• 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.
    • Distribution, Growth And Egg Production Of Euphausiids In The Northern Gulf Of Alaska

      Pinchuk, Alexei I.; Hopcroft, Russell (2006)
      The euphausiids Thysanoessa inermis, Thysanoessa spinifera and Euphausia pacifica are key pelagic grazers and important prey for many vertebrates in the Gulf of Alaska (GOA). This thesis provides the first account of distribution, egg production, growth, development, and temporal variability in abundance of the euphausiids in relation to environmental variations in the northern GOA. T. inermis and T spinifera were abundant on the shelf within 120-130 km from the coast, while E. pacifica originated from offshore and was advected onto the shelf during summer. E. pacifica produced multiple broods with brood size strongly related to ambient chlorophyll a concentrations. In contrast, T. inermis released eggs once in the season and its brood size did not depend on chlorophyll content. Early development of these species showed a remarkably similar response to changes in temperature. The highest molting increments were observed during the spring phytoplankton bloom for T. inermis, and in summer for T. spinifera and E. pacifica, suggesting coupling with food availability. The molting rates were strongly influenced by temperature. Growth rates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm d-1 or 0.023 d -1 for T. inermis) and July (0.091 mm d-1 or 0.031 d-1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm d -1 (0.016 d-1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5�C) and ambient chlorophyll-a concentration fit a Michaelis-Menten curve (r2=0.48), but such relationships were not significant for T. spinifera or E. pacifica. Reproduction of T. inermis occurred during April in 1998 and 2003, and was extended through May in 1999-2002. The spawning of T. inermis and T. spinifera was related to the spring diatom bloom on the inner shelf, while the spawning of E. pacifica occurred later in season, when the water temperature increased. A strong increase in abundance of T. inermis, associated with the extended colder phase in the North Pacific, indicates that progressive cooling in 1999-2002 may have resulted in greater reproductive success of early spawning T. inermis on the inner shelf.
    • Diversity and community structure of eukaryotic phototrophs in the Bering and Chukchi seas

      Lekanoff, Rachel M.; Collins, R. Eric; McDonnell, Andrew M.P.; Danielson, Seth L. (2020-05)
      The phytoplankton of the Bering and Chukchi seas support highly productive ecosystems characterized by tight benthic-pelagic coupling. In this study, we focus on the northern Bering and Chukchi seas, considering them as one ecosystem. This community has historically been dominated by diatoms; however, climate change and accompanying warming ocean temperatures may alter primary producer communities. Using metabarcoding, we present the first synoptic, high-throughput molecular phylogenetic investigation of phytoplankton diversity in the Bering and Chukchi seas based on hundreds of samples collected from June to September in 2017. We identify the major and minor taxonomic groups of diatoms and picophytoplankton, relative abundances of genera, exact sequence variants (201 for diatoms and 227 for picophytoplankton), and describe their biogeography. These phylogenetic insights and environmental data are used to characterize preferred temperature ranges, offering insight into which specific phytoplankton (Chaetoceros, Pseudo−nitzschia, Micromonas, Phaeocystis) may be most affected as the region warms. Finally, we investigated the likelihood of using shipboard CTD data alone as predictive variables for which members of phytoplankton communities may be present. We found that the suite of environmental data collected from a shipboard CTD is a poor predictor of community composition, explaining only 12.6% of variability within diatom genera and 14.2% variability within picophytoplankton genera. Clustering these communities by similarity of samples did improve predictability (43.6% for diatoms and 32.5% for picophytoplankton). However, our analyses succeeded in identifying temperature as a key driver for certain taxa found commonly throughout the region, offering a key insight into which common phytoplankton community members may be affected first as the Alaskan Arctic continues to warm.
    • Diversity, abundance and fate of ice algae and phytoplankton in the Bering Sea

      Szymanski, Anna; Gradinger, Rolf; Iken, Katrin; Collins, R. Eric (2014-12)
      Sea ice algae are an essential part of Arctic and subarctic ecosystems. They significantly contribute to total algal primary production, serve as an early spring food source for both pelagic and benthic biota, and can seed the spring phytoplankton bloom during periods of ice melt. In the subarctic Bering Sea, virtually nothing has been known about the composition of the ice algal community, its magnitude, and its connection to pelagic and benthic ecosystems. This study, therefore, focused on the diversity, abundance, and ultimate fate of ice algae in the Bering Sea using sea ice, water and sub-ice sediment trap samples collected during two spring periods: ice growth (March to mid-April) and ice melt (mid-April to May) in 2008 and 2009. Ice algal species composition was comparable to those in Arctic regions. The phytoplankton species inventory was similar to that found in the overlying ice, suggesting that the spring phytoplankton were seeded from the ice algae. Algal abundance in the ice was on average three orders of magnitude higher than in the water column throughout both periods, as the extensive Bering Sea ice cover in 2008-2009 delayed the phytoplankton bloom. There was a substantial increase in the vertical flux of algal cells beneath the ice during the period of ice melt, but measurable amounts appeared as early as mid-March. The majority of this flux was composed of healthy algal cells, making it a rich food source for benthic organisms. Differences in the relative species composition between ice and trap samples indicate that algal fate was influenced by the species specific sinking rate of algal cells, among other factors, in the water column. In conclusion, ice algae in the Bering Sea are diverse and abundant, and contribute to both pelagic and benthic systems.
    • Diving physiology of the ringed seal: adaptations, capability and implications

      Ferren, Howard Jennings (1980-08)
      Adaptations that influence duration of diving in the ringed seal, Phoaa (Pusa) hispida were examined. Mean blood volume was 234 ml/kg lean body mass (LBM) and oxygen capacity was 30.7 ml O2/100 ml of whole blood, yielding a total blood oxygen capacity of 70 ml O2/kg LBM. Abrupt and prolonged bradycardia occurred upon submersion. Experimental dives indicated submersion durations of up to 18 minutes before the onset of physiological dysfunction. The percentage of LBM represented by the brain is least in the relatively large Weddell seal (0.2%), greater in the harbor seal (0.7%) (the compared species) and greatest in the ringed seal (1.4%); this sets the requirement for minimum obligatory oxygen consumption. The differences observed in diving durations between the three species is considered to be mainly the consequence of brain/body size relationship.
    • Dungeness crab depth distribution: effects of sea otters

      Scheding, Karen A. (2004-05)
      The distribution and abundance of Dungeness crabs in the Glacier Bay area were observed with a submersible in five bays with and three bays without sea otters. A matrix design was used with three levels of sea otter occupation and three depth categories. Goals of this study were to determine: 1) the depth distribution of crabs; 2) if depth was a refuge from sea otter predation; and, 3) the habitat of ovigerous female aggregations. Scuba was used to calibrate submersible counts and collect substrate samples; crab pots were used to confirm submersible sightings. Abiotic and biotic variables were analyzed to interpret distribution data and aggregation sites. A regional, long-term crab survey dataset was also examined. Sea otters may have decreased crab abundance in shallow waters. Two aggregations of ovigerous Dungeness crabs were observed in shallow water with sand substrate. However, only 1% of the 33 km of transects were classified as sand, suggesting that sand may be a limiting resource. No conclusions could be made about the independent effects of sea otter presence or depth due to strong interaction. Submersible observations, crab pot surveys, and marine topography together however, point towards a shift in crab depth distribution with sea otter presence
    • Dynamics of a migratory fish population with applications to the management of sablefish in the Northeast Pacific Ocean

      Heifetz, Jonathan; Quinn, Terrance J. II (1996)
      Quantitative models are developed to describe the dynamics of an age-structured migratory fish population subject to exploitation. Migration rates are quantified, alternative ways of apportioning harvest among areas are examined, and the dynamics of a migratory population is described within the general theoretical framework of a projection matrix model. Application of these modeling efforts is within the context of the sablefish (Anoplopoma fimbria) fishery in the North Pacific Ocean. A Markov model that includes natural and fishing mortality, tag reporting and shedding rates, and migration is used to quantify migration rates of tagged sablefish among fishery regulatory areas. Estimates of annual migration rates out of an area are in the range 19-69% for small (<57 cm fork length (FL)), 25-72% for medium (57-66 cm FL), and 27-71% for large (>66 cm FL) sablefish. The predominant direction of migration along the continental slope is eastward for large sablefish and westward for small sablefish. Most estimates of migration are precise, unconfounded, and robust to perturbations of input constants. An age-structured model that includes migration is constructed to examine harvest policies for sablefish. Areal estimates of yield-per-recruit depends on the geographic distribution of recruitment. In general, when evaluated under the current annual exploitation rate of 10%, apportioning harvest among areas based on areal estimates of biomass and apportionment based on the steady-state distribution of biomass give similar results. A policy of apportionment based on a weighted moving average of areal estimates of available biomass is preferred to others. This policy adapts to current information about geographic distribution of biomass, reduces the effects of measurement error, and does not require estimates of migration probabilities for implementation. The reproduction, mortality and migration of an age-structured fish population are incorporated into a projection matrix model. The model is parameterized to include areal specificity in the stock-recruitment relationship and events such as larval dispersion that is decoupled from local reproduction. For the sablefish fishery where direction of movement is age dependent, fishing at a common rate among areas may be detrimental to the population in a given area. Area-specific fishing strategies can be devised to meet management objectives such as maintenance of areal spawning potential.