost of digesting different types of fish was determined inside this metabolic chamber by measuring the amount of oxygen the fur seal consumed, and the amount of carbon dioxide produced during digestion.


Conversely, fish that were high in fat, such as herring, required the least energy to digest and resulted in the highest energetic gain.

Quality vs. quantity

“Our take-home message is that when it comes to diet, quality is more important than quantity and even diversity,” says Diaz Gomez. “If northern fur seals can sustain a high-quality diet of fatty fish and squid, they don’t need a lot of it. But if they rely on low-quality pollock, they must eat much more to realize the same energetic gains.”
The results provide further support to the nutritional stress hypothesis, and provide a good foundation for future discussions on how humans and marine mammals can share resources in a fragile and dynamic ocean ecosystem.
 

PublicationsPUBLICATION

Net energy gained by northern fur seals (Callorhinus ursinus) is impacted more by diet quality than by diet diversity.
Diaz Gomez, M, D.A.S. Rosen and A.W. Trites. 2016.
Canadian Journal of Zoology 94:123-135.
abstract
Understanding whether northern fur seals (Callorhinus ursinus (L., 1758)) are negatively affected by changes in prey quality or diversity could provide insights into their on-going population decline in the central Bering Sea. We investigated how six captive female fur seals assimilated energy from eight different diets consisting of four prey species (walleye pollock (Gadus chalcogrammus Pallas, 1814, formerly Theragra chalcogrammus (Pallas, 1814)), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847), capelin (Mallotus villosus (Muller, 1776)), and magister armhook squid (Berryteuthis magister (Berry, 1913))) fed alone or in combination. Net energy was quantified by measuring fecal energy loss, urinary energy loss, and heat increment of feeding. Digestible energy (95.9%-96.7%) was high (reflecting low fecal energy loss) and was negatively affected by ingested mass and dietary protein content. Urinary energy loss (9.3%-26.7%) increased significantly for high-protein diets. Heat increment of feeding (4.3%-12.4%) was significantly lower for high-lipid diets. Overall, net energy gain (57.9%-83.0%) was affected by lipid content and varied significantly across diets. Mixed-species diets did not provide any energetic benefit over single-species diets. Our study demonstrates that diet quality was more important in terms of energy gain than diet diversity. These findings suggest that fur seals consuming low-quality prey in the Bering Sea would be more challenged to obtain sufficient energy to satisfy energetic and metabolic demands, independent of high prey abundance.

keywords     northern fur seal, Callorhinus ursinus, net energy, mixed-species diets, diet quality
show/hide abstract View Reference Learn more about what was found

 
 

Electronic tags reveal secrets of  foraging fur seals

Northern fur seals in the eastern Bering Sea spend most of their lives foraging underwater and breeding on remote islands. To study their behavior, scientists depend on electronic tags to track an individual animal’s movements as it searches for food.

Modern technology now allows researchers to follow the second-by-second movements of seals at sea to determine where they go and what they are doing.

Modern technology now allows researchers to follow the second-by-second movements of seals at sea to determine where they go and what they are doing.


In a recent Consortium study,
Brian Battaile (University of British Columbia) and colleagues analyzed the data recorded by electronic tags that were temporarily attached to 83 northern fur seals in the eastern Bering Sea. The study was published in the scientific journal Marine Mammal Science.
Chad Nordstrom, Brian Battaile and Andrew Trites ― part of the field team on St. Paul Island.

Chad Nordstrom, Brian Battaile and Andrew Trites ― part of the field team on St. Paul Island.


By combining the data from different types of tags, the researchers were able to retrace the animals’ movements at an extremely high resolution, revealing an unprecedented glimpse of northern fur seals in the wild.

Fine-Scale Foraging

A female northern fur seal from St. Paul Island, Alaska, carrying biologging tags to collect data on where and how she obtains food in the Bering Sea. The tags are later removed and any residual glue on the fur falls off when the animal molts. Research was conducted under NMSF Permit #14329

A female northern fur seal from St. Paul Island, Alaska, carrying biologging tags to collect data on where and how she obtains food in the Bering Sea. The tags are later removed and any residual glue on the fur falls off when the animal molts.


“Our study was part of a much larger project in the Bering Sea that investigated how walrus, seabirds and northern fur seals find their prey and make a living,” says Battaile. “We used sophisticated tags that collect data 16 times per second, which gave us incredibly detailed information about what the seals were doing.”
Using this data, the scientists reconstructed and compared the foraging tracks of fur seals from two breeding islands in the eastern Bering Sea—St. Paul and Bogoslof Islands. St. Paul Island historically hosted the world’s largest breeding population of northern fur seals, but has been declining at an annual rate of 4.2% since 1998. Just 250 miles south of St. Paul, the small Bogoslof Island population has been increasing at an annual rate of 10.1% since 1997.
“We expected the animals that were going offshore from St. Paul Island to behave similarly to those going offshore from Bogoslof Island,” says Battaile. “We figured they’d be targeting the same types of prey.”
“We found there were two types of fur seals at St. Paul—one that foraged offshore and the other that stayed over the continental shelf. According to our calculations, the behavior of the Bogoslof seals was similar to the on-shelf St. Paul animals, while the offshore St. Paul seals had different foraging behaviors.”

 Data Dilemma

A leading theory suggests that lactating females on St. Paul Island are unable to capture enough calorie-rich food to produce enough lipid-rich milk to support their pups. As a result, the pups cannot store enough fat prior to weaning and have difficulty surviving their first year as they learn to forage. This makes it critically important to better understand the foraging behaviors of lactating females.

A bird’s eye view of where one of the female fur seals traveled. The red stars show the recorded GPS locations of the seal, and the green box highlights a location that the seal crossed 4 times. Until now, biologists have been joining the GPS locations and assuming the seals swim in straight lines between them. However, data from the Daily Diary tag allowed the actual swimming paths to be calculated, and showed how much more swimming the seals do than previously recognized from straight line calculations.

A bird’s eye view of where one of the  tracked female fur seals traveled. The red stars show the recorded GPS locations of the seal, and the green box highlights a location that the seal crossed 4 times. Until now, biologists have been joining the GPS locations and assuming that seals swim in straight lines between them. However, data from the Daily Diary tag allowed the actual swimming paths to be calculated, and showed how much more swimming the seals do than previously recognized from straight line calculations.


“We knew the St. Paul animals traveled further away from land than the Bogoslof animals, but the new tags showed us that the distances swum were much greater than ever reported. This tells us that the animals from St. Paul are working even harder to obtain food than anyone previously thought―and corroborates the nutritional stress theory.”
Each increase in technology brings a better understanding of the lives of marine mammals. New generations of electronic tags and improved statistical techniques have brought new insights into the foraging habits and movement of northern fur seals—but not without challenges.
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A wet northern fur seal (center) that has just arrived on shore at St. Paul Island after about 7 days feeding at sea calls to find her pup.


“Marine mammal research has often been at the forefront of technological developments. In our case, the resolution of the data we collected and our analysis of fur seal foraging behavior was at a finer-scale than anyone has ever been able to do before. Similar technological advances should allow oceanographers to collect finer-spatial scale data on chlorophyll concentrations and sea-surface temperatures to match our fur seal data,” says Battaile. “Then we will be able to put all the puzzle pieces together to get the complete picture of how fur seals are exploiting the Bering Sea and why the feeding conditions are so different between the two fur seal islands.”
 
 

PublicationsPUBLICATION

Foraging a new trail with northern fur seals (Callorhinus ursinus): Lactating seals from islands with contrasting population dynamics have different foraging strategies, and forage at scales previously unrecognized by GPS interpolated dive data.
Battaile, B.C., C.A. Nordstrom, N. Liebsch and A.W. Trites. 2015.
Marine Mammal Science 31:1494-1520.
abstract
We reconstructed the foraging tracks of lactating northern fur seals (Callorhinus ursinus) from two eastern Bering Sea islands (St. Paul Island and Bogoslof Island) using linear interpolation between GPS locations recorded at a maximum of four times per hour and compared it to tri-axial accelerometer and magnetometer data collected at 16 Hz to reconstruct pseudotracks between the GPS fixes. The high-resolution data revealed distances swum per foraging trip were much greater than the distances calculated using linearly interpolated GPS tracks (1.5 times further for St. Paul fur seals and 1.9 times further for Bogoslof fur seals). First passage time metrics calculated from the high resolution data revealed that the optimal scale at which the seals searched for prey was 500 m (radius of circle searched) for fur seals from St. Paul Island that went off-shelf, and 50 m for fur seals from Bogoslof Island and surprisingly, 50 m for fur seals from St. Paul that foraged on-s helf. These area-restricted search scales were significantly smaller than those calculated from GPS data alone (12 km for St. Paul and 6 km for Bogoslof) indicating that higher resolution movement data can reveal novel information about foraging behaviors that have important ecological implications.

keywords     foraging ecology, biologging, northern fur seal, Callorhinus ursinus, marine mammal, Bering Sea, magnetometer, accelerometer, spatial analysis, area restricted search
show/hide abstract View Reference Learn more about what was found

Do feeding strategies drive resilience?

Many thousands of years ago, the ancient ancestors of today’s seals and sea lions moved from their terrestrial homes into the oceans. Over the subsequent epoch, they gradually adapted to their new aquatic environment by altering both their behavior and their physical features. In the process, they developed at least three key strategies to catch fish and other aquatic prey: biting, suction, and jetting water.
These strategies have proven variously effective—some species have survived and thrived to the present day, while others went extinct.
As Consortium scientists uncover the causes of the rapid decline of Steller sea lions and northern fur seals in the North Pacific Ocean over the past 30 years, it is increasingly clear that a root cause is the interactions between these predators and their prey. Could a possible explanation lie in their evolutionary and hunting strategy history?

Steller sea lions with trainers at the Open water research station.

Steller sea lions with Vancouver Aquarium trainers at the Consortium’s Open Water Research Station.


To better understand the evolution of feeding strategies in Steller sea lions and northern fur seals, Prof. Christopher Marshall (Texas A&M University) undertook an innovative foraging study at the Vancouver Aquarium and the Consortium’s Open Water Research Station. The study was recently published with co-authors Drs. David Rosen and Andrew Trites (UBC) in the Journal of Experimental Biology.

Surprising Result

“We were interested in the techniques these animals use to acquire their prey,” Marshall says. “We looked at Steller sea lions and northern fur seals, and were expecting a similar finding to my previous work with harbor seals—that these animals are all generalists and they’ll use biting when they can, and suction when they can, and hydraulic jetting when they can.”
Marshall explains that bearded seals, belugas, walruses, and to a lesser degree Steller sea lions, can shoot powerful jets of water from their mouth to flush out an animal from a crevice, or pry loose an animal attached to a rock. Scientists call this behavior ‘hydraulic jetting.’ He says suction and hydraulic jetting are particularly useful for bottom feeding around rocky areas.
“There’s some data on wild animals that show they actually do this, and our study has been able to measure and quantify that performance,” he says.
Marshall and colleagues prepared an underwater feeding station by drilling a grid of holes into a large sheet of plexiglass. Behind some of those holes, a recessed plexiglass cylinder imitated a crevasse. The scientists placed fish into each hole and each cylinder, offering animals two choices: they could go for either the food sticking out of a hole, or the food lying in a recessed cylinder.

Subjects feeding from the experimental apparatus. (A) Top-down view of a Steller sea lion feeding from the apparatus. (B) A northern fur seal displaying wide gape with no lateral gape occlusion. (C) A Steller sea lion using suction and vibrissae. (D) A northern fur seal using vibrissae while using a biting feeding mode.

Seals and sea lions feeding from the experimental apparatus. (A) Top-down view of a Steller sea lion feeding at depth. (B) A northern fur seal displaying wide gape with no lateral gape occlusion. (C) A Steller sea lion using suction and vibrissae. (D) A northern fur seal using vibrissae while using a biting feeding mode.


“They usually went for the fish sticking out of the hole because it was visible,” says Marshall. “They could either bite it or suction it, and we looked at the frequency of suction versus biting. But to access the fish in the recessed cylinder they had to use suction. To our surprise, the northern fur seals didn’t even try to suction, they just nibbled at the edges of the cylinder. We had never come across a marine animal until now that only uses biting. Almost all aquatic animals use some sort of suction, but northern fur seals don’t.”

A Question of Resilience

On the other hand, Marshall characterizes the Steller sea lions—which effectively used both biting and suction—as the ultimate generalists, from a biomechanical perspective.
“The cool thing about Steller sea lions is that they can feed probably anywhere,” he says. “They showed a preference for suction, which is very good for feeding in shallow areas, and for getting fish out from under rocks so they can chase it down and grab it. If they need to take really big prey, we have a good indication that the biting feeding mode is successful for them.”

Steller sea lion skull on left, northern fur seal on right.

Steller sea lion skull on left, northern fur seal on right showing the relative differences in dentition and body size.


“This broad feeding repertoire likely mean they’re resilient and adaptable to feeding on many different items,” Marshall says, “and they should be able to adapt to a shift in prey resources.” In contrast, he suspects that northern fur seals specialize on small mesopelagic prey, which rise from the deep scattering layer at night, and they may not fare well in a regime shift or in competition with commercial fisheries.
“People have thought that when mammals returned to the sea, biting was probably the first feeding mode, and suction gradually became a cool way to feed for some species,” Marshall says. “Northern fur seals never got there, which suggests that they’re still exhibiting their ancestral feeding mode, but Steller sea lions did. Because Steller sea lions have the broader feeding repertoire, they can feed on a greater variety of prey, in more diverse habitats.” However, there is a limit to this resiliency if prey abundance is reduced in the North Pacific.
 

PublicationsPUBLICATION

Feeding kinematics and performance of basal otariid pinnipeds, Steller sea lions and northern fur seals: implications for the evolution of mammalian feeding.
Marshall, C. D., D. A. S. Rosen and A. W. Trites. 2015.
Journal of Experimental Biology 218:3229-3240.
abstract
Feeding performance studies can address questions relevant to feeding ecology and evolution. Our current understanding of feeding mechanisms for aquatic mammals is poor. Therefore, we characterized the feeding kinematics and performance of five Steller sea lions (Eumetopias jubatus) and six northern fur seals (Callorhinus ursinus). We tested the hypotheses that both species use suction as their primary feeding mode, and that rapid jaw opening was related to suction generation. Steller sea lions used suction as their primary feeding mode, but also used a biting feeding mode. In contrast, northern fur seals only used a biting feeding mode. Kinematic profiles of Steller sea lions were all indicative of suction feeding (i.e. a small gape, small gape angle, large depression of the hyolingual apparatus and lip pursing). However, jaw opening as measured by gape angle opening velocity (GAOV) was relatively slow in Steller sea lions. In contrast to Steller sea lions, the GAOV of northern fur seals was extremely fast, but their kinematic profiles indicated a biting feeding mode (i.e. northern fur seals exhibited a greater gape, a greater gape angle and minimal depression of the hyolingual apparatus compared with Steller sea lions). Steller sea lions produced both subambient and suprambient pressures at 45 kPa. In contrast, northern fur seals produced no detectable pressure measurements. Steller sea lions have a broader feeding repertoire than northern fur seals, which likely enables them to feed on a greater variety of prey, in more diverse habitats. Based on the basal phylogenetic position of northern fur seals, craniodental morphological data of the Callorhinus lineage, and the performance data provided in this study, we suggest that northern fur seals may be exhibiting their ancestral feeding mode.

keywords     Otariidae, Callorhinus ursinus, Eumetopias jubatus,suction, biting, fossil pinnipeds
show/hide abstract View Reference Learn more about what was found

Sitka, one of 4 Steller sea lions trained to wear a harness carrying scientific instruments while swimming and diving in Indian Arm - a steep-sided glacial fjord near the Open Water Research Station.

Sitka, one of 4 Steller sea lions trained to wear a harness carrying scientific instruments while swimming and diving in Indian Arm – a steep-sided glacial fjord near the Open Water Research Station.


In a quiet fjord near the city of Vancouver, a dedicated group of scientists and trainers are making waves in the scientific community. Since 2003, researchers at the Open Water Research Station have studied a small group of trained Steller sea lions in an open ocean environment. It is the first facility in the world to provide scientists with an in-depth understanding of how Steller sea lions behave in the wild by conducting controlled experiments with sea lions under human care.
Elizabeth Goundie (The University of British Columbia) recently conducted research at the Open Water Research Station to study what factors influence the foraging behavior of Steller sea lions for her Master’s thesis. Her study of foraging efficiency across varying levels of prey abundance was published in the Journal of Experimental Marine Biology and Ecology.
“Steller sea lion populations in western Alaska have declined by over 80% since the 1970’s, and we’re not sure why,” Goundie says. “A number of people have speculated that fisheries reduced the biomass of prey available to sea lions, and I wanted to investigate what changes should have been observed in sea lion foraging behavior if sea lions encountered reduced prey abundance.”

Prey Patch

While past studies at the Station have focused on measuring the energy expended during foraging, Goundie measured both the energy expended and the energy gained by sea lions—a cost-benefit analysis, if you like. She also looked at how changes in sea lion behavior due to changes in prey availability affected both sides of the equation (i.e., foraging efficiency). To do this, she created different artificial ‘prey patches’—large clusters of fish that wild sea lions would typically feed in.
The sea lions at the Open Water Research Station are trained to dive to varying depths, where they are rewarded with chunks of herring fed through a long tube that descends 10 or 40 m (33 – 130 ft) from the surface. From the surface, Goundie simulated high- and low-density prey patches by delivering either a generous portion of herring or a conservative serving.
“When the ‘prey’ were less abundant, the sea lions gave up earlier on their dives,” Goundie says, “and that produced a lower foraging efficiency—greater effort for less reward. Because they weren’t foraging for very long, they spent more of the dive doing ‘unprofitable’ things that cost energy, such as transiting to and from the feeding tube, and spending more time at the surface recovering from the dives. All of that spent energy was not replaced because they gave up earlier on the ‘profitable’ part of the dive.”

DCIM100GOPRO

The Steller sea lions dove to the end of PVC pipes 10 or 40 m (33-130 ft) from the surface where they would find either high or low densities of herring to feed upon.

Efficient Fishers

Surprisingly, Goundie found that the relationship between prey availability and foraging efficiency is not constant. Her high-density prey patch, which offered three times more food than the low-density patch, prompted a five-fold increase in foraging efficiency.
Of course, this also means that when the reverse was true—when Goundie simulated prey scarcity—the sea lions foraged five times less efficiently. They effectively experienced double jeopardy by performing proportionally far less effectively in a prey patch that contained less prey to start with. In the wild, she says, this means that sea lions that encounter reduced prey abundance would have difficulty meeting their daily energy requirements, and would show noticeable changes in their body conditions.

Sitka and her star researcher - Elizabeth Goundie.

Sitka and her star researcher – Elizabeth Goundie.


Goundie says her findings may open the door to more behavioral studies with trained Steller sea lions that test basic scientific theories on “optimal” foraging behavior, and aid in understanding what is happening to sea lions in the wild that may be experiencing changes in their prey base.
“The animals at the Open Water Research Station are excellent representatives of their wild counterparts,” she says. “Working with them allowed us to bring to life some of the excellent theoretical models of sea lion populations. It was an incredible experience to work with such talented trainers, technicians and animals. They took my research ideas and made them into reality.”
 

PublicationsPUBLICATION

Low prey abundance leads to less efficient foraging behaviour in Steller sea lions.
Goundie, E.T., D. A. S. Rosen and A.W. Trites. 2015.
Journal of Experimental Marine Biology and Ecology 470:70-77.
abstract
Breath-hold divers should adjust their dive behaviors to maximize the benefits and minimize the costs of foraging on prey patches of different densities at different depths. However, few studies have quantified how animals respond to changes in prey availability (depth and density), and how this affects their foraging efficiency. We tested the effects of changes in prey availability on the foraging behavior and efficiency of Steller sea lions (Eumetopias jubatus) by measuring diving metabolic rate, dive durations, and food intake of 4 trained sea lions diving in the open ocean on controlled prey patches of different densities at different depths. Sea lions completed bouts of 5 consecutive dives on high- or low-density prey patches at two depths (10m and 40m). We found that the rate of energy expenditure did not change under any of the imposed foraging conditions (meanąSD: 0.22ą0.02 kJ min−1 kg−1), but that the proportion of time spent consuming prey increased with prey patch density due to changes in diving patterns. At both depths, sea lions spent a greater proportion of the dive bout foraging on prey patches with high prey density, which led to high rates of energy gain (4.3 ą 0.96 kJ min−1 kg−1) and high foraging efficiency (cost:benefit was 1:20). In contrast, the sea lions spent a smaller proportion of their dive bout actively feeding on prey patches with low prey density, and consequently had a lower energetic gain (0.91 ą 0.29 kJ min−1 kg−1) and foraging efficiency (1:4). The 5-fold differences in foraging efficiency between the two types of prey patches were greater than the 3-fold differences that we expected based on differences in food availability. Our results suggest that sea lions faced with reduced prey availability forage less efficiently and therefore would have greater difficulty obtaining their daily energy requirements.

keywords     Dive behavior, Diving energetics, Foraging efficiency, Optimal foraging, Steller sea lion
show/hide abstract View Reference Learn more about what was found

richard-beamishDr. Richard Beamish

From the Pacific Biological Station, Nanaimo, BC

Thursday, October 29, 2015

2:00 – 4:00 pm Openhouse: Learn about IOF research from students and researchers

5:00 – 7:00 pm Keynote lecture with reception to follow

Ground Floor Theatre, 2202 Main Mall
Aquatic Ecosystem Research Laboratory
Institute for the Oceans and Fisheries


 

To register for the event, visit Eventbrite or email: larkinlecture@oceans.ubc.ca

logos

 

Are Steller sea lion populations affected by commercial fishing?

Scientists have proposed a number of possible explanations behind the mysterious decline of Steller sea lions in Western Alaska since the 1970s. One of the more controversial possibilities is that intense commercial fishing has reduced the amount of fish available to Steller sea lions. In ecological terms, this is called competition. Yet no scientific study has shown that competition with commercial fisheries is responsible for the alarming decline in sea lion populations.

FIGURE 1: Sea lion with fisheries boat looming in the background..................

Do Steller sea lions co-exist or compete with fisheries?  It is a perplexing question that is not easily answered.


In an ambitious new study, Consortium researchers explored the complex relationships between sea lion population trends, fishery catches, and the estimated amount of fish available to sea lions. The researchers compiled and analyzed an astonishing array of data from 2000-2008 that focused on 33 sea lion rookeries in Alaska and three key fish species important to both sea lions and humans. The study was published in the journal PLoS ONE.
Conservation vs. Catch
“This is a topic that people feel very strongly about,” says Tabitha Hui, the lead author of the study, who completed the work as her Master’s thesis at the University of British Columbia. “The three fish species we studied are the three biggest fisheries in Alaska, worth millions of dollars every year, so the stakes were high.”
Hui and her collaborators created a number of very high-resolution ecosystem models to study the interactions between sea lion populations, commercial fisheries and the fish stocks. They identified only three significant relationships in over 300 simulations, and found no evidence that commercial fisheries have had a strong impact on sea lion populations during this time period (2000-2008).
figure

Annual catches in tons per 9×9 km2 of (a) walleye pollock (2003), (b) Pacific cod (2002) and (c) Atka mackerel (2004). Total amounts of fish removed by fisheries within 10, 20, 50 and 100 km of each sea lion rookery (red, cyan, orange and purple rings respectively) were calculated by summing the total biomass of catches within each of the
respective rings. (From Hui et al. 2015)


“The most novel aspect of our study is the accessibility model we built to determine the availability of fish for Steller sea lions,” Hui says. “There have been plenty of studies on Steller sea lion behavior and a lot of detail on dive profiles, but nobody has taken the movement data and linked it to foraging efficiency and the accessibility of fish to sea lions. Up until now, the calculations have been based on an assumption that, ‘this area has this many fish, and one sea lion eats so many fish per day for a year,’ to produce a general estimate of foraging efficiency.”
Despite the study’s innovative and rigorous methods, Hui is cautious about drawing definitive conclusions because of the limitations of her data, which were affected by a significant change in fisheries policy in 2000.
“I only had fish biomass data for alternate years from 2000-2004, which restricted the prey fields I could build,” she notes. “From 2000 onward, commercial fishers were not permitted to fish within 20 nautical miles of any sea lion rookery. Sea lions tend to forage close to home, so this policy change effectively removed the potential for any competition to occur between humans and sea lions for the same fish whether or not it had ever occurred. As a result, our data didn’t show much difference between a fishing scenario and a no-fishing scenario. Prior to 2000, the argument is that there was a lot more commercial fishing, which could have begun the sea lion decline. The decline started in the late 1970s, but we don’t have much data on those two decades.”
Prudent policy
Over the course of her research, Hui has engaged stakeholders in all sides of the debate, from commercial fishers to conservationists to consumers.
“Our results show that the current regulations appear to be working—that fishing beyond 20 nautical miles from a rookery does not seem to be impacting sea lions,” she says.
Hui believes a monitoring program should be an essential part of any effort to change the current fishing regulations. She also believes that if restrictions are reduced, they should be reduced incrementally over several years so that any impacts that might occur can be closely monitored.
“Competition for resources is an important issue,” she says. “We need to find a balance between using and conserving our natural resources, and it’s a very difficult balance to calculate. That’s the attraction for me—the importance and the difficulty of the research.”
 

PublicationsPUBLICATION

Assessment of competition between fisheries and Steller sea lions in Alaska based on estimated prey biomass, fisheries removals and predator foraging behaviour.
Hui, T.C.Y., R. Gryba, E.J. Gregr and A.W. Trites. 2015.
PLoS ONE Vol 10(5): e0123786
abstract
A leading hypothesis to explain the dramatic decline of Steller sea lions (Eumetopias jubatus) in western Alaska during the latter part of the 20th century is a change in prey availability due to commercial fisheries. We tested this hypothesis by exploring the relationships between sea lion population trends, fishery catches, and the prey biomass accessible to sea lions around 33 rookeries between 2000 and 2008. We focused on three commercially important species that have dominated the sea lion diet during the population decline: walleye pollock, Pacific cod and Atka mackerel. We estimated available prey biomass by removing fishery catches from predicted prey biomass distributions in the Aleutian Islands, Bering Sea and Gulf of Alaska; and modelled the likelihood of sea lions foraging at different distances from rookeries (accessibility) using satellite telemetry locations of tracked animals. We combined this accessibility model with the prey distributions to estima te the prey biomass accessible to sea lions by rookery. For each rookery, we compared sea lion population change to accessible prey biomass. Of 304 comparisons, we found 3 statistically significant relationships, all suggesting that sea lion populations increased with increasing prey accessibility. Given that the majority of comparisons showed no significant effect, it seems unlikely that the availability of pollock, cod or Atka mackerel was limiting sea lion populations in the 2000s.

keywords     Eumetopias jubatus, walleye pollock, Pacific cod, Atka mackerel, accessibility, prey distribution, CPUE, linear mixed-effects models
show/hide abstract View Reference Learn more about what was found

 

Trites-1552
Saturday November 28, 2015
9:30am – 17:30pm

Join us for presentations as well as discussion on issues that concern us all. This meeting is open to students, researchers, educators, businesses and others involved with marine mammals. Anyone in one or more of these categories is welcome to attend.

Please register on Eventbrite here or email bc.symposium@oceans.ubc.ca before November 20, 2015, to indicate that you will attend. Lunch and refreshments will be provided, but we need to know how many people to plan for. There will also be a social evening (6:00-9:00 pm) where pizza can be purchased.

The Agenda will be distributed at the meeting. Please email bc.symposium@oceans.ubc.ca before November 20, 2015 if you would like to make a five minute presentation or less about your research, sightings or recent activities. Longer presentations on topics of general interest are welcomed. We would also like to know if there are any issues that should be discussed by the group at large.

We look forward to hearing from you and seeing you at:

9:30 am on Saturday, November 28, 2015 @ 2202 Main Mall, Vancouver, B.C.

Marine Mammal Research Symposium
University of British Columbia
Aquatic Ecosystem Research Laboratory
2202 Main Mall
Vancouver, BC V6T 1Z4
Canada

Feeling stressed? It’s a common complaint, but stress isn’t a uniquely human condition. Marine mammals also experience stress, especially when their environment changes. Changes in the ocean food supply, for example, can cause nutritional stress in Steller sea lions, which can cause a population to decline.

jerome-1
 
While there is currently no easy way to assess the nutritional status of Steller sea lions in the wild, the emerging field of nutrigenomics is promising. In a new Consortium study led by Dr. Jérôme Spitz (University of British Columbia), researchers demonstrated that biomarkers in blood samples can be used to identify nutritional stress in Steller sea lions. The study was published in the Journal of Comparative Biochemistry and Physiology, Part A.
“Nutrigenomics is a branch of genomics that explores the link between gene expression and nutrition,” says Spitz. “Until now, nutrigenomics has focused on identifying disease markers in human health, but we believe it is time to apply this technology to study and protect endangered species, such as Steller sea lions.”
With further development, such a molecular tool can be used to assess the health of wild marine mammals, Spitz says. 

Taking blood samples

Taking blood samples

Blood Biomarkers

Working with four trained, female Steller sea lions housed at the Vancouver Aquarium, the team of scientists studied the effects of controlled feeding regimes that reproduced the acute and chronic nutritional stress thought to occur in wild sea lions. Using blood samples taken at key points in each trial, the scientists extracted the RNA of white blood cells and measured the response of eight genes known to react to diet restriction in terrestrial mammals. They looked for genes that typically control biological processes such as metabolism, immune response and cell growth.
The results of the study showed that marine mammals respond at a molecular level to nutritional stress in much the same way as terrestrial mammals. Under nutritional stress, the sea lions down-regulated the cellular processes involved in immune response and oxidative stress, and they up-regulated those involved in inflammatory responses and metabolic processes.
“It is often the case that environmental or human pressures are identified too late to prevent or contain a population decline,” says Spitz. “This is especially true for species like Steller sea lions that are long-lived, slow to reproduce and occupy a wide range of habitats. Nutrigenomic studies like ours have the potential to determine if nutritional stress is occurring, and provide early-warning indicators of nutritional stress that can prompt measures to mitigate a population decline.”

spitz2

Feeding one of the captive Steller sea lions at the Vancouver Aquarium

Promising Results

Spitz notes that the approach the he and his colleagues tested should be developed further to account for other factors that influence nutritional stress—including age, reproductive status, and infection.
In the meantime, the results of their study are encouraging and suggest that nutrigenomics is a promising tool to assess, mitigate and monitor nutritional stress in Steller sea lions and other marine mammals.
“The impacts of fishing and climate change are transforming our oceans,” says Spitz. “Marine mammals are challenged to adapt to these rapid changes, but there are solutions. It’s up to all of us to protect marine wildlife.”
 

PublicationsPUBLICATION

A nutrigenomic approach to detect nutritional stress from gene expression in blood samples drawn from Steller sea lions.
Spitz, J., V. Becquet, D.A.S. Rosen and A.W. Trites. 2015.
Comparative Biochemistry and Physiology: Part A 187:214-223.
abstract
Gene expression profiles are increasingly being used as biomarkers to detect the physiological responses of a number of species to disease, nutrition, and other stressors. However, little attention has been given to using gene expression to assess the stressors and physiological status of marine mammals. We sought to develop and validate a nutrigenomics approach to quantify nutritional stress in Steller sea lions (Eumetopias jubatus). We subjected 4 female Steller sea lions to 3 feeding regimes over 70-day trials (unrestricted food intake, acute nutritional stress, and chronic nutritional stress), and drew blood samples from each animal at the end of each feeding regime. We then extracted the RNA of white blood cells and measured the response of 8 genes known to react to diet restriction in terrestrial mammals. Overall, we found that the genomic response of Steller sea lions experiencing nutritional stress was consistent with diet restriction regulation in terrestrial mammals. Our nutritionally stressed sea lions down-regulated some cellular processes involved in immune response and oxidative stress, and up-regulated pro-inflammatory responses and metabolic processes. Nutrigenomics appears to be a promising means to monitor nutritional status and contribute to mitigation measures needed to assist in the recovery of Steller sea lions and other at-risk species of marine mammals.

keywords     Genomics, Expression profile, q-PCR, Diet, restriction, Biomarker, Monitoring
show/hide abstract View Reference Learn more about what was found

In 1997, the U.S. National Marine Fisheries Service classified the Western Alaskan population of Steller sea lions as Endangered. Reacting to concerns about a population crash — some 200,000 sea lions had disappeared without a trace since 1977 — and assuming the culprit was overfishing, federal authorities abruptly halted fishing near sea lion habitats in the Gulf of Alaska, Bering Sea and Aleutian Islands.

maschner-2013

An Aleut hunter in the Bering Sea with an anchored Russian ship in the background (watercolor by Louis Choris, 1816)


The ban baffled the indigenous fishers of the Alaskan Peninsula and the Aleutian Islands, who have subsisted on Steller sea lions for more than 10,000 years. How could the decline be caused by overfishing when local fishers were catching more cod and pollock than they had in generations? Convinced that the decline in Steller sea lions had nothing to do with overfishing, the indigenous people of Western Alaska turned to Dr. Herbert Maschner (Idaho State University) for help.
Maschner, an anthropologist and archaeologist who grew up in Fairbanks, has been actively researching and collecting data on human history in Alaska for more than 25 years. Lending his considerable expertise in Alaskan history and pre-history to the Consortium’s multidisciplinary scientific research program, Maschner uncovered new insights and information on the relationship between humans and Steller sea lions since the last Ice Age.
Steller sea lions

Adult females with Steller sea lion pups playing in shallow waters.


In a new paper published in Fish and Fisheries, Maschner and colleagues provide a thorough historical context for the current Steller sea lion decline, offering critical insights into five of the leading scientific explanations behind its cause (fisheries competition, environmental change, predation by killer whales, anthropogenic effects, and disease).
Dynamic Landscape
“Humans, and especially biologists, have a notion that everything in the past was static and everything modern is changing because of human interactions,” Maschner says. “They don’t think of humans on the landscape. But the past was a highly dynamic landscape that included humans, and that landscape responded to many of the same problems that species face today.”
In the study, Maschner and colleagues present anthropological and archaeological evidence that Steller sea lion numbers have repeatedly declined and recovered over the past 4,500 years. Maschner says that historical observations by locals, explorers, and others since the late 1800s have consistently associated low Steller sea lion populations with high populations of Pacific cod and walleye pollock. According to these observations, Steller populations were most recently at critically low numbers during the 1870s-1930s—long before the first scientific census in 1956.
maschner3
“The problem is really one of shifting baselines—except there are no baselines!” Maschner explains. “Populations throughout history are so dynamic that we don’t know whether today’s Steller sea lion decline was actually a crash, or whether they are just going back to a normal level.” He points to the population counts in the 1960s and 1970s, which biologists consider a benchmark for “pristine” numbers of Steller sea lions before the harvests and commercial fisheries of the last 40 years. Maschner notes that these surveys were taken during a period in which Steller sea lions were relatively abundant, the ocean climate was cooler, and humans had stopped harvesting sea lions in meaningful numbers.
Maschner also suggests the possibility that a good portion of the North Pacific marine ecosystem has adapted to human harvesting—and that accordingly, the behavioral ecology of Steller sea lions may have adapted to a certain level of harvesting by humans. He presents archaeological evidence showing that Steller sea lions have historically avoided human settlements when sea lion populations were low, and they ventured closer to humans when sea lion populations were abundant. He also provides evidence that larger human populations have historically not overexploited sea lion populations—in fact, the opposite was frequently true.
“Our data show that the whole idea of a pre-European environment that was rich and static and abundant was a figment of imagination,” Maschner says. “There were warm periods in the past when Steller sea lions declined, and the humans that harvested them also declined.”
Climate is Key
Indeed, the human activities that Maschner believes will contribute most to the decline or recovery of Steller sea lions are activities that enhance or diminish climate change.
“During warm periods, primary productivity goes down,” he explains. “The kind of zooplankton that support fish populations also change, and the overall productivity of the Pacific Ocean drops considerably. This reverses during cold periods, and the cycle mimics the rise and fall of sea lion populations. We can’t solve the problem of Steller sea lion populations unless we solve climate change.”
Steller sea lions -- caption?

Steller sea lions hauled out above the ocean swells.


The new study provides strong archaeological and anthropological evidence to support the current ocean climate hypothesis proposed in Trites, Miller, Maschner et al. (2007)—that that the key driver of Steller sea lion population declines or recoveries are periodic “regime shifts” in ocean climate, the most recent of which occurred in 1977. Maschner and colleagues suggest that while factors like removals by people and predation by killer whales did not cause the current decline, they may have made it worse.
Maschner calls the current study a “great collaboration between biology and the social sciences” and cautions against viewing the Steller sea lion decline as a purely scientific problem unique to the 21st century.
“Government policy and management decisions are made using scientific fisheries models that say, ‘before fishing, this is what the ocean looked like,’” he says. “The problem is, there hasn’t been a ‘before fishing’ for 10,000 years.”
 

PublicationsPUBLICATION

The decline of Steller sea lions (Eumetopias jubatus) in the North Pacific: insights from indigenous people, ethnohistoric records and archaeological data.
Maschner, H. D. G., A. W. Trites, K. L. Reedy-Maschner and M. Betts. 2014.
Fish and Fisheries 15:634-660.
abstract
A number of hypotheses have been proposed to explain the most recent decline (1977-2012) of Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska and Aleutian Islands. We examined hypotheses about fisheries competition, environmental change, predation, anthropogenic effects, and disease using observations of modern Aleut and archaeological, ethnohistoric, and ethnographic data from the western Gulf of Alaska and Aleutian Islands. These data indicate that Steller sea lion numbers have declined and recovered repeatedly over the past 4,500 years and were last at critically low numbers during the 1870s-1930s. Steller sea lions appear to have been more abundant during the cool periods—and lower during the warmer periods. Observations by local peoples, explorers, early government surveyors, and biologists since the late 1800s suggest that low populations of Steller sea lions have been associated with high populations of Gadidae fishes (Pacific cod – Gadus macrocephalus and walleye pollock – Theragra chalcogramma), and are consistent with the ocean climate hypothesis to explain the decline of sea lions. They suggest that removals by people and killer whales (Orcinus orca) did not cause the sea lion declines, but could have compounded the magnitude of the decline as sea lion numbers approached low densities. Archaeological, anthropological and ethnohistorical analyses demonstrate that fluctuations have occurred in the North Pacific over hundreds to thousands of years, and provide context for understanding the changes that occur today and the changes that will continue to occur in the future.
show/hide abstract View Reference Learn more about what was found

Are young northern fur seals vulnerable to changes in ocean temperature?

Each fall, thousands of northern fur seals leave their summer island homes and take to the chilly waters of the Bering Sea to begin their annual winter migration. Most will follow a route that takes them into the North Pacific Ocean, with some traveling as far south as California, through a wide range of ocean temperatures.

Two northern fur seal pups amongst sleeping adult females on the Pribilof Islands.

Two northern fur seal pups amongst sleeping adult females on the Pribilof Islands.


For the most vulnerable members of this migration—the four-month-old pups beginning their life at sea—survival will depend on their ability to conserve energy, stay warm, and catch enough fish to keep them going until they return to their natal rookeries almost two years later. Two new Consortium studies, recently published in Marine Mammal Science, investigated the ability of young fur seals to regulate their internal temperature across a range of ocean temperatures.
“Northern fur seals are small, naïve animals that look like they should not be able to survive in the Bering Sea, except that they have these incredibly thick fur coats,” says Dr. David Rosen, a co-investigator in both studies. “Our main question was whether cooler water temperatures might cause young and vulnerable fur seals to require more energy to stay warm. We also wanted to know whether water temperatures might determine where they are found in the ocean.”
Thermal Neutral Zone
The two studies progressively followed six female northern fur seals, raised at the Vancouver Aquarium, through their first four years of life. Using a range of temperatures that northern fur seals might naturally encounter in the wild, the scientists sought to establish a “thermal neutral zone” (TNZ) for younger northern fur seals—the range of temperatures within which they do not need to expend any additional metabolic energy to stay warm or cool down. The TNZ varies across marine mammal species and has not been well studied in fur seals.
Michi, one of the young fur seals that participated in the study at the Vancouver Aquarium

Meechi, one of the young fur seals that participated in the study at the Vancouver Aquarium


“The northern fur seal pups seemed to have a broad TNZ,” says Alex Dalton, lead author of one of the studies, and who recently completed a Master’s of Zoology under Dr. Rosen and Dr. Andrew Trites. “For the most part, the older pups were  thermally neutral within water temperatures of 2-18 degrees Celsius throughout the year. This means that the range of water temperatures they would encounter throughout their migration is probably not placing any additional energetic demands on them.”
Dalton emphasizes that these studies are different from past TNZ research on northern fur seals, because they took place over four years, which allowed the scientists to gather data across all seasons and look for differences as the pups grew. “In the first two years of life, our study suggests that the fur seals would have to expend additional energy to keep warm in water below approximately 4-7 degrees Celsius”, notes Dr. Rosen. “However, our follow-up study of the fur seals when they were a few years older shows an increased ability to withstand much colder water temperatures.”
Driving Migration
Rosen believes that several factors seem to trigger the fur seals’ annual migration,  including storms and cooler air temperatures. He believes cooler sea surface temperatures may also play a role.
“Most younger fur seals probably could not survive winter in the Bering Sea,” Rosen explains. “The cooler surface temperatures may help to initiate the migration but they did not seem to be a driving factor in determining the route. In other words, the lower thermal limit did not match the migration pattern, which suggests they are migrating well within their thermal neutral zone and not just trying to stay ahead of the cold water.”
 Monthly average sea surface temperatures recorded in November between the Bering Sea (2 C at top of map) and Hawaii (22 C - bottom of map).  Most fur seal pups are in the Bering Sea in November (dashed circle) and migrate into the warmer waters of the North Pacific Ocean as winter approaches.

Monthly average sea surface temperatures recorded in November between the Bering Sea (2 °C at top of map) and Hawaii (22 °C – bottom of map). Most fur seal pups are in the Bering Sea in November (dashed circle) and migrate into the warmer waters of the North Pacific Ocean as winter approaches.


If thermoregulation is not driving the migration route, except under extreme environments, Rosen believes the probable motivation is food sources.
“This relates back to a key question of whether a decrease in the availability of prey is adding to the decline in northern fur seal populations in the Bering Sea, as opposed to changes in ocean climate or more frequent winter storms,” Rosen says. He is also the lead author in a follow-up study recently published in Conservation Physiology, which found that nutritionally stressed young northern fur seals are better able to regulate their temperature in winter than in summer.
Dalton is interested in following up his study by investigating the reasons for the differences between thermoregulation abilities of northern fur seals versus sea otters, which are equally well known for their thick fur coats but significantly higher energetic requirements.
 

PublicationsPUBLICATIONS

Broad thermal capacity facilitates the primarily pelagic existence of northern fur seals (Callorhinus ursinus).
Dalton, A.J.M., D.A.S. Rosen and A.W. Trites. 2014.
Marine Mammal Science 30:994-1013.
abstract
Thermoregulatory capacity may constrain the distribution of marine mammals despite having anatomical and physiological adaptations to compensate for the thermal challenges of an aquatic lifestyle. We tested whether subadult female northern fur seals (Callorhinus ursinus) experience increased thermoregulatory costs in water temperatures potentially encountered during their annual migration in the Bering Sea and North Pacific Ocean. Metabolic rates were measured seasonally in 6 captive female northern fur seals (2.75 to 3.5 yr old) in ambient air and controlled water temperatures of 2, 10, and 18 °C. Rates of oxygen consumption in ambient air (1 – 18 °C) were not related to environmental temperature except below 2.5 °C (winter only). However, metabolism was significantly higher during the fall seasonal trials (Sept – Oct) compared to other times of year, perhaps due to the costs of molting. The fur seals appeared thermally neutral in all seasons for all water temperat ures tested (2 – 18 °C) except during the summer when metabolic rates were higher in the 2 °C water. Comparing this broad thermal neutral zone to the average sea surface temperatures potentially encountered during annual migrations indicates wild fur seals can likely exploit a large geographic area without added thermal metabolic costs.
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Thermal limits in young northern fur seals, Callorhinus ursinus.
Rosen, D.A.S. and A.W. Trites. 2014.
Marine Mammal Science 30(3):1014-1028.
abstract
The thermoregulatory abilities of northern fur seals (Callorhinus ursinus) during their first two years in the frigid waters of the North Pacific Ocean may limit their geographic distribution and alter the costs for exploiting different species of prey. We determined the thermoneutral zone of 6 young northern fur seals by measuring their metabolism in ambient air and controlled water temperatures (0-12 °C) from ages 8 to 24 mo. We found that the ambient air temperatures within our study (overall 1.5-23.9 °C) did not affect resting metabolic rates. Calculated lower critical temperatures in water varied between 3.9 and 8.0 °C, while an upper critical temperature in water was only discernible during a single set of trials. These thermal responses provide insight into the possible physiological constraints on foraging ecology in young northern fur seals, as well as the potential energetic consequences of ocean climate change and altered prey distributions.

keywords     Northern fur seal, Callorhinus ursinus, thermoregulation, metabolism, bioenergetics
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Short-term episodes of imposed fasting have a greater effect on young northern fur seals (Callorhinus ursinus) in summer than in winter.
Rosen, D. A. S., B. L. Volpov and A. W. Trites. 2014.
Conservation Physiology 2:1-9.
abstract
Unexpected shortages of food may affect wildlife differently depending on the time of year it occurs. We imposed 48-hr fasts on six female northern fur seals (Callorhinus ursinus; ages 6 ? 24 months) to identify times of year when they might be particularly sensitive to interruptions in food supply. We monitored changes in their resting metabolic rates and their metabolic response to thermal challenges, and also examined potential bioenergetic causes for seasonal differences in body mass loss. Pre-fast metabolism of the fur seals while in ambient air or submerged in 4 ?C water was higher during summer (Jun-Sep) than winter (Nov-Mar), and submergence did not significantly increase metabolism indicating a lack of additional thermoregulatory costs. There was no evidence of metabolic depression following the fasting periods, nor did metabolism increase during the post-fast thermal challenge, suggesting that mass loss did not negatively impact thermoregulatory capacity. However, the fur seals lost mass at greater rates while fasting during the summer months when metabolism is normally high to facilitate faster growth rates (which would ordinarily have been supported by higher food intake levels). Our findings suggest that summer is a more critical time of year than winter for young northern fur seals to obtain adequate nutrition.
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Into the Field

Chinook and coho are two of British Columbia’s most valuable salmon species.  However, their numbers are at an all-time low, especially in the Strait of Georgia. Dramatic declines in salmon abundance began in the 1970s as harbor seal numbers increased, which has led scientists (and fishermen) to suspect that seal predation may be impeding recovery of chinook and coho salmon.

Harbor seals in Cowichan Bay rest and give birth on floating piles of logs destined for a nearby saw mill.

Harbor seals in Cowichan Bay rest and give birth on floating piles of logs destined for a nearby saw mill.

Salmon have not returned to their historic levels, despite being harvested at relatively low rates for the last few decades.  This lack of recovery might be due to loss of habitat, competition and climate change. However, previous studies suggest that harbor seals may also be playing a significant role.

Chinook salmon

Chinook salmon

Previous research has addressed how many adult fish are eaten by seals, but relatively little attention has been given to how many juvenile salmon are eaten during the spring, when young fish migrate from their natal streams into the marine environment. Predation on juvenile fish is much less visible than predation on adult fish, and may explain the poor recovery of salmon.

UBC Graduate Student Ben Nelson is studying whether seal predation on adults and juveniles is responsible for the poor recovery of salmon in Cowichan Bay on Vancouver Island. Numbers of chinook and coho salmon were once large in the Cowichan River, and have dropped to low levels in recent years, while the local seal population has nearly tripled since the late-1980s.

From April to November of 2014, Ben is observing seal behavior and collecting harbor seal “scats” to estimate the percentage of their diet that is comprised of salmon. Luckily, seals that inhabit Cowichan Bay spend a lot of time hauled out on log booms in the inner bay, making collection of scats simple and efficient. Residents of Cowichan Bay are assisting in counting the number of seals using the log booms.

Ben Nelson in the field.

Ben Nelson in the field.

The scat samples are being processed in a genomics laboratory at UBC to quantify the amount of salmon DNA in each sample. The diet information generated from these samples will be used to estimate the number of salmon eaten annually in Cowichan Bay, and will be incorporated into mathematical models that simulate the dynamics of salmon populations.

Ben’s study will ultimately help to understand how salmon respond to fishing, natural mortality (i.e., seal predation) and other environmental factors. The models will simplify a very complex ecological system, and will allow scientists and fisheries managers to test hypotheses about why salmon have declined. Results from the Cowichan Bay study will be used to make broader inferences about the Strait of Georgia ecosystem and the interactions between seals and salmon.

This research is being supported by the Pacific Salmon Foundation and the Canadian Fisheries Research Network.

 Ben Nelson is an PhD candidate at UBC’s Marine Mammal Research Unit.



Counting salmon smolts as they pass down the throat of a seal one fish at a time

Have you ever used a key fob to open a locked door, or driven through a toll booth without stopping because you had an ID card on your windshield?  If so, chances are you were using Radio Frequency Identification (RFID) technology. These simple devices transmit a weak radio signal with a unique identification number as they pass near an RFID scanner. It allows the door to grant you access to the room, and toll booths to charge you the appropriate fee.

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The harbor seal Hermes wearing a fish-tag reader that contains an antennae, batteries, and an electronics board. Neil Fisher photo (Vancouver Aquarium)

UBC Researchers, Austen Thomas and Brian Battaile, are developing this same RFID technology to identify and record how many salmon smolts are being eaten by harbor seals in the Strait of Georgia. They have been developing a satellite tag containing an RFID scanner with Wildlife Computers that can be carried on the head of a seal to read RFID microchips that are regularly implanted in salmon smolts. Fisheries managers implant PIT (Passive Integrated Transponders) tags, which contain RFID microchips, in young salmon to monitor survival during downstream migration. These are the same types of tags used by veterinarians to keep track of dogs and cats.

Scanners placed in rivers can log each time a salmon smolt carrying a PIT tag passes by, and are used to determine how many smolts survive. This led Thomas and Battaile to ask, “Why don’t we put the scanner on a seal?” What seemed like a crazy idea at the time has turned into a viable method for estimating how many smolts are consumed by seals.

With funding from the Pacific Salmon Foundation, Thomas and Battaile tested the first prototype RFID tag —a head mounted PIT tag scanner for seals—that can detect each ingested salmon smolt and transmit that information via satellite.

Hermes approaching a young coho salmon that has a tag inserted into its abdominal cavity. The fish-tag reader on Hermes’ head will record the number of the tag as it passes down the seal’s throat.

Hermes approaching a young coho salmon that has a tag inserted into its abdominal cavity. The fish-tag reader on Hermes’ head will record the number of the tag as it passes down the seal’s throat.

Thomas and Battaile worked with Vancouver Aquarium staff on a feasibility study that determined which types of PIT tags could be detected, and how long the battery would last. They fed Hermes (one of the Aquarium’s harbor seals) coho salmon smolts that had been implanted with different types of PIT tags, and measured the detection rates under different conditions. The prototype tag was held on the seal’s head by a strip of Velcro, and was removed between trials by the trainers (who trained Hermes to wear his hat with pride!).


The research team found that the RFID tag was able to detect when the seal ate the larger salmon smolts (i.e., coho and steelhead), and that the batteries lasted several weeks, sufficient to cover the typical smolt outmigration window. Results were presented at the recent Salish Sea Ecosystem Conference in Seattle, Washington.

The next step is to refine the technology so that other species of salmon smolts (such as chinook) can also be detected. With any luck, you may see a harbor seal swimming around the Strait of Georgia with a jaunty tag-reading hat in 2015!

 

 

Austen Thomas is a Ph.D. Candidate at UBC’s Marine Mammal Research Unit.
Brian Battaile is a Researcher for the Marine Mammal Research Consortium.


Diving into beer and suds — marine mammal style!

Beer and biology are well known associates on an individual level, and were recently shown to go especially well together at an institutional level at the University of British Columbia.

As part of Alumni Weekend, North Coast Brewing Company hosted a beer-tasting session at UBC’s Fisheries Centre. The event showcased North Coast’s support of UBC’s Marine Mammal Research Unit and exposed members of the University community to the products of this California-based microbrewery.

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Mark Ruedrich (President and Brewmaster of North Coast Brewing) discusses the art of beer making with one of the volunteers.

Guests listened to a brief presentation by Mark Ruedrich (President and Brewmaster of North Coast Brewing) and Dr. Andrew Trites (MMRU Director) before sampling four different beers and learning about their production. Two of their beers have a particularly strong connection to marine mammals — Scrimshaw Pilsner and Red Seal Ale, and a special edition of Steller IPA is on its way.

Students, alumni and invited guests were able to sample four different beers produced by Mark Ruedrich and learn  how they were made.

Students, alumni and invited guests were able to sample four different beers produced by Mark Ruedrich and learn how they were made.

It was the striking sea lion on the Red Seal label that led UBC Research Technician Brandon Russell to contact North Coast Brewing two years earlier.   Brandon works at the Open Water Research Station with Steller sea lions that are trained to swim in the open ocean to collect data needed to determine why numbers are declining in Alaska.  He called the Brewery to talk about sea lions and was put through to Mark, a zoology alumnus from NC State University. Mark moved to Fort Bragg on the Mendocino coast to pursue a career in marine biology, and ended up starting the brewery in 1988.

outreach3

The beer was served at four different stations situated among the marine mammal skeletons suspended throughout the Fisheries Centre.

red-seal-aleVisits between Fort Bragg and Vancouver have uncovered many parallels between running a brewery and operating a research station. They have also brought together a great group of people with common values and passions about beer, marine mammals and the health of our coastal waters.

Thank you North Coast Brewing for your support of the Marine Mammal Research Unit. We look forward to working together and continuing to pair beer and biology!


Steller sea lion diving awarded Gold Medal

gerlinsky-tFor more than 125 years, one gold medal has been awarded each year to the graduate student who has achieved the most outstanding academic record as a Master’s student completing a thesis. This year, MMRU’s Carling Gerlinskywas chosen to receive the award from among approximately 1,000 Master’s graduates at the University of British Columbia for her research on the diving ability of Steller sea lions. Carling received her medal at the recent convocation ceremonies on behalf of the Governor General of Canada.

Carling started her thesis with a single question and, as with all good science, ended up answering many more.  Among her discoveries was that Steller sea lions will never win any medals for diving! They have an incredibly short aerobic dive limit (just 3 minutes) compared to other seals and sea lions, and that nutritionally stressed sea lions have increased blood volume (counter to all predictions).

With three publications under her belt from her MSc thesis, Carling has set her mark on the world of diving physiology.

Sensitivity to hypercapnia and elimination of CO2 following diving in Steller sea lions (Eumetopias jubatus).
Gerlinsky, C.D., D.A.S. Rosen and A.W. Trites. 2014.
Journal of Comparative Physiology B. 184:535-544.
View Reference

Steller sea lions (Eumetopias jubatus) have greater blood volumes, higher diving metabolic rates and a longer aerobic dive limit when nutritionally stressed.
Gerlinsky, C.D., A.W. Trites and D.A.S. Rosen. 2014.
Journal of Experimental Biology 217:769-778.
show/hide abstract View Reference

High diving metabolism results in a short aerobic dive limit for Steller sea lions (Eumetopias jubatus).
Gerlinsky, C. D., D. A. S. Rosen and A. W. Trites. 2013.
Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. 186:699-708.
show/hide abstract View Reference

 

 Does nutritional status influence diving behavior in Steller sea lions?

If you have ever searched for a gas station while your fuel gauge light is on, you might appreciate the daily dilemma of a Steller sea lion that is nutritionally stressed. Before you can fill up your tank, you must use up some of your remaining fuel to find a gas station—but you risk running out of fuel before you get there.

gerlinsky-here

Female Steller sea lions with dependent pups or juveniles must find adequate prey to produce the energy rich milk needed to sustain their young.


Many people believe that Steller sea lions in the western Aleutian Islands are nutritionally stressed because of a shortage of Atka mackerel—and are effectively driving on empty fuel tanks. Their survival depends on finding enough healthy food to provide energy for metabolism and reproduction. But diving for food requires energy, and a sea lion must balance the energy expended while foraging with the energy gained from the food it captures.
gerlinsky4

Boni was one of 4 female Steller sea lions that participated in the open water diving trials conducted by Carling Gerlinsky.


This scenario—should it be what is actually happening in the western Aleutian Islands—poses important questions for scientists. Does an undernourished sea lion dive as efficiently as a healthy sea lion? Does nutritional status change diving behavior? These questions are at the heart of a new Consortium study led by Carling Gerlinsky and recently published in The Journal of Experimental Biology.
Measuring Diving Efficiency
“Last year, we published a study that indirectly measured the maximum amount of time a Steller sea lion can stay underwater before it uses up the oxygen in a single breath,” Gerlinsky says. “The calculated Aerobic Dive Limit gives us a measure of the diving efficiency of an average sea lion.”
In her recent follow-up study, Gerlinsky wanted to know whether weight loss affected the aerobic dive limit and overall diving behavior. She worked with the same four adult female Steller sea lions that participated in her previous study, but this time the animals had lost ten percent of their body mass under a supervised diet—simulating a widespread nutritional stress speculated to have occurred in wild populations.
Surprisingly, Gerlinsky and her colleagues found that the aerobic dive limit increased from 3.0 minutes in unstressed animals to 3.3 minutes in nutritionally stressed animals, meaning nutritionally stressed sea lions could forage for slightly longer on the oxygen in a single breath.
Limits to Foraging
“We found that nutritionally stressed animals didn’t seem to have a compromised ability to dive and forage,” Gerlinsky notes. “If anything, they had capacity to dive longer and deeper due to an increased aerobic dive limit, but they needed to spend more time on the surface to recover between dives.”
gerlinsky5

Each sea lion traveled aboard the Steller Shuttle to Indian Arm (the southernmost fjord in North America) where they swam and dove freely below the platform, and surfaced within the metabolic dome within the center of it. Air expelled by the sea lions was sampled through the blue tube by the oxygen and CO2 analyzers aboard the research vessel Steller Pilot to determine the energetic cost of each dive.


On the flipside, Gerlinsky says, “nutritionally stressed animals require a lot more food to regain the weight they have lost, so they forage less efficiently because their metabolic rate hasn’t changed. They still need the same amount of food as they always did, but they’re operating from an energy deficit. However, they seem to have capacity to dive longer and potentially obtain more food while foraging.”
There is a limit to how much time a sea lion can spend foraging, Gerlinsky notes. Longer foraging trips cost more energy and reduce the amount of time that females could otherwise spend feeding their young. More time at sea also increases the risk of predation.
While the long-term consequences of “running on empty” are unclear, establishing the aerobic dive limit for Steller sea lions is proving to be a useful baseline measurement for health. Carling Gerlinksy’s ongoing efforts are helping to refine its usefulness in understanding the real-life challenges faced by the declining Steller sea lions in Alaska’s western Aleutian Islands.

PublicationsPUBLICATION

Steller sea lions (Eumetopias jubatus) have greater blood volumes, higher diving metabolic rates and a longer aerobic dive limit when nutritionally stressed.
Gerlinsky, C.D., A.W. Trites and D.A.S. Rosen. 2014.
Journal of Experimental Biology 217:769-778.
abstract
Marine mammal foraging behavior inherently depends on diving ability. Declining populations of Steller sea lions may be facing nutritional stress that could affect their diving ability through changes in body composition or metabolism. Our objective was to determine whether nutritional stress (restricted food intake resulting in a 10% decrease in body mass) altered the calculated aerobic dive limit (cADL) of four captive sea lions diving in the open ocean, and how this related to changes in observed dive behaviour. We measured diving metabolic rate (DMR), blood O2 stores, body composition and dive behaviour prior to and while under nutritional restriction. We found that nutritionally stressed sea lions increased the duration of their single long dives, and the proportion of time they spent at the surface during a cycle of four dives. Nutritionally stressed sea lions lost both lipid and lean mass, resulting in potentially lower muscle O2 stores. However, total body O2 stores increased due to rises in blood O2 stores associated with having higher blood volumes. Nutritionally stressed sea lions also had higher mass-specific metabolic rates. The greater rise in O2 stores relative to the increase in mass-specific DMR resulted in the sea lions having a longer cADL when nutritionally stressed. We conclude that there was no negative effect of nutritional stress on the diving ability of sea lions. However, nutritional stress did lower foraging efficiency and require more foraging time to meet energy requirements due to increases in diving metabolic rates and surface recovery times.

keywords     Steller sea lion, blood volume, nutritional stress, diving metabolism, oxygen stores, dive behavior
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New research details northern fur seal foraging patterns along ocean fronts

Each summer, the female northern fur seals on Alaska’s remote Pribilof Islands go hunting. Leaving the safety of the land for days at a time, they must find enough food to give them the energy to continue nursing their newborn pups. If they are lucky, they’ll find a large patch of prey in one place. If not, they’ll graze along the way until their instincts call them home.

nordstrom-hero

Pups and adult female northern fur seals look on as a bull makes threatening calls.


What causes this pattern of behavior? Where do northern fur seals go when they are at sea, and how do they know where to find food?
These questions are at the core of two new studies led by Chad Nordstrom (UBC Marine Mammal Research Unit) and published in Deep-Sea Research II.
Working with 87 lactating female fur seals fitted with high-tech tracking tags, Nordstrom analyzed thousands of dive profiles logged over dozens of foraging trips, some of which lasted over one week. The data from the tags gave him detailed insights on how far and how deep the seals travel, and where they stop to eat.

Animation showing two northern fur seals originating from St. Paul Island foraging along a submesoscale surface front over the central shelf-break and basin of the eastern Bering Sea. Individual fur seals are represented by colored lines. Fronts are depicted as dark bands and are 4-day snapshots; and time of day is shown at the bottom in GMT.

“I wanted to know why the fur seals were foraging in those locations,” Nordstrom says. “In order to answer that question I needed to collect more advanced oceanographic data, and I was lucky enough to collaborate with a group of researchers who were doing just that.”

nordstrom-4

Fur seal researchers (from left to right) John Gibbens, Chad Nordstrom, Andrew Trites, and Al Baylis


Fine-scale Ocean Fronts
Nordstrom joined the Patch Dynamics Team of the Bering Sea Integrated Ecosystem Research Program, a team of oceanographers and biologists who were mapping the intricate interplay between the physical ocean and the life within it. The collaboration gave Nordstrom a chance to compare the oceanographic data from his tags—produced by foraging fur seals—with measurements taken aboard a ship.
“It’s a little like tracing the outline of a picture and then coloring it in,” Nordstrom explains. “When environmental variables like ocean temperatures are collected by a ship or a satellite, it paints a broad picture that misses the

A daily diary tag carried by northern fur seals to record water temperature, depth, light levels, acceleration, and directional movement as frequently as 16 times per second.


nitty-gritty details. By tracking tagged animals as they move around and collect data about their environment, we could fill in the information gaps by looking at the data in finer detail than anyone had before.” 

Some of Nordstrom’s tagged fur seals would linger in particular spots and then head home directly. Others would run a predictable circuit of the ocean. But the patterns were inconsistent, and Nordstrom’s data couldn’t explain this behavior—until he began to overlay fine-scale maps of ocean currents generated by an oceanographer.
“That’s when everything started to make sense,” Nordstrom says. “It turns out the seals were eating along narrow ribbons of current, which acted like an invisible fence to concentrate prey in one place.”
“These small-scale anomalies—ocean fronts—are like currents within a current,” Nordstrom explains, “which channel zooplankton into corridors. A concentration of zooplankton at the face of an ocean front attracts fish and squid, which in turn attract larger predators like fur seals.”

Water temperatures (ranging from 0-10C) of the eastern Bering Sea at 1m (left panel) and 50m (right panel). Data were collected from ships and northern fur seals in 2009. Anomalously cold and warm eddies are circled in the right panel.


Location Matters
Nordstrom’s studies compared two cohorts of fur seals—one on St. Paul Island and one on Bogoslof Island. He was surprised to find that fur seals from St. Paul Island ventured three times farther and stayed at sea twice as long as fur seals from Bogoslof Island. This suggests that prey may be less concentrated near St. Paul Island, requiring lengthier foraging trips.The take-home message, Nordstrom says, is that location matters for northern fur seals.
“Female northern fur seals are tied to one rookery when they are raising their pups,” Nordstrom says. “So the availability of high-quality prey around them has a huge impact on their choices when foraging. The availability and proximity of prey to nursing females, which is largely determined by the location of ocean fronts, could determine the fate of an entire population.”

PublicationsPUBLICATIONS

Foraging habitats of lactating northern fur seals are structured by thermocline depths and submesoscale fronts in the eastern Bering Sea.
Nordstrom, C. A., B.C. Battaile, C. Cotté and A. W. Trites. 2013.
In Deep-Sea Research II: Topical Studies in Oceanography.  88-89:78-96.
abstract
The relationships between fine-scale oceanographic features, prey aggregations, and the foraging behavior of top predators are poorly understood. We investigated whether foraging patterns of lactating northern fur seals (Callorhinus ursinus) from two breeding colonies located in different oceanographic domains of the eastern Bering Sea (St. Paul Island shelf; Bogoslof Island˜oceanic) were a function of submesoscale oceanographic features. We tested this by tracking 87 lactating fur seals instrumented with bio-logging tags (44 St. Paul Island, 43 Bogoslof Island) during JulyˆSeptember, 2009. We identified probable foraging hotspots using first-passage time analysis and statistically linked individual areas of high-use to fine-scale oceanographic features using mixed-effects Cox-proportional hazard models. We found no overlap in foraging areas used by fur seals from the two islands, but a difference in the duration of their foraging trips˜trips from St. Paul Island were twice as long (7.9 d average) and covered 3-times the distance (600 km average) compared to trips from Bogoslof Island. St. Paul fur seals also foraged at twice the scale (mean radius = 12 km) of Bogoslof fur seals (6 km), which suggests that prey were more diffuse near St. Paul Island than prey near Bogoslof Island. Comparing first passage times with oceanographic covariates revealed that foraging hotspots were linked to thermocline depth and occurred near submesoscale surface fronts (eddies and filaments). St. Paul fur seals that mixed epipelagic (night) and benthic (day) dives primarily foraged on-shelf in areas with deeper thermoclines that may have concentrated prey closer to the ocean floor, while strictly epipelagic (night) foragers tended to use waters with shallower thermoclines that may have aggregated prey closer to the surface. Fur seals from Bogoslof Island foraged almost exclusively over the Bering Sea basin and appeared to hunt intensively along submesoscale fronts that may have converged prey within narrow bands near the surface. Bogoslof fur seals also foraged closer to their island which was surrounded by strong surface fronts, while fur seals from St. Paul Island traveled4100 km and extended some trips off-shelf to the basin to forage at similar oceanographic features. The relative distribution and accessibility of prey-concentrating oceano- graphic features can account for the observed inter-island foraging patterns, which may in turn have population level consequences for the two fur seal colonies.

keywords     Habitat selection, First-passage time, Submesoscale features, Finite-size Lyapunov exponent,Cox proportional hazard model, Alaska, Eastern Bering Sea
show/hide abstract View Reference Learn more about what was found

Northern fur seals augment ship-derived ocean temperatures with higher temporal and spatial resolution data in the eastern Bering Sea.
Nordstrom, C.A., K. J. Benoit-Bird, B.C. Battaile and A.W. Trites. 2013.
Deep Sea Research II 94:257-273.
abstract
Oceanographic data collected by marine vertebrates are increasingly being used in biological and physical studies under the assumption that data recorded by free-ranging animals are comparable to those from traditional vertical sampling. We tested this premise by comparing the water temperatures measured during a 2009 oceanographic cruise with those measured during 82 foraging trips by instrumented northern fur seals (Callorhinus ursinus) in the eastern Bering Sea. The animal-borne data loggers were equipped with a fast-response temperature sensor and recorded 6,492 vertical profiles to depths ≥ 50 m during long distance (up to 600 km) foraging trips. Concurrent sampling during the oceanographic cruise collected 247 CTD casts in the same 5-week period. Average temperature differences between ship casts and seal dives (0.60 ± 0.61 °C), when the two were within 1 day and 10 km of each other (n = 32 stations), were comparable to mean differences between adjacent 10 km ship casts (0.46 ± 0.44 °C). Isosurfaces were evaluated at region wide scales at depths of 1 m and 50 m while the entire upper 100 m of the water column was analyzed at finer-scales in highly sampled areas. Similar trends were noted in the temperature fields produced by ships or seals despite the differences in sampling frequency and distribution. However, the fur seal dataset was of higher temporal and spatial resolution and was thereby able to visualize finer-detail with less error than ship-derived data, particularly in dynamic areas. Integrating the ship and seal datasets provided temperature maps with an unprecedented combination of resolution and coverage allowing fine-scale processes on-shelf and over the basin to be described simultaneously. Fur seals (n = 65 trips) also collected 4,700 additional profiles post ship cruise which allowed ≥1 °C warming of the upper 100 m to be documented through mid-September, including regions where ship sampling has traditionally been sparse. Our data show that hydrographic information collected by wide-ranging, diving animals such as fur seals can contribute physical data comparable to, or exceeding those, of traditional sampling methods at regional or finer scales when the questions of interest coincide with the ecology of the species.
show/hide abstract View Reference Learn more about what was found

 

Open water research provides clues to behavior in wild populations

Western Alaska’s declining Steller sea lion populations live in remote and inaccessible parts of the North Pacific Ocean, making them elusive research subjects. As a result, many basic questions about their diet, behavior and physiology remain unanswered.

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Carling Gerlinsky on the diving platform with Hazy and two Steller sea lion trainers from the Vancouver Aquarium. The diving study was conducted in Indian Arm, the southernmost fjord in North America. Shown on the platform are the pipes (left) that were screwed together to various depths and the custom-made pump (right) used to send fish down the pipes to depths of up to 50 m. The sea lions were trained to surface inside the dome (center) between each dive.


These questions attracted Carling Gerlinsky to the Consortium’s Open Water Research Station, which offered her a unique opportunity to study the diving behavior and physiology of Steller sea lions. Her findings were recently published in the Journal of Comparative Physiology B.
“What drew me to the Open Water Research Station was the ability to work with trained animals that are diving realistically in the open ocean,” says Gerlinsky, “while still being able to control aspects of their behavior.”
gerlinsky2

Carling used her smart phone to record how long each sea lion spent in the dome and the number of breaths they took. She later analyzed the concentrations of oxygen and carbon dioxide in the dome to determine the energetic cost of each dive.


Aerobic Dive Limit
Gerlinsky sought to answer a basic but important physiological question: how long can a Steller sea lion hold its breath before it depletes its oxygen reserves? This is an important question to answer because of the implications it has for interpreting the meaning of the relatively short duration of dives observed for Steller sea lions in the wild.  However, measuring the breath holding ability of marine mammals (the aerobic dive limit – ADL) is difficult. Because of this, researchers often use a proxy measure called the calculated ADL (cADL).
“Calculated ADL gives a good indication of what sea lions are capable of doing based on body oxygen stores, compared to what we actually see them doing in the wild,” says Gerlinsky. “For example, if we see wild sea lions making consistently longer dives, close to or beyond their aerobic limit, it might indicate scarce prey.”
Working with eight trained female Steller sea lions, Gerlinsky estimated the oxygen stores in the blood, muscles and lungs of each. This involved taking blood samples, body composition measurements, and measuring the amount of oxygen consumed over a series of dives to different depths. She then combined these measurements using a mathematical formula to calculate that the dive limit of a Steller sea lion using its onboard oxygen was just 3 minutes for a single dive!
Caption goes here

All of the sea lions wore harnesses when free swimming that carried scientific instruments to measure time, depth and movement.


“Our finding follows closely with what we see wild Steller sea lions doing in Alaska where they have declined,” Gerlinsky said. “We’ve worked with trained animals for many years and we know they are capable of diving for five, six, and sometimes seven minutes. In the wild, dive durations range significantly but they average two or three minutes, and usually not more than four minutes.”
Gerlinsky also found that the level of activity—diving vigorously in open water versus in a shallow aquarium setting—didn’t affect the aerobic dive limit, suggesting that the ability to store oxygen is more likely a genetic trait than a function of activity.
“This is just one instance in which basic, fact-driven research can contribute to solving a larger puzzle, she says. “We never know when some fundamental piece of knowledge about sea lions might end up being important in the field.”
 

PublicationsPUBLICATION

High diving metabolism results in a short aerobic dive limit for Steller sea lions (Eumetopias jubatus).
Gerlinsky, C. D., D. A. S. Rosen and A. W. Trites. 2013.
Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. 186:699-708.
abstract
The diving capacity of marine mammals is typically defined by the aerobic dive limit (ADL) which, in lieu of direct measurements, can be calculated (cADL) from total body oxygen stores (TBO) and diving metabolic rate (DMR). To estimate cADL, we measured blood oxygen stores, and combined this with diving oxygen consumption rates (VO(2) recorded from 4 trained Steller sea lions diving in the open ocean to depths of 10 or 40 m. We also examined the effect of diving exercise on O(2) stores by comparing blood O(2) stores of our diving animals to non-diving individuals at an aquarium. Mass-specific blood volume of the non-diving individuals was higher in the winter than in summer, but there was no overall difference in blood O(2) stores between the diving and non-diving groups. Estimated TBO (35.9 ml O(2) kg(-1) )was slightly lower than previously reported for Steller sea lions and other Otariids. Calculated ADL was 3.0 min (based on an average DMR of 2.24 L O(2) min(-1)) and was signific antly shorter than the average 4.4 min dives our study animals performed when making single long dives-but was similar to the times recorded during diving bouts (a series of 4 dives followed by a recovery period on the surface), as well as the dive times of wild animals. Our study is the first to estimate cADL based on direct measures of VO(2) and blood oxygen stores for an Otariid and indicates they have a much shorter ADL than previously thought.
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The status of marine mammal populations is of growing concern to a wide range of individuals. Questions are being asked about the impact of human activities on marine mammals and the effect of marine mammals on fish stocks. These uncertainties may have repercussions on people, marine mammals, and the health of the ecosystem.

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MARINE MAMMAL RESEARCH NEWSLETTER

October 2013 (Issue  8)

FROM THE FIELD …
Counting on some good news. Steller sea lions continue to increase and establish new breeding sites in BC. [more]

 

 


NUMBER CRUNCHING
Can a new technology help answer an old conservation question? Counting DNA sequences in seal scats may reveal proportions of prey species consumed. [more]

 


INTO THE LAB …
Figuring out the cost of a good dinner. Researchers are determining how changes in numbers and distribution of fish affect Steller sea lions. [more]

 


SCIENCE IN DEPTH
White-sided dolphins are making a resurgence in nearshore waters. How much energy does it take to fuel these aquatic acrobats? [more]

 


Steller sea lion research

SCIENCE OUTREACH
Social media – connecting scientists and the public.

[more]


THIS JUST IN
DNA diets, fur seal thermometers, seismic testing bowhead whales, forage fish energy densities, and energy hungry white-sided dolphins. Check out our latest peer reviewed publications….[more]

 

 

 

 




population
 Saturday, November 23, 2013 – 9:30am – 5:00pm

UNIVERSITY OF BRITISH COLUMBIAAQUATIC ECOSYSTEM RESEARCH LABORATORY
GROUND FLOOR, AERL, 2202 MAIN MALL
VANCOUVER, B.C.  V6T 1Z4

Registration Fee: 0

Advanced: $0 (pre-register by Nov 15)

Late: $5 (cash only at the door)

Join us for presentations as well as discussion on issues that concern us all. This meeting is open to researchers, educators and businesses involved with marine mammals and anyone in one or more of these categories is welcome to attend.

Please email bc.symposium@fisheries.ubc.ca before November15, 2013, to indicate that you plan to attend. Lunch and refreshments will be provided, but we need to know how many people to plan for.  There will also be a social evening (6:00-9:00 pm) where beer and pizza can be purchased.

The Agenda will be distributed at the meeting. Please email bc.symposium@fisheries.ubc.ca  before November 15, 2013 if you would like to make a five minute presentation about your research. Longer presentations on topics of general interest are welcomed.  We would also like to know if there are any issues that should be discussed by the group at large.  We look forward to hearing from you and seeing you at:

9:30 am on Saturday, November 23, 2013

Telephone: (604) 822-8181

Email: bc.symposium@fisheries.ubc.ca

 

New insights into the complex relationship between fur seals and pollock

A multidisciplinary team of scientists tracked the foraging patterns of northern fur seals to understand how they interact with walleye pollock, an important fish stock. What the researchers discovered may have significant implications for how the commercial pollock fishery is managed, and how declining populations of northern fur seals are protected.

Northern Fur Seals

Northern fur seals at night


Alaska’s remote Pribilof Islands are home to the largest breeding population of northern fur seals and some of the largest populations of seabirds in the North Pacific Ocean. Nourished by an apparent abundance of walleye pollock and other prey—the declines of seabird and fur seal populations breeding on the Pribilofs has scientists puzzled. Is there more to the relationship between these predators and their prey than meets the eye?
Kelly Benoit-Bird at work

Observing thick-billed murres


To answer this and other questions, a diverse team of researchers participated in the Bering Sea Project — a large, interdisciplinary ecosystem study funded by the North Pacific Research Board — to gather critical data about top predators and their prey. Two of the inter-related studies, led by oceanographer Dr. Kelly Benoit-Bird, were recently published in the journals PLOS One and Marine Ecology Progress Series. They present a new understanding of how northern fur seals, thick-billed murres and black-legged kittiwakes behave with respect to their prey.
Three Top Predators
“We conducted field studies in the Bering Sea over two summers,” says Benoit-Bird. “In the first study, we wanted to determine the specific ‘hot spots’ where northern fur seals and two species of seabirds foraged for prey, and how they lined up with juvenile pollock in those areas. All three predators sought out small, dense schools of juvenile fish that aggregated within a larger prey field. We found that what matters to them is not the overall number of fish in a region, but how and where fish aggregate on a small scale.”
Sea gull

Black-legged kittiwake


The small-scale distribution of prey, or patchiness, is a much better predictor of a predator’s success than an overall concentration of prey, says Benoit-Bird. In other words, a predator is more likely to find food if it swims from one dense patch of prey to another — like a baseball player running the bases, she says — than if it swims through one large, diffuse aggregation.
Benoit-Bird notes that many management practices take into account the differences between regional aggregations of fish — but often do not consider the patchiness within them. “For predators, we now know that how prey is distributed is critical,” she says, “especially when three key predators with very different foraging strategies give us the same message. It’s a much stronger statement.”
Fur Seal Foraging
The second study focused on the foraging behavior of northern fur seals, employing innovative tracking tags that logged each seal’s movements in three dimensions, multiple times per second. This provided Benoit-Bird and her colleagues with a sophisticated set of behavioral data that could be plotted against the location of pollock prey patches.
northern fur seal

Northern fur seal resting


“We learned a lot about the foraging behavior of northern fur seals, and some of it is really surprising,” says Benoit-Bird. “For example, previous studies that analyzed scat (feces) on Bogosloff Island showed that fur seals don’t eat very much pollock, but their foraging movements in the water are really focused on juvenile pollock. This tells us that they’re using juvenile pollock as a basis for foraging even while they’re searching for other things to eat, like squid or mesopelagic fish.”
Using her baseball analogy, Benoit-Bird describes the fur seals as swimming between “bases” of pollock, but perhaps doing their most important eating between the bases. “To me, this suggests that while pollock may not be their preferred food, this strategy provides a basic safety net if they can’t find anything better to eat.”
A New Way of Seeing
Benoit-Bird’s job as a scientist is to find the story in the data. At first, the data she and her colleagues collected told a confusing story. “We weren’t finding predator-prey relationships that made any sense,” she says. “We had to go back to the data and let the animal’s behaviors guide us to the right answer. The exciting part was saying to them, ‘Tell us what matters, tell us what you’re looking at, what was it that made you pick this spot?’ and then having them teach us a new way of seeing them.”
benoit-bird-pollock

Juvenile walleye pollock


The Bering Sea Project enabled Benoit-Bird and her colleagues to study how multiple species interact in the same space and time, offering an unprecedented opportunity to collect and analyze multidisciplinary sets of data. This collaborative effort is lending new insights into the interactions between marine predators and their prey that could have profound implications for fish and wildlife management.
“We’re working with agencies responsible for assessing pollock stocks in the Bering Sea to optimize their survey protocols, so that they can accomplish their current objectives while taking into account new information from our science,” Benoit-Bird says. “Our work can potentially help them collect new information that we can analyze over time, giving better insights into long-term trends like regime shifts in ocean climate. We can’t go backward in time to the last oceanic regime shift, but we can think about how to move forward.”
 

PublicationsPUBLICATIONS

Prey patch patterns predict habitat use by top marine predators with diverse foraging strategies.
Benoit-Bird, K. J., B. C. Battaile, S. A. Heppell, B. Hoover, D. Irons, N. Jones, K. J. Kuletz, C. A. Nordstrom, R. Paredes, R. M. Suryan, C. M. Waluk and A. W. Trites. 2013.
PLoS ONE Vol 8(1):e53348.
abstract
Spatial coherence between predators and prey has rarely been observed in pelagic marine ecosystems. We used measures of the environment, prey abundance, prey quality, and prey distribution to explain the observed distributions of three cooccurring predator species breeding on islands in the southeastern Bering Sea: black-legged kittiwakes (Rissa tridactyla), thick-billed murres (Uria lomvia), and northern fur seals (Callorhinus ursinus). Predictions of statistical models were tested using movement patterns obtained from satellite-tracked individual animals. With the most commonly used measures to quantify prey distributions - areal biomass, density, and numerical abundance - we were unable to find a spatial relationship between predators and their prey. We instead found that habitat use by all three predators was predicted most strongly by prey patch characteristics such as depth and local density within spatial aggregations. Additional prey patch characteristics and physic al habitat also contributed significantly to characterizing predator patterns. Our results indicate that the smallscale prey patch characteristics are critical to how predators perceive the quality of their food supply and the mechanisms they use to exploit it, regardless of time of day, sampling year, or source colony. The three focal predator species had different constraints and employed different foraging strategies – a shallow diver that makes trips of moderate distance (kittiwakes), a deep diver that makes trip of short distances (murres), and a deep diver that makes extensive trips (fur seals). However, all three were similarly linked by patchiness of prey rather than by the distribution of overall biomass. This supports the hypothesis that patchiness may be critical for understanding predator-prey relationships in pelagic marine systems more generally.
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Foraging behavior of northern fur seals closely matches the hierarchical patch scales of prey.
Benoit-Bird, K. J., B. C. Battaile, C. A. Nordstrom and A. W. Trites. 2013.
Marine Ecology Progress Series 479:283-302.
abstract
Marine prey often occur in hierarchical mosaics whereby small, high-density patches are nested inside of larger, lower density aggregations. We tested the extent to which the foraging behavior of a marine predator (northern fur seal Callorhinus ursinus) could be explained by the hierarchical patch structure of a dominant prey species (juvenile walleye pollock Theragra chalcogramma) in the eastern Bering Sea. Comparing the movements of satellite-tracked fur seals with ship-based acoustic surveys of prey revealed that fur seals did not randomly search for prey, but instead showed deviations in the distribution of step-lengths (distances between their foraging patches) corresponding to the distances between aggregations of prey. Scales of prey distribution varied between Bering Sea shelf and deep-water slope habitats, while spatial scale distributions of fur seals showed corresponding changes, indicating that their search strategies were not innate patterns decoupled from the environment. Fur seals tended to avoid the smallest prey patches in both shelf and slope habitats. They also avoided prey patches that were separated by large distances. Fur seals responded to several levels of prey patchiness simultaneously, resulting in strong correlations between predator and prey over the entire range of aggregation scales observed in juvenile pollock. Our results indicate that, despite having a varied diet, fur seal foraging paths were defined by juvenile pollock aggregations. The presence of hierarchical, scale-dependent aggregation in both predator and prey provides new insights into fur seal behavior and a means to predict the dynamics of their interactions with prey.

keywords     Patchiness, Spatial scale, Predator–prey, Foraging behavior, Hierarchical, Northern fur seal, Juvenile walleye pollock
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At the heart of unraveling the precipitous decline of Western Alaska’s Steller sea lions are two key questions: What do they eat? And how much do they need to survive? But determining the diet of an animal that forages in the murky depths of the North Pacific Ocean is no easy feat.

rosen-tollit

Steller sea lions


Through a process of analyzing scat (feces) collected from on-shore mating and resting areas, scientists can determine a sea lion’s most recent meals but they cannot describe long-term dietary trends. Recently, new techniques have been developed that may help scientists look farther into a sea lion’s dietary history. In a paper published in the journal Marine Ecology Progress Series, Drs. David Rosen and Dominic Tollit (University of British Columbia) evaluated the usefulness of one method as it relates to Steller sea lions and northern fur seals.
“We focused our study on Quantitative Fatty Acid Signature Analysis, or QFASA, which was developed by Dr. Sara Iverson at Dalhousie University. It is a way of looking at the unique chemical makeup of a predator, and then backcasting the kind of prey it has eaten and how much,” says Dr. Rosen. “It’s based on the idea that ‘you are what you eat’—sort of.”
Calibration Coefficients Needed to Account for Real-World Physiology
“When a sea lion eats a fish, it absorbs some of the fish’s fatty acids into its blubber layer,” Rosen explains. “At the molecular level, this process creates a unique chemical signature in the sea lion’s blubber that is partly made up of the biochemistry of the different types of fish it eats. If the diet changes over the long term, the signature changes, too.” For Rosen and Tollit, this type of information about long-term dietary trends could provide valuable insights into the role of different diets in pinniped population changes.
rosen-tollit-2

Collecting Steller sea lion scat


Rosen and Tollit’s study focused on a key step in the QFASA process which generates a “physiological correction factor” called the calibration coefficient. QFASA attempts to match the known chemical signatures of the prey to its predator, but the predator’s physiological processes can alter the chemical signature of the prey once it is eaten. Calibration coefficients mathematically transform the chemical signature that appears in the predator, to the one that originally appears in the fish it consumed.
“Calibration coefficients might be unique for different groups of predators, but no calibration coefficients existed for any sea lions or fur seals,” says Rosen. “So the initial goal of our study was to come up with the first set of calibration coefficients for this group of animals.”

Rosen and Tollit worked with a cohort of trained Steller sea lions and northern fur seals housed at the Vancouver Aquarium. The animals were fed strict diets of herring and/or eulachon, and then blubber samples were analyzed using the QFASA method to establish a unique set of calibration coefficients for Steller sea lions and northern fur seals. They also re-examined some previously published work using harbor seals as a comparison.

rosen-tollit3

Northern fur seal at the Vancouver Aquarium


Implications for Field Research
“Our results showed a clear difference between the phocids (harbor seals) and otariids (fur seals and sea lions) as expected for such different groups of animals. What surprised us was the significant difference in calibration coefficients between the sea lions and fur seals that both ate herring,” says Rosen. There was also a surprising difference in the apparent calibration coefficients generated when the Steller sea lions were eating different types of fish. “This was all a bit shocking,” Rosen says, “because it suggests that the calibration coefficients generated in past captive studies may not be as widely applicable as scientists had thought.”

Hence, the development of the first calibration coefficients for Steller sea lions and northern fur seals provides a sobering perspective on what scientists currently know and don’t know—and it comes with a warning against misapplying species-specific calibration coefficients in studies with other species.

“Field researchers should be judicious in applying the specific calibration coefficients for the species they are studying. They should also be conservative when drawing conclusions about the diets of sea lions and fur seals derived from QFASA,” Rosen emphasizes.

rosen-tollit4

Steller sea lion at the Vancouver Aquarium

 

“Using the wrong calibration coefficient for a predator – even one that is closely related – can bring biases and misinterpretations about what the seals and sea lions actually eat.” He suggests that field researchers should not rely on a single technique to produce accurate results in something as complex as diet reconstruction, and a novel method such as QFASA should be used in conjunction with other analytical approaches.

Rosen believes it’s important for scientists to understand the limitations of their ability to answer key management questions—such as, what do they eat, and how much? “If you take the data past the point of the reliability of the technique itself,” he says, “you can incur some extreme consequences for the management and protection of the species.”

April 22, 2013
SEE PUBLICATION:

Effect of phylogeny and prey type on fatty acid calibration coefficients in three species of pinnipeds - implications for the QFASA dietary quantification technique.
Rosen, D. A. S. and D.J. Tollit. 2012.
Marine Ecology Progress Series 467:263-276.
abstract
Quantitative fatty acid signature analysis (QFASA) has been proposed as a technique for determining the long-term diet of animals. The method compares the fatty acid (FA) profiles of predators and potential prey items to estimate relative prey intake. We tested the assumptions of a key step in QFASA, the correction of predator FA signatures for metabolic processes through sets of calibration coefficients (CCs). We conducted long-term controlled feeding studies with captive Steller sea lions consuming herring and eulachon and northern fur seals consuming herring. We compared the results with data from harbour seals eating herring to evaluate the effects of phylogeny and prey type on individual CCs. Even within the limited extended dietary FA subset recommended for use by other researchers, we found that at least 41% of the CCs differed by family (otariid vs. phocid seals) and 58% differed by predator species (sea lion vs. fur seal), suggesting that CCs may be highly species- specific. We also found that 64% of the CCs differed by prey type (sea lions consuming herring vs. eulachon), which raises some fundamental implementation issues. We also found significant differences in diet predictions when the herring- and eulachon-derived sets of CCs were applied to an actual multi-species diet. CCs are presently used as a simple mathematical attempt to describe potentially complex biochemistry. The results of this study raise questions regarding the validity of using CCs derived from an alternative predator species, and highlight some fundamental issues regarding QFASA methodology that need to be addressed through further controlled studies.
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In the marine world, high-energy prey make for high-energy predators. And to survive, these marine predators need to sustain the right kind of high-energy diet. Not just any prey will do, suggests a new study by researchers from the University of British Columbia and University of La Rochelle, in France.
Common-Dolphin-Delphinus-delphis-2Published in the online journal PLOS ONE, the study is the first to show that the survival of whales and dolphins depends on the quality of their diets, which has implications for fisheries management and marine conservation.
“The conventional wisdom is that marine mammals can eat anything,” says co-author Andrew Trites, from the University of British Columbia. “However, we found that some species of whales and dolphins require calorie rich diets to survive while others are built to live off low quality prey—and it has nothing to do with how big the whales and dolphins are.”
The team compared the diets of 11 species of whales, dolphins and porpoises in the Northeast Atlantic Ocean, and found differences in the qualities of prey consumed that could not be explained by the different body sizes of the predators. The key to understanding the differences in their diets was to look at their muscle performance.
“High energy prey tend to be more mobile, and require their predators to spend more energy to catch them,” says Trites. “The two have co-evolved.”

A beached fin-whale (Balaenoptera physalus) being  measured by members of the French Stranding Network.

A beached fin-whale (Balaenoptera physalus) being
measured by members of the French Stranding Network.


Jérôme Spitz from the University of La Rochelle in France, the study’s first author, says the research will help assess the impact of resource changes to marine mammals.
“Species with high energy needs are more sensitive to depletion of their primary prey,” says Spitz, now a post-doctoral fellow at the University of British Columbia. “It is no longer a question of how much food do whales and dolphins need, but whether they are able to get the right kinds of food to survive.”
March 27, 2013
PUBLICATION:
Cost of living dictates what whales, dolphins and porpoises eat: the importance of prey quality on predator foraging strategies.
Spitz, J., A.W. Trites, V. Becquet, A. Brind'Amour, Y. Cherel, R. Galois and V. Ridoux. 2012.
PLoS ONE. Vol 7(11):e50096.
abstract
Understanding the mechanisms that drive prey selection is a major challenge in foraging ecology. Most studies of foraging strategies have focused on behavioural costs, and have generally failed to recognize that differences in the quality of prey may be as important to predators as the costs of acquisition. Here, we tested whether there is a relationship between the quality of diets (kJ g-1) consumed by cetaceans in the North Atlantic and their metabolic costs of living as estimated by indicators of muscle performance (mitochondrial density, n = 60, and lipid content, n = 37). We found that the cost of living of 11 cetacean species is tightly coupled with the quality of prey they consume. This relationship between diet quality and cost of living appears to be independent of phylogeny and body size, and runs counter to predictions that stem from the well-known scaling relationships between mass and metabolic rates. Our finding suggests that the quality of prey rather than th e sheer quantity of food is a major determinant of foraging strategies employed by predators to meet their specific energy requirements. This predator-specific dependence on food quality appears to reflect the evolution of ecological strategies at a species level, and has implications for risk assessment associated with the consequences of changing the quality and quantities of prey available to top predators in marine ecosystems.
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How does scientific marking and tagging affect marine mammals?

For decades, field researchers have applied paints, dyes, brands and telemetry tags to wild animals to track their movements and behaviors in nature. But does tagging or marking a wild animal change its behavior over time? Do marked marine mammals experience pain or suffering that changes their normal behavior on land or in water? How can we know?

Steller sea lion branding

A female Steller sea lion branded as a pup at Forrester Island in Southeast Alaska
and later photographed using a summer haulout in British Columbia.


These questions, framed in a new Consortium study published in the journal Wildlife Research, address important gaps in scientific understanding that could profoundly influence future field research. Animal welfare studies, such as this one, offer an important new dimension to the Consortium’s interdisciplinary field research program.
Motivated by her interest in the welfare of wild animals, PhD student Kristen Walker (University of British Columbia) and her colleagues reviewed a number of published studies that involved tagging and marking marine mammals. They found that very few studies focused on long-term impacts of marking on animal health, growth and behavior. They believe scientists have an opportunity to improve the way in which these types of field research are conducted and reported.
“After conducting an online literature search we found only 39 studies published since 1980 that specifically addressed the effects of marking on marine mammals, the majority of which were published after 2000,” says Walker, having since earned her PhD from UBC’s Animal Welfare Program. “Not all studies set out to test the direct effects of marking though—many only mentioned marking effects in passing. More studies have focused on the short-term effects of a device on an animal, but not the long-term effects.”
Steller sea lion branding

A female northern fur seal from St. Paul Island, Alaska, carrying biologging tags to collect data on where and how she obtains food
in the Bering Sea. The tags are later removed and any residual glue on the fur falls off when the animal molts. Research was conducted under NMSF Permit #14329

There was a wide range in the studies looking at marking effects. Some studies measured whether placing a satellite transmitter on a seal affected swimming behaviors, while others studied the pain associated with the controversial practice of hot-iron branding on sea lions. Others measured the overall survival of a group of tagged animals within a population.

“Our analysis identified the need for more species-specific studies to be conducted,” says Walker. “It may be problematic to generalize the results of studies between different species, such as elephant seals and bottlenose dolphins, because species may react differently to a particular device.”

ETHICAL STANDARDS

In the remote waters of the North Pacific Ocean, tagging and marking has played a critical role in helping scientists to identify and track endangered seals and sea lions. Consortium researchers have always approached this type of research with the highest ethical standards, says Science Director and study co-author Andrew Trites.

“Working one-on-one with sea lions and fur seals at the Vancouver Aquarium has profoundly influenced the ways in which we study marine mammals,” says Trites. “We can’t conserve wildlife if we rely on techniques that alter natural behaviors and physiological responses, because this would generate unreliable scientific results. Conservation and the welfare of animals must go hand in hand.”
Walker and Trites recommend that future studies with marked animals should use a standard format for reporting, which would include detailed descriptions of the methodology, monitoring and sampling design, and practices used to minimize the impacts of marking. This common framework would allow scientists to more closely compare published studies and choose the least harmful approach to tagging or marking.

Steller sea lion at open water station

Steller sea lion at open water research station

Steller sea lion branding

Kristen Walker makes behavioral observations of Steller sea lions at the Alaska SeaLife Center as part of her PhD research conducted under NMFS Permit #881-1890


The study conducted by Walker and colleagues describes eleven guidelines for minimizing the impact of marking on study animals, six of which are from previously published studies while five are new recommendations. The authors encourage researchers to publish all results of marking effects—especially studies that find a negative impact on the animals or the data, which often go unpublished. These studies provide important knowledge for adapting and refining approaches to marking and tagging.
BRIDGING THE GAP
As a Master of Science graduate student, Walker became concerned for the welfare of individual animals involved in field research. “I was working with sea otters who were being surgically implanted with radio-telemetry devices,” she says. “When I asked what would happen to the animals after surgery, little was known except that they typically survive—there was no mention of the pain associated with the surgery or how the surgery and tags might affect their long-term behavior. I was surprised to learn there was very little research conducted in this area. I decided to focus my future research efforts on trying to measure the impacts of marking devices to help reduce the possible suffering of tagged animals.”
Since then, Walker has tried to conduct research that can bridge the gap between animal welfare, which focuses on the individual animals, and conservation science, which focuses at the population level. “Combining these two disciplines allows for more attention to be placed on the individual animal, while still meeting overall conservation program goals,” she says.
Walker believes that a new movement to incorporate animal welfare practices into population-level studies is replacing an older mentality of sacrificing a few animals for the good of the many. She and other scientists are calling for increased funding for research in this area.
 

PUBLICATION:
A review of the effects of different marking and tagging techniques on marine mammals.
Walker, K. A., A. W. Trites, M. Haulena and D. M. Weary. 2012.
Wildlife Research 59:15-30.
abstract
Wildlife research often requires marking and tagging animals to collect data on survival, reproduction, movement, behaviour and physiology. Identification of individual marine mammals can be carried out using tags, brands, paint, dye, photogrammetry, telemetry and other techniques. An analysis of peer-reviewed articles published from January 1980 to April 2011 addressing the effects of marking revealed a preponderance of studies focussed on short-term effects such as injuries and behavioural changes. Some marking techniques were reported to cause pain and to change swimming and haul-out behaviour, maternal attendance, and duration of foraging trips. However,marking has typically not been found to affect survival. No published research has addressed other possible long-term effects of marking related to injuries or pain responses. Studies of the more immediate effects of marking (mostly related to externally attached devices such as radio-transmitters) have shown a variety of different types and magnitudes of responses. It is important to note that studies failing to find treament differences are less likely to be published, meaning that the present and any other reviews based on published literaturemay be a biased sample of all research conducted on the topic. Publishing results that found no or low impacts (i.e. best practices) as well as those that found significant impacts on animals should both be encouraged. Future research under more controlled conditions is required to document acute effects of marking, including injury and pain, and to better understand longer-term effects on health, reproduction and survival. We recommend that studies using marked animals standardise their reports, with added detail on methodology, monitoring and sampling design, and address practices used to minimise the impact of marking on marine mammals.
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Steller sea lions

Steller sea lions

Markus Horning spent the summer of 1998 in the remote Aleutian Islands, conducting research aboard the research ship M/V Tiglax. He spent many late nights pondering the absence of scientific data behind the steep decline of the region’s Steller sea lion populations.

“We needed data from the animals that had disappeared,” says Horning, now based at Oregon State University. “The experiments at the time focused on the animals that were healthy and accessible on land, not the ones that were sick or dying at sea. We rarely saw dead animals on rookeries or haulouts, where most sea lion studies were based.” This led to biased sampling, he explains, which he believes led to skewed scientific advice on the overall health of the population.

Horning’s experiences aboard the Tiglax inspired him to spend the next several years developing a Life History Transmitter that could be harmlessly carried by young sea lions and which would monitor them throughout their life. Most importantly, it would collect valuable information at the end of their lives about when, where and why they died.

Pattern of Predation

In 2012, Horning and co-author Jo-Ann Mellish (Alaska Sea life Centre) published in the journal PloS ONE an analysis of life history data they had collected from 2005-2011. Over that time, 16 of the 36 tagged sea lions had died, which was not a surprise to Horning. What did surprise him was the way in which most had died. “In 14 of 16 cases, the animals were killed by a predator, such as a transient killer whale or a large shark,” Horning explains. “Steller sea lions have a hard life, and many die young—fewer than half make it to reproductive age. But based on our findings, almost all of that mortality may be due to predation rather than starvation, disease, trampling, or competition. We believe none of those factors are nearly as impactful as predation.”

Horning and Mellish’s study challenges a highly cited 2007 study by Holmes et al., who created a demographic model and suggested the decline was largely due to a drop in birth rates. Horning says that model, which was “broadly embraced as the conceptual centerpiece of policy and management,” largely ignored the impacts of predation. In response, Horning and Mellish devised a density-dependent conceptual framework to consider the role of predation in population dynamics.

Conceptual Thinking

 “Our framework is really a thinking exercise, a what-if scenario that we play through,” he says. “We’re not trying to work with numbers, we’re simply asking questions like, Is it possible that certain demographic information is driven by predation and not just by the decline in birth rates? In this case, yes, it’s possible that these things are linked, which highlights knowledge gaps and gives us an idea of what to look for.”

How a Life History Transmitter Works

From 2005-11, Horning and Mellish implanted two small Life History Transmitters in 16 juvenile Steller sea lions in a surgical suite at the Alaska SeaLife Center. The second tag was a fail-safe in case the first tag stopped working properly.

Each tag constantly records the surrounding temperature, the amount of light, and the types of tissue surrounding the tag. These and other data are uploaded to a satellite whenever the sea lion surfaces.

When the host animal dies, the tag records a change in the surrounding temperature. In a violent (predatory) death, the tag is instantly liberated as the animal is dismembered, and the tag records a sudden drop in temperature and an increase in light levels.

In a non-violent death, the tag usually stays inside the body and records a gradual cooling. As the body decomposes or is scavenged, the tag is released and floats to the surface where it senses light. “Plugging this information into our conceptual framework, one impact of predation may be to crimp recruitment, or the number of young animals who eventually reach reproductive age,” Horning says. “This leads to fewer adult females in a population who are capable of giving birth. This alone could easily make it look as if the birth rate has gone down.”According to the data collected by Horning and Mellish’s life history transmitters, predation rates on Steller sea lions were higher in the first year after weaning, and declined after that. Predators seemed to take young sea lions more often than older ones.

Killer whales preying on Steller sea lions

Steller sea lions with transient killer whale.

Even if birth rate was constant, Horning says predation could drive the decline of a population because of density dependence—an ecological concept that states the behavior of an animal may change as the density of its predators or prey changes. This concept allowed Horning and Mellish to explore a number of hypothetical ecological scenarios.

“Imagine if 1,000 transient killer whales ate 5,000 Steller sea lions per year,” Horning explains. “This wouldn’t have much of an impact in a population of 200,000 Steller sea lions. But if the sea lion population declines to 20,000 and the predators’ behavior doesn’t change, those 5,000 Stellers eaten each year now have a huge impact on population trajectory. However, because it is more difficult to find prey in a smaller population, the killer whales would likely start looking for something else. These are the types of questions we ask in a density-dependent framework.”

Advice for Managers

Horning and Mellish reject the recent hypothesis that juvenile survival rates have recovered while birth rates have declined. Instead, they suggest that predation on juvenile sea lions is the single largest impediment to the recovery of the species in the eastern Gulf of Alaska, and they call for demographic models that use age-structured census data, so the effects of predation on different age classes can be understood.

Horning cautions against extrapolating the results of this study too widely, noting: “Our model is not talking about what triggered the decline of Steller sea lions. We’re talking about what is driving the population trajectory right now in the eastern Gulf of Alaska, in the context of this thinking exercise.”

He does hope the density-dependent conceptual framework will jump-start a languishing discussion on how to effectively manage Steller sea lion populations in the face of predation. He notes that fisheries managers often assess the health of a population by looking at birth rate, not death rate—but Horning believes this is an overly simplistic model.

“We can’t point out anything more than saying there’s a lot of predation,” Horning admits, “and the response of fisheries managers could be, so what? But our conceptual model helps to consider the potential impacts of changes in predation, recruitment and the birth rate. For example, our model suggests that simply increasing the birth rate won’t necessarily overcome the impacts of predation—only reducing predation will help to restore a balance.”

 

PUBLICATION


2012
 
Predation on an upper trophic marine predator, the Steller sea lion: evaluating high juvenile mortality in a density dependent conceptual framework.
Horning, M. and J.-A.E. Mellish. 2012.
PLoS ONE. Vol 7(1):e30173
abstract
The endangered western stock of the Steller sea lion (Eumetopias jubatus) ˆ the largest of the eared seals ˆ has declined by 80% from population levels encountered four decades ago. Current overall trends from the Gulf of Alaska to the Aleutian Islands appear neutral with strong regional heterogeneities. A published inferential model has been used to hypothesize a continuous decline in natality and depressed juvenile survival during the height of the decline in the mid-late 1980‚s,followed by the recent recovery of juvenile survival to pre-decline rates. However, these hypotheses have not been tested by direct means, and causes underlying past and present population trajectories remain unresolved and controversial. We determined post-weaning juvenile survival and causes of mortality using data received post-mortem via satellite from telemetry transmitters implanted into 36 juvenile Steller sea lions from 2005 through 2011. Data show high post-weaning mortality by predation in the eastern Gulf of Alaska region. To evaluate the impact of such high levels of predation, we developed a conceptual framework to integrate density dependent with density independent effects on vital rates and population trajectories. Our data and model do not support the hypothesized recent recovery of juvenile survival rates and reduced natality. Instead, our data demonstrate continued low juvenile survival in the Prince William Sound and Kenai Fjords region of the Gulf of Alaska. Our results on contemporary predation rates combined with the density dependent conceptual framework suggest predation on juvenile sea lions as the largest impediment to recovery of the species in the eastern Gulf of Alaska region. The framework also highlights the necessity for demographic models based on age-structured census data to incorporate the differential impact of predation on multiple vital rates.
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Pribilof Islands

Every October in Alaska’s remote Pribilof Islands, thousands of four-month-old northern fur seals take to the frigid waters of the Bering Sea. They don’t return for nearly two years. Exactly how they survive in those first two years remains a mystery, but scientists do know it is a critical period for growth and survival.If a young fur seal can find enough energy-rich food in summer, it can endure the scarce winter months. But how much food is enough, and what kinds of fish are best? Can we predict how much food an entire population might need?
These questions are at the heart of a new Consortium study that examines the digestive capacity of young northern fur seals. The study, published in the Canadian Journal of Zoology, gathered important baseline estimates of the maximum food intake levels of young fur seals, in summer and winter, and the consequences of differences in food intake during these seasons.

Northern Fur Seal Pup

“Young animals are usually living on the edge at the best of times, and it doesn’t take much to push them over that edge so that they don’t survive,” says Dr. David Rosen (UBC Marine Mammal Research Unit), the study’s lead author. “This study gives us a better idea of where that edge might be and what might push them over it.”
northern fur seal eatingSatiation Study
Over three months, six female northern fur seals housed at the Vancouver Aquarium were given unlimited access to Pacific herring for eight hours a day. The seals were divided into two groups that were fed either daily or every other day, allowing Rosen and colleagues to study the effects of periodic interruptions in their food supply.The feeding trials were replicated in summer, when the seals were 10-13 months old, and in winter, when the seals were 17-19 months old.
The study produced three key results. First, the seals appeared to be satiated (or “full”) after consuming about 26% of their body mass in herring in summer, and 20% in winter. Rosen compares this to a food buffet: although people stack their plates full, there’s a limit to how much they can actually eat. The seals consistently ate the same amount in both seasons (2.9 kg/day), but Rosen says the consumption relative to body mass appears lower in winter because they typically weigh more in winter.
Second, the seals that fasted on alternate days did not eat more on feeding days to compensate for not eating the day before. The constant rate of feeding between the daily group and the alternating group was a surprise—the scientists had expected the seals to respond to an interruption in their food supply by eating more.
northern fur seal weigh inThird, the seals gained less weight in winter than in summer, despite an unlimited food supply and consistent feeding rates in both seasons. “Surprisingly, when the seals ate more food, they didn’t convert that into growth very efficiently,” says Rosen, pointing out that growth is not just regulated by how much food is eaten, but also by how their physiology uses that food.
“In the summer the extra food they were eating turned into higher growth rates, but they’re down-regulating their physiology at times of year such as in winter months when they’re likely less able to find high-quality prey,” he says. “They’re just not set up to process huge amounts of food in winter, and it was probably just passing through their system.”
Data for decision-makers
The seasonal changes in growth and in food requirements for northern fur seals have important implications for wildlife managers, Rosen says, who suggests that food resources such as fish stocks need to be managed on a seasonal basis. The baseline data produced by this study are useful in ecosystem models that attempt to forecast the interactions between northern fur seal populations, their prey and their environment.
“We normally don’t have the opportunity to see northern fur seals at this age because they’re at sea,” Rosen says. “We learned that they really need to eat certain amounts of prey at certain times of year because that’s when they’re physiologically programmed to grow. They’re like a revved-up engine, and if they don’t get the fuel they need, they lose body mass and become less healthy—and they might not be able to make up that deficit later in life.”
 
PUBLICATION

Rates of maximum food intake in young northern fur seals (Callorhinus ursinus) and the seasonal effects of food intake on body growth.
Rosen, D., B.L. Young and A.W. Trites. 2012.
Canadian Journal of Zoology 90:61-91.
abstract
Accurate estimates of food intake and its subsequent affect on growth are required to understand the interaction between an animals‚ physiology and its biotic environment. We determined how food intake and growth of 6 young northern fur seals (Callorhinus ursinus L., 1758) responded seasonally to changes in food availability. Animals were given unrestricted access to prey for 8 hr per day on either consecutive days or on alternate days only. We found animals offered ad libitum food on consecutive days substantially increased their food intake over normal Œtraining‚ levels. However, animals that fasted on alternative days were unable to compensate by further increasing their levels of consumption on subsequent feeding days. Absolute levels of food intake were highly consistent during winter and summer trials (2.7 ˆ 2.9 kg d-1), but seasonal differences in body mass meant that fur seals consumed more food relative to their body mass in summer (~27%) than in winter (~20%). Despite significant increases in absolute food intake during both seasons, the fur seals did not appear to efficiently convert this additional energy into mass growth, particularly in the winter. These seasonal differences in conversion efficiencies and estimates of maximum intake rates can be used to generate physiologically realistic predictions about the effect of changes in food availability on an individual fur as well as the consequences for an entire population.
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New study examines how transient killer whales communicate

first published March 2012
For transient killer whales on the hunt, making the slightest sound can mean the difference between a hard-won meal and an empty stomach. Their marine mammal prey—mostly seals and sea lions—have finely tuned hearing that quickly alerts them to danger.

Transient Killer whale
Transient killer whale with Steller sea lions on the rocks.

As a result, transient killer whales have complex rules around the audible clicks, whistles and pulsed calls they make. While echolocation clicks are primarily used for navigation and prey detection, pulsed calls and whistles are important social signals that help members of a group to recognize one another, stay together, and coordinate behaviors.
In a recent study published in the journal Behavioral Ecology and Sociobiology, Consortium scientists conducted the first-ever investigation into how transients use whistles compared to their fish-eating cousins, the resident killer whales.
“Here, we investigated the whistling behavior of mammal-eating killer whales and, based on divergent social structures and social behaviors between residents and transients, we expected to find differences in both whistle usage and whistle parameters,” write co-authors Dr. Volker Deecke of the Marine Mammal Research Unit at the University of British Columbia, and Dr. Rüdiger Riesch of the Department of Biology at North Carolina State University.

Transient whistle
spectogram

Listen to sound sample:
Transient Whistle sample

Riesch and Deecke had hypothesized that transient killer whales should use whistles preferentially over pulsed calls in many contexts because whistles are higher in frequency and therefore not audible to other species over the same distances as pulsed calls. However, they found no support for their hypothesis. Instead of switching from calls to whistles, transient killer whales seem to go completely mum—presumably because even the less detectable whistles can still reduce hunting success by alerting their potential prey to their presence.
The Strong, Silent Type
Riesch and Deecke painstakingly analyzed approximately 60 hours of recordings of West Coast transients ranging from Monterey Bay, California to Glacier Bay, Alaska. Using real-time spectrographic analysis, they searched the recordings for whistles, then analyzed the acoustic profile of each whistle and classified it as stereotypical (frequent and recurring) or variable (infrequent or unique).

Transient whistle
spectogram

Transient Whistle sample 2

Their results showed that West Coast transient killer whales whistled only after making a kill or when they were engaged in social activities, as indicated by tail- and fin-slaps, breaches and spy-hops, and they were almost completely silent during all other activities. All West Coast transients seem to share a population-specific repertoire of stereotypical whistles that is clearly distinct from and less complex than that of resident killer whales.
The acoustic profiles of transient whistles showed properties more consistent with a “public” broadcast communication than a “private” one designed to avoid eavesdroppers. Transient whistles generally have lower dominant frequencies, narrower frequency ranges, a shorter duration and fewer frequency modulations—making them more similar to the public whistles of resident killer whales.
Why Whistle?
Does this mean that transient killer whale whistles serve an entirely different purpose than resident whistles? The authors speculate that while the acoustic profiles of resident and transient whistles were very different, they could share a similar function in instances such as food sharing after a kill. In these types of activities, the rate of transient whistles increased. In instances such as foraging, it appears that transients prefer not to communicate at all than risk alerting their prey.
“Hence, the main strategy of transients to minimize detection by potential prey is to limit vocal communication to certain behavioral contexts, making detection based on whistle recognition by prey impossible during foraging, regardless of a potential receiver’s hearing capabilities,” write Riesch and Deecke. “This in turn seems to have relaxed the selection on making whistles acoustically private.”
In the complex underwater world of transient killer whales, a whistle can be a dead giveaway to potential prey. Whistles are only welcome after a kill is made and there is no longer a need for stealth, which may explain why the behavioral context of resident and transient whistles are so different.
PUBLICATION:

Whistle communication in mammal-eating killer whales (Orcinus orca): further evidence for acoustic divergence between ecotypes.
Riesch, R. and V.B. Deecke. 2011.
Behavioral Ecology and Sociobiology 65:1377-1387.
abstract
Public signaling plays an important role in territorial and sexual displays in animals; however, in certain situations, it is advantageous to keep signaling private to prevent eavesdropping by unintended receivers. In the northeastern Pacific, two populations of killer whales (Orcinus orca), fish-eating resident killer whales and mammal-eating transient killer whales, share the same habitat. Previous studies have shown that residents use whistles as private signals during close-range communication, where they probably serve to coordinate behavioral interactions. Here, we investigated the whistling behavior of mammal-eating killer whales, and, based on divergent social structures and social behaviors between residents and transients, we predicted to find differences in both whistle usage and whistle parameters. Our results show that, like resident killer whales, transients produce both variable and stereotyped whistles. However, clear differences in whistle parameters between ecotypes show that the whistle repertoire of mammal-eating killer whales is clearly distinct from and less complex than that of fish-eating killer whales. Furthermore, mammal-eating killer whales only produce whistles during milling after kill and surface-active behaviors, but are almost completely silent during all other activities. Nonetheless, whistles of transient killer whales may still serve a role similar to that of resident killer whales. Mammal-eating killer whales seem to be under strong selection to keep their communication private from potential prey (whose hearing ranges overlap with that of killer whales), and they appear to accomplish this mainly by restricting vocal activity rather than by changes in whistle parameters.
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Using DNA analysis to solve a dietary dilemma

The mysterious decline of Steller sea lions in Western Alaska presents a complex scientific puzzle with many possible causes. One leading hypothesis suggests that changes in the availability of their key prey causes “nutritional stress” that affects their ability to survive and reproduce. This prompts several important questions: what kinds of prey are Steller sea lions eating, and how does this pattern vary between regions?
bowles-wild
Seeking answers to these questions involves a combination of field and laboratory research, says Ella Bowles (The University of British Columbia), who led a study testing the effectiveness of a sophisticated DNA analysis technique called real-time polymerase chain reaction (PCR) to advance dietary research in the field. Her study was recently published in Molecular Ecology Resources.
“The main disadvantage in field research is that it’s difficult to assess what and how much a Steller sea lion is eating, when they spend so much time in the water, foraging out of view,” says Bowles. “We needed to find a non-invasive way to assess their diet that didn’t involve watching the animals forage.”
 

steller sea lions

Steller sea lions at the Vancouver Aquarium being fed in Bowles’ feeding trials


 
Bowles’ study builds on prior research that proposes techniques for analyzing the contents of feces, or scat, collected from wild Steller sea lions. She tested the use of real-time PCR—a widely used DNA visualization technique—to determine the relative proportions of DNA from different types of prey found in scat samples.
DNA Cocktails
The primary goal of Bowles’ study was to verify the accuracy of real-time PCR in estimating the quantity of prey in a fecal sample. Her first step was to analyze a series of “DNA cocktails” she created by extracting DNA from rockfish, herring, squid and eulachon and combining them in various proportions. When the PCR analysis returned a result that was within 12% of the actual prey proportions, she knew she was ready to test her technique on field samples.
Scat Sampling
Fortunately, Consortium researchers had archived many fecal samples from a diet study conducted with Steller sea lions at the Vancouver Aquarium in 2006. Bowles extracted the DNA from these samples and found an encouragingly consistent and accurate picture of the diet consumed by the animals. This affirmed her technique, but left her with a nagging question: what about the huge range of diets across different areas of the North Pacific? What happens when the relative proportions of consumed prey changes?
Scat sampling

Scat sampling


Bowles constructed a third study in which she fed 10 different diets to captive Steller sea lions at the Vancouver Aquarium, and analyzed the scats they produced. By focusing on the mitochondrial DNA (mtDNA) of each prey type in the scat samples, she was able to quantify the relative amounts of mtDNA in a sample to within 12%, including mtDNA from very small proportions of prey in single samples.
Advancing Policy
“My study focused on two components: what sea lions are eating, and how much,” Bowles says. “We showed that real-time PCR analysis can accurately provide quantitative information from fecal material, and I certainly see other researchers using this as a springboard to study other top-level species, such as walrus or northern fur seals.”
Bowles at work
Bowles acknowledges that real-time PCR is just one of several tools which, used together, provide an accurate snapshot of Steller sea lion diets. However, she is excited at the potential of real-time PCR to offer a potentially game-changing tool for wildlife management in a number of species, including terrestrial animals. She says the quantitative information it provides about diets could eventually be incorporated into complex ecosystem models, which in turn may be used to evaluate fisheries and wildlife management policies governing entire populations.
“We still need a model to connect the proportion of prey consumed with the total prey biomass in a region,” Bowles acknowledges. “But real-time PCR can be done very quickly to establish an instantaneous snapshot of an area, which is useful for field researchers. It is a nice complement to other analytic techniques, and it helps to provide a more complete picture of the relationship between Steller sea lions and their prey.”
 

PUBLICATION

Proportion of prey consumed can be determined from faecal DNA using real-time PCR.
Bowles, E., P.M. Schulte, D.J. Tollit, B.E. Deagle and A.W. Trites. 2011.
Molecular Ecology Resources 11:530-540.
abstract
Reconstructing the diets of pinnipeds by visually identifying prey remains recovered in faecal samples is challenging because of differences in digestion and passage rates of hard parts. Analyzing the soft-matrix of faecal material using DNA-based techniques is an alternative means to identify prey species consumed, but published techniques are largely non-quantitative, which limits their usefulness for some studies. We further developed and validated a real-time PCR technique using species-specific mitochondrial DNA primers to quantify the proportion of prey in the diets of Steller sea lions (Eumetopias jubatus), a pinniped species thought to be facing significant diet related challenges in the North Pacific. We first demonstrated that the proportions of prey tissue DNA in mixtures of DNA isolated from four prey species could be estimated within a margin of ~12% of the percent in the mix. These prey species included herring Clupea palasii, eulachon Thaleichthyes pacificus, squid Loligo opalescens and rosethorn rockfish Sebastes helvomaculatus. We then applied real-time PCR to DNA extracted from faecal samples obtained from Steller sea lions in captivity that were fed 11 different combinations of herring, eulachon, squid and Pacific ocean perch rockfish (Sebastes alutus), ranging from 7-75% contributions per meal (by wet weight). The difference between the average percentage estimated by real-time PCR and the percentage of prey consumed was generally less than 12% for all diets fed. Our findings indicate that real-time PCR of faecal DNA can detect the approximate relative quantity of prey consumed for complex diets and prey species, including cephalopods and fish.
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Scientists believe the precipitous decline of Western Alaska’s sea lion populations is driven by changes in the availability of their prey. However, relatively little is known about how much food they need to remain healthy, or how much energy they expend in day-to-day activities like swimming and foraging.
young2
Two new Consortium studies led by Beth Young evaluated the relationship between feeding, activity, heart rate, and energy expenditure. While scientists cannot directly measure the energy a wild sea lion expends, previous studies have established an equation that predicts oxygen consumption (a proxy for energy expenditure) based on heart rate, which is easily measured.
However, the previous equation was calibrated with animals that were resting on land and not feeding. Young and colleagues investigated whether this equation could apply to animals swimming at sea and searching for food.
“An exercise treadmill is a good analogy for how energy expenditure can be estimated from heart rate,” Young says. “The treadmill’s heart rate monitor predicts the number of calories we burn when running or walking, according to a specific equation for that type of exercise. But it does not consider your digestive state, and it is not accurate for other types of exercise. Our study attempted to calibrate a similar equation for sea lions when they are diving or feeding, and not just while they are resting on dry land.”
Land and sea
Young and colleagues examined three potential influences on the relationship between heart rate and oxygen consumption: environment (land vs. water), feeding (fed vs. fasted), and diving (single vs. consecutive). In the first of two studies, published in the Journal for Comparative Physiology, they measured heart rate and respiration in captive Steller sea lions on dry land, in water, and in open water. The sea lions had either been recently fed or had fasted overnight.
“Environment made a big difference,” Young notes. “The relationship between heart rate and oxygen consumption was completely different on land than in water, which suggests that a separate equation is needed to estimate energy spent in swimming animals.”
This is probably because marine mammals have an automatic dive response in water that is absent on land, Young says, which lowers the heart rate and shunts blood away from the extremities.
“The dive response in marine mammals is part voluntary and part involuntary, and it varies with the depth and duration of the dive,” says Young. “Even submergence in shallow water can cause a mild involuntary dive response. We see the same thing in humans — our heart rate drops when we submerge our faces in cold water, even for a few seconds.”
Young and colleagues had expected that feeding would also influence the relationship between heart rate and oxygen consumption in both environments, but found that feeding only had an effect if the sea lion was in water. On land, the equation held true whether the animal was fed or fasted. The size of the meal also had an effect on the heart rate relationship in water, but not on land.
Dives and debts
In a related study published in the Journal of Experimental Biology, Young and colleagues measured heart rate and respiration in active Steller sea lions after single dives and successive dives, or dive bouts. Unlike previous diving studies with captive animals, these dives were made in an open water environment and simulated natural underwater foraging, including feeding at realistic depths (up to 40m) and diving for realistic lengths of time (2-8 min).

young

Steller sea lion wearing a harness holding a heart rate monitor.

“We demonstrated that heart rate can predict oxygen consumption in individual dives, and that neither depth nor dive duration changed that relationship,” says Young. “But a different equation is needed for dive bouts. We found the relationship only held true over complete dive cycles that included the surface interval following the dive bout.”

A diving animal incurs an oxygen debt during the dives that is paid back at the surface, Young explains. In a single dive, the oxygen debt likely is not large enough to change the relationship between heart rate and oxygen consumption, but over multiple dives the animal accumulates a greater oxygen debt, which does influence that relationship.
In the wild
Ultimately, Young believes her research provides researchers with valuable insights to help assess metabolic rates of wild Steller sea lions.
“By temporarily attaching a heart rate data logger on a wild sea lion, one could predict metabolic rate from its heart rate — with the right equations,” she says. “This is particularly important in identifying how much energy nutritionally stressed animals expend, because it enables us to estimate how much food they need to eat to remain healthy. It also helps fisheries managers assess how much fish is required by wild sea lion populations, versus how much is available.”
Heart rate can predict metabolism, Young concludes, but it cannot be done using a single predictive equation. The relationship between heart rate and energy expenditure differs according to whether the sea lion is on land or in water, whether it has a full or empty stomach, and whether it is diving to depth or swimming along the surface. Thus, separate equations are needed to distinguish among environmental, digestive and diving states. Young recommends modifying the current equations that are based on fasting animals to account for the more realistic activities that sea lions undertake in the wild.
 
September 7, 2011
PUBLICATION:

Environment and feeding change the ability of heart rate to predict metabolism in resting Steller sea lions (Eumetopias jubatus).
Young, B. L., D.A.S. Rosen, M. Haulena, A. G. Hindle and A.W. Trites. 2011.
Journal of Comparative Physiology-B 118:105-116.
abstract
The ability to use heart rate (fh) to predict oxygen consumption rates (VO2) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established fh:VO2 relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed whether fh could accurately predict VO2 in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations to describe the fh:VO2 relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh:VO2 relationship on land. However, Steller sea lions in water displayed a different fh:VO2 relationship after consuming a 4 kg meal compared to the fasting condition. Incorporating comparable published fh:VO2 data from Steller sea lions showed a distinct effect of feeding after a 6 kg meal. Ultimately, our study illustrated that both feeding and physical environment are statistically relevant when deriving VO2 from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current bioenergetic models with data gathered using these predictive fh:VO2 equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological, behavioral, and environmental states.
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Dive behaviour impacts the ability of heart rate to predict oxygen consumption in Steller sea lions (Eumetopias jubatus) foraging at depth.
Young, B. L., D. A. S. Rosen, A. G. Hindle, M. Haulena and A. W. Trites. 2011.
Journal of Experimental Biology 214:2267-2275.
abstract
The predictive relationship between heart rate (fH) and oxygen consumption (VO2) has been derived for several species of marine mammals swimming horizontally or diving in tanks to shallow depths. However, it is unclear how dive activity affects the fH:VO2 relationship and whether the existing equations apply to animals diving to deeper depths. We investigated these questions by simultaneously measuring the fH and VO2 of Steller sea lions (Eumetopias jubatus) under different activity states (surface resting or diving), types of dives (single dives or dive bouts), and depths (10 or 40m). We examined the relationship over dives only and also over dive cycles (dive + surface interval). We found that fH could only predict VO2 over a complete single dive cycle or dive bout cycle (i.e. surface intervals had to be included). The predictive equation derived for sea lions resting on the surface did not differ from that for single dive cycles. However, the equation derived over dive bout cycles multiple dives + surface intervals) differed from those for single dive cycles or surface resting, with similar fH for multiple dive bout equations yielding higher predicted VO2 than that for single dive bout cycles (or resting). The fH:VO2 relationships were not significantly affected by dive duration, dive depth, water temperature or cumulative food consumed under the conditions tested. Ultimately, our results demonstrate that fH can be used to predict activity-specific metabolic rates of diving Steller sea lions, but only over complete dive cycles that include a post-dive surface recovery period.
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As Steller sea lions decline in parts of the North Pacific Ocean, Consortium scientists are working to understand how sea lions can be affected by changes in their ocean environment.
Swimming and diving are key activities that consume a good deal of metabolic energy. By measuring the energetic “costs” associated with foraging dives and with surface swimming between locations, scientists can estimate the potential impacts of shifts in the ocean environment. A change in ocean currents or ice patterns could affect the location of important prey, or restrict access to key foraging grounds.
hindle
Working with trained Steller sea lions in an open water environment, Consortium researchers conducted two studies investigating the energetic cost of transiting between locations, and the physiological response to shallow and deep dives. The studies were published in Aquatic Biology and the Journal of Experimental Marine Biology and Ecology.
Cost of Commuting
Commuting between shore and prey fields accounts for a significant portion of a sea lion’s energy budget. For nursing females who cannot leave their pups for long, it is especially important to make each trip as energy efficient as possible.
hindle2“Considerable research has focused on the energetics of otariid diving, particularly on the relationship between diving exercise and foraging effort,” writes lead author Dr. Allyson Hindle of the Marine Mammal Research Unit at UBC, who led both studies. “On the other hand, studies directly addressing transit swimming are less numerous, with many confined by experimental logistics to surface swimming only.”

Hindle and colleagues overcame those experimental logistics by conducting their study in open water with Steller sea lions trained to follow a moving boat at different speeds and depths. The scientists measured the duration of each transit dive as well as overall body activity. The study used activity as a proxy for metabolic expenditure, and the researchers measured fore-flipper stroking and overall dynamic body acceleration (ODBA) in three dimensions.

“Sea lions appeared to increase efficiency while transiting at depths that approached three times their body diameters,” the authors report, suggesting an optimal depth for commuting to and from foraging areas. Transiting at faster speeds required more frequent and powerful flipper strokes, while transiting against the tidal flow produced either a more powerful stroke or a parallel increase in stroke frequency.
“Our data demonstrate that small changes in the physical environment affect transiting in Steller sea lions,” note the authors, “and imply that altered prey fields or changing ocean conditions can carry energetic consequences.”
hindle3
Dive Dilemna
In a separate study, Hindle and colleagues measured behavioral and physiological changes in the same trio of Steller sea lions during shallow and deep dives. Like all marine mammals, the physiology of Steller sea lions is adapted to prolonged breatholding and underwater activity. The automatic dive response, called bradycardia, automatically slows the heart rate and shunts blood away from non-essential areas to conserve oxygen.
This seemingly contradictory response to exercise – which in an aerobic environment would elevate the heart rate and increase circulation – presents a physiological conundrum. Of particular interest to scientists is the point at which the dive response overrides the exercise response.
hindle4“Our study objective was to determine the relationship between heart rate and underwater locomotion in a diving Steller sea lion,” the authors write. They measured diving heart rate using heart rate monitors and measured activity using ODBA and flipper stroking. They also compared the patterns of bradycardia over single dives and bouts of consecutive dives.
The dive depth and distance simulated realistic wild scenarios for foraging Steller sea lions. The sea lions in this study displayed bradycardia during all dive trails regardless of depth, but the degree of bradycardia varied with depth.
“We found the mean heart rate of Steller sea lions trained to voluntarily dive to depths of up to 40m dropped by 40% while diving, and noted that mean bradycardia was 9% greater during shallow (10m) compared to deep (40m) dives,” write Hindle and colleagues. “Longer dives resulted in lower heart rates, but only when they were shallow; on the other hand, minimum instantaneous heart rate decreased consistently with dive duration.
“Ultimately,” the authors conclude, “our data support the speculation that Steller sea lion locomotory muscles become hypoxic during diving, regardless of dive depth.”
January 14, 2011
 
PublicationsRELATED PUBLICATIONS:

Dive response differs between shallow- and deep-diving Steller sea lions (Eumetopias jubatus).
Hindle, A.G., B.L. Young, D.A.S. Rosen, M. Haulena and A.W. Trites. 2010.
Journal of Experimental Marine Biology and Ecology 394:141-148.
abstract
Muscle exercise correlates with oxygen use, tissue perfusion and heart rate (fH) in terrestrial animals, but the relationship between these physiological processes is less clear in diving animals. We found the mean heart rate of Steller sea lions trained to voluntarily dive to depths up to 40m dropped by 40% while diving, and noted that mean bradycardia was 9% greater during shallow (10m) compared to deep (40m) dives. Longer dives resulted in lower heart rates, but only when they were shallow; on the other hand, minimum instantaneous fH decreased consistently with dive duration. In general, instantaneous fH did not reflect activity over short timescales. Our data suggest that our sea lions invoked a different dive response depending on whether they dove to shallow or deep depths. During shallow (10m) dives only, the correlation between activity and fH was indicative of vascular compromise between diving and exercise. However, during deep dives (40m), there was no such correlation, suggesting that locomotory activity was uncoupled from dive bradycardia, which was possibly mediated by an absence of blood flow to active muscle. For both diving scenarios, surface fH correlated with dive activity, suggesting that some underwater locomotory costs were deferred to the post-dive surface interval. Ultimately, our data support the speculation that Steller sea lion locomotory muscles become hypoxic during diving, regardless of dive depth.
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Swimming depth and ocean currents affect transiting costs in Steller sea lions (Eumetopias jubatus).
Hindle, A.G., D.A.S. Rosen and A.W. Trites. 2010.
Aquatic Biology 10:139-148.
abstract
Transit costs associated with commuting between resting sites ashore and foraging areas at sea are an appreciable portion of foraging expenditures in pinnipeds. We examined transit swimming in three Steller sea lions (Eumetopias jubatus) trained to follow a moving boat at different speeds and depths. We measured dive behavior (duration) and focused specifically on activity measures (fore-flipper stroking and ODBA, an overall measure of body motion), which may be proxies for metabolic expenditure. Sea lions appeared to increase efficiency while transiting at depths that approached three times their body diameters (mean depth = 151 ± 1 cm SEM, n = 87). Although the response was not uniform for all tested scenarios, all of the significant adjustments we observed to dive behavior and swimming mechanics supported an increased efficiency at this depth. An increase in transit speed (4.5 versus 3.5 knots surface speed) was associated with elevated flipper stroke frequencies (+5%) and stroke output (ODBA•stroke-1, +48%). Sea lions transiting against the flow of a tidal current had reduced dive durations (-10%), while total ODBA was consistently elevated (+8% overall). This response to tidal flow was accompanied either by elevated ODBA•stroke-1 (3.5 knots) or a parallel increase in stroking (4.5 knots). Our data demonstrate that small changes in the physical environment affect transiting in Steller sea lions, and imply that altered prey fields or changing ocean conditions can carry energetic consequences.
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The sleek dorsal fin of a killer whale is an unmistakable sight in any ocean, but to the practiced eye of a marine biologist, a fin is as good as a fingerprint. Clues from the fin’s shape,  the unique pattern of naturally acquired scarring and the pigmentation of the adjacent “saddle patch” help biologists to identify individual whales and their family group.

predator-kw

NE Pacific Transient killer whales in the Aleutian Islands, Alaska. Photograph taken during research conducted under permit 782-1719 issued by National Marine Fisheries Service (U.S.) under the authority of the Marine Mammal Protection Act. Photo: Dave Ellifrit, NOAA Alaska Fisheries Science Center


Subtle differences in morphology and pigmentation can signal a fish-eating resident whale or a marine mammal-eating transient. While the predictable seasonal appearance of the residents has provided scientists with ample opportunity for study, relatively little is known about the transients, which appear and disappear with confounding abruptness.

In central Alaska, transient killer whales pose difficult questions to biologists studying endangered Steller sea lions. Are hungry transients contributing to a local decline of Steller sea lions? How many transients are active in the area, and how much do they eat? Could killer whale predation push Steller sea lion populations over the brink?


Photographic Evidence
To answer these and other questions, a team of scientists analyzed thousands of photographs of dorsal fins to estimate the number of transients in coastal waters around breeding rookeries of endangered Steller sea lions from the central Gulf of Alaska to the central Aleutian Islands. Funding from the Consortium and other research partners supported a combination of field research and statistical analysis to estimate the total population of transients in the area, the results of which were recently published in the journal Marine Biology.
“With a study area of nearly 220,000 km2, it would have been impossible to survey the entire area uniformly from a ship,” says Dr. John Durban, a population ecologist at the NOAA Alaska Fisheries Science Centre and the study’s lead author. “Transients also move in and out of this area, occur in social groups and gathering near food sources, so we couldn’t design a classic mark-recapture survey with an equal probability of sighting and re-sighting in all areas. Instead, we gathered all available photo-identification data to estimate sighting probabilities and therefore the number of undetected whales.”

predator2

Photographs showing examples of natural markings used to identify individual killer whales.


Durban and colleagues identified 154 individual transients from 6,489 photographs collected between July 2001 and August 2003. Most of the photographs they examined were of fish-eating residents and were excluded from the study. Based on the remaining photographs, the team conducted a complex statistical analysis to estimate a total of 345 transients in the area.
Previous studies have suggested that fewer than 40 killer whales could have caused the recent Steller sea lion decline in the Aleutian Islands, if their predation was focused entirely on sea lions.
“Our abundance estimate shows that there are sufficient mammal-eating killer whales to cause substantial impacts through predation, depending on their dietary preferences and movement patterns,” Durban says.
The researchers provide one important qualifier: not all 345 transients were in the area at the same time. The abundance estimate, they note, refers to the number of killer whales that used the study area at some time during the study period, and does not imply that all remained within the area for the entire duration of the study. This creates both a temporal and a spatial variation in predatory pressure on coastal marine mammals. Specifically, the study also suggests that transient populations were gathering and moving away from the near-shore waters over the study period, Durban notes. “This will reduce the average risk of predation for coastal marine mammals,” he says.
Study area

Study area


“In the regional context of the Gulf of Alaska and Aleutian Islands, this study provided a relatively precise estimate of the number of mammal-eating killer whales using coastal waters,” says Durban. “Notably, these waters covered much of the range of the endangered western stock of Steller sea lions, and there is considerable interest in the role of killer whale predation in possibly reducing and now limiting the numbers of Steller sea lions and other marine mammals in this region.”
Durban anticipates that this approach will be useful to other land- or sea-based research studies where abundance estimation is required but survey design and capture probabilities cannot always be directly controlled. “This will particularly be the case for large study areas, but is also typical when using non-standard approaches such as photo identification or genetic identification.”
November 22, 2010
SEE PUBLICATION:
Photographic mark-recapture analysis of clustered mammal-eating killer whales around the Aleutian Islands and Gulf of Alaska.
Durban, J., D. Ellifrit, M. Dahlheim, J. Waite, C. Matkin, L. Barrett-Lennard, G. Ellis, R. Pitman, R. LeDuc and P. Wade. 2010.
Marine Biology 157:1591-1604.
abstract
We used photographic mark-recapture methods to estimate the number of mammal-eating "transient" killer whales using the coastal waters from the central Gulf of Alaska to the central Aleutian Islands, around breeding rookeries of endangered Steller sea lions. We identified 154 individual killer whales from 6,489 photographs collected between July 2001 and August 2003. A Bayesian mixture model estimated seven distinct clusters (95% probability interval = 710) of individuals that were differentially covered by 14 boat-based surveys exhibiting varying degrees of association in space and time. Markov Chain Monte Carlo methods were used to sample identification probabilities across the distribution of clusters to estimate a total of 345 identified and undetected whales (95% probability interval = 255487). Estimates of covariance between surveys, in terms of their coverage of these clusters, indicated spatial population structure and seasonal movements from these near-shore waters, suggesting spatial and temporal variation in the predation pressure on coastal marine mammals.
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The sea lions and fur seals in the Consortium’s captive research program work with researchers to test hypotheses that explain why their numbers have declined in Alaska.  They also help to develop and test new technologies that can be taken to the field to collect data from their wild counterparts.  The following video report highlights the important contribution of the marine mammals housed at the Vancouver Aquarium to solving some of the perplexing marine mysteries that are unfolding around the world.

This movie requires the Quicktime plug-in to be viewed. If you do not have it, please download the quicktime plug-in here:
 
SEE PUBLICATION:

Prey capture attempts can be detected in Steller sea lions and other marine predators using accelerometers.
Viviant, M., A.W. Trites, D.A.S. Rosen, P. Monestiez and C. Guinet. 2010.
Polar Biology 33:713-719.
abstract
We attached accelerometers to the head and jaw of a Steller sea lion (Eumetopias jubatus) to determine whether feeding attempts in a controlled setting could be quantified by acceleration features characteristic of head and jaw movements. Most of the 19 experimental feeding events that occurred during the 51 dives recorded resulted in specific acceleration patterns that were clearly distinguishable from swimming accelerations. The differential acceleration between the head-mounted and jaw-mounted accelerometers detected 84% of prey captures on the vertical axis and 89% on the horizontal axis. However, the jaw-mounted accelerometer alone proved to be equally effective at detecting prey capture attempts. Acceleration along the horizontal (surge)-axis appeared to be particularly efficient in detecting prey captures, and suggests that a single accelerometer placed under the jaw of a pinniped is a promising and easily implemented means of recording prey capture attempts.
show/hide abstract View Reference Learn more about what was found

nfs4A recent experience with young northern fur seals resulted in unexpected insights into the physiology of fur seals, and stronger synergy between researchers and marine mammal trainers. The results represent a breakthrough in the world of conservation and animal care.
The experience began when a 5-member team from the University of British Columbia and the Vancouver Aquarium brought 6 female northern fur seals from St. Paul Island in the Bering Sea to Vancouver. The fur seals had just weaned and were about to depart on their 2-year journey at sea.
“This is a critically important time for young fur seals,” remarked Dr. Andrew Trites, Research Director of the Marine Mammal Research Consortium and one of the team members that went to St. Paul to capture the animals. “In many species of mammals, the transition from milk to solid food is a major hurdle that determines whether they will survive to become breeding members of the population. Unfortunately, since fur seals disappear at sea for two years, it is that part of their lives that scientists know the least about. That is why we wanted to bring young fur seals to Vancouver — to figure out whether these early formative years are connected to the population declines we have seen in the wild”.

 nfs_billyThe fur seals began providing data as soon as they arrived at the Marine Mammal Energetics and Nutrition Laboratory at the Vancouver Aquarium. They quickly adapted to their new settings under the guidance and professional training and veterinary staff. However, the research and care team quickly realized something was very different about these young fur seals compared to the Steller sea lions and harbor seals they were used to working with.
 
“We very quickly got the fur seals eating fish, and they seemed very relaxed in their new environment,” said Billy Lasby, head pinniped trainer. “However, after several weeks, we noticed that they really were not gaining much weight. Weight gain is something we expect and use as a measure of health, but these little guys just were not putting on much weight, despite every other aspect of their behavior and medical tests indicating they were doing well. Some of them actually started to lose weight as the winter progressed. We tried all sorts of things to increase their food intake and body mass — but with no success. Often they just threw it up if we gave them more to eat.”
nfs-3
“It became a bit of an issue,” remembers Dr. David Rosen. “Here we are trying to conduct all of this research, including changes in food availability, and at the same time the vet staff wants us to feed, feed, feed. And the training staff is feeling stuck in the middle. We managed to complete all of our studies, and found the animals started to gain weight again by spring”.
It was only after Dr. Rosen began analyzing the data and thinking about the natural ecology of northern fur seals that things became clearer. “Our winter data showed that we were dealing with a creature that was physiologically tuned to just trying to survive winter in the North Pacific Ocean. They had extremely low metabolism, and were very efficient at converting food into energy — but their physiology was not really set up to process a lot of food and turn it into growth.” This would explain why the training staff had such difficulty getting the fur seals to eat lots and put on weight – they simply are not set up to do that.”
During spring and summer, the physiology of the animals underwent a dramatic change. “Metabolism increased, food intake surged, and the fur seals seemed driven to convert food into mass as quickly as possible. This is what we were expecting to see from young seals and sea lions.” However, the fur seals also lost dramatic amounts of body mass when they did not get enough to eat.
Dr. Rosen feels that the trainers and scientists were dealing with two very different creatures, physiologically, and that this dualism makes perfect sense when viewed in terms of the natural ecology of fur seals living in the North Pacific. “We think that during the winter we were dealing with an animal that was more attuned to making the most of sparse resources and riding out any short periods of poor food availability. They are really keyed to just survive these initial harsh months. Then during the spring and summer, the fur seals may ramp up their physiology to take advantage of more predictable and plentiful food resources in the North Pacific, resulting in higher growth that ultimately affects their ability to survive and reproduce. The downside is that the consequences can be quite severe if they cannot find prey because they have such a huge metabolic engine to keep fuelled.”
For both the trainers and researchers, the results of the studies provide novel insights. “In their second winter with us”, remarks Billy Lasby, “they again cut back
their food intake and lost weight. However, now we knew it was part of their normal life history and could deal with it more easily from a husbandry and research perspective.”
 

2It fits in the palm of your hand, looks straight out of a James Bond film, and promises to help solve a long-standing problem for marine mammal researchers. It’s called an accelerometer, and it’s revolutionizing the way scientists observe feeding behavior in marine mammals.
The foraging habits of mammals that feed at sea are notoriously difficult to study, particularly in low-visibility polar environments. Yet researchers require data on feeding behavior to determine the well-being of marine populations — especially those in serious decline, like certain groups of Steller sea lions in the North Pacific.
Fortunately, the accelerometer promises to solve this quandary. This tiny electronic device can measure and record the acceleration of head and jaw motion, which in a recent study of hooded and harbor seals was shown to be the most prominent indicator of prey capture events.
Marine Mammal Consortium researchers decided to see if the gadget could detect prey capture as successfully with Steller sea lions. The research team was comprised of Morgane Viviant and Cristophe Guinet of France’s Centre National de la Recherche Scientifique, Andrew Trites and David Rosen of the University of British Columbia, and Pascal Monestiez of the Institut National de la Recherche Agronomique. The results of their study were recently published in Polar Biology.
DSC_2237
High-tech Pinniped

The study involved outfitting a Steller sea lion at the Vancouver Aquarium with an accelerometer temporarily placed on its head and another under its lower jaw. Since the lower jaw is the only mobile part of a sea lion’s skull, the researchers reasoned that its movement (relative to the skull) would be the only one detectable during prey capture.
The Steller sea lion was the envy of her low-tech pool-mates. As she swam after herring, the accelerometers recorded each opening and closing of her jaws. A video camera synchronized to the accelerometers allowed the researchers to confirm that the movements detected by the accelerometers corresponded with individual prey capture events.
1
Overall, the researchers found that the accelerometers were an accurate means of recording prey capture through jaw motions. However, they also found that a single accelerometer attached to the lower jaw worked just as well as two devices.
Oh, the Possibilities
While the accelerometers in this experiment could not record the precise number of herring consumed, they successfully measured the number and timing of prey encounters — all crucial details for the researchers. Accelerometers placed on the body can also measure flipper beat frequency, and 3D models can even record the animal’s turning angle. The team concluded that this tiny device will give marine mammal researchers an easy and accurate way to judge foraging success and resource quality.
 
SEE PUBLICATION:

Prey capture attempts can be detected in Steller sea lions and other marine predators using accelerometers.
Viviant, M., A.W. Trites, D.A.S. Rosen, P. Monestiez and C. Guinet. 2010.
Polar Biology 33:713-719.
abstract
We attached accelerometers to the head and jaw of a Steller sea lion (Eumetopias jubatus) to determine whether feeding attempts in a controlled setting could be quantified by acceleration features characteristic of head and jaw movements. Most of the 19 experimental feeding events that occurred during the 51 dives recorded resulted in specific acceleration patterns that were clearly distinguishable from swimming accelerations. The differential acceleration between the head-mounted and jaw-mounted accelerometers detected 84% of prey captures on the vertical axis and 89% on the horizontal axis. However, the jaw-mounted accelerometer alone proved to be equally effective at detecting prey capture attempts. Acceleration along the horizontal (surge)-axis appeared to be particularly efficient in detecting prey captures, and suggests that a single accelerometer placed under the jaw of a pinniped is a promising and easily implemented means of recording prey capture attempts.
show/hide abstract View Reference Learn more about what was found

 
 
 

To land-dwellers, a sea lion’s life looks fairly uneventful: swim, eat, sleep and reproduce. In fact, a sea lion leads a rather dramatic life. Sea lions and all marine mammals, for that matter live in environments that are continuously changing, particularly with regards to food supply. An animal’s ability to respond to these changes determines whether or not it will live to swim, eat, sleep, and reproduce another day.

endocrine_wild

Survival largely depends on how the animal regulates energy intake and expenditure when times get tough. Fortunately, they can defer these decisions to a powerful internal headquarters: the endocrine system. This complex system of glands secretes hormones that regulate the body, influencing an animal’s physiological responses in times of food shortages.
hormones2A team of Consortium researchers recently got to know the Steller sea lion’s endocrine system more intimately by finding out how hormone changes during periods of food shortage are influenced by an animal’s age, diet, and the season.
The research team comprised Tiphaine Jenniard du Dot, David Rosen, and Andrew Trites from the University of British Columbia Fisheries Centre; Julie P. Richmond from the University of Connecticut’s Department of Animal Science, and Alexander S. Kitaysky of the Institue of Arctic Biology (University of Alaska Fairbanks). Their study was published in Comparative Biochemistry and Physiology.
Honing in on hormones
The researchers focused on the three groups of hormones primarily involved in the endocrine response to nutritional stress: the somatotropic hormones including the insulin-like growth factor-1 (IGF-I), the thyroid hormones (T3 and T4), and glucocorticoids such as cortisol. They chose eight captive female Stellers (five three-year-olds and three five-year-olds), and reduced the animals’ food intake for significant periods in both summer and winter. One test group was given a smaller ration of its usual herring diet (a high-fat fish), while the other received a normal amount of fish but were switched to pollock (a low-fat, low-energy fish). After the test period, both groups returned to eating their normal herring regime.
endocrine_ag3The researchers found that the Stellers’ levels of stress hormones (cortisol) and growth hormones (IGF-I) measured via blood samples changed as the animals lost and regained weight. In fact, they were able to link each hormone to a different strategy for preserving energy (lipid versus lean mass catabolism). Thyroid hormones, on the other hand, could not be linked to any physical changes they observed.
The researchers also found that young animals show greater hormone changes than their elders, and that the type of fish they received (high-energy or low-energy) made little difference on hormone levels.
Another step forward
The team concluded that studying a Steller sea lion’s cortisol and IGF-I levels could help them detect and better understand nutritional stress, as well as the energetic strategy animals use to cope with it. The study brought them yet another step closer to understanding how Steller sea lions cope with the unpredictable environments they call home.
 
SEE PUBLICATION:

Changes in glucocorticoids, IGF-I and thyroid hormones as indicators of nutritional stress and subsequent refeeding in Steller sea lions (Eumetopias jubatus).
Jeanniard du Dot, T., D.A.S. Rosen, J.P. Richmond, A.S. Kitaysky, S.A. Zinn and A.W Trites. 2009.
Comparative Biochemistry and Physiology, Part A 152:524-534.
abstract
Physiological responses to changes in energy balance are tightly regulated by the endocrine system through glucocorticoids, IGF-I and thyroid hormones. Changes in these hormones were studied in eight captive female Steller sea lions that experienced changes in food intake, body mass, body composition, and blood metabolites during summer and winter. During a period of energy restriction, one group of sea lions was fed reduced amounts of Pacific herring and another was fed an isocaloric diet of walleye pollock, after which both groups returned to their pre-experimental diets of herring. Cortisol was negatively and IGF-I was positively associated with changes in body mass during periods of energy restriction (mass loss associated with increase in cortisol and decrease in IGF-I) and refeeding (body mass maintenance associated with stable hormone concentrations in summer and compensatory growth linked to decrease in cortisol and increase in IGF-I in winter). Cortisol and IGF-I were also correlated with changes in lipid and lean mass, respectively. Consequently, these two hormones likely make adequate biomarkers for nutritional stress in sea lions, and when combined provide indication of the energetic strategy (lipid vs lean mass catabolism) animals adopt to cope with changes in nutrient intake. Unlike type of diet fed to the sea lions, age of the animals also impacted hormonal responses, with younger animals showing more intense hormonal changes to nutritional stress. Thyroid hormones, however, were not linked to any physiological changes observed in this study.
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rosen_izzyScientific questions — like whether nutritional stress has led to the decline of Steller sea lion populations — are too large to be answered by a single experiment or study. Rather, scientists carefully examine one particular aspect of the overall hypothesis to test. Their individual results are added to the assemblage of scientific knowledge. However, at some point, these disparate chunks of understanding must be put together into a cohesive framework to readdress the validity of the original question.
In this way, answering a scientific question is a little like completing a jigsaw puzzle. Each experiment is akin to an individual piece, but the big picture can only be clearly seen when those pieces are put together in a logical fashion.
Consortium researcher Dr. David Rosen (UBC Marine Mammal Research Unit) recently undertook a comprehensive review of the evidence from studies of captive animals that could be used to evaluate the validity of the Nutritional Stress hypothesis as an explanation for the decline of Steller sea lions in the wild. His work was published in the journal Mammal Review. Put simply, the Nutritional Stress Hypothesis states that Steller sea lion populations in the North Pacific are in decline due to inadequate nutrition, caused by changes in the quality and quantity of their prey.
rosen_cahmberThrough the years, researchers have scrutinized the validity of the Nutritional Stress hypothesis using a variety of techniques, including controlled studies with seals and sea lions in the laboratory. Each of these studies has examined individual aspects of the hypothesis and used different techniques. Dr. Rosen’s review examines all of these divergent studies published to date that can be used to support or strike down the Nutritional Stress hypothesis, whether that was the original aim of the study or not. The task was made particularly difficult by the differences in study aims and techniques. In the end, however, a cohesive picture emerged of how nutritional stress might occur in the wild and how it would affect individual Steller sea lions.
The first conclusion was that all prey species are not created equal. Scientists had previously linked declining local populations with ‘low quality’ prey such as walleye pollock or Atka mackerel, but studies with captive sea lions confirmed that these nutritional differences were magnified when the fish were digested by animals.
Second, sea lions could in theory make up for the lack of quality food by simply eating more low-energy prey without negatively impacting their growth or body composition. But in reality, this is not always possible. Juvenile digestive systems, for example, cannot handle large quantities of low-quality prey required to fuel their high energy requirements.
When sea lions could not consume enough prey to meet their energy needs — either because of decreased quality or availability — low quality prey appeared to cause additional problems. For example, Steller sea lions become less capable of making seasonally-appropriate energy allocation decisions under the influence of large amounts of low-quality prey.
rosen_2However, the exact impacts of consuming sub-optimal amounts or types of prey depend on a host of factors, including season, prey quality, age, and duration of the nutritional stress. In short, while poor quality prey tend to have more negative effects on individual sea lions, the actual effects are complicated to predict.
While the review presented a consistent picture of the possible immediate causes and effects of nutritional stress, Dr. Rosen acknowledged that such laboratory studies have their limitations. They were not designed to identify the source of nutritional stress in declining Steller populations (e.g. climate change, fisheries competition, etc), but rather to pinpoint the conditions under which changes in sea lion prey cause nutritional stress, and the physiological impacts of these changes. This knowledge will ultimately enable researchers to piece together the bigger picture.
 
SEE RELATED PUBLICATION:

Steller sea lions Eumetopias jubatus and nutritional stress: evidence from captive studies.
Rosen, D.A.S. 2009.
Mammal Review 39:284-306.
abstract
1. Numbers of Steller sea lions Eumetopias jubatus in the North Pacific have declined. According to the Nutritional Stress Hypothesis, this decline is due to reduced food availability. Data from studies conducted on pinnipeds in the laboratory are used here to test whether the Nutritional Stress Hypothesis can explain the decline of Steller sea lions. 2. Overall, there is strong evidence for biologically meaningful differences in the nutritional quality of major prey species. Steller sea lions can partly compensate for low-quality prey by increasing their food consumption. 3. There appear to be no detrimental effects of low-lipid prey on sea lion growth or body composition when sea lions can consume sufficient quantities of prey. However, the ability to increase consumption is physiologically limited, particularly in young animals. Overall, it is more difficult to maintain energy intake on a diet of low-quality prey than on a normal diet. 4. Under conditions of inadequate food intake (either due to decreased prey availability or quality, or increased energy requirements) the overall impacts of nutritional stress are complex, and are dependent upon season, prey quality, age, and the duration and intensity of the nutritional stress event. 5. Studies on pinnipeds in the laboratory have been instrumental in identifying the conditions under which changes in sea lion prey can result in nutritional stress, and the nature of the physiological impacts of nutritional stress events.
show/hide abstract View Reference Learn more about what was found

 


dudot2-b As the far lesser-known adage goes, “It ain’t easy being marine.” This especially applies to the wild Steller sea lion, which faces harsh environmental conditions, predators galore, and regular periods during which it is forced to go with less food. But the stocky Steller is a survivor.
The question for marine researchers is: how? Typically, a pinniped sensing hard times ahead first attempts to conserve energy by increasing its digestive efficiency and reducing the energy it loses as waste. But sometimes these measures aren’t enough, and the animal must make a tough decision: how best to allocate the limited energy it acquires through food. Should it go to growth? Stored energy? Or thermoregulation? The sea lion must get its priorities straight — and fast.
Scientists have long speculated on potential strategies, but until recently, no one had actually determined how marine mammals allocate energy when faced with food shortages. The team behind this study comprised Consortium researchers Tiphaine Jenniard du Dot, David A.S. Rosen, and Andrew W. Trites, all of the University of British Columbia. Their results were published in Physiological and Biochemical Zoology.

dudut2_b

Schematic and simplified partitioning of the gross energy intake in an animal


Desperate Times Require Desperate Measures
Hypothesizing that pinnipeds might allocate energy differently according to the seasons and the quality of food available, the researchers divided a group of female Steller sea lions in two groups, and limited each group’s food intake for 28 days in winter and summer. The first group dined on small amounts of herring (a high-quality fish), while the second received pollock (an energetically lower-quality prey).
dudotd
The researchers found that during the summer, both groups compensated for the lack of energy intake by using up their internal energy stores. In winter, both groups allocated less
energy to overall maintenance functions such as metabolism and allocated more energy to sustaining thermoregulatory capacity (the ability to keep body temperature constant). As in the summer, they once again released stored energy.
But the researchers also observed a crucial difference between the two groups of sea lions. During the summer, Team Herring allocated more energy to foraging and less to thermoregulation — a practical decision for wild sea lions given the tendency for fish to be more abundant and waters warmer in summer. In winter, when fish are likely scarcer and less predictable, the behavior of the sea lions was consistent with an animal that foraged less, such as reducing activity levels and maintaining thermoregulatory capacity. Team Pollock, on the other hand, did not make the same sensible energy decisions.
 
By studying the energy-allocation choices made by both groups, the researchers concluded that the sea lions dining on herring when times were tough adjusted better to environmental conditions than those fed pollock. This suggests that low-energy food sources might not trigger the physiological and behavioral mechanisms needed to adjust to food shortages, which would take a toll on the animal’s fitness in the long run.
SEE RELATED PUBLICATION:
Energy reallocation during and after periods of nutritional stress in Steller sea lions: low-quality diet reduces capacity for physiological adjustments.
Jeanniard du Dot, T., D.A.S Rosen and A.W. Trites. 2009.
Physiological and Biochemical Zoology 89:516-530.
abstract
Two groups of female Steller sea lions (Groups H and P) were subjected to periods of energy restriction and subsequent re-feeding during winter and summer to determine changes in energy partition among principal physiological functions and the potential consequences to their fitness. Both sea lion groups consumed high-quality fish (herring) before and after the energy restrictions. During restrictions, Group H was fed a lower quantity of herring and Group P a caloric equivalent of low-quality fish (pollock). Quantitative estimates of maintenance and production energies and qualitative estimates of thermoregulation, activity and basal metabolic rate were measured. During summer, all animals compensated for the imposed energy deficit by releasing stored energy (production energy). Group H also optimized the energy allocation to seasonal conditions by increasing activity during summer when fish are naturally abundant (foraging effort) and by decreasing thermoregulation capacity when waters are warmer. During winter, both groups decreased the energy allocated to overall maintenance functions (basal metabolic rate, thermoregulation and activity together) in addition to releasing stored energy, but preserved thermoregulatory capacity. Group H also decreased activity levels in winter when foraging in the wild is less efficient, unlike Group P. Overall, sea lions fed pollock did not change energy allocation to suit environmental conditions as readily as those fed herring. This implies that low energy density diet may further reduce fitness of animals in the wild during periods of nutritional stress.
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It might not be the most glamorous aspect of a biologist’s work, but the study of fecal matter is an invaluable (if messy) part of reconstructing an animal’s life history. Recently, however, Consortium researchers ushered this age-old research method into the 21st century by integrating DNA technology into the examination of animal scat.

Researchers with their loot of scat

Researchers with their loot of scat


The aim of the study was to determine the effects pinnipeds have on their prey populations — and by extension, on fisheries. In order to understand this, they needed to find out exactly what pinnipeds eat. Traditionally, researchers have reconstructed pinniped diets by probing scat samples for telltale treasures like fish skeletal remains (aptly known as “hard parts”), but this does not always account for the less-identifiable components of the scat’s “soft parts”. For example, if a predator only consumes the fleshy parts of the prey, skeletal remains will not be evident in the scat.
The researchers believed that DNA analysis of scat holds the key to unlocking the secrets of pinniped diets. They aimed not only to compose a comprehensive list of prey species, but also compare the effectiveness of this new technology to the old. The research team comprised Dominic Tollit and Andrew Trites of the UBC Fisheries Centre; Kristina Miller, Angela Schulze and Peter Olesiuk of the Pacific Biological Station; Susan Crockford of Pacific IDentifications; and Tom Gelatt and Rolf Ream of the Alaska Fisheries Science Centre. Their findings were recently published in Ecological Applications.
 
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Wanted: Adventurous Fin-footed Eater
When it came to choosing a subject for the study, the researchers did not have to look far. With a penchant for fish and cephalopods, the Steller sea lion has a broad diet, and therefore is an excellent subject. Its diet has also been well studied since its western population numbers began to plummet in the 1980s. Plus, the Steller sea lion came with a mystery: though researchers had long understood its fondness for salmon, the salmon bones they recovered from the fecal samples largely failed to pinpoint the salmon species most important to its diet.
The research team collected scat samples in British Columbia and the eastern Aleutian Islands, and analyzed them through polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The DNA they extracted from the scat included that of over 40 different species of fish and cephalopods. Unexpectedly, they also found at least seven species of crustaceans such as spot prawns and Dungeness crab. Whether or not the sea lions had targeted the crustaceans or had consumed fish that had eaten the crustaceans is not known.
 
Steller sea lion scat collection site locations

Steller sea lion scat collection site locations


Researchers using DNA analysis can now identify many more species and 20% more by number (occurrences) than they could using traditional methods of determining diets.
The researchers also solved one of the sea lion mysteries by finding that pink and chum followed by Chinook were the most important salmon prey. But in running the DNA analysis they also revealed a perplexing discovery when they found that two of the fifty-six scats collected in the Eastern Aleutian islands contained the DNA of Atlantic Salmon — presumably escapees that traveled to Alaska from salmon farms in British Columbia or further south.
Changing the Way We Think About Scat
The team concluded that DNA techniques can refine results not only in diet studies of pinnipeds whose scats lack hard parts, but also in diet studies of marine piscivores (fish-eaters) in general, including crustaceans, penguins, sea birds, and fish. DNA scat techniques have also been used to confirm the predator’s sex and the species and molecular techniques can determine hormones and parasites in scat. So while they might not raise scat science to the level of acceptable dinner conversation, they will surely continue to change the face of traditional research methods.
September 16, 2009
PublicationsRELATED PUBLICATION:
Development and application of DNA techniques for validating and improving pinniped diet estimates.
Tollit, D.J., A.D. Schulze, A.W. Trites, P.F. Olesiuk, S.J. Crockford, R.R. Ream T.S. Gelatt and K.M. Miller. 2009.
Ecological Applications 19:889-905.
abstract
Polymerase chain reaction techniques were developed and applied to identify DNA from >40 species of prey contained in fecal (scat) soft part matrix collected at terrestrial sites used by Steller sea lions (Eumetopias jubatus) in British Columbia and the Eastern Aleutian Islands, Alaska. Sixty percent more fish and cephalopod prey were identified by morphological analyses of hard parts compared with DNA analysis of soft parts (hard parts identified higher relative proportions of Ammodytes sp., Cottidae and certain Gadidae). DNA identified 213 prey occurrences of which 75 (35%) were undetected by hard parts (mainly Salmonidae, Pleuronectidae, Elasmobranchii and Cephalopoda), and thereby increased species occurrences by 22% overall and species richness in 44% of cases (when comparing 110 scats that amplified prey DNA). Prey composition was identical within only 20% of scats. Overall, diet composition derived from both identification techniques combined did not differ significantly from hard part identification alone, suggesting that past scat-based diet studies have not missed major dietary components. However, significant differences in relative diet contributions across scats (as identified using the two techniques separately) reflect passage rate differences between hard and soft digesta material and highlight certain hypothesized limitations in conventional morphological-based methods (e.g., differences in resistance to digestion, hard part regurgitation, partial and secondary prey consumption), as well as potential technical issues (e.g., resolution of primer efficiency and sensitivity, and scat subsampling protocols). DNA analysis of salmon occurrence (from scat soft part matrix and 238 archived salmon hard parts) provided species-level taxonomic resolution that could not be obtained by morphological identification, and showed that Steller sea lions were primarily consuming pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. Notably, DNA from Atlantic salmon (Salmo salar) that likely originated from a distant fish farm was also detected in two scats from one site in the Eastern Aleutian Islands. Overall, molecular techniques are valuable for identifying prey in the fecal remains of marine predators. Combining DNA and hard part identification will effectively alleviate certain predicted biases, and will ultimately enhance measures of diet richness, fisheries interactions (especially salmon related ones) and the ecological role of pinnipeds and other marine predators, to the benefit of marine wildlife conservationist and fisheries managers.
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The Fasts of Life

Unappealing as it may be to most humans, fasting is a fact of life for Steller sea lions. Females endure long periods without food while nursing, and males fast while defending breeding territory. Even pups and juvenile sea lions must overcome hunger while waiting for their mothers to return from feeding at sea.
Researchers have long been aware of the Steller’s propensity to fast, but have not known what happens to the animals’ physiology during that time. Three possibilities are that they obtain energy from stored lipids, stored proteins or some combination of the two. Studies of other animals that frequently fast such as bears and penguins have shown they use their lipid stores for energy rather than their protein stores to survive fasting. Whether or not Steller sea lions employ a similar mechanism to survive fasting is unknown.
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A team of biologists recently tackled this question in a unique way. Rather than measure how much protein and lipid each animal had before and after fasting, the researchers focused on taking blood samples to measure the concentration of blood metabolites. Blood metabolites are by-products of metabolic (or chemical) processes that reflect changes in the types of reserves (lipids and proteins) an animal uses to meet its energy requirements.
 
The researchers studied both juvenile and subadult Steller sea lions, hoping to determine not only how well blood metabolites indicate fasting and nutritional status, but also whether the Stellers’ ability to fast changes seasonally and with age. The research team comprised Lorrie Rea of the Alaska Department of Fish and Game, Michelle Berman-Kowalewski of the University of Central Florida, and David Rosen and Andrew Trites of the University of British Columbia. Their results were published in Physiological and Biochemical Zoology.
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Five-star Fasters
The researchers experimentally fasted nine Steller sea lions aged 2 to 6 years old during both their breeding and non-breeding seasons. Each of the animals was fasted for one to two weeks based on predictions made from observations of sea lions in the wild about how long their subjects could maintain homeostasis (a state of internal equilibrium) while fasting.
rea2The sea lions proved themselves to be accomplished fasters; not one showed signs of dehydration or irreversible biochemical effects of fasting. The researchers did, however, observe significant differences between the fasting abilities of the different age groups. The subadult Stellers relied on the lipid reserves and conserved their protein stores during the breeding season, which is a time of year when they would naturally experience fasting in the wild. However, the subadult sea lions were less able to protect their protein stores during the non-breeding season when they would not normally experience food shortages. In contrast, the juvenile sea lions appeared to be better adapted to surviving a fast during the non-breeding season than during the breeding season.
Fast Facts
The research team concurred that while metabolite concentrations in blood samples cannot accurately predict exactly how long an animal has been fasting, they can help determine whether a sea lion has been without food for longer that usual. They also found that the ability of sea lions to spare protein by relying more on catabolizing lipids during fasting seems to be determined by the proportion of body fat that an animal has prior to fasting. This is one of the most important discoveries because it also explains the seasonal difference between the different age classes of sea lions. Such findings ultimately help the researchers to identify animals and populations that are nutritionally stressed.
August 20, 2009
 

PublicationsPUBLICATIONS

Seasonal differences in biochemical adaptation to fasting in juvenile and subadult Steller sea lions (Eumetopias jubatus).
Rea, L.D., M. Berman-Kowalewski, D.A.S. Rosen, and A. W.Trites. 2009.
Physiological and Biochemical Zoology 82:236-247.
abstract
Nine Steller sea lions (Eumetopias jubatus) aged 1.756 yr were experimentally fasted for 714 d during the breeding and nonbreeding seasons to identify changes in plasma metabolites that are indicative of fasting and to determine whether the ability of sea lions to fast varies seasonally or with age. Although some animals approached the limit of their protein-sparing ability by the end of our fasting experiments, there was no sign of irreversible starvation biochemistry. Plasma blood urea nitrogen (BUN) concentrations decreased in all animals within the first week of fasting, reflecting a shift to a fasting-adapted state; however, significant increases in plasma BUN concentration at the end of the nonbreeding season fasts suggest that subadult Steller sea lions were not able to maintain a protein-sparing metabolism for a full 14 d during the nonbreeding season. In contrast, juveniles were able to enter protein sparing sooner during the nonbreeding season when they had slightly higher initial percent total body lipid stores than during the breeding season. Subadult and juvenile sea lions had low circulating ketone body concentrations compared with young sea lion pups, suggesting an age-related difference in how body reserves are utilized during fasting or how the resulting metabolites are circulated and catabolized. Our data suggest that metabolite concentrations from a single blood sample cannot be used to accurately predict the duration of fast; however, threshold metabolite concentrations may still be useful for assessing whether periods of fasting in the wild are unusually long compared with those normally experienced.
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Ecopath was conceived by Dr. Polovina (NOAA) and advanced by Drs. Pauly, Christensen and Walters (UBC Fisheries Centre) — and has become the most widely used approach to analyzing and understanding marine ecosystems. It is considered to be one of the top ten breakthroughs in NOAA’s 200 years of history.
heyman2
The strength of Ecopath lies in its ability to represent complex ecosystems using simple equations and limited data and computing power. Since being incorporated into a dynamic simulation model called Ecosim, it can also track ecosystem changes over time and space. It has revolutionized the understanding of complex marine ecosystems by allowing scientists to explore the ecosystem effects of fishing, environmental changes, and management policy options.
A conference celebrating and reviewing 25 years of progress using the Ecopath approach in fisheries management and ecosystem analysis will be held from August 30 to September 1, 2009 at the University of British Columbia (conference.ecopath.org). One of the keynote speakers will be Dr. Sheila Heymans of the Scottish Association for Marine Science who will talk about her use of Ecopath and Ecosim to conduct ecological network analysis, and how she used it to assess the ecosystem status of the Gulf of Alaska.
As Dr. Heymans will discuss, mapping an ecosystem’s trophic connections (i.e. food webs) is a complicated process that usually produces a jumble of data, which can overwhelm the most stoic researcher. “Ecological network analysis” is the process of teasing the most important information out of this mass, and finding patterns that might not be immediately obvious—such as which energy pathways are important to keep ecosystems functioning. Ecological Network Analysis was pioneered by Prof. Robert Ulanowicz from the University of Maryland.
Dr. Heymans and the UBC Fisheries Centre’s Sylvie Guenette and Villy Christensen used the Ecopath with Ecosim software to analyze two marine ecosystems in Alaska—the Aleutian Islands and Southeast Alaska and the effects that climate change and fishing have had on them. The ecosystems are currently in very different states due to differences in fishing and climate over the past 40 years. The researchers hoped that by using computer software to simulate the ecosystems over that time period, they might explain the different changes that occurred.

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Figure 1: Food web of the Aleutian Islands with only > 10% of diet contributions shown.


Finding answers in indices
The research team studied a variety of complex indices—including, for example, the Finn cycling index, which quantifies the importance of cycles in ecosystems—in hopes that these would explain the dissimilar changes that occurred in the ecosystems over the past 40 years.
The researchers found that the Aleutian Islands ecosystem changed substantially after the 1977 regime shift (a large change in oceanic conditions that spreads throughout the food web), which resulted in a large decline in the main top predators (Steller sea lions, sharks, and skates). In contrast, the researchers found that the Southeast Alaska ecosystem did not change much at all until a similar shift in 1989-1990. The indices reflected differences between ecosystems.
A useful tool
Ecological network analysis is a new approach to understanding ecosystem dynamics that holds a great deal of potential. Not only does it allow researchers to extract the most important information from large, unruly masses of data, but it can also be useful for ecosystem managers, who can use indices to predict ecosystem changes before they occur.
Although it still involves large quantities of data and substantial computing power, ecological network analysis is gaining a reputation as a promising tool. With programs like Ecopath making the process easier, its popularity should continue to grow.
 

PublicationsPUBLICATIONS

Evaluating network analysis indicators of ecosystem status in the Gulf of Alaska.
Heymans, S.J.J., S. Guenette and V. Christensen. 2007.
Ecosystems 10:488-502.
abstract
This is the first study on the emergent properties for empirical ecosystem models that have been validated by time series information. Ecosystem models of the western and central Aleutian Islands and Southeast Alaska were used to examine indices of ecosystem status generated from network analysis and incorporated into Ecopath with Ecosim. Dynamic simulations of the two ecosystems over the past 40 years were employed to examine if these indices reflect the dissimilar changes that occurred in the ecosystems. The results showed that the total systems throughput (TST) and ascendency (A) followed the climate change signature (Pacific decadal oscillation, PDO) in both ecosystems, while the redundancy (R) followed the inverse trend. The different trajectories for important species such as Steller sea lions (Eumetopias jubatus), Atka mackerel (Pleurogrammus monopterygius), pollock (Theragra chalcograma), herring (Clupea pallasii), Pacific cod (Gadus macrocephalus) and halibut (Hippoglossus stenolepis) were noticeable in the Finn cycling index (FCI), entropy (H) and average mutual information (AMI): not showing large change during the time that the Stellers sea lions, herring, Pacific cod, halibut and arrowtooth flounder (Atheresthes stomias) increased in Southeast Alaska, but showing large declines during the decline of Steller sea lions, sharks, Atka mackerel and arrowtooth flounder in the Aleutians. On the whole, there was a change in the emergent properties of the Aleutians around 1976 that was not seen in Southeast Alaska. Conversely, the emergent properties of both systems showed a change around 1988, which indicated that both systems were unstable after 1988.
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Protecting natural habitats rarely occurs without sparking controversies—usually among those whose livelihoods depend on resources within the protected areas. Conservation can thus come at a significant economic cost.
In the Gulf of Alaska and Bering Sea, restricting fisheries within areas deemed to be critical habitat for Steller sea lions may or may not have resulted in serious financial losses for the fishing industry. This uncertainty reflects the fact that there has been no reliable method to estimate the opportunity costs, or the costs of not fishing in protected areas.
berman1
To address this obvious need, Matthew Berman of the Institute of Social and Economic Research at the University of Alaska teamed up with researchers from the University of British Columbia (Edward Gregr, Gakushi Ishimura, Ryan Coatta, Rowenna Flinn, Rashid Sumaila, and Andrew Trites). Their aim was to develop a “scientifically defensible” method of valuing habitat-driven fishery closures, and to apply this method to a relevant issue, namely the effects of the 2001 Steller sea lion habitat closures on groundfish trawl fisheries in the North Pacific. Their findings were published in Fisheries Centre Research Reports.
 

Figure 1: Estimated spatial economic values of shore-based Pacific cod fisheries in the Gulf of Alaska during the summer-fall 2001, showing higher value areas in darker colors. Circles surrounding sea lion haulouts and rookeries identify Steller sea lion critical habitat, while the rectangles show other areas closed to fisheries. The red rectangle shows the Chiniak Gully Research Area, which was closed to commercial fishing to allow the Alaska Fisheries Science Center to conduct research on the effects of the pollock fishery on pollock abundance and distribution.

Figure 1: Estimated spatial economic values of shore-based Pacific cod fisheries in the Gulf of Alaska during the summer-fall 2001, showing higher value areas in darker colors. Circles surrounding sea lion haulouts and rookeries identify Steller sea lion critical habitat, while the rectangles show other areas closed to fisheries. The red rectangle shows the Chiniak Gully Research Area, which was closed to commercial fishing to allow the Alaska Fisheries Science Center to conduct research on the effects of the pollock fishery on pollock abundance and distribution.


Considering Space
According to the researchers, there is a growing consensus that management of fisheries needs to consider spatial differences in habitat and the resources they provide at different times of the year. Past economic analyses of habitat closures have attempted to account for spatial considerations, but have not addressed the variations and complexities of the ocean environment. Berman’s team designed a new method to differentiate habitat among a large number of small areas within the Gulf of Alaska and Bering Sea, and among different fisheries (at-sea and shore-based trawl fleets).
The researchers hypothesized that environmental variables would play important roles in their analysis—that conditions such as surface temperature, wave height, and salinity can explain and predict the spatial distribution of fish, which in turn influences the distribution of fishing effort. They analyzed environmental variables using satellite images, oceanographic modeling, and bathymetry techniques (to measure sea floor and depth) at 3-km and 9-km spatial scales and two-week and one-month intervals—and used these data to predict fish biomass and fisheries catch per unit of effort (CPUE), which, combined with spatial regulatory and cost factors, could explain the spatial distribution of fishing effort over time.
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A Crucial Tool for the Future
Through an extensive statistical analysis of the variables, Berman’s team found that the 2001 Critical Habitat Closures cost the North Pacific groundfish trawl fisheries 5 to 40 percent of their total potential net earnings, although cost estimates varied widely between at-sea and shore-based trawl fleets. They also found strong empirical support for their hypotheses—that environmental conditions can predict the spatial distribution of fish, which can in turn predict the distribution of fishing effort.
The researchers report that the new set of methods they developed to estimate the value of ocean fisheries can easily be generalized to evaluate fishery closures in time and space for any protected species or for marine conservation generally. Certainly, with pending proposals to close additional areas to fishing in the North Pacific, this is potentially a crucial tool to ensure that responsible decisions are made to manage fisheries, protect people’s livelihoods, and safeguard species that are at risk.
March 3, 2009

PublicationsPUBLICATIONS

Economic valuation of critical habitat closures.
Berman, M., E.J. Gregr, G. Ishimura, R. Coatta, R. Flinn, U.R. Sumaila and A.W. Trites. 2008.
In Fisheries Centre Research Reports. Vol 16(8) pp. 102
abstract
We developed methods to estimate the spatial variation in economic values of ocean fisheries, and applied the methods to estimate the cost of closing groundfish fisheries in Steller sea lion Critical Habitat in the Bering Sea and Gulf of Alaska. The research addressed two related goals: (1) explicitly linking spatial variability of fisheries biomass and profitability over time to environmental variables; and (2) developing estimates of opportunity costs of time and area closures to the fishing industry at scales relevant to management. The approach involved two stages of statistical analyses. First, environmental conditions measured at 3 km and 9 km spatial scales and two-week and one-month intervals were used to predict fish biomass and fisheries catch per unit of effort (CPUE). Environmental variables included bathymetry, remotely sensed physical and biological observations, and output from a physical oceanographic circulation model. Second, we used predicted CPUE and spatial regulatory and cost factors to explain the spatial distribution of fishing effort over time. Our results suggested that 2001 Critical Habitat closures cost the North Pacific groundfish trawl fisheries 5-40 percent of their total potential net earnings. The improved methods for estimating opportunity costs of fisheries closures we present have direct applications to evaluating boundary changes to marine protected areas and other spatial management decisions. Limitations include the extensive data requirements and the need to bootstrap confidence intervals. If further research demonstrates the robustness and stability of the estimated relationships over time, the methods could project spatial fishery effects of climate variability and change, leading to dynamic spatial models linking fisheries with ecosystems.
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Does time of year affect recovery from nutritional stress?

Winter in the North Pacific Ocean is considered the most difficult time of year for Steller sea lions, largely due to the amount of energy they must spend foraging and keeping warm in rough winter seas. But the summer breeding season has its own unique metabolic demands on sea lions, and a critical change in food supply in either season could have dire consequences.
dudot_field
How do these seasonal environmental changes affect the health and dynamics of entire populations of Steller sea lions? With the assistance of trained animals housed at the Vancouver Aquarium, U.B.C. researchers Tiphaine Jeanniard du Dot, David Rosen, and Andrew Trites studied how sea lions respond physiologically to changes in quantity and type of food, and whether these responses differ between summer and winter.
dudot-dudotStudies have shown that a nutritionally stressed sea lion—experiencing a prolonged change in the quantity or quality of its diet—will lose different amounts of lipid (fats, oils, etc.) and protein tissues depending on the season and the quality of diet. Loss of lipid and protein can in turn affect the survival and reproduction of sea lions. Where most dietary studies concentrate on the period of nutritional restriction, the current study (published in the Journal of Experimental Marine Biology and Ecology) focused on how well the individual animals recovered after the stress had passed.
Seasonal Study
The experiment involved three 28-day phases and was conducted in the summer and repeated in the winter. Eight trained sea lions were separated into two groups and assigned different diets. The first group (Group H) ate varying quantities of Pacific herring throughout the experiment. The second group (Group P) ate herring in the first phase but switched to a restricted diet of less-nutritious walleye pollock for the second phase, and then resumed eating regular quantities of nutritious herring during the final phase. Although they ate different fish, both groups were assigned restricted diets during the second phase.
Researcher and trainer prepare to measure blubber thickness of the Steller sea lion using an ultrasound machine.

Researcher and trainer prepare to measure blubber thickness of the Steller sea lion using an ultrasound machine.

Researcher and trainer prepare to measure blubber thickness of the Steller sea lion using an ultrasound machine.


The researchers found that in both summer and winter, Group H lost significantly more lipids and less lean mass (protein) than Group P, which was fed pollock during the restricted phase. The response of Group H was consistent with the predicted pattern of nutritional stress, in which sea lions use up their lipid reserves in order to preserve protein tissue. The researchers were surprised to note that Group P lost a high proportion of protein while consuming restricted levels of pollock – which could lead to muscle impairment and vital organ failure in the long term. Each of the sea lions increased their rates of mass gain and returned to their pre-experimental weight during winter, but not during summer.
“Critical” Summer Period
“Nutritional stress has been commonly assumed to be more strenuous during winter than summer,” the authors write. “However, our results showed not only that sea lions withstand periods of mild nutritional stress more easily in winter, but they also are able to recover more easily from it in winter compared to the summer.”
Measuring blubber thickness while Willo rests with her head inside a plastic head guard.
Indeed, the sea lions appeared to need a large increase in energy intake in summer to recover from any loss of body mass. Without this dietary boost, the researchers note, a wild sea lion would risk remaining in a suboptimal state throughout the summer that would ultimately decrease its ability to breed. Consequently, the authors maintain, summer may be a more critical period than winter for a sea lion recovering from mild nutritional stress because of evolutionary processes that shaped the sea lion’s physiology to contend with uncertainty and predictability in environmental conditions. Prey species tend to have higher energy content during summer and occur in more predictable conditions compared to winter. As such, sea lions may be physiologically pre-adapted to better contend with food shortages in winter than in summer.
The study contributes significantly to the overall understanding of the consequences of nutritional stress on Steller sea lions, and provides new insights into the seasonal effects of a diet of low-energy fish. However, the reasons behind the seasonal difference in the capacity of sea lions to recover from nutritional stress remain unclear, leaving the door open for further investigation.

PUBLICATION

Steller sea lions show diet-dependent changes in body composition during nutritional stress and recover more easily from mass loss in winter than in summer.
Jeanniard du Dot, T., Rosen, D. A. S. , Trites, A. W. 2008.
Journal of Experimental Marine Biology and Ecology 367(1):1-10.
abstract
Controlled feeding experiments were undertaken with captive Steller sea lions (Eumetopias jubatus) to assess seasonal (winter vs. summer) physiological responses of individual animals to reduced quantities and qualities of food that are hypothesised to occur in the wild. Eight animals were randomly divided into two experimental groups fed isocaloric diets: Group H ate Pacific herring (Clupea pallasi) throughout the experiment while Group P was switched to walleye pollock (Theragra chalcogramma) during a 28-day food restriction (after a 28-day baseline) and back to herring during a 28-day controlled re-feeding. Diet type did not impact the rates of body mass lost when food was restricted, but did influence the type of internal energy reserve (protein vs lipids) the sea lions predominantly used. In both summer and winter, Group H lost significantly more lipids and less lean mass than Group P that was fed pollock during the restriction phase. The response of Group H was consistent with the predicted pattern of nutritional stress physiology (i.e. protein sparing and utilization of lipid reserves). Group P lost a surprisingly high proportion of body protein while consuming restricted levels of pollock, which could lead to muscle impairment and vital organ failure on a long-term basis. When given increased amounts of herring during the controlled re-feeding phase, the capacity of both groups to compensate for the previous mass loss was found to depend on season and was independent of previous diet. All of the sea lions increased their rates of mass gain and returned to their pre-experimental weight during winter, but not during summer. Some intrinsic energetic plasticity related to seasonal adaptation to the environment may render winter an easier period than summer to recover from nutritional stress.
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maschner_fishPacific cod are among the most heavily fished species in the Northern Hemisphere, and once-thriving populations have significantly declined in many parts of the world. In the Gulf of Alaska, the Pacific cod fishery is generally thought to be sustainable, but managers have limited resources and only a few decades of recorded data from which to base their conclusions.
Researchers addressed this problem using a new interdisciplinary approach that reconstructed the past. By combining palaeoecological data with biological data, they extended limited data sets from a half-century to several thousand years, giving scientists and fisheries managers a better idea of how current trends fit into the bigger picture.
In order to assess the general sustainability of the modern fishery in the Gulf of Alaska, researchers sought to determine whether industrialized fishing has affected the size of Pacific cod and whether climate change affects cod size and abundance. This study, authored by Herbert Maschner (Idaho State University), Matthew Betts (Canadian Museum of Civilization), Katherine Reedy-Maschner (Idaho State University), and Andrew Trites (University of British Columbia), was recently published in Fishery Bulletin.
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“The fish that stops”
The study took place on Sanak Island, in the western Gulf of Alaska, where the Aleut people have lived and fished for thousands of years, and where well-preserved shell mounds (or “middens”) now offer windows into their ancient ways and the conditions they faced. The researchers chose eight such sites spanning the period between 2550 B.C. and 1540 A.D. They excavated and measured the size and abundance of large numbers of fish bones from all sites, comparing these sizes to those of modern cod. They also looked into the effects of climatic changes over that time span.
 

The North Pacific and the western Gulf of Alaska region showing Alaska and the location of Sanak Island where bones were collected at archeological sites to determine whether a change in fish size was evident over the 4500 archeological record.

The North Pacific and the western Gulf of Alaska region showing Alaska and the location
of Sanak Island where bones were collected at archeological sites to determine whether
a change in fish size was evident over the 4500 archeological record.


The findings showed that although the size and relative abundance of Pacific cod fluctuated over the years, modern cod are fairly similar in size to their ancient ancestors. They also showed that Pacific cod tend to periodically vanish in great numbers, only to reappear in greater numbers later (which explains why the Aleut word for Pacific cod translates to “the fish that stops”).
This disappearing act seems to be linked to natural changes in ocean climate called regime shifts. While periods of warming seem to cause cod numbers to fall, the researchers found that Pacific cod populations do appear to recover quickly when the climate cools again. According to the study, regime shifts do not appear to affect cod body size.
Bones in the lab

Bones in the lab


A sign of sustainability
The palaeoecological data led the research team to conclude: “The changes in fish length between the prehistoric and modern eras in the Gulf of Alaska are more consistent with natural fluctuations than with harvesting pressure,” indicating that “current Pacific cod fisheries management and harvesting techniques in the western Gulf of Alaska are working.”
The palaeoecological data also points to an association between low ocean temperatures and low cod abundance, leading the authors to conclude that global warming may well become a complicating factor in the ability of fisheries managers to sustain abundant cod populations.
 
PublicationsRELATED PUBLICATION:
A 4500-year time series of Pacific cod (Gadus macrocephalus) size and abundance: archaeology, regime shifts, and sustainable fisheries.
Maschner, H. D. G., M. W. Betts, K. L. Reedy-Maschner and A. W. Trites. 2008.
Fishery Bulletin 106:386-394.
abstract
4500-year archaeological record of Pacific cod (Gadus macrocephalus) bones from Sanak Island, Alaska, was used to assess the sustainability of the modern fishery and the effects of this fishery on the size of fish caught. Allometric reconstructions of cod length for eight prehistoric time periods indicated that the current size of the near shore, commercially fished cod stocks is statistically unchanged from that of fish caught during 4500 years of subsistence harvesting. This finding indicates that the current Pacific cod fishery that uses selective harvesting technologies is a sustainable commercial fishery. Variation in relative cod abundances provides further insights into the response to punctuated changes in ocean climate (regime shifts) and suggests that Pacific cod stocks can recover from major environmental perturbations. Such palaeofisheries data can extend the short time-series of fisheries data (<50 y) that form the basis for fisheries management in the Gulf of Alaska and place current trends within the context of centennial- or millennial-scale patterns.
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Researchers Develop Predictive Model to Improve Legislation

Federal laws that designate so-called Critical Habitat for Steller sea lions have played a key role in driving conservation policy for these marine mammals in Alaska, but the information this designation was based on is now dated. Consortium researchers have used more recent knowledge to better predict the occurrence of sea lions at sea, providing policy makers with new tools to refine and update current legislation designating Critical Habitat.
Legislation such as the US Endangered Species Act (1972) plays an important role in designating and protecting habitat that is critical to the survival of a population or species. In the case of western Alaska’s endangered Steller sea lion populations, areas designated as Critical Habitat currently include all major haulouts and rookeries and their associated aquatic zones extending 20nmi (37km) seaward, in addition to some larger presumed foraging areas in the Bering Sea (Figure 1).

Building a Predictive Model
“We used published information about foraging behavior, terrestrial resting sites, bathymetry, and seasonal ocean climate to develop hypotheses relating life history traits and physical variables to the at-sea habitat of Steller sea lions,” the authors write. One hypothesis predicted, for example, that optimal foraging opportunities for Steller sea lions occur near depths of 200m (656ft), based on consistent reports that maximum densities of both bottom-dwelling and free-swimming fish also occur at that depth.

Figure 1: The spatial extents of the study area showing major Steller sea lion terrestrial sites (black symbols), platform of opportunity (POP) sightings of Steller sea lions (green symbols), and designated Critical Habitat (black line). The coastline is in gray and the marine portion is shaded from light to dark in increasing depth.
When this Critical Habitat was designated in 1993 it was likely based on the best available knowledge. This model of Critical Habitat has formed the basis for all subsequent protective legislation for Steller sea lions. However, the rationale for selecting these particular boundaries has never been fully explained or justified. Do they accurately represent habitat that sea lions frequent and rely upon year-round? Or could knowledge gained in the intervening years be used to develop a more robust and defensible definition of Critical Habitat for this species?
To answer these and other questions, Consortium researchers Edward Gregr and Andrew Trites (both of the University of British Columbia) developed a series of habitat models to predict the probability of sea lions occurring on a fine scale within the Gulf of Alaska and Bering Sea. The study was recently published in Marine Ecology Progress Series.
Building a Predictive Model
“We used published information about foraging behavior, terrestrial resting sites, bathymetry, and seasonal ocean climate to develop hypotheses relating life history traits and physical variables to the at-sea habitat of Steller sea lions,” the authors write. One hypothesis predicted, for example, that optimal foraging opportunities for Steller sea lions occur near depths of 200m (656ft), based on consistent reports that maximum densities of both bottom-dwelling and free-swimming fish also occur at that depth.
The researchers then divided the survey area – from Southeast Alaska to the end of the Aleutian Island chain – into grids of 3 x 3 km2 (3.47 square miles). Applying the eight broad hypotheses, which considered both the accessibility and suitability of sea lion habitat, they developed a series of habitat models predicting the probability of sea lions occurring at sea within each grid (e.g., Fig 2). These models were then compared with actual at-sea observations of sea lions (Fig. 3) using a skewness test to assess how the predicted probabilities related to the observations.

Gregr-Trites

Figure 2 – The best performing habitat prediction for adult females during winter
(non-breeding season). The model was based on depth and sea surface height variability. Model
predictions of 0.0 are shown as white to clearly delimit the spatial extent of non-zero values.

Gregr-Trites figure 3

Figure 3 – A comparison of the designated model for Steller sea lions (red line) to the best performing predictive model based on hypothesized depth and front suitability. The HS1 model captured 43.7% of the POP observations, while the designated model captured 36.1%. The POP data are overlaid in (b) to support comparisons of the relative model performance.

The results were encouraging. The habitat maps produced for adult female sea lions, for example, captured a higher proportion (43.7%) of actual at-sea observations than did the current Critical Habitat model (36.1%).

A Novel Technique
Many studies have described pinniped foraging behavior, but few have used the information gleaned from such studies to develop predictions of where sea lions will occur. The quantitative approach used by Gregr and Trites to describe fine-scale, at-sea distributions of Steller sea lions across their Alaskan range has not been previously attempted, but the authors maintain that such a prediction is necessary to effectively design, implement and evaluate any measures intended to protect Steller sea lion populations.

“Our results show that explicitly stating a priori hypotheses about the relationships between species distributions and physical and biological factors, and subsequently validating the resulting predictions, moves conservation biology and resource management closer to understanding ecosystem function, and places the debate of delineating habitat where it should be—on the state of available knowledge and how the animals are believed to be distributed.”

The skewness test played a key role in the model development. Developed by the authors, this test allows presence-only data to be used as a measure of model performance. The authors write “Our goal was to demonstrate that a deductive model could be built with some quantitative rigor in the absence of range-wide survey data. Skewness provides both a quantitative and visual interpretation of how well the predictive models achieve this.”
This study opens the door for future habitat models with higher resolutions and smaller spatial extents to address more local movements of sea lions, and eventually, of other wide-ranging marine predators. However, the authors note that a more comprehensive habitat-based definition of Critical Habitat will require developing hypotheses for other age and sex classes, such as juveniles, but this will require more complex at-sea data than is currently available.
November 24, 2008
 
 

A novel presence-only validation technique for improved Steller sea lion Eumetopias jubatus critical habitat descriptions.
Gregr, E.J. and A.W. Trites. 2008.
Marine Ecology Progress Series 365:247-261.
abstract
We used published information about foraging behaviour, terrestrial resting sites, bathymetry, and seasonal ocean climate to develop hypotheses relating life history traits and physical variables to the at-sea habitat of a wide-ranging marine predator, the Steller sea lion (Eumetopias jubatus). We used the hypotheses to develop a series of habitat models that predicted the probability of sea lions occurring within 3 x 3 km2 grids overlaid on the Gulf of Alaska and Bering Sea; and compared these deductive model predictions with opportunistic at-sea observations of sea lions (presence-only data) using 1) a likelihood approach in a small area where effort was assumed to be uniformly distributed, and 2) an adjusted skewness (Skadj) test that evaluated the distribution of the predicted values associated with true presence observations. We found the Skadj statistic was comparable to the likelihood test when using pseudo-absence data, but it was more powerful for assessing the relative performance of the different predictive spatial models. We also found that the habitat maps we produced for adult female sea lions using the deductive modelling approach captured a higher proportion of presence observations than the current habitat model (Critical Habitat) used by fisheries managers since 1993 to manage Steller sea lions. Such improved predictions of habitat are necessary to effectively design, implement, and evaluate fishery mitigation measures. The deductive approach we propose is suitable for modelling the habitat use of other age- and sex- classes, and for integrating these age/sex class specific models into a revised definition of Critical Habitat for Steller sea lions. It can also be readily used to identify the at-sea habitat of other central place foragers.
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New Model May Help to Quantify Prey Consumption

Harbor seals play an important predatory role in the North Pacific Ocean, and the types of fish they prefer to eat are well known. But scientists know little about the relative proportion of those fish in the diet (e.g., how much salmon is eaten compared to herring?). This knowledge would be useful to fisheries managers, for example, in projecting the impact of Harbor seals on various fish stocks.
nordstrom
A new research technique has put scientists one step closer to quantifying the diet of Harbor seals and other marine mammals. Rather than relying on imperfect procedures, such as extracting fish bones from feces or stomach contents, scientists can analyze the chemical remains of prey species contained in the blubber to determine their relative proportions in the diet.
Consortium researchers recently tested an analytic method, termed Quantitative Fatty Acid Signature Analysis (QFASA), on a group of Harbor seals. The study, authored by Chad Nordstrom, Lindsay Wilson, Dominic Tollit (each of the University of British Columbia) and Sara Iverson (Dalhousie University), was recently published in Marine Ecology Progress Series.
Quantifying Fatty Acids
The study was conducted over a six-week period and involved 21 Harbor seals temporarily housed at the Vancouver Marine Mammal Rescue facility. Each seal was estimated to be less than a month old, representing a dietary “clean slate.” The seals received one of three diets: smelt only, herring only, or three weeks of smelt and three weeks of herring. A blubber biopsy was taken from each animal at the beginning, middle, and end of the study.
 

nordstrom2

Fig. 1. Feeding regimes for (a) Herring Only, (b) Smelt Only, and (c) Smelt-Herring treatment groups over 42 days. Number of seals (N) sampled at each biopsy noted for each group. Coloured arrows indicate diet fed (white = homogenate & herring, black = herring, grey = smelt).


Under these controlled circumstances, the researchers sought to determine whether the QFASA model would correctly identify the known, six-week dietary regimes. QFASA analysis is based on the principle that long-chain fatty acids from prey species, each of which have a unique and identifiable chemical “signature”, are predictably incorporated into the predator’s blubber. Once the predator’s own fatty acid signature is obtained from the biopsy sample, it can be compared with a library of established fatty acid signatures from potential prey.
However, not all of the 68 fatty acids that may be present in Harbor seal blubber are obtained from their diet; some may be created by the seals through metabolism. Thus the researchers proposed to use a “reduced subset” of 35 fatty acids that appear most strongly associated with diet. Further, to correct for any changes to the prey’s fatty acid signature that may occur during digestion, the researchers obtained a species-specific calibration coefficient. The calibration coefficient and the fatty acid subset are two important inputs into the QFASA model that could significantly influence the results. Thus the researchers also sought to assess the sensitivity of the model to these two key inputs.
Promising Model
The study showed that over 42 days of captive feeding, the QFASA model could directly distinguish which seals were on single-species diet. However, results were inconclusive for the seals on mixed diets. The researchers found that the reliability of the results was most strongly influenced by the calibration coefficient and the fatty acid subset that were input into the model.
Thus the QFASA model shows promise in eventually helping researchers to evaluate the quantitative composition of predator’s diets. The current study demonstrated that the model is effective in assessing a constant diet, but further research is needed to effectively quantify mixed diets, especially those containing an unknown array of prey species. QFASA may prove useful in research on wild marine mammal populations once its effectiveness has been established though further captive studies.
July 21, 2008
PublicationsPUBLICATION
Evaluating Quantitative Fatty Acid Signature Analysis (QFASA) using harbour seals (Phoca vitulina richardsi) in captive feeding studies.
Nordstrom, C.A., L.J. Wilson, S.J. Iverson and D.J. Tollit. 2008.
Marine Ecology Progress Series 360:245-263.
abstract
Quantitative fatty acid (FA) signature analysis (QFASA) has recently been developed to estimate the species composition of predator diets by statistically comparing FA signatures of predator adipose tissue with that of their potential prey. Captive feeding trials were used to test the technique with newly-weaned harbour seals (Phoca vitulina richardsi, N = 21). Two groups of seals were fed monotypic diets of either Pacific herring (Clupea pallasii) or surf smelt (Hypomesus pretiosus) for 42 days while a third group was fed smelt (21 days) followed by herring (21 days). Blubber biopsies were taken dorsally at day 0, 21 and 42. Specific calibration coefficients (CC) required by QFASA were developed from 4 juvenile harbour seals and in some cases differed by two-fold with previously reported phocid CC. QFASA diet estimates were evaluated using 2 CC sets, 15 FA subsets and a library of 3 – 11 potential prey species. Diet switches were best tracked using the harbour seal CC and a new FA subset. Overall prey misclassifications were apparent (mean = 12%, range = 4 – 25%) when modeled with 8 additional prey not fed, often consistent with overlapping prey FA signatures. Blubber FA turnover rates were not strictly linear and in the order of 1.5 – 3 months in newly-weaned animals. Following model parameter optimization, QFASA estimates reflected major diet trends in the feeding study, but were sensitive to the CC and FA subsets used as well as to prey species with similar FA signatures. Our results have important implications in the application of QFASA to study pinniped diets in more complex conditions.
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r_kLike most mammals, Steller sea lions require varying amounts of food throughout the year, according to such appetite-influencing factors as age, sex, and the reproductive cycle. Yet the availability of sufficient food in any given season is beyond their control, and a shortage of prey in a time of great energetic need can lead to long-term health effects.
How might recent changes in the availability of key prey such as walleye pollock, a major winter food source for Steller sea lions in western Alaska, affect the sea lion populations that depend on them? Could the seasonal pollock fishery play an exacerbating role? Little is known about how critical prey shortages affect the physiology of individual sea lions in each season.
To this end, Consortium researchers worked with captive Steller sea lions to study their hormonal levels – which mediate seasonal changes in physiology – in response to periods of food restriction across all seasons. The results of the study, by David Rosen and Saeko Kumagai (of the Marine Mammal Research Unit at the University of British Columbia), are published in the Journal of Comparative Physiology B.
rk2
The Role of Hormones
A previous study by the authors found that when captive Steller sea lions were subjected to short-term periods of food restriction, they lost more body mass in winter than in other seasons. The current study examines the seasonal relationship between key hormones and physiological changes (in body mass, body composition, and metabolism) during periods of food restriction. The researchers studied seasonal differences in initial levels of three hormones (triiodothyronine or T3, thyroxine or T4, and cortisol) and one blood metabolite (blood urea nitrogen, or BUN) in captive Steller sea lions. Cortisol is usually elevated in response to stresses such as a restricted diet or increased mass loss. Similarly, elevated BUN levels have traditionally been used as an indicator of nutritional stress in wildlife management. The principal thyroid hormones, T3 and T4, affect metabolism in mammals and can alter growth rates.
Competition for Prey
The sea lions were fed restricted diets for up to nine days in each season and lost an average of ten percent of their initial body mass. “Overall, restricted energy intake during the winter resulted in the greatest decreases in T3 and body mass and the greatest increases in cortisol and BUN, and the opposite results in summer,” the authors write. “This suggests that the Steller sea lions had a greater physiological reaction to food restriction during colder seasons (non-breeding seasons), and that they were probably less impacted in warmer seasons (breeding seasons).”
rosenkumagai_walleyeImportantly, the study suggests that sea lions may be more physiologically susceptible to short, severe reductions in prey during the winter, which coincides with the timing of the Alaskan pollock roe fishery. This also corresponds to the time of year when pollock densities may require sea lions to forage for longer and to consume more pollock prey to meet their higer seasonal energetic needs.
“Thus, while competition between fisheries and sea lions is still a contentious hypothesis, the potential effects of such interactions would appear to be greater in the winter,” the authors note.
These results serve several important purposes. They provide a clearer understanding of the underlying physiological responses and bioenergetic priorities of Steller sea lions at different times of year, and they also test the ability of certain blood parameters to be used as indicators of nutritional stress. Finally, they can be used to help refine current fisheries legislation by offering empirical experimental results. Together, this represents a valuable contribution toward measuring and identifying nutritional stress and its underlying causes among populations of wild Steller sea lions.
 

PUBLICATION


2008
 
Hormone changes indicate that winter is a critical period for food shortages in Steller sea lions.
Rosen, D.A.S., Kumagai, S. 2008.
Journal of Comparative Physiology B 178:573-583.
abstract
Given that many marine mammals display seasonal energetic priorities, it is important to investigate whether the impact of unexpected food restriction differs during the year. Steller sea lions (Eumetopias jubatus) fed restricted diets for up to 9 days during spring, summer, fall, and winter lost an average of 10% of their initial body mass. We tracked changes in the levels of three hormones (cortisol, total thyroxine—TT4, total triiodothyronine—TT3) and one blood metabolite (blood urea nitrogen—BUN) following a food restriction in relation to season, body mass, body composition, and metabolism. Degree of changes in cortisol, TT3, and BUN after food restriction was significantly affected by season. The greatest changes in cortisol (+231%), BUN (+11.4%), TT4 (-23.3%), and TT3 (-35.6%) occurred in the winter (November/December) when rates of body mass loss were also greatest. Changes in cortisol levels were positively related to total body mass loss, while changes in TT3 levels were negatively related. While greater increases in BUN were related to greater rates of mass loss, the use of BUN levels as an indicator of metabolic state is complicated by the type and level of food intake. The observed changes in hormone levels support morphological data suggesting Steller sea lions may be more strongly impacted by short-term, reduced energy intake during winter than at other times of the year.
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Scientists Seek to Reduce Disturbance on Rookeries
To better understand the diet of wild Steller sea lions populations, Consortium scientists visit haulouts and rookeries to collect fecal (scat) samples, which they then analyze for prey remains. However, scat collection often requires displacing the animals that are onshore, which can be disruptive in breeding areas (rookeries) at certain times of year.
trites_3
To reduce disturbance on rookeries, scientists proposed using scats from adjoining bachelor male (non-breeding) haulouts as a proxy. If the scats of non-breeding males are similar enough in composition it may eliminate the need to disturb breeding females. This hypothesis was recently tested and published in the journal Aquatic Mammals by Dr. Andrew Trites (University of British Columbia) and Donald Calkins (formerly at the Alaska Department of Fish and Game, and now at the Alaska SeaLife Center).
Sampling Protocol
“We sought to develop a scat-sampling protocol that would minimize disturbance to Steller sea lions during the breeding season yet would yield accurate data about what sea lions eat,” the authors write. They compared scats from sexually mature Steller sea lions at one male haulout with those from three female-dominated rookeries at Forrester Island in southeast Alaska.
If the diet of bachelor bulls was similar enough to that of nearby breeding females, it could be useful as a proxy in future studies. That is, it could help to predict the diet of females without sampling the breeding population and with minimal intrusion on the nearby bachelor bulls. Further, if the scats indicated a similar diet among the females, samples collected from one rookery could help to predict the diets of all breeding females in the vicinity, further reducing disturbance.
tritesShared Diet
“We found that it is not necessary to sample scats from all of the breeding sites that make up the Forrester Island complex because females using these rookeries all have the same diet,” the authors reported. Female diets contained gadids, salmon and small oily forage fish, with fewer rockfish, flatfish, cephalopods, and other fishes.
trites_2Compared to females, males consumed significantly fewer salmon and more pollock, flatfish, and rockfish. These dietary differences suggest that males and females may forage in separate areas, or that their relative physical size affects their ability to capture certain prey.
This study shows that female diets can be determined from samples collected at a single site within a rookery complex. Thus, a rotating schedule of scat collection from one breeding group could determine the diet of all local breeding females while reducing long-term disturbance in the population. Unfortunately, the male diet at Forrester Island differed sufficiently from that of breeding females to prevent its use as a proxy for female diet.
To ensure the long-term conservation of the species, scientists must balance the need to accurately determine what Steller sea lions eat with the cost of obtaining this information. Future comparisons of dietary information from other rookeries and haulouts in Alaska will help to determine how many rookeries and haulouts need to be sampled to accurately determine what Steller sea lions are eating.
June 2, 2008
SEE PUBLICATION:

Diets of mature male and female Steller sea lions differ and cannot be used as proxies for each other.
Trites, A.W., and D.G. Calkins. 2008.
Aquatic Mammals 34:25-34.
abstract
Disturbance of otariid breeding sites (rookeries) to determine diet from fecal remains (scats) could be eliminated if the diets of males using adjoining bachelor haulouts could be used as a proxy for diets of breeding females. We collected scats from sexually mature Steller sea lions (Eumetopias jubatus) at one male resting site (haulout) and three female dominated breeding sites (rookeries) at Forrester Island, Southeast Alaska (June-July, 1994–1999) to test whether the diets of bachelor bulls differed from that of breeding females. Female diets were fairly evenly distributed between gadids, salmon and small oily fishes (forage fish), and contained lesser amounts of rockfish, flatfish, cephalopods and other fishes. Female diet did not differ significantly between the 3 rookeries, but did differ significantly from that of males. Males consumed significantly fewer salmon, and more pollock, flatfish and rockfish compared to females. The males also consumed larger pollock compared to females. These dietary differences may reflect a sex-specific difference in foraging areas or differences in hunting abilities related to the disparity in physical sizes of males and females. The similarity of the female diets between rookeries suggests that female diets can be determined from samples collected at a single site within a rookery complex. Unfortunately, summer diets of breeding females cannot be ascertained from hard parts contained in the scats of mature male Steller sea lions.
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Scientists Measure Underwater Acceleration in Three Dimensions


As part of the ongoing effort to conserve dwindling Steller sea lion populations in the North Pacific Ocean, scientists are working to better understand how much food sea lions require and how they behave when foraging underwater for food. A key element of this research is finding a way to calculate how much energy a diving sea lion expends.
Naturally, this information is difficult to obtain from wild Steller sea lions diving in the ocean. However, a recent study using trained Steller sea lions diving in a controlled open water environment suggests a novel way to estimate the energetic cost of foraging.
The study, authored by Andreas Fahlman (UBC Marine Mammal Research Unit); Rory Wilson (University of Wales Swansea); and UBC’s Caroline Svärd, David Rosen and Andrew Trites, was recently published in the journal Aquatic Biology.
Measuring Activity
Previous studies have attempted to estimate the energetic cost of foraging by measuring heart rate or dive duration, both of which have produced imperfect results. By measuring activity, or movement at depth, the researchers sought a less invasive way to assess metabolism than traditional methods, such as surgically implanted heart rate monitors.
“Three Steller sea lions were trained to participate in free-swimming, open-ocean experiments designed to determine if activity can be used to estimate the energetic cost of finding prey at depth,” the authors write.
The three female sea lions were trained to voluntarily dive to fixed targets at depths of 10-50 metres (32-164 feet), and to resurface inside a floating dome. Devices in the dome measured the amount of carbon dioxide in the lungs after the dive, providing a measurement of energy expenditure via gas exchange. Attached to each sea lion was a harness containing an accelerometer that measured the direction and acceleration of all underwater movements.

The researchers compared the measurements obtained from the dome against those from the accelerometer, in an attempt to determine whether activity could be as effective as gas exchange in estimating metabolism (energy used). Finally, they sought to derive an equation to predict the metabolic rate (energy spent) over a complete dive event (the dive + the interval at the surface), to varying depths.
Positive Results
The team used the acceleration data to calculate the overall dynamic body acceleration (ODBA), a proxy for activity. They found that ODBA correlated well with the diving metabolic rate calculated from the dome’s gas exchange data. The results also corresponded with similar studies that used heart rate to estimate metabolic rate.
Overall, the study successfully showed that collecting acceleration data in three dimensions – a simple, non-invasive technique – can accurately estimate the field metabolic rate of wild Steller sea lions and other diving mammals and birds. By collecting additional data, the researchers hope to further refine their results, dividing the dive cycle into the cost of true diving and the cost of resting at the surface. This information is needed to refine estimates of how much food sea lions require in the wild.

PublicationsPUBLICATION

Activity and diving metabolism correlate in Steller sea lion Eumetopias jubatus.
Fahlman, A., R. Wilson, C. Svärd, D.A.S. Rosen and A.W. Trites. 2008.
Aquatic Biology 2:75-84.
abstract
Three Steller sea lions Eumetopias jubatus were trained to participate in free-swimming, open-ocean experiments designed to determine if activity can be used to estimate the energetic cost of finding prey at depth. Sea lions were trained to dive to fixed depths of 10 to 50 m, and to re-surface inside a floating dome to measure energy expenditure via gas exchange. A 3-axis accelerometer was attached to the sea lions during foraging. Acceleration data were used to determine the overall dynamic body acceleration (ODBA), a proxy for activity. Results showed that ODBA correlated well with the diving metabolic rate (dive + surface interval) and that the variability in the relationship (r2 = 0.47, linear regression including Sea lion as a random factor) was similar to that reported for other studies that used heart rate to estimate metabolic rate for sea lions swimming underwater in a 2 m deep water channel. A multivariate analysis suggested that both ODBA and dive duration were important for predicting diving metabolic cost, but ODBA alone predicted foraging cost to within 7% between animals. Consequently,collecting 3-dimensional acceleration data is a simple technique to estimate field metabolic rate of wild Steller sea lions and other diving mammals and birds.
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