Non-refereed Publications

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

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Marine mammal predator – prey interactions occur over different spatial and temporal scales, making it difficult to empirically decipher the influences they have on one another and on their ecosystems. However, their coexistence suggests that marine mammal predators and their prey have had profound influences on each other’s behaviors, physiologies, morphologies, and life-history strategies. The diversity of niches filled by marine mammals makes it difficult to generalize about the evolutionary consequences of their interactions with prey, beyond stating the obvious: marine mammals have adapted to catch food, while their prey have adapted to avoid being caught. On the shorter ecological time scale, marine mammals can affect the abundance of other species by consuming or outcompeting them. They can also indirectly affect the abundance of nontargeted species by consuming one of their predators, and can have strong impacts on the overall dynamics and structure of their ecosystems. One of the best tools for understanding marine mammal predator – prey interactions is the ecosystem model. However, more work is required through experimental manipulations and observational studies to evaluate the choices made by marine mammals and the costs of obtaining different species of prey.

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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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As part of our investigations into Steller sea lion habitat use and fisheries economics, we have prepared a collection of physical oceanographic data for the eastern North Pacific and the Bering Sea. Data include rectified grids of chlorophyll-a concentrations, sea surface temperature, slope of sea surface temperature, sea level anomaly, wind speed, current velocity and direction, mixed layer depth, and bathymetry. Geographic Information System-compatible raster (gridded) data were created from available on-line sources as both monthly and long-term averages. Monthly averages were produced for all available years for each sensor at a spatial scale of 9x9 km2 for the Gulf of Alaska and Bering Sea. We prepared long-term averages (climatologies) at 3x3 km2 for the northern Gulf of Alaska, and for the entire eastern North Pacific we prepared each source data set at its native resolution. We evaluated the sea surface temperature data at the 9x9 km2 scale using available quality data, and improved the data provided by interpolating through low quality pixels. Considerable processing was required to create a continuous North Pacific perspective, and to ensure that the data sets were correctly aligned at the different spatial scales. We also present 2-week averaged data from the output of a Regional Ocean Modelling System (ROMS) implemented for the northern Gulf of Alaska (3x3 km2) for the year 2001. These data provide a representation of the changing, vertical structure of the ocean. Given the significant investment to create a rectified data collection, we have prepared the data for distribution to interested researchers. The ROMS data are provided in MS Access format, and the remote sensing data as binary float files. Federal Geographic Data Committee (FGDC)-compatible metadata have been prepared. The data described herein are available from the Marine Mammal Research Unit web site or on request.

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We are using demographics, scat analysis, and genetic measurements of Steller sea lions (SSLs)to understand the factors affecting population status throughout Alaska. Steller sea lions are listed as threatened throughout Southeast Alaska including Glacier Bay National Park where they frequent at least five terrestrial sites, including a recently established rookery on Graves Rock. Breeding season counts in GBNP increased at ~6 percent/yr between 1989 and 2002. Brand resighting during 2003 revealed 16 western stock SSLs seen within the park. Survival to two months of age was 90 percent. Fifty pups were branded at Graves Rock in 2002. It is necessary to mark more animals to estimate annual survival rates of juveniles and adults. Sandlance and pollock were top prey items at Graves Rock and South Marble Island. Mitochondrial DNA analysis indicates that the Graves Rock rookery was established in part by females from the western sea lion stock (west of 144° W longitude).

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We constructed ecosystem models using the Ecopath with Ecosim software to evaluate whether predation by killer whales might explain the decline of Steller sea lions since the late 1970s in the western Aleutian Islands. We also sought to understand why sea lions increased in the presence of killer whales in Southeast Alaska. Modeling results reproduced the time series of abundances for exploited species and sea lions in both ecosystems. Simulation results suggest that killer whale predation contributed to the decline of sea lions in the western Aleutians, but that predation was not the primary cause of the population decline. Predation could however have become a significant source of mortality during the 1990s when sea lions numbers were much lower. In Southeast Alaska, predation was also found to be a significant source of mortality in the 1960s when sea lions were low, but ceased to control population growth through the 1980s and 1990s. Overall, the ecosystem models suggest that large populations of Steller sea lions can withstand predation, but that small populations are vulnerable to killer whales.

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A team of researchers from Simon Fraser University and the University of British Columbia have designed and built a prototype implanted wireless tag for monitoring Steller sea lions. This paper reviews the system level RF design aspects, and estimates the RF link range.

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Little is known about the mechanism in which decreased nutrient intake influences the physiology of Steller sea lions. By investigating the factors that link nutrition, fat metabolism and lean tissue accretion, we can assess the impact of decreased nutrient intake on energy storage and lean tissue growth, which may have implications for survival. Captive Steller sea lion females (n = 8, 2 to 5 year of age) were used to examine changes in the somatotropic axis in response to decreased nutrient intake. Animals were placed on a normal herring maintenance diet for 1 month. After this 1 month ‘baseline’ period four animals were placed on a herring submaintenance diet and four animals were fed an isocaloric Pollock submaintenance diet for 1 month. During the 1 month submaintenance period, the animals lost 10 to 15% of their body mass. In the 1 month re-alimentation period, only three animals increased mass to their initial value. Concentrations of IGF-I followed the expected pattern paralleling changes in intake. Concentrations of GH were more variable than IGF-I. Concentrations of IGFBP generally followed the expected response based on domestic animal research. The overall concentration of IGFBP-3 declined with decreased nutrient intake. In contrast, IGFBP-2 increased with decreasing nutrient intake.

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Marine mammals face distinct environmental conditions that can translate into unique physiological challenges. Studies of foraging behavior in marine (diving) mammals have primarily focused on how the physiological constraint of aerobic dive limits defines their strategies. However, there are other physiological constraints that shape foraging patterns in marine mammals that are often neglected. This paper discusses the interaction of three broad physiological processes that impose limitations on foraging patterns: the physiological demands of prey acquisition (foraging), prey processing (digestion), and thermoregulation. The theoretical framework presented allows us to review and synthesize the complex physiological interactions that shape foraging behavior at the individual level. Observed foraging behavior is an integration of a multitude of competing demands on an animal. The aim of this framework is to enhance our understanding of these processes and direct areas of future research.

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The North Pacific is a hot-bed for understanding how marine populations are impacted by humans as well as by environmental conditions. The 'Thompson-Burkenroad debate' has been ongoing since the late-1940s: what drives the marked fluctuations in Pacific halibut that has been observed over the past century' Dr William Thompson, who started up the work of the International Pacific Halibut Commission, IPHC, argued that the changes in halibut abundance could be fully explained by changes in fishing pressure, i.e. that they were the result of successful management on the part of IPHC, while his adversary, Dr Martin Burkenroad questioned if the populations trends could be accounted for by fishing pressure on its own, or if wasn't rather a question of environmental factors impacting halibut recruitment. While Thompson and Burkenroad actually never debated the relative role of fisheries and the environment ' indeed it may well be that they would actually agree that one factor in itself would not suffice to give us the full explanation their debate has lived on, and both sides still have proponents arguing for one over the other. Examining the Pacific halibut trends now, nearly 60 years after the debate started, still yields inconclusive answers only. We cannot name the culprit. The debate has widened since Thompson and Burkenroad's days, and we regularly hear about regime shifts in connection with the North Pacific. A notable debate in this context has emerged, seeking explanations for why the Steller sea lions have declined to become threatened in major parts of their North Pacific distribution area, while increasing in others. A multitude of explanations have been brought forward, and considerable research has been aimed at understanding the importance of nutritional conditions, of predators and of prey, of competition with commercial fisheries, of parasites and diseases, of the Pacific Decadal Oscillation Index, and of the potential impact of incidental culls, to mention some. As for the halibut, no conclusive explanation has emerged. Asking then, if the non-emergence of a single clear explanation may be due to the Steller sea lion being impacted by a combination of factors the North Pacific Universities Marine Mammal Research Consortium and the North Pacific Marine Science Foundation initiated a project 'Ecosystem analysis of Steller sea lion dynamics and their prey' through NOAA funding. The project, which was the brain child of Andrew Trites (Director of the Marine Mammal Research Unit, Fisheries Centre), employs ecosystem modelling of North Pacific ecosystems (Southeast Alaska, the Central Gulf of Alaska and the Western Aleutian Islands) in an attempt to evaluate (quantify) the relative role the various factors may have played in determining population trends. The methodologies applied for the modelling along with some of the preliminary findings from the study are described in this report. Notably, the models indicate that no single factor by itself can explain the population trends of Steller sea lion, several have to be invoked. In parallel to the work centered on Steller sea lion, the UBC 'Sea Around Us' project (www.seaaroundus.org) through funding from the Pew Charitable Trusts initiated a series of workshops aimed at evaluating the relative role of fisheries and environmental factors for North Pacific ecosystems. Bringing together researchers from the Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo; the NOAA Alaska Fisheries Science Center, Seattle; the University of Washington, School of Fisheries, Seattle; and the University of British Columbia, Fisheries Centre, Vancouver, to analyze a series of ecosystems ranging from the Bering Sea to the Northern California Current, and coordinate the methodologies. We present descriptions of some studies in this report, while most of the findings are published separately. The present report also includes a reconstruction of North Pacific whale catches for the 20th century, which served to estimate the whale population at different periods in Southeast Alaska and the Western Aleutians. Finally, in the interest of preparing future work related to evaluating nutritional aspects of North Pacific ecosystems we have included a compilation of the energy content of invertebrates, fish and mammals in the Gulf of Alaska.

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We examined or obtained information on specimens of Steller sea lions in museums and other collections. We report on 1740 specimens (complete or partial skulls) in 44 collections in Canada, Germany, Japan, the Netherlands, Russia, the United Kingdom, and the United States. At least several hundred other specimens also exist, mainly in Japan and Russia. Collection dates range from 1842 to the present. Geographically, specimens are well represented in both ?Western? and ?Eastern? regions (separated at 144 W longitude): 509 and 956, respectively. Collection localities within Alaskan regions 2 (Eastern Gulf of Alaska) to 8 (Eastern Bering Sea) are represented by 290 specimens; another 566 specimens are from Japan and Russia and 462 from Alaska region 1 (Southeastern Alaska) southwards. Thus specimens are well spread across the species? breeding range, including areas of population decline. Representation is also good for the period of population decline and earlier per! iods: 442 specimens are from before 1960, 352 from 1960-69, 370 from 1970-79, and 487 from 1980 onwards. There are some problems with quality of data, and with seasonal and geographic representation, but we conclude that ample specimens exist to permit research pertinent to population declines in parts of the species? range.

abstract
The objectives of this study were to compare Resting Metabolic Rate (RMR) from animals in the eastern and western Alaskan populations to discern whether there is any evidence of nutritional stress. Oxygen consumption data were collected from captive Steller sea lions held at the Vancouver Aquarium, Vancouver, BC and from free-ranging Steller sea lions captured from western and eastern Alaskan stocks. In water, RMR ranged from 33.3 to 56.7 MJ/day for sub-adult animals (109-158 kg, 2.9-4.6 times predicted for an adult animal) and from 20.0 to 26.6 MJ/day for pups (57-59 kg, 3.3-4.3 times predicted) at 2°C. RMR, generally decreased with increasing water temperature, but the relationship was not statistically significant. Reduced body condition had a noticeable impact on RMR in juvenile sea lions at colder water temperatures. The results of the present study suggest that young sea lions would be subject to even greater thermoregulatory demands if their body condition were reduced.

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This experiment examined the response of a suite of hematologic parameters to experimentally induced nutritional stress in a group of captive Steller sea lions. The goal was to identify a suite of parameters that could be used to diagnose comparable conditions among wild Steller sea lions. Previous studies, many with ruminant mammals, have shown that there are significant changes in blood characteristics with nutritional status. However, it is equally clear that there is no overwhelming choice of blood parameter to indicate nutritional stress across different species. Therefore, species-specific empirical tests such as the one carried out in the current study are essential to place results from wild studies in a biologically meaningful context.

abstract
This experiment examined the response of a suite of hematologic parameters to experimentally induced nutritional stress in a group of captive Steller sea lions. The goal of this study was to identify a suite of parameters that could be used to diagnose comparable conditions among wild Steller sea lions. The experiments were conducted with four captive female Steller sea lions. They were alternated between isocaloric diets of Atka mackerel (4.9-6.7% lipid w.w.) and herring (10.3-13.4% lipid). The level of food intake (~35.6 kJ d-1) was set a priori at a level estimated to produce a 10-15% loss of initial body mass over the 29-day trials. Body mass was measured daily (± 0.1 kg), and body composition was determined at the start and end of each trial by deuterium dilution technique. Nine of the blood parameters measured in this study showed consistent changes over the 29-day period of induced nutritional stress. White blood cell counts, platelet counts, phosphorous levels, alkaline phosphatase levels, and serum Fe levels all showed consistent decreases, whilst red blood cell counts, hemoglobin levels, hematocrit levels, and gamma GT levels, showed consistent increases. Only one of the blood parameters showed a significantly different response in relation to diet - blood urea nitrogen (BUN) levels showed a consistent increase on the Atka mackerel diet and a consistent decrease on the herring diet (P=0.029). Sea lions on the Atka mackerel diet showed a mean percentage increase in BUN level of 9.2%, and a mean percentage decrease of 4.9% on the herring diet. Previous studies, many with ruminant mammals, have shown that there are significant changes in blood characteristics with nutritional status. However, it is equally clear that there is no overwhelming choice of blood parameter to indicate nutritional stress across different species. Therefore, species-specific empirical tests such as the one carried out in the current study are essential to place results from wild studies in a biologically meaningful context.

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Ecosystem models were constructed for the Antarctic and the Bering Sea that incorporate current understanding of biological interactions of species within the ecosystem (i.e., who eats whom and how much). Within the limitations that are inherent to simulations, both models suggest that removal of large whales had little measurable effect on lower trophic levels or on the dynamics of other species in their polar ecosystems. Trophic interactions failed to explain the magnitude of changes in the biomass of the major species groups in the Antarctic and Bering Sea. Nor did fin-fisheries appear to have had a significant effect on the abundance of non-targeted species. This may mean that environmental effects (which were not modeled) play an important role in influencing the dynamics of marine ecosystems. Oceanographic factors such as changes in water temperature or ocean currents likely result in variations in ecosystem production and species recruitment patterns which are not captured by our Ecopath models. The Ecopath modeling approach is a powerful means of synthesizing knowledge about ecosystems and the factors that influence ecosystem dynamics. They provide a straightforward means for estimating trophic levels and niche overlaps with other species to assess the potential for resource competition. While the models failed to support the hypotheses that large whales play a significant structural role in the Antarctic and Bering Sea ecosystems, they do support what most already know ?- i.e., that populations of large whales are easily reduced to low numbers, but take a long, long time to recover. They also help in recognizing the need to consider factors other than food web interactions when assessing the status of cetaceans, as well as highlighting the potential tradeoffs that can result when other species are removed from ecosystems.

abstract
In June 1997,we conducted a test of the hypothesis that the current Steller sea lion decline is due to nutritional stress. Steller sea lions were studied at two of the central Aleutian Islands, Seguam and Yunaska, and at the Forrester Island rookery complex in southeast Alaska. Trip durations and the percent time spent at sea were much shorter for Steller sea lions from Seguam Island compared to those from the Forrester Island rookery. Dives at Seguam Island were shorter and shallower, but more frequent than those at Forrester Island The short trips at Seguam Island generally consisted of a single bout of uninterrupted dive cycles while at Forrester Island the trips were broken into dive bouts of varying length separated by periods spent traveling or resting at the surface. However, on average, the percent of a trip spent submerged was not significantly different. Another measure of foraging effort, the vertical travel distance per unit time at sea, was about 1. 5 times greater for Steller sea lions at Forrester Island. The at-sea field metabolic rates, however, were similar for both groups. Data on the time and distance elapsed from departure on a foraging trip until commencement of “foraging dives ” shows that at both rookeries Steller sea lions appear to begin searching for prey very soon after entering the water. However , the mean time from departure to first prey ingestion, identified by the stomach temperature record, was about five times longer for Steller sea lions at Forrester Island than at Seguam Island. The rough estimation of prey intake rate at Seguam Island was about two times greater than at Forrester Island. Therefore, it would appear that in 1997,adult female Steller sea lions at Seguam Island found suitable prey more quickly, and once they found it were able to ingest it at a much higher rate than Steller sea lions at Forrester Island. From this study it appears that a directly measured difference in prey availability may account for the observed difference in prey capture rate. This greater capture rate by Steller sea lions at Seguam Island may partially explain the greater pup growth rates observed there compared to Forrester Island. The lack of a single highly abundant prey species and the larger Steller sea lions population at Forrester Island may result in longer search times for Forrester Island Steller sea lions. An important value of this and the related studies to date is that we were able to demonstrate a correlation between prey availability, foraging success, and pup growth, a parameter that is potentially indicative of future survival and therefore adult female reproductive success.

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We estimated the incidental mortality of harbor porpoise (Phocoena phocoena) in selective salmon fisheries in southern British Columbia from reports received from federal fisheries observers (2001) and license holders (1997 - 2001). Data sheets were developed to record prevailing conditions at the time of a harbor porpoise entanglement event. These were incorporated into the existing Federal Fisheries Observer Program. Data collection occurred throughout the 2001 - commercial salmon fishing season in the coastal waters of southern British Columbia. Neither the seine net, nor the troll salmon fisheries reported entanglements in 2001. All observer reported entanglements of small cetaceans were phocoenids and all were caught in gill nets. In total, four porpoises were incidentally caught – each in a different statistical licensing area (licensing areas 12, 21, 25, 121). Two of these four (50%), were released alive. The two by-caught harbour porpoises that could not be released alive, died in the gill nets before either the observer or the vessel's crew were aware of the collision. When mitigative actions were effected, live release resulted. At a minimum, the porpoises sustained superficial lacerations from the rescue efforts and the gill net collision. Morphometric and scan zone data indicated that the by-caught harbour porpoise were likely solitary juveniles. A total of 979 gill and seine net license holders were sent a questionnaire regarding their knowledge and experiences with harbour porpoise. Of these, 27.6% returned their completed questionnaires: 250 were used in the final analysis. Respondents had an average of 33.5 years fishing experience, with two-thirds of them reporting a multi-gear career. Respondents expressed a keen willingness to participate and provided details of their harbour porpoise experiences, as well as information about other small cetacean encounters. Respondents reported a total of 14 incidents, involving 19 harbour porpoise incidentally caught between 1997 and 2001. All were with gill nets and most involved single animals. The license holders reported a 52.6% overall release rate, with a 100% release rate for those found alive. Damage to gear was usually caused by the rescue efforts, rather than by the entangled porpoises. Human intervention was required, as none of the phocoenids were able to disentangle themselves. Porpoises appeared to respond well to human intervention and handling, as indicated by the few reports of mortality occurring during a rescue (ancillary reports prior to the 1997 - 2001 focus period). The license holder's responses indicated that most of the incidental catch events occurred in Salmon Statistical Licensing Areas 4, 8, 12, 21 and 22. Based on the number of by-caught porpoises reported through the observer program, the total theoretical mortality for southern BC (Statistical Areas D and E) is 20 animals per 810 boat days fished, or 80 porpoises for the 2001 fishing effort. Given that harbour porpoise accounted for all observer reported phocoenid mortality, this translates to an estimated mortality of 80 harbour porpoise for the 2001 effort. Poisson distribution 95% confidence levels determined annual phocoenid mortality between 11 and 102 animals for southern BC (Salmon Licensing Areas D and E). It is likely that the proportions of harbour to Dall's porpoise killed annually are variable based on differential overlap of gill net fisheries with phocoenid spatial and temporal distribution. This estimate was based on a very small sample size and assumed that catch rates were the same across all statistical areas. However, this assumption is questionable given that harbour porpoise and fishing effort have heterogeneous distributions. A second estimate derived from the province-wide career experiences of license holders (1997 - 2001) yielded an estimated incidental catch of 14.1 harbour porpoise per year, with an annual mortality of 6.6 animals and Poisson distribution 95% confidence levels of 23 - 61 porpoises killed annually. Our estimates suggest that fewer than 100 harbour porpoise are killed each year by commercial salmon gill net fisheries. However, the biological significance of our estimates of mortality is unknown due to a lack of information about numbers and rates of birth, and natural mortality of BC harbour porpoise. What we do know is that fishery caused mortality of harbour porpoise continues throughout the province, including trans-boundary areas with Washington State, even in times of reduced fishing effort. This has special significance for any populations that are at risk of gear entanglement in both US and Canadian waters, and to any populations, which are small or have restricted ranges. The fact that mortality occurs in a highly regulated fishery raises the possibility that considerably higher mortality may have occurred in times of more permissive fisheries. If so, reduced fishery related mortality today, may mean the recovery of harbor porpoise populations historically diminished by fisheries. This in turn, underlines the need for further monitoring in southern BC and implementation of standardized reporting of harbor porpoise by-catch from central and northern regions. Approximately half of the observer and license holder reported incidentally caught porpoises were released alive. This speaks well to the efforts of gill net fishermen in British Columbia. Further efforts to reduce harbor porpoise by-catch and increase live release rates must be practical to a commercial fishing situation and must consider the effects to the efficiency of the target species fisheries. A number of recommendations stem from our study to reduce incidental catch and increase live release rates. These include further investigation into selective gill net fishery modifications, improving observer training specific to marine mammals, rescue and release protocols and augmenting harbor porpoise biological research. Time or area restrictions and the introduction of acoustic net alarms do not appear to be appropriate management tools at this time, due to the uncertainty associated with the estimates of mortality, the lack of knowledge about harbor porpoise biology and the apparent rarity of occurrence per boat day fished or per respondent license holder.

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Changes in the quality or quantity of food can have a dramatic effect on the population status of wild animals. Unfortunately, it is difficult to assess (or define) whether nutritional stress is a contributing factor to the decline of any particular species.The “nutritional quality ” of a diet to an animal is a complex matter to assess given the range of components that can influence its value.The effects of different diets on animal health are equally complex, and are particularly difficult to assess in large, wild animals. Research by the North Pacific Universities Marine Mammal Research Consortium with captive Steller sea lions is evaluating the possible mechanisms by which dietary changes might adversely affect the nutritional or health status of individual animals, and ultimately the population as a whole. The research investigates the three potential proximate mechanisms by which changes in diet might impact Steller sea lions:a decrease in energy intake, a decrease in the intake of some essential element, and the over-consumption of an element detrimental to sea lion health.

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We compiled an annotated bibliography of Steller sea lion literature that identifies the areas of research that have been undertaken to date, and whether or not they address the leading hypotheses proposed to explain the population decline in Alaska. We identified 272 scientific papers with a primary research focus on Steller sea lions. Of these, 111 articles were peer-reviewed publications in scientific journals, and 161 were other forms of publication (e.g., technical reports, unpublished reports, dissertations, etc.). The total number of Steller sea lion articles published per decade has risen exponentially from 4 in the 1940s to 128 in the 1990s. The bulk of scientific studies have focused on population distribution, population dynamics, ecology, census data, nutrition and behavior. Subject areas that have received low research attention include predation on Steller sea lions, captive studies, metabolism and parasitology. Only 59 of the 272 scientific articles contained information relevant to testing one of the 12 hypothesized causes of the Steller sea lion decline. The most frequently addressed hypothesis concerned juvenile mortality (25 papers). This was followed by starvation, competition with fisheries, human predation and regime shifts. Only 1 of the 272 articles addressed the role that killer whale predation may be playing in the decline of Steller sea lions. To date, over 9,228 pages pertaining to Steller sea lions have been printed (1,148 pages of primary publications and 8,080 pages of other publications). The relative number of articles that address or provide significant information to assess hypothesized causes of the population decline are few (< 30% of the sea lion literature per decade).

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The impact that fishing operations may have on marine mammals and other components of marine ecosystems is a major concern today. Fisheries, in addition to causing by-catch mortalities, affect marine mammals through direct and indirect competition for the same food sources. Our goal was to assess the potential trophic impact of fisheries on mammal populations in the North Atlantic by quantifying the overlap in resource exploitation in space and time using high-resolution modeling and mapping. We developed a relatively simple model to estimate feeding requirements (specified by food type) and population biomass of all North Atlantic marine mammal species. Main model input parameters were population abundance, sex-specific mean body mass, standardized diet compositions, and weight-specific feeding rates. A spatial model was constructed using a geographic information system to link annual food consumption estimates to the corresponding species-specific, rasterized distributional ranges. Spatially explicit food intake (expressed as proportions of total food intake per ½ degree latitude/longitude square) was further refined by incorporating information about habitat preferences and feeding patterns. Superimposing the geographically matching fisheries catches (generated by a similar rule-based model) allowed the calculation of overlap between fisheries catches and marine mammal consumption. The model indicates that, in the North Atlantic, total food consumption of marine mammals in the 1990s was three times higher than total fisheries catches. However, spatially disaggregating consumption and specifying intake by food type showed actual resource overlap to be quite low. Areas of high overlap in the North Atlantic are concentrated along the East coast of North America (35o – 53° N) and in European shelf waters. This visualization of geographical ‘hotspots’ of marine mammal-fisheries interactions may help to identify areas of conflict, realized or potential. Hence the meta-analysis approach taken here may serve as a useful management tool in the context of defining marine mammal critical habitat and efficient MPAs design.

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The status report for killer whales that was accepted by COSEWIC in May 1999 contains a comprehensive summary of what was known about killer whales until the late 1990s. Since then, three significant sets of studies have been published with new information about contaminant concentrations, population genetics, and population sizes of killer whales in British Columbia. This new information has bearing on the listing of killer whales in Canada.

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Alternative animal models are desirable to assess the role of nutrition on the population dynamics of marine mammals. If an appropriate model could be found, it might be possible to identify population consequences and risks that face sea otters forced to eat fish after depleting local invertebrates, or for sea lions which switch from a fatty fish to a lean fish. From the arguments raised above, the rat appears to be a feasible model for studying marine mammal nutrition. A preliminary study exploring the effects of nutrition on population dynamics via parameters of growth and reproductive success is feasible. Although mink and harbor seal models are superior in their similarity to other marine mammals, the difficulty and time involved in breeding them is either extremely labor intensive or prohibitive. Again, the regular, five day cycle of the rat and shorter generation time allow for parameters of fertility and offspring viability in response to different diets to be examined in a cost effective and economic way. Additionally, because of the extensive use of rats in other nutritional studies, many signs and symptoms of specific nutritional shortcomings are known and easily detected. If a reliable model can be implemented in the study of marine mammal population dynamics, research can explore aspects of physiology nor available when using captive marine mammals or mammals in the wild. Development of a model also has the potential to reduce the number of mammals taken from the wild for scientific study, thereby helping to preserve many threatened species.

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Compared to terrestrial mammals, marine mammals are generally perceived as having elevated metabolic rates and insatiable appetites, attributable to maintaining their high body core temperatures in a cold aquatic environment. The perception that marine mammals have higher metabolic rates than terrestrial mammals of similar body size is reinforced by a substantial body of literature that dates over half a century (Sergeant, 1973; Lavigne, 1982) and is further supported by reports of captive marine mammals ingesting large quantities of food (Sergeant, 1969, 1973; Bonner, 1982). However, within the past two decades, this convention has been challenged. Lavigne et al. (1986) failed to reject the hypothesis that physically mature phocids (true seals) have similar basal metabolic rates (BMRs) as terrestrial mammals of similar body weight, when measured under standard conditions. Innes et al. (1987) found similar results when comparing feeding rates (FRs) of seals and whales. However, much research has been conducted on the FRs and BMRs of marine mammals since these studies were completed. In our study, we re-investigated whether basal metabolic and feeding rates of marine mammals are similar to those predicted for terrestrial mammals. We also explored relationships between taxa and were able to predict the basal metabolic rates of species of marine mammals not previously studied. These estimates can also be used to assess the amount of prey consumed by species of marine mammals whose metabolisms have never been determined in the field or in the lab.

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Dry-matter digestibility and energy digestive efficiency were measured in six juvenile Steller sea lions (Eumetopias jubatus) fed three diets each consisting of a single species: herring, pollock, and squid. Two of the animals were also fed pink salmon. Dry-matter digestibility (DMD) and digestive efficiency (DE) were measured using the energy and manganese concentration in fecal and food samples. DE values were high for all prey species (herring: 95.4 ± 0.7% (mean ± SD), pollock: 93.9 ± 1.4%, salmon: 93.4 ± 0.5%, squid: 90.4 ± 1.3%). Steller sea lions appear to digest prey of high energy density more efficiently than prey of low energy density. DMD values were also high for all prey species (herring: 90.1 ± 1.8%, pollock: 86.5 ± 3.4%, salmon: 87.3% ± 2.6, squid: 90.5 ± 1.2%). The low DMD value for pollock compared with herring and squid was due to the high proportion of bony material in pollock. There was a strong linear relationship between DE and DMD for each prey type, but the terms cannot be used interchangeably. DE measures are more meaningful than DMD in conveying the energetic benefits derived by sea lions from different types of prey. Species-specific measures of the digestible energy obtained from an array of prey items are a necessary component in understanding the bioenergetic consequences of consuming different prey species.

abstract
Over the past 10 years there has been increasing criticism of management decisions that are based on single species approaches and a call for the implementation of ecosystem approaches. The major criticism of single species models is that they cannot predict changes in community struc ture. Unfortunately, our experience in modeling the Bering Sea shows that these same criticisms can also be leveled against ecosystem models. We employed trophic mass balance models (Ecopath and Ecosim) to examine some possible explanations for the changes that occurred in the Bering Sea between the 1950s and 1980s. We removed fish and mammals from the modeled system and tracked how other components of the eco system responded. Our mass balance models indicate that neither whal ing nor commercial fisheries were sufficient to explain the 400% increase in pollock biomass and other changes that may have occurred between the two time periods. The simulations further suggest that environmental factors, affecting recruitment or primary production, may be more impor tant in determining the dynamics of the Bering Sea ecosystem than preda tor prey interactions alone. These findings illustrate that mass balance models that do not account for the impact of climate variability on year class strength cannot provide reliable estimates of trends in marine fish production. However, our models can show how predation and fishing can affect trophic interactions among species. As such, ecosystem models are a useful scientific tool to identify gaps in understanding and data needs, but are unlikely to ever replace single species models. They may instead complement and provide parameters to single species models. Ecosystem models such as ours are still in the early stages of develop ment and will become increasingly more important as a management tool as they begin to incorporate spatial and oceanographic/climatic information.

abstract
Fasting in bears, penguins and phocid seals is accompanied by predictable changes in plasma metabolite concentrations related to alterations in the body reserves that are catabolized and illustrate a species’ ability to limit protein degradation during long-term fasting (see review in Castellini and Rea 1992, Nordoy et al. 1993, Rea 1995). Steller sea lions (Eumetopias jubatus) also undergo periods of fasting in their natural environment; adult females fast while nursing pups on the rookery, males defend breeding territories and young pups fast on the rookeries while their mothers are at sea foraging. Five juvenile Steller sea lions were fasted ‘in captivity (with free access to fresh water) for 9 to 14 days to test the hypothesis that juvenile Steller sea lions also exhibit changes in key plasma metabolites indicative of biochemical adaptation to fasting. The secondary objective of this study was to determine if blood metabolite concentrations could be used as biochemical indicators of nutritional status in free-ranging juvenile Steller sea lions.

keywords     blood chemistry, body mass, fasting, juvenile Steller sea lions, #2

abstract
When faced with decreases in energy intake, an animal has two conditions, hunger stimulates increased foraging activity, a strategy of short-term expenditure off-set by a reasonable-expectation of foraging success. However, when faced wit increased energy h periods of predictable or prolonged shortages of energy intake (although not necessarily energy availability), the animal should limit energy expenditures. The most common response to experimental undernutrition or fasting in homeotherms is metabolic depression. Invoking such physiologic responses that limitenergy expenditures limits tissue loss and delays death by starvation. Some species of marine mammals have exhibited metabolic depression, although its occurrence, scope, and triggers are still unclear. This study was designed to document the extent of metabolic depression in Steller sea lions. It investigated the role of energy and food intake on metabolic depression, and the relationship between changes in body mass and the scope of metabolic depression.

abstract
The population of summer chinook that spawn in British Columbia's Puntledge River once numbered about 3,000 fish, but declined following expansion of hydroelectric development in the early 1950s. By 1965, only a few hundred fish remained. Following enhancement efforts (construction of a spawning channel, fish way, and fishing closures and restrictions), the population slowly recovered and reached a high of 1,200 in the mid 1980s. Numbers of males increased more rapidly than females, which on average outnumber females by a ratio of two-to-one. A second, and potentially more disastrous decline began in 1990. Only 208 spawners returned in 1995 compared to 1,629 five years earlier. Males return to the river before females and are significantly younger and smaller than females. Differences in body size and numbers may be partly explained by size selectivity of fisheries that release undersized fish. Chinook that use the spawning channel are physically smaller than those that stay in the river to spawn. In 1980, fisheries intercepted 74% of the summer chinook as they returned to the puntiedge River compared to 9% that were taken by harbour seals. In 1990, fisheries and seals caught 32% and 24%, respectively. The problems faced by the summer chinook are varied and complex. It is not clear whether the Puntledge River can ever again sustain the historic numbers that once made it one of the most important producers of chinook salmon in British Columbia. Development of a conservation plan is urgently needed for the Puntledge River summer chinook and should be given high priority given the recent low levels of spawning escapements, and evidence of high mortalities incurred at sea and in the terminal area. -1v

abstract
During the summers of 1991 to 1994 (July 1 - August 31), the movements of vessels and killer whales (Orcinus orca) were monitored during daylight hours in the Robson Bight - Michael Bigg Ecological Reserve, in Johnstone Strait, British Columbia. Numbers of whales using the Ecological Reserve increased through the month of July, peaking in early to mid August, and dropping thereafter. Diurnally, increases occurred from morning to midafternoon in numbers of whales and the amount of time spent within the Reserve. Whales spent an average of 12% of their time resting in the Ecological Reserve, 25% rubbing and 63% engaged in other activities. They travelled through all four zones of the Reserve with equal frequency, but spent significantly more time in the rubbing beach zone than in any of the other three zones. Over 75% of the vessels that entered the Ecological Reserve were commercial fishing vessels. Fishing activity rose sharply through the last week of July, peaking in early August. This was followed by a smaller peak in commercial activity during the last week of August. Low numbers of recreational vessels entered the Reserve throughout the summer with a small peak in activity during the last week of July. Vessel activity was highest at the western end of the Reserve and lowest at the eastern end (at the rubbing beaches). Considerable variability was observed in abundance and activity levels of whales and vessels from day to day, and from hour to hour. This meant that although general trends could be described from the large number of observations, it was not possible to accurately predict either boat or whale activity for a given day or time. Vessel activity does not appear to have marked effects on the presence of whales in the Ecological Reserve. However, the movement of whales within the Ecological Reserve does appear to be affected by vessels. Whales were more likely to move to a different zone or to leave the Reserve entirely when vessels were present, and were more likely to leave the rubbing beach zone than any other zone of the Reserve. Continued research on the effects of vessel activity on killer whales in the Ecological Reserve is recommended and should include: continued analysis of existing data; posing well defined questions to guide research design; collecting detailed information on whale behaviours, vessel numbers and vessel activities; and rigorously collecting data on whales and vessels from the waters immediately adjacent to the Ecological Reserve

abstract
The size of Steller sea lion populations in the Gulf of Alaska and Aleutian Islands was estimated by applying life table statistics to counts of pups and adults (non-pups) at rookery sites. Total population size was 5.10 times the number of pups counted or 3.43 times the number of adults counted. Only 55% of the adult population return to rookeries during the summer. Data compiled from published and unpublished sources for all 39 major rookeries in Alaska suggest that the total number of Steller sea lions (including pups) rose from 250 000 to 282 000 between the mid 1950s and the mid 1970s. Since 1980 it has decreased by over 70% (roughly 5% per year) to about 76 000 animals in 1992. Most of the decline appears to have slowed or stopped within two subareas of these large regions- the eastern Aleutians and western Gulf of Alaska. Increases have been occurring in the smaller populations of southeast Alaska. It is not known why these changes have occurred.

keywords     abundance, Steller sea lions, Alaska, decline, #2

abstract
The goal of our study was to assess the status of Steller sea lions in Alaska, review their population biology, and develop a simulation model to explore the role that harvesting and incidental kills by fisheries may have played in the sea lion decline. We also attempted to relate the population declines to the amount of fish caught in the Gulf of Alaska and Aleutian Islands, and to the number of vessels fishing from 1950 to 1990. Using life tables to estimate population size, the numbers of Steller sea lions were estimated for all rookeries for which information was available in each of six areas in the Gulf of Alaska and Aleutian Islands. The total population appears to have risen from 150,000 to 210,000 from the mid 1950s to 1967. The population was then stable for roughly ten years, then increased to 225,000 by 1979. Since then it has decreased to about 85,000. Most of the decline took place in Area 3 (Kodiak region) but there were also significant declines in Areas 4 to 6 (westward of Kodiak). Increases have occurred in the smaller populations of Areas 1 and 2 (southeast Alaska and Prince William Sound). A major growth in domestic fisheries occurred after the declaration of 200 mile zones. The traditional fisheries for salmon, herring and halibut were augmented by major groundfish fisheries. The decline in the numbers of Steller sea lions has been coincidental with the growth in the numbers and size of vessels and the increase in catch. The stabilization in the numbers of Steller sea lions in the Gulf of Alaska from 1956 to 1980 can be attributed to the direct effect of incidental capture in fishing gear, the shooting of sea lions and the harvesting of adults and pups. However, these factors explain but a small portion of the recent population decline, from 1980 to the present. Some sea lions are missing in the arithmetic of population dynamics which cannot be accounted for by movements of animals from one area to another. Whether these losses are caused by the removal of food resources is a circumstantial possibility, but evidence of local abundance of food resources at particular times of the year for particular segments of the population is needed to build a convincing case. Other causes, such as diseases and parasites must also be kept in mind as possible contributing factors. Research on Steller sea lions should focus on the decline in abundance since 1980, changes in body size, the diet at various seasons of the year, bioenergetics and nutritional requirements, and assessment of local abundance of various food items. Long term research on the ecosystem dynamics of the region will be necessary for long term management of all living resources but how best to focus that research is a matter of current scientific debate that will not be resolved quickly.