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Marine Mammal Research News:

Sneak peak into the lives of killer whales

UBC researchers captured some amazing underwater video this week from the back of a killer whale showing a pod of killer whales travelling and interacting together. Read Article 



Bowhead whales MMRUBowhead whales feed year-round in Cumberland Sound, Nunavut

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

Read Article


A Window into the Lives of Resident Killer Whales

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.


Growth and development of North Pacific gray whales (Eschrichtius robustus).
Agbayani, S., S.M.E. Fortune and A.W. Trites. 2020.
Journal of Mammalogy, DOI:10.1093/jmammal/gyaa028
Understanding variability in growth patterns of marine mammals provides insights into the health of individuals and status of populations. Body growth of gray whales (Eschrichtius robustus) has been described for particular life stages, but has not been quantified across all ages. We derived a comprehensive growth equation for gray whales by fitting a two-phased growth model to age-specific length data of eastern North Pacific gray whales that were captured, stranded, or harvested between 1926 and 1997. To predict mass-at-age, we used the allometric relationship between mass and length. We found that on average (± SD), calves were 4.6 ± 0.094 m and 972 ± 27 kg at birth, and reached 8.53 ± 0.098 m and 7,645 ± 162 kg by the end of their first year of life (n = 118). Thus, calves almost double (2×) in length and octuple (8×) in mass while nursing, and are effectively about two-thirds of their asymptotic adult length and one-third of their maximum mass when weaned. The large sample of aged individuals (n = 730) indicates that gray whales live up to ~48 years and have a life expectancy of < 30 years. Adult females attain a mean (± SD) asymptotic size of 13.2 ± 0.054 m and 20,706 ± 249 kg, while the smaller males average 12.6 ± 0.054 m and 19,812 ± 249 kg at ~40 years of age. Females are thereby ~4% longer and heavier than males. These age-specific estimates of body size can be used to estimate food requirements and assess nutritional status of individuals.

keywords     eastern gray whale, growth curves, length, life expectancy, longevity, mass, morphometrics, Putter model, sexual dimorphism
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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.
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.
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Prey composition impacts lipid and protein digestibility in northern fur seals, Callorhinus ursinus.
Diaz Gomez, M., D.A.S. Rosen, I.P. Forster and A.W. Trites. 2020.
Canadian Journal of Zoology 68:681-689.
Pinnipeds have specific macronutrient (protein, lipid) requirements to satisfy physiological functions, yet little is known about how diet characteristics affect macronutrient digestibility. We measured relative and absolute lipid and protein digestibility in six female northern fur seals (Callorhinus ursinus (Linnaeus 1758)) fed eight experimental diets composed variously of four prey species (Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes 1847), walleye pollock (Gadus chalcogrammus Pallas 1814, formerly Theragra chalcogrammus (Pallas 1814)), capelin (Mallotus villosus (Müller 1776) and magister armhook squid (Berryteuthis magisterial (Berry 1913)). We quantified how digestibility was affected by proximate composition of the diet (%lipid or protein), levels of food mass and macronutrient intake, and tested for any potential benefit of multi-species diets. Overall, digestibility of both protein and lipid were high across diets, although macronutrient retention of lipids (96.0–98.4%) was significantly higher than protein (95.7–96.7%) for all but the two highest protein diets. Increased levels of protein intake resulted in increased protein retention, but decreased lipid digestibility. There was no evidence that mixed-species diets provide greater macronutrient digestibility over single-species diets. The results suggest that high to moderate lipid diets are more beneficial to northern fur seals as they lead to increased levels of lipid retention without large decreases in protein digestibility. This raises concerns that dietary factors may be contributing to the population declines of northern fur seals in the Bering Sea.

keywords     Northern fur seal, Callorhinus ursinus, diet composition, macronutrients, lipid digestibility, protein digestibility
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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.
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.
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Predation by Pacific great blue herons on juvenile salmon.
Sherker, Z.T. 2020.
In Zoology. M.Sc. Thesis, University of British Columbia, Vancouver. 68 pages
An array of foragers prey on salmon in rivers and estuaries while salmon smolts out-migrate from their natal streams-and may account, in part, for the poor returns of adult salmon to the Salish Sea. However, the Pacific great blue heron (Ardea herodias fanning) has not been identified as a predator of smolts despite being regularly seen near salmon streams. I investigated the role that herons may be playing in the depredation of salmon by scanning fecal remains under heron nests for Passive Integrated Transponder (PIT) tags that had been implanted in wild and hatchery-reared salmon smolts from 2008-2018. These nests were located in three heron rookeries that were within 35 km of the mouth of the Cowichan, Big Qualicum, and Capilano Rivers. Using a mobile PIT antenna, I recovered 1,199 smolt tags, representing a minimum annual predation rate of 0.3-1.3% of all smolts in the three rivers. Correcting for tags consumed by herons and defecated outside of the rookery raised the estimated proportion of smolts to 0.7-3.2% of the outmigrating fish, but predation rates as high as 6% were documented during a low river-flow year in the Cowichan River. The distribution and timing of tag depositions under the heron nests indicated that most great blue herons prey on salmon smolts and that consumption occurs in late spring during the chick-rearing phase of the breeding season. Energetic analyses suggest that smolt consumption provides a substantial proportion of the heron chick diet during a time of peak energy demand. Predation on smolts occurred primarily in the lower rivers and upper estuaries. Smaller salmon smolts were significantly more susceptible to heron predation in all systems, and predation rates were comparable between wild and hatchery-reared smolts. Recovering so many tags from smolts at heron rookeries was unexpected and indicates that great blue herons are a new predator of wild and hatchery-reared juvenile salmon. Locations of heron rookeries relative to salmon bearing rivers are likely good predictors of heron impacts on local salmon runs, and a potential means to assess coast-wide effects of great blue herons on salmon recovery.
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