• Dealing with uncertainties in integrated age-structured assessment models

      Hulson, Peter-John F.; Quinn, Terrance II; Norcross, Brenda; Marty, Gary; Adkison, Milo; Hanselman, Dana (2012-05)
      Dealing with uncertainties in integrated age-structured assessment (ASA) models has become a central focus at all levels of fish stock assessment and management. My goal in this thesis was to uncover layers of uncertainty in ASA models. There were two major components to this approach: (1) dealing with uncertainty in datasets used in ASA models through examining effective sample size, and (2) dealing with uncertainty in ASA model structure through examination of effective number of parameters and simulations of school and stock structure. From the dataset uncertainty perspective, I investigated age and length composition datasets by first identifying possible sources of error and then by evaluating if it is feasible to include this error within ASA models. From the structural uncertainty perspective, I compared historical ASA models with spatially-explicit and metapopulation scale ASA models. Sources of uncertainty in age and length composition datasets include the spatial distribution of schools and age aggregation of fish within schools. To account partially for this error at the survey design level, the optimal approach is to sample from a greater number of schools, even if the sample size within any particular school is reduced. Also, it is possible to include this error within ASA models by parameterizing and estimating effective sample size with the Dirichlet distribution. Reduced uncertainty in parameters and management quantities resulted from spatially-explicit and metapopulation ASA models when compared to historical ASA model structures. Further, with possible climate change influences on fish populations use of spatially-explicit and metapopulation ASA models will allow stock assessment scientists to accurately and more precisely predict sustainable harvest levels.
    • Decadal Variability In The Arctic Ocean: Greenland-Iceland-Norwegian Seas Ice-Ocean-Atmosphere Climate System

      Dukhovskoy, Dmitry Stanislavovich; Johnson, Mark; Proshutinsky, Andrey (2003)
      This study investigates the decadal variability of the Arctic Ocean---Greenland, Iceland, Norwegian Seas (GIN Sea) system and possible mechanisms driving variability. The theoretical foundation of this work is the theory of Proshutinsky & Johnson [1997] that two major climate states of the Arctic---Anticyclonic Circulation Regime (ACCR) and Cyclonic Circulation Regime (CCR)---are driven by variations in the freshwater contents of the Arctic Ocean and the GIN Sea. It is hypothesized that the Arctic Ocean and the GIN Sea form an auto-oscillatory ice-ocean-atmosphere climate system with a quasi-decadal period of interannual variability. The system is characterized by two stages: (1) cold Arctic (ACCR)---warm GIN Sea with weak interaction between the basins; (2) warm Arctic (CCR)---cold GIN Sea with intense interaction between the basins. Surface air temperature and dynamic height gradients between the basins drive the auto-oscillations. This study investigates interactions between the Arctic Ocean and the GIN Sea. To test the hypothesis, a simple model of the Arctic Ocean and Greenland Sea has been developed. The Arctic shelf processes have been parameterized in a box model coupled with an Arctic Ocean module. Both the Arctic Ocean and Greenland Sea modules are coupled with a thermodynamic ice model and atmospheric models. Several model experiments have been conducted to adjust the model and to reproduce the auto-oscillatory behavior of the climate system. One of the major results of this work is the simulation of auto-oscillatory behavior of the Arctic Ocean---GIN Sea climate system. Periodical solutions obtained with seasonally varying forcing for scenarios with high and low interaction between the regions reproduce major anomalies in the ocean thermohaline structure, sea ice volume, and fresh water fluxes attributed to ACCR and CCR regimes. According to the simulation results, the characteristic time scale of the Arctic Ocean---GIN Sea system variability reproduced in the model is about 10--15 years. This outcome is consistent with theory of Proshutinsky and Johnson [1997] and shows that the Arctic Ocean---GIN Sea can be viewed as a unique auto-oscillating system.
    • Decomposition and adsorption of peptides in Alaskan coastal marine sediments

      Luo, Honghong (1994)
      In organic-rich coastal sediments, hydrolyzable amino acids make up a substantial fraction of the sedimentary content of organic nitrogen. How this organic nitrogen resists decomposition and is preserved in sediments is poorly understood. In order to investigate the factors controlling mineralization and preservation of hydrolyzable amino acids, decomposition and adsorption of peptides were studied in suboxic and anoxic pore water and sediments from Resurrection Bay (RB) and Skan Bay (SB), Alaska. Five tritium-labeled peptides, basic di-lysine, acidic di-glutamic acid, and neutral di-alanine, tri-alanine and hexa-alanine, were used as tracers. In filtered pore water, the hydrolysis rates were usually low. The exception was that the initial enzymatic hydrolysis of di-alanine and di-glutamic acid was rapid in SB pore water. The hydrolysis rates of both peptides increased with concentration. In sediments, hydrolysis was found to be the rate-limiting step of peptide decomposition. Alanyl and glutamyl peptides were hydrolyzed faster than lysyl peptide, and the hydrolysis rates among alanyl peptides decreased with increasing molecular weight. Peptide hydrolysis was affected more by molecular structure than by oxic or anoxic conditions. Adsorption of lysyl peptide to sediments was greater than that of other peptides. Basicity enhanced peptide adsorption more than increased molecular weight. Sedimentary organic matter was mainly responsible for peptide adsorption. The different patterns of peptide adsorption in RB and SB sediments were related to the greater total organic carbon concentration in SB sediment. Some of the peptide adsorption was irreversible. Adsorbed peptides were more resistant to biological decomposition than dissolved peptides. Adsorption may be an important step in the process of peptide preservation in sediments, and thus the preservation of sediment organic matter during early diagenesis.
    • Defining genetic population structure and historical connectivity of snow crab (Chionoecetes opilio)

      Albrecht, Gregory T.; Hardy, Sarah M.; Lopez, J. Andres; Hundertmark, Kris J. (2011-08)
      The snow crab (Chionoecetes opilio) is a valuable commercial resource within the Bering Sea, as well as other areas in the North Pacific and Atlantic Oceans. Large populations are known to exist within the Chukchi and Beaufort Seas, including recently discovered commercial sized individuals (Beaufort). However, genetic connectivity throughout these regions has not been examined until now. Based on seven polymorphic microsatellite loci, relatively low population genetic structuring occurs throughout the Alaskan region (Gst = 0.001). This homogeneity is likely due to long-distance larval dispersal, adult migrations, and a possible recent population expansion following the last glacial maximum. Furthermore, meta-population analysis was conducted for Alaskan and Northwest Atlantic stocks. Although significant genetic divergence characterizes the West Greenland stock in relation to all other populations, low divergence (Gst = 0.005) was found between Atlantic Canada crabs and those from the Alaska region. Larval dispersal between regions is highly unlikely due to the transit distance. Therefore, low divergence is likely the result of a recent population expansion into the Northwest Atlantic <5000 years ago.
    • Delayed effects of oil exposure on fish

      Hicken, Corinne E.; Stekoll, Michael S.; Incardona, John P.; Smoker, William W.; Rice, Stanley D. (2012-05)
      Polycyclic aromatic hydrocarbons (PAHs) are continuously added to aqueous environments through point source and non-point source pollution and can cause deleterious effects on exposed fish populations. Historically, studies have shown that acute PAH exposure causes only short-term effects in adult fish which were resolved when the exposure ended. Chronic exposure to PAHs, however -- even at the less susceptible juvenile and adult stages -- can cause a host of effects including lesions, lower body length and weight, and reduced swimming ability. More recently studies of embryonic fish have demonstrated that much lower PAH concentrations can cause lethal and sub-lethal effects on those embryos and can cause delayed effects on the fish that are not seen until adulthood. This study used zebrafish (Danio rerio) to examine the effects of 48-hour weathered crude oil exposure on both the embryonic fish exposed and the adult fish exposed as embryos but raised in clean water. Oil exposed embryos had increased mortality, pericardial edema, intracranial hemorrhage, and higher cytochrome P4501A (CYP1A) activity. Adult fish exposed as embryos had decreased critical swim speed and rounder hearts than the control fish. These effects may culminate in decreased fitness of the exposed fish population.
    • Delineation of Yakutat foreland coho salmon (Oncorhynchus kisutch) stocks using otolith chemistry

      Jones, Matthew A. (2007-08)
      Otolith chemistry was utilized to identify suspected coho salmon sub-stock populations on the Yakutat Foreland of southeast Alaska. In order to demonstrate that otolith chemistry might be successful in sub-stock differentiation, water samples were collected from four adjacent river systems and chemically segregated by collection site. Juvenile coho salmon and adult coho salmon were collected from the same four river systems and were subsequently analyzed for levels of select Ba, Ca, Mg, and Sr isotopes in all otolith edge and core regions using laser ablation-inductively coupled plasma-mass spectrometry. Otolith Sr⁸⁷/Ca⁴⁸ and Mg²⁴/Ca⁴⁸ were used to segregate collection sites, identify sub-stock populations, and infer straying rates for coho salmon on the Yakutat Foreland. Juvenile core and edge otolith chemistry returned moderate to high classification accuracy for three out of four collection' sites (60%-92%) in statistical discriminant analyses. Adult core otolith chemistry could not segregate samples according to collection site in three out of four sites (7%-50%). Yakutat Foreland otolith chemistry analysis results allowed for (1) differentiation of adjacent freshwater systems, (2) a significant amount of coho salmon stock delineation, and (3) a higher suggested rate of straying from natal sites than coho salmon in other locations.
    • Density and distribution of meiofauna in the northeastern Chukchi Sea

      Hajduk, Marissa; Blanchard, Arny; Hardy, Sarah; Bluhm, Bodil (2015-05)
      Meiofaunal communities in the northeastern Chukchi Sea (Alaska) are poorly known and were investigated to determine coarse taxonomic composition, distributional patterns, and density and biomass. Core samples were taken in August through October 2012 from van Veen grabs at depths of 20-45 m, in order to assess meiofauna community structure and associations with environmental and biological variables. Overall, density and biomass were dominated by nematodes, harpacticoid copepods, and foraminifera. Total meiofaunal density (9-13 ind. cm-2) was lower than in some deeper polar regions (e.g., Yermak Plateau and Nansen Basin), but generally fell within the range of published estimates for the Arctic and sub-Arctic. Total region-averaged biomass (27.4 mg C m-2) was similar to estimates for the deep Arctic Makarov and Amundsen Basins, but was much lower than shallow and productive sub-Arctic regions such as the Oosterschelde estuary (North Sea, Netherlands) and intertidal areas in Kongsfjorden (Svalbard), and some Arctic locations in the Barents Sea. The ratio of meiofaunal to macrofaunal biomass (1:438) was comparable to estimates from less productive Arctic basins and from fjords, but was unexpectedly lower than other productive polar shelves (e.g., Barents Sea shelf). Regression analysis and Canonical Correspondence Analysis (CCA) ordination suggest water depth, % mud, and TOC are important predictors of nematode and harpacticoid copepod densities, whereas temperature, TOC, and macrofaunal biomass were correlated with meiofaunal community structure. These variables are proxies for the topographic control and water circulation in the region, and suggest circulation with advected nutrient input as the primary driving force behind community density and distribution patterns.
    • Describing Forage Fish Availability In Coastal Waters Of The Kodiak Archipelago, Alaska

      Guo, Lei; Wynne, Kate; Foy, Robert; Coyle, Kenneth; Hillgruber, Nicola; Schaufler, Lawrence (2010)
      Assessing the availability of forage fishes is key to understanding fluctuations in populations of apex predators that prey upon them, including pinnipeds and seabirds in the Gulf of Alaska. In this study, multiple aspects of forage fish availability were measured in coastal waters of the Kodiak Archipelago, Alaska, in May (2004 & 2005), August (2004 & 2005), November (2006), and April (2007). Efforts were focused on four pelagic species that consistently dominated midwater trawl catches and have been described as important prey for upper trophic level predators around the Archipelago: walleye pollock (Theragra chalcogramma), Pacific herring (Clupea pallasii), capelin (Mallotus villosus), and eulachon (Thaleichthys pacificus). Fatty acid and stomach content analyses were combined to estimate the diet composition of these forage fishes as a means of identifying the immediate source of energy they transfer to upper trophic level taxa. Values of copepod-originated fatty acids indicated underestimation of dietary copepods by stomach content analysis, which suggests that fatty acid analysis should be used to supplement conventional methodologies in forage fish field studies. Lipid content and fatty acid composition were highly variable within species, suggesting that the use of average values at the species level should be avoided in fine-scale ecological investigations. Mesoscale horizontal distribution and energy density of forage fishes were measured in May and August (2005) to assess the prey fields available to local apex predators over critical periods of their life history. Dense post-spawning aggregations formed seasonal energetic "hotspots", exemplified by herring schools on the northwest side of the Archipelago in May and capelin schools on the northeast side in August. Results presented in this dissertation offer key information needed to identify energetic pathways of significance to upper trophic level consumers in the Kodiak Archipelago. Understanding local trophic interactions and their role in regional apex predator population fluctuations will improve efforts to develop trophodynamic models and ecosystem-based fishery management plans in the North Pacific Ocean.
    • Determinants of life history variability in the chinook salmon (Oncorhynchus tshawytscha) of Western Alaska

      Siegel, Jared E.; McPhee, Megan; Adkison, Milo; Brown, Randy (2017-05)
      Chinook Salmon from western Alaska have experienced recent declines in abundance, size, and age at maturity. Declines have led to hardships for the region's dependent subsistence and commercial users. Thus there is a managerial need to better understand factors effecting life-history expression in these populations. I used retrospective scale analysis and run reconstructions to investigate the causes of declines in age at maturity and the effect of the marine environment on growth, maturation, and survival in two western Alaskan Chinook Salmon populations subject to long-term monitoring: the East Fork Andreafsky River and the Kogrukluk River (tributaries of the Yukon River and Kuskokwim River respectively). The expression of age at maturation exhibited sex-specific responses to variability in growth. Additionally, thresholds for maturation, as described by a newly presented measure of maturation reaction norms that accounts for growth history, were found to have declined in both sexes. This can be interpreted as indirect evidence that observed declines in age at maturity represent an evolutionary response. I also found that sea surface temperatures in the Bering Sea exert strong control on the expression of life history variability. Warmer sea surface temperatures appear to lead to a younger age at maturity, largely through the vector of augmented growth. However, warmer sea surface temperatures additionally appeared to decrease the average age of male recruits by lowering growth thresholds for early male maturation. Despite the demonstrated relationship between Bering Sea surface temperatures and age at maturation, a lack of a temporal trend in sea surface temperatures during the period of analysis (1977-2013) suggests that temperature alone cannot explain documented declines in average age. However, this result suggests that the average age at maturation of western Alaskan Chinook Salmon will continue to decline with future predicted warming of the Bering Sea as a consequence of climate change.
    • Determining the effects of Asian pink and chum salmon on Western Alaska chum salmon growth

      Minicucci, Tessa J.; McPhee, Megan V.; Yasumiishi, Ellen M.; Adkison, Milo; Beckman, Brian (2018-08)
      Increased hatchery production and favorable ocean conditions have resulted in historically high abundances of Pacific salmon (Oncorhynchus spp.) in the North Pacific Ocean. Despite these conditions, chum salmon (O. keta) have experienced reductions in growth, body size, and increases in age at maturity throughout their range. In western Alaska, dramatic declines in the abundance of chum salmon between 1997-2001 resulted in numerous fishery and economic disasters among commercial and subsistence users. Chapter 1 reviews existing data on salmon diet and ocean distribution to address the potential for competition between western Alaska chum salmon and Asian pink (O. gorbuscha) and chum salmon in the Bering Sea. Western Alaska chum salmon reside in the Bering Sea during their summer foraging months where they overlap with abundant populations of Russian pink salmon (primarily wild origin) and Japanese chum salmon (primarily hatchery origin). Chum and pink salmon occupy a similar feeding niche, and during years of high pink salmon abundance chum salmon have been observed to alter their ocean distribution and rely more heavily on gelatinous zooplankton species as a primary food source. This spatial and diet overlap suggests that inter- and intra-specific competition might contribute to reduced growth and increased age at maturity of western Alaska chum salmon. Chapter 2 uses retrospective scale analysis coupled with linear mixed-effects modeling to investigate the potential for such competition between Asian pink and chum salmon abundance and the growth of chum salmon that rear in the Bering Sea. Chum salmon scale samples were collected through in-river fisheries on the Kuskokwim River during 1973-2014 and from incidental catches of chum salmon in the Bering Sea Aleutian Island walleye pollock (Gadus chalcogrammus) fishery during 2001-2016. Linear mixed-effects models demonstrated a strong negative relationship between Bethel chum salmon growth and the abundance of Japanese hatchery chum salmon. Chum salmon intercepted in the Bering Sea did not exhibit increased growth during 2012-2014 despite reductions in Japanese hatchery releases of chum salmon in 2011 as a result of the Tōhoku Earthquake and tsunami. We did not observe a relationship between Bethel chum salmon growth and the abundance of wild Russian pink salmon. Understanding how salmon populations interact while at sea will assist fishery managers in conserving threatened salmon stocks, particularly as Pacific Rim nations consider increasing production of hatchery salmon.
    • Development And Application Of A Methodology To Estimate Regional Natural Conditions For Trace Metals In Marine Sediments Of Southcentral Alaska's Coastal Region

      Dasher, Douglas H.; Kelley, John J.; Duffy, Lawrence; Mueter, Franz; Naidu, A. S.; Perkins, Robert (2010)
      Increasing levels of resource development and population growth along Alaska's relatively pristine coastline require responsible environmental stewardship that is based on scientifically defensible monitoring and assessment. This thesis develops a methodology to assess the spatial distribution of coastal sediment trace metals and estimate their natural condition along Alaska's coastline. Marine sediments provide a better integrated long-term signal for naturally occurring and anthropogenic chemicals than repeated water measurements. The first of three manuscripts reports on marine sediment trace metal concentrations from a probabilistic sampling survey of Alaska's Southcentral coastal region. Results are described on a proportional basis, i.e., percent of estuary area, for the distribution of As, Cd, Cr, Cu, Pb, Hg, Ni, Ag, and Zn in the sediments. With the exception of naturally elevated Cr and Ni at a site bounded by a chromite ore body, sediment trace metal concentrations measured represent non-analmous levels. The second manuscript develops natural conditions for fluvial trace metal inputs from two major Southeast Alaska coastal watersheds: Cook Inlet and Copper River. The stream sediment trace metal natural conditions place levels in the adjacent coastal sediments into context. Two exploratory data analysis techniques, the Tukey Box plot and Median + 2 Median Absolute Deviation, combined with geochemical mapping are used to develop stream sediment trace metal natural conditions. The third manuscript builds on the first two to develop a methodology to estimate coastal sediment natural conditions. Population estimates for the cumulative area 90% UCB 95% sediment trace metal of interest obtained from the sampling survey methodology and screened reference sites is used to establishing an upper threshold value for regional natural conditions. While this work establishes natural condition marine sediment trace metal levels for this region, the significance of these levels from an ecotoxciological perspective remains to be established. Additional studies are needed along other sections of Alaska's coastline, coupled with biological assessments, if Alaska is to develop relevant sediment quality guidelines.
    • Development, growth, and egg production of Centropages abdominalis and Neocalanus flemingeri from the eastern subarctic Pacific

      Slater, Laura Michelle (2004-08)
      Copepods dominate oceanic mesozooplankton in terms of abundance and biomass thus contributing a significant source of secondary production. I determined development, growth, and egg production of Centropages abdominalis and Neocalanus flemingeri at temperatures representative of the northern Gulf of Alaska in spring. Median development times from eggs to adults were 42 and 59 days for C. abdominalis at 5 and 7°C, respectively, and 117 days from eggs to copepodite stage five for N. flemingeri at 5°C. Average copepodite growth rates were 0.08 and 0.17 d⁻¹ for C. abdominalis at 5 and 7°C, respectively, and 0.15 d⁻¹ for N. flemingeri at 5°C. In situ egg production of C. abdominalis was 37 ± 22 eggs female⁻¹ d⁻¹ (mean ± S.D.), corresponding to a growth rate of 0.14 d⁻¹. Lifetime fecundity of N. flemingeri determined at 5°C was 535 ± 258 eggs female⁻¹ (mean ± S.D.). Comparing these results to in situ populations reveals that C. abdominalis may be food limited during the summer and fall, while N. flemingeri is likely not food limited in late spring. Overall, this information helps clarify the life history patterns of these two species and allows production to be estimated and models of secondary production created for conditions within the Gulf of Alaska.
    • Diet and movement of depredating male sperm whales (Physeter macrocephalus) in the Gulf of Alaska

      Wild, Lauren A.; Mueter, Franz; Straley, Janice; Sigler, Michael; Witteveen, Briana; Andrews, Russ (2020-05)
      Sperm whales (Physeter macrocephalus) remove fish from commercial fishing gear in high latitude foraging grounds. This behavior, known as depredation, occurs in the Gulf of Alaska (GOA) sablefish longline fishery and has increased in frequency and severity since the mid-1990s. Sperm whale foraging ecology and movements in the GOA are poorly understood but are important considerations to how depredation impacts fishery resources and whale behavior. The goals of this dissertation were to use stable isotope analysis to evaluate trophic connections between sperm whales and their prey, estimate the proportional contribution of various prey items to sperm whale diets, and use satellite tag data to evaluate movement and diving behavior of sperm whales in the GOA. Understanding isotopic variability in cetacean skin is important to evaluating dietary information from this tissue; thus, in chapter 1, I first analyzed the stable isotope ratios among layers of cetacean skin to determine how much variability there was within and across layers of cetacean skin. Results showed horizontal layers of cetacean skin to be significantly different isotopically, suggesting evidence of a dietary time series in layers of cetacean skin, where the innermost skin layer represents the most recent diet. These results were used in my second chapter to isolate the most recent diet of sperm whales from the inner layer of skin, and then to estimate proportional contributions of different prey to sperm whale diets. Results showed that the sperm whales sampled prefer sablefish, dogfish, skates, and rockfish, and that the proportional contribution of sablefish to sperm whale diets has increased over the past 15 years as depredation has increased in severity. Chapter three presented an analysis of twenty-nine satellite tags placed on depredating sperm whales in the GOA between 2007 and 2016 to explore movement and diving behavior and how these behaviors may be linked to prey preferences found in chapter 2. Tagged sperm whales in the GOA preferred the continental slope habitat and made long migrations along the slope toward Mexico and the Gulf of California, speeding up and switching behaviors from foraging to transiting when they left the GOA. Dive depths and durations exhibited individual variability and were significantly correlated to light levels, lunar cycles, sablefish fishery catch-per-unit-effort, and seafloor depth. Results suggest diving behavior tracks that of primary groundfish prey items, and dive depths become shallower in areas of high sablefish densities, as inferred from fishery catches, potentially reflecting depredation behavior. Together these results provide a much-improved understanding of the impact of depredation on sperm whale dietary preference, and show insights into the importance of the GOA as a foraging ground for endangered sperm whales.
    • Diet composition and fate of contaminants in subsistence harvested northern sea otters (Enhydra lutris kenyoni) from Icy Strait, Alaska

      Brown, Kristin Lynn; Atkinson, Shannon; Andrews, Russel; Pearson, Heidi (2020-05)
      Northern sea otters (Enhydra lutris kenyoni) in Southeast Alaska have experienced a significant population increase since their successful reintroduction to the area after previous near extirpation owing to historic fur trading. The purpose of this study was to examine sea otter diet and metals contamination in an area of Southeast Alaska with the most robust increases in sea otter numbers, Glacier Bay/Icy Strait, with the intent of gathering baseline data for a healthy population of sea otters and as a reflection of the local coastal environmental health of the area. This research was a collaborative effort with Alaska Native subsistence hunters and the Alaska Department of Environmental Conservation. In Chapter 1, sea otter stomachs (n=25) were obtained in April 2015 and April 2016 from Alaska Native subsistence hunters in Icy Strait, Alaska. There were no differences in sea otter diet between years. Bivalves dominated the sea otter diet. Northern horsemussels (Modiolus modiolus) made up the greatest proportion of the diet (0.46 ± 0.48). Fat gaper clams (Tresus capax) and northern horsemussels were found in the highest proportion of stomachs (0.64 and 0.60, respectively). There was not an apparent trend between sea otter age and the minimum number of total prey items, stomach contents mass, or mean frequency of occurrence of the top four prey species. Sea otters from this study are likely to be dietary generalists throughout their lives. In Chapter 2, brain, gonad, kidney, and liver tissues, as well as stomach contents were analyzed for arsenic, cadmium, copper, lead, total mercury, and selenium for the 2015-harvested sea otters that were also referenced in Chapter 1 (n=14). In general, arsenic and lead had the highest concentrations in stomach contents, cadmium and selenium were highest in the kidneys, and copper and total mercury were highest in the livers. While brains and gonads had the lowest metals concentrations of any tissue, the metal with the greatest concentration within the brain was copper, and within the gonads was selenium. Concentrations of arsenic, cadmium, total mercury, and lead demonstrated a relationship with sea otter length. In general, all the mean metals concentrations for these sea otters were below published effects threshold values for marine mammals. Only total mercury demonstrated biomagnification from the stomach contents (i.e., the prey) to all higher-level tissues. Selenium health benefit values were positive in all sea otter tissue types analyzed in the present study, indicating that concentrations of selenium had an overall health benefit in protecting those tissues against mercury toxicity. Evaluating how contaminants concentrate and get distributed in tissues of top trophic levels provides an indication for potential exposure to humans and demonstrates how these keystone species act as indicators of local coastal ecosystem health. The results of studies on dietary exposure and metals contamination in top trophic level consumers such as sea otters can be used in monitoring the health of sea otter populations and the local environment that they inhabit.
    • Dietary effects on protein turnover in three pinniped species, Eumetopias jubatus, Phoca vitulina, and Leptonychotes weddellii

      Inglis, Susan D.; Castellini, Michael; Atkinson, Shannon; Barboza, Perry; Carpenter, James; Rea, Lorrie (2019-05)
      The role of dietary protein in pinniped (seal and sea lion) nutrition is poorly understood. Although these marine mammals derive the majority of their daily energetic needs from lipid, lipids cannot supply essential amino acids which have to come from protein fractions of the diet. Protein regulation is vital for cellular maintenance, molt, fasting metabolism, exercise and development. Proteins are composed of linked amino acids (AA), and net protein turnover is the balance between protein synthesis from component AA, and degradation back to AA. Protein regulation is influenced by dietary intake and quality, as well as physiological and metabolic requirements. In this work, pinniped diet quality was assessed through comparisons of amino acid profiles between maternal milk, blood serum, and seasonal prey of wild juvenile Steller sea lions (Eumetopias jubatus) in Southcentral Alaska. Both Pacific herring (Clupei pallasi) and walleye pollock (Gadus chalcogramma) showed similar patterns to milk in essential and branched chain amino acid content. Serum amino acid profiles suggest the juvenile sea lions were not in protein deficit at the time of capture. Protein metabolism in the blood and urine was assessed through turnover studies using amino acid tracers. The turnover kinetics of ¹⁵N-labelled glycine in the blood amino acid and protein pool, red blood cells, and urine urea were measured in wild adult female Weddell seals (Leptonychotes weddellii) in the Antarctic. Labelled glycine moved quickly into serum protein and red blood cells (1-2 hours) and urinary urea (2-4 hours). The turnover rates in the blood amino acid and urine urea pools demonstrated a reduced turnover rate associated with molting. Lastly, whole body protein turnover experiments using a single bolus ¹⁵N-labelled glycine tracer method with endproduct collection of blood, feces and urine were conducted on 2 Cohort groups of captive Alaskan harbor seals over 2 years. Season was found to have the greatest effect on whole body protein turnover, which increased during the winter and decreased in the summer molt. Conversely, protein intake decreased during the winter and increased in the summer molt. This pattern corresponded with an increase in mass and protein synthesis in the winter, while mass decreased and protein degradation rates increased in molting seals. Weaning also influenced the patterns with reduced protein turnover in newly weaned animals that had recently transitioned from milk to a fish diet. This project presents results on whole body protein turnover rates in nonfasting pinnipeds and reveals that protein turnover is strongly regulated by developmental and seasonal physiological and metabolic demands.
    • Diets of four eelpout species (genus Lycodes) in the U.S. Beaufort Sea based on analyses of stomach contents and stable isotopes of nitrogen and carbon

      Apsens, Sarah J.; Norcross, Brenda; Iken, Katrin; Mueter, Franz; López, Andres (2017-12)
      Eelpouts of the genus Lycodes are an abundant group of demersal fishes in the U.S. Beaufort Sea. Currently eelpout diet and the exact role of eelpouts in the Arctic food web are poorly understood. Additionally, if and how eelpouts avoid intra- and interspecific competition for resources is unknown. In this study, diets of four common Beaufort Sea eelpout species were analyzed with respect to along-shelf (longitude) gradients, across-shelf (depth) gradients, and ontogeny (fish body length) to determine diet composition and patterns of resource partitioning. Diets of the four most numerous eelpout species were analyzed using a combination of stomach contents and nitrogen and carbon stable isotope analyses: Adolf's Eelpout Lycodes adolfi, Canadian Eelpout L. polaris, Archers Eelpout L. sagittarius, and Longear Eelpout L. seminudus. Nitrogen stable isotopes of fish tissue were analyzed to determine trophic level and carbon stable isotopes to determine if origin sources of carbon in food web pathways of eelpout diets differed among species. Fishes were collected in the central (2012) and eastern (2013 and 2014) Beaufort Sea in August and September as part of the U.S.-Canada Transboundary program. Prey groups Polychaeta, Amphipoda, Isopoda, Ophiuroidea, and Copepoda composed a large proportion of the diet by percent weight for all four species of Lycodes, but their relative contributions differed among the species examined. This study indicated that eelpouts feed almost exclusively on benthic prey and avoid interspecific competition by occupying different habitat space and having different diets. Intraspecific similarity in diet composition was low suggesting these fish have diverse diets even among individuals of the same species. Fish length was associated with changes in diet composition for L. adolfi and L. sagittarius, but not L. polaris and L. seminudus. Longitude and depth were correlated with shifts in diet composition for L. sagittarius, but not the other three species. Lycodes polaris occupied a lower trophic level than the other three eelpout species based on nitrogen stable isotope values. Despite differences in the across-shelf distribution between L. polaris and the three deep-water eelpout species, carbon sources of diet were indistinguishable among the four eelpout species. Ecological information on abundant Arctic fish species like eelpouts is needed for long-term ecosystem monitoring, which is especially important in light of pronounced climate changes and increased human activities in the Arctic.
    • Diets of juvenile flatfishes near Kodiak Island, Alaska

      Holladay, Brenda A. (2001-12)
      Flathead sole, Pacific halibut, rock sole, and yellowfin sole were found co-existing near Kodiak Island as juveniles (<200 mm) during late summer. Dietary differences were attributed to fish species, size, and depth-sediment characteristics of their habitat. Two to three size classes were assigned within each species. Across all habitats, significant differences in dietary composition, stomach fullness, and diet diversity were found between size classes of different flatfish species. Within a single depth-sediment habitat, flatfishes of different species and size classes ate similar prey. Seven of nine species size classes had similar prey composition across multiple habitats. Significant differences in dietary composition across habitats were detected only for small Pacific halibut and small rock sole. The juvenile flatfishes near Kodiak were opportunistic feeders, and appeared to select habitat based on parameters other than the presence of specific prey taxa.
    • Diets, distribution and population dynamics of Arctic cod (Boreogadus saida) in Arctic shelf ecosystems

      Marsh, Jennifer M.; Mueter, Franz; Danielson, Seth; Iken, Katrin; Quinn, Terrance J. II (2019-05)
      With climate warming and longer open-water seasons in the Arctic, there is an increased interest in shipping, oil exploration and the expansion or development of commercial fisheries. Anticipated natural and anthropogenic changes are expected to alter the Arctic shelf ecosystems, including their fish communities. As a component of the Arctic Ecosystem Integrated Survey (Arctic Eis), this project presented a unique opportunity to assess the ontogenetic, spatial and temporal variability in the distribution, abundance and trophic roles (trophic level and diet sources) of key fish species in the Chukchi Sea. For my dissertation, I addressed three objectives to advance our understanding of Arctic cod (Boreogadus saida) as a key component of Arctic ecosystems. First, I characterized the current range of variability in trophic roles within the system and explored the role of advection in shaping the fish communities' diet (isotopic signatures) with a focus on Arctic cod. Second, I examined environmental and biological influences on the distribution and abundance of Arctic cod and provided an updated stock assessment for the Chukchi Sea. Finally, I broadened the geographic scope and used available time series of survey data at the southern margin of their range in the Pacific (eastern Bering Sea) and Atlantic (Newfoundland/Labrador shelves) sectors to assess the influence of temperature, predators and competitors on their distribution. Compared to age-1+ Arctic cod, age-0 Arctic cod had a less diverse diet regardless of water mass and were limited to colder temperatures. Together, this suggests that younger Arctic cod are more vulnerable to climate change. Estimates of egg production and early survival suggest that the numbers of mature Arctic cod present in the survey area during summer are unlikely to produce the observed high abundances of age-0 Arctic cod in the Chukchi Sea. Moreover, Arctic cod distributions in their southern ranges were highly influenced by temperature and to a lesser extent by competitors and predators. When temperatures were warmer, Arctic cod occupied a smaller area. These results inform the management of Arctic cod in a rapidly changing environment and provide benchmarks against which to assess future changes.
    • Dispersal patterns and summer oceanic distribution of adult dolly Varden from the Wulik River, Alaska, evaluated using satellite telemetry

      Courtney, Michael B.; Seitz, Andrew; Zimmerman, Christian; Scanlon, Brendan (2015-05)
      In Arctic Alaska, Dolly Varden Salvelinus malma is highly valued as a subsistence fish; however, little is known about oceanic dispersal or ecology. This study addresses this knowledge gap, by using a fisheries independent method, pop-up satellite archival tags (PSATs). In spring of 2012 and 2013, we attached 52 PSATs to Dolly Varden in a river in northwestern Alaska, which flows into the Arctic Ocean, to examine the marine dispersal, behavior and habitat occupancy of this species. Tagged Dolly Varden demonstrated two types of dispersal, including offshore and nearshore dispersal. The offshore type was the first documented northwesterly dispersal and occupancy of Outer Continental Shelf (OCS) areas of the Russian Chukchi Sea. While occupying this area, tagged Dolly Varden demonstrated affinity for the first 5 m of the water column, diel patterns in depth occupancy, and dive depths of up to 50 m, while experiencing a thermal environment of generally 3-7°C. During the nearshore dispersal type, Dolly Varden transited in coastal areas of northwest Alaska, likely returning to their natal rivers to spawn. While in nearshore areas, tagged Dolly Varden always occupied shallow waters (< 6 m), and experienced a rapidly changing thermal environment (± 15°C), including some waters temperatures cooler than -1°C. This study demonstrates that PSATs offer an alternative and effective platform with which to study several aspects of large adult Dolly Varden dispersal and ecology in areas where it is not practical or feasible to capture these fish, such as in coastal and offshore regions of Arctic Alaska. Additionally, the results of this study have increased our knowledge of the summer marine distribution, behavior and thermal environment of Dolly Varden in Arctic regions of Alaska, and this knowledge is important to several stake holders for the conservation of this important subsistence species.
    • Distribution and movement of juvenile tanner crabs Chionoecetes bairdi in Glacier Bay National Park

      Nielsen, Julie Kristine (2005-12)
      Spatial segregation of adult and juvenile Tanner crabs was observed in conjunction with glacial landscape features during a comprehensive systematic survey of Glacier Bay National Park, Alaska, in 2002. Hot spots (clusters of high values) of catch per unit effort for juveniles occurred mainly in two narrow glacial inlets, whereas most adult hot spots occurred in the central portion of the bay. Overall, juveniles were associated with shallower depths and warmer temperatures than adults. However, in juvenile hot spot areas, where adults were rare, juveniles were associated with greater depths and colder temperatures than adults. Glaciated landscapes may provide spatial refuges from predation and nursery areas for juveniles. Tagging methods with high trans-molt retention need to be developed for direct measurement of ontogenetic movement. A laboratory study was conducted to determine trans-molt survival and retention of Floy T-bar tags in juvenile Tanner crabs. Approximately half of crabs in all tagging treatments survived and retained tags through a molt. Trans-molt retention of Floy tags is hindered by complex morphology of the Tanner crab carapace.