Now showing items 1-20 of 467

    • Effects of elevated sediment levels from placer mining on survival and behavior of immature arctic grayling

      Scannell, Patrick O. (1988-12)
      The effect of placer mining effluents on Arctic grayling (Thymallus arcticus) fingerling and egg survival was tested in mined and unmined streams in interior Alaska. Also the influence of turbidity on Arctic grayling reactive distance and avoidance behavior was tested in a laboratory choice chamber. Arctic grayling fingerlings suffered less than 1% mortality during a 96-hr toxicity test in both clear (mean NTU = 1.4) and mined (mean NTU = 445) streams. Arctic grayling eggs did not show significantly (p > 0.1) higher mortality in mined streams than in unmined streams. In a laboratory choice chamber test, Arctic grayling avoided water with a turbidity above 20 NTU (nephelometric turbidity units). Arctic grayling reactive distance diminished proportional to the natural logarithm of turbidity.
    • Effects of climate variability and fishing on gadid-crustacean interactions in subarctic ecosystems

      Marcello, Laurinda; Mueter, Franz; Eckert, Ginny; Kruse, Gordon (2011-12)
      Snow crab (Chionoecetes opilio) are a vital economic and biotic resource to many subarctic ecosystems. Their abundance varies greatly, but what causes large changes in production and early life survival is unknown. My overall goal is to improve our understanding of snow crab population dynamics during early life history stages. Chapter 1 provides background information on subarctic ecosystems, addresses possible mechanisms of population control and potential drivers of variability, describes snow crab life history, and reviews recent population trends in snow crab and their major cod predators. Chapter 2 details a regression study examining the effects of snow crab spawning stock biomass, environmental conditions, and Pacific cod (Gadus macrocephalus) or Atlantic cod (Gadus morhua) biomass on snow crab recruitment. This study compares three ecosystems: the eastern Bering Sea, the Newfoundland-Labrador Shelf, and the southern Gulf of St. Lawrence. Cold ocean conditions during early life history were associated with increased snow crab recruitment or recruitment indices in all three ecosystems. However, there was no consistent observed effect of spawning stock biomass or gadid predation on subsequent recruitment. The dominant role of environmental conditions in driving snow crab recruitment highlights the importance of an ecosystem-based management approach for these stocks.
    • Traditional knowledge and fish biology: a study of Bering cisco in the Yukon River Delta, Alaska

      Runfola, David Michael; Sutton, Trent; Carothers, Courtney; Norton, David W.; Schneider, William (2011-05)
      Relatively little is known about the biology of whitefishes (subfamily Coregoninae) in Alaska. To address this shortcoming, I combined social and biological science methods to examine whitefish in the Yukon River delta, Alaska. This study had two objectives: (1) to collaborate with Yup'ik subsistence fishers in sharing their knowledge of whitefish; and (2) to describe the life history of Bering cisco Coregonus laurettae. In August 2004, interview participants discussed Yup'ik traditional knowledge of whitefish. Participants shared knowledge of Bering cisco and other whitefish species. Interviews demonstrated the need for greater awareness of traditional knowledge, and the importance of communicating this knowledge with scientists. In addition, 120 Bering ciscoes were collected in August 2005 and 2006 with gill nets in the Yukon River delta, Alaska. Bering ciscoes ranged in fork length from 146 to 490 mm (mean = 321 mm) and in weight from 32 to 735 g (mean = 304 g). Fish ranged in age from 0 to 6, with one age-11 individual observed. Diet analysis showed that Bering ciscoes fed primarily on sticklebacks. My study records important social and biological data regarding Bering cisco, linking ethnography and fish biology as a means of investigating this poorly understood species.
    • Growth physiology of juvenile red king crab, Paralithodes camtschaticus, in Alaska

      Westphal, Miranda J.; Tamone, Sherry; Eckert, Ginny; Siddon, Christopher (2011-08)
      Lack of recovery, following collapse of the Alaskan red king crab, Paralithodes camtschaticus, fishery, has prompted research directed towards rehabilitating the species. To better inform rehabilitation efforts aimed at increasing survival and growth of P. camtschaticus in their first year of life, I compared individual growth of hatchery-raised and wild-caught juvenile crabs in the laboratory and then compared both sets of laboratory individuals with cohorts from the field. To understand molt cycles, hemolymph was collected from age-0 and age-3 crabs to quantify circulating molting hormones (ecdysteroids) and the duration of premolt. Size, growth increment, molt interval, and cumulative molt interval did not differ significantly between hatchery-raised and wild-caught crabs. No consistent differences existed in CL between hatchery, wild-laboratory and field-surveyed juveniles for most months, although spine lengths of hatchery-raised and wild-caught crabs were significantly longer than field-surveyed crabs most months. Patterns of circulating ecdysteroids resembled published profiles for other crustacean species. Peak ecdysteroid levels occurred regularly (approximately 17 d) prior to ecdysis despite varying molt intervals. Age-0 and age-3 juveniles spent approximately 39 % and 32 % of the molt cycle in premolt, respectively. Overall, hatchery-raised and wild P. camtschaticus were markedly similar with respect to growth.
    • Fishing for pollock in a sea of change: a history and analysis of the Bering Sea pollock fishery

      Strong, James; Criddle, Keith R.; Adkison, Milo D.; Kruse, Gordon H. (2011-08)
      The development and evolution of the eastern Bering Sea fishery for walleye pollock (Theragra chalcogramma) is retraced, its current economic and institutional structure is modeled, and the resiliency of that structure to substantive changes in pollock biomass and fuel costs is explored. Small variations in exvessel prices, total allowable catches, or allocation of catches between seasons and among industry sectors can lead to large changes to first wholesale revenues. Similarly, changes in fuel prices, changes in technology, changes in regulation, and changes in the spatial distribution of catches can lead to changes in harvesting or processing costs. Together, these changes affect the relative profitability of the inshore and offshore sectors, which can, in turn, affect the benefits that accrue to communities, the evolution of regulation, and create pressure to reallocate sector shares. The model indicates that first wholesale revenues are maximized when pollock harvests are maximized. However, legal barriers to the transfer of allocations between sectors can lead to under-harvests when product prices are low, fuel costs are high, or when the most productive fishing grounds are in the northwest regions of the eastern Bering Sea Exclusive Economic Zone.
    • 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.
    • Incorporating stakeholder input in research priorities for the Aleutian Islands

      Wadsworth, Rachael Margaret; Criddle, Keith R.; Muse, Ben; Kruse, Gordon H. (2012-12)
      Federal law requires that resource management agencies consider stakeholder input in the selection of preferred alternatives for proposed actions. Not only do stakeholders contribute unique perspectives on the impact of alternative actions and the desirability of various policy objectives, including stakeholders in the decision process adds to the perceived legitimacy of those decisions. Incorporating stakeholder input is legally required and advantageous to sustainable governance of the oceans and implementation of a National Ocean Policy such as ecosystem-based management. Agencies use a variety of formal and informal mechanisms to solicit and incorporate stakeholder input. In this study, we compare expert panel and stakeholder rankings of research and information needs in the Aleutian Islands region to see if stakeholder preferences are consistent with those of resource managers and experts when the analytical hierarchy process is used to prioritize those research and information needs. Normalized individual ratings were averaged across interest groups and compared to ratings averaged across all respondents. Spearman rank-order correlations were used to test the statistical significance of differences between groups and against the overall mean. Sensitivity analyses were used to check the robustness of the rankings across groups. We found a high level of association between rankings by an expert panel and rankings by stakeholders and little sensitivity to the make-up of stakeholders. These results suggest that the analytical hierarchy process can serve as a useful mechanism for organizing stakeholder input for environmental planning and resource management.
    • Kelp forests and barren grounds: phlorotannin production and holdfast community structure in the Aleutian dragon kelp, Eualaria fistulosa

      Schuster, Martin D.; Konar, Brenda; Iken, Katrin; Coyle, Kenneth (2012-12)
      The canopy forming kelp Eualaria fistulosa inhabits two organizational states throughout the Aleutian archipelago, kelp forests and barren grounds. Urchin abundance and behavior determines which state dominates in any given area. Sporophyll phlorotannin content and holdfast epibiont fauna were investigated at multiple islands along the Aleutian archipelago to determine how the organizational state affects the production of secondary metabolites and the taxon richness, abundance and biomass of holdfast communities. Barren ground sporophylls had higher phlorotannin content than kelp forest sporophylls, although grazing rates on sporophylls from each state did not differ during in situ grazing experiments. The taxon richness, abundance and biomass of holdfast communities were similar between kelp forests and barren grounds at all islands, although these communities varied among islands and were mostly driven by holdfast volume. These results suggest that physical differences such as light and nutrient availability in the kelp forest structure between organizational states may be responsible for differences in phlorotannin content, but that these differences are not reflected in the holdfast community structure. It appears that barren ground holdfast communities are remnants of a once forested area.
    • A test of local adaptation in seasonally separate subpopulations of pink salmon (Oncorhynchus gorbuscha)

      Manhard, Christopher V.; Gharrett, Anthony; Smoker, William; Adkison, Milo (2012-12)
      Differences in fitness related traits were observed between first generation (F₁) hybrid and control lines of temporally distinct subpopulations of pink salmon (Oncorhynchus gorbuscha). The lines were cultured in a common freshwater environment, released to sea together, and collected at their natal stream as adults. Early-and late-run pink salmon, which are partially genetically isolated by the time at which they return to Auke Creek in Southeast Alaska to spawn, were crossed to create F₁ and F₂ hybrid groups in the even- and odd-year brood lines. Marine survival of controls exceeded that of F₁ hybrids of the even-year brood line, whereas no difference in marine survival between those experimental groups was detected in the odd-year brood line. First generation hybrids expressed intermediate time of return relative to controls in both brood lines. Second generation hybrids exhibited similar embryonic development rates to controls in both brood lines. These results demonstrate that removal of a genetic barrier as fine as that which occurs within a brood line and location can disrupt local adaptation in a population of pink salmon, which may cause outbreeding depression in hybrids and may potentially reduce the overall biodiversity and productivity of the population.
    • Impacts of sea otter predation on commercially important sea cucumbers (Parastichopus californicus) in Southeast Alaska

      Larson, Sean D.; Eckert, Ginny L.; Woodby, Douglas A.; Kruse, Gordon H. (2012-12)
      Consequences from management actions, particularly those regarding species reintroductions, are not always immediately apparent. After sea otters were extirpated from Southeast Alaska in the 18th and 19th century fur trade, it is presumed that marine invertebrate stocks grew in the absence of sea otter predation. Since reintroduction in the 1960s, the Southeast Alaska sea otter population has grown, with great potential to deplete the commercially important sea cucumber, Parastichopus californicus. This study evaluates the interaction with and impacts of sea otters on sea cucumbers using foraging observations and sea cucumber density data collected for fishery management. Sea otter diets, in terms of edible biomass, include about only 5% cucumbers, and yet sea otters are depleting sea cucumbers; declines in sea cucumber density at sea otter affected transects ranged from 26 to 100%. Sea otter predation should be included in sea cucumber fishery management, possibly as an additional form of mortality in the surplus production model, as a step toward ecosystem based management.
    • Evaluation of prey composition and nutritional value of diets of free-ranging harbor seals (Phoca vitulina) from Tugidak Island

      Geiger, Gretchen L.; Atkinson, Shannon; Carpenter, James; Horstmann-Dehn, Larissa; Wynne, Kate (2012-12)
      Changes in climate can cause shifts in ecosystem structure that can affect quantity or quality of prey available to predator populations. Due to sex or age-specific behaviors of predators, certain classes within a population may be more severely impacted by changes in their diet. This study evaluated prey composition and nutritional value of summer diets of harbor seals (Phoca vitulina richardii) from Tugidak Island, Alaska from 2001-2009. The MIXIT-WIN program was used to estimate the nutritional value of average harbor seal diets. Changes in relative abundance of certain prey species were correlated to sea surface temperature anomalies. Despite changes in prey composition, the nutritional value of the average harbor seal diet did not change. Fecal corticosteroid metabolite profiles were analyzed to identify age and sex of individual harbor seals from scats. Profiles obtained from a known adult male harbor seal could be differentiated from those of known adult female and juvenile male seals. Similar profiles were observed in unknown age and sex samples. Even though diet diversity differed between these groups, the nutritional quality of consumed diets was not significantly different. Tugidak Island harbor seals have flexible diets allowing them to capitalize on available prey to maintain their nutritional intake.
    • Subsistence salmon fishing in Beaufort Sea communities

      Cotton, Shelley S.D.; Carothers, Courtney; Craighead George, John (2012-12)
      Environmental change, combined with observations of increasing numbers of salmon in subsistence fisheries, has generated a need for more information about salmon use, abundance, and distribution in the Arctic. Ethnographic research was conducted in Barrow and Nuiqsut, Alaska, in 2010 and 2011 with 41 active fishermen and elders. Salmon catches were perceived to be increasing; however, perceptions about changing salmon abundance were mixed. While pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta) have been observed in subsistence fisheries in the central North Slope region for over 50 years, only within the last 10 to 20 years has local use of these resources begun to increase. In this region, salmon are less important as a subsistence resource compared to whitefish species (Coregonus spp.). However, many fishermen participating in the Elson Lagoon gill net fishery near Barrow have begun to target salmon. Harvest estimates for this fishery in 2011 indicated that chum salmon and pink salmon catches comprise the majority of all fish caught (42% and 23%, respectively). Chinook salmon (O. tshawytscha) have been increasingly targeted, but catches are generally low. While sockeye salmon (O. nerka) numbers were perceived to have increased on the North Slope, catches of this species are rare. Only a few stray coho salmon (O. kisutch) have been captured in this region. Informants identified new stream systems where salmon are present and spawning, suggesting possible distribution shifts. Fishermen in both communities reported developing knowledge of salmon and are increasing their use of salmon as a subsistence resource.
    • Characterizing the fish community in turbid Alaskan rivers to assess potential interactions with hydrokinetic devices

      Bradley, Parker T.; Seitz, Andrew; Sutton, Trent; McPhee, Megan; Burr, John (2012-12)
      The Yukon and Tanana rivers are two large, glacially turbid rivers in Alaska, where hydrokinetic projects are being explored for feasibility of electricity production. Downstream migration behavior of fishes in these rivers is poorly understood; as a result, the potential impacts of hydrokinetic devices, which will be placed in the deepest and fastest part of the river, on fishes are unknown. Downstream migrating fishes were sampled during the ice-free season along the river margins of the Yukon River in 2010 and the river margins and mid-channel of the Tanana River in 2011. Results suggest that the river margins in the Yukon and Tanana rivers are primarily utilized by resident freshwater species, the mid-channel is utilized by Pacific salmon (Oncorhynchus spp.) smolts, and only chum salmon (Oncorhynchus keta) smolts utilize both of these areas. Some species exhibited distinct peaks and trends in downstream migration timing including longnose suckers (Catostomus catostomus), whitefishes (Coregonine), Arctic grayling (Thymallus arcticus), lake chub (Couesius plumbeus), Chinook salmon (O. tshawytscha), coho salmon (O. kisutch), and chum salmon. As a result of these fishes' downstream migration behavior, hydrokinetic devices installed in surface waters of the middle of the river channel will have the most potential interactions with Pacific salmon smolts during their downstream migration to the ocean from May through July.
    • Pacific herring juvenile winter survival and recruitment in Prince William Sound

      Sewall, Fletcher; Norcross, Brenda; Mueter, Franz; Kruse, Gordon; Heintz, Ron; Hopcroft, Russ (2020-05)
      Small pelagic fish abundances can vary widely over space and time making them difficult to forecast, partially due to large changes in the number of individuals that annually recruit to the spawning population. Recruitment fluctuations are largely driven by variable early life stage survival, particularly through the first winter for cold temperate fishes. Winter survival may be influenced by juvenile fish size, energy stores, and other factors that are often poorly documented, which may hamper understanding recruitment processes for economically and ecologically important marine species. The goal of this research was to improve understanding of recruitment of Pacific herring (Clupea pallasii) within Prince William Sound (PWS) through recruitment modeling and by identifying factors influencing winter survival of young-of-the-year (YOY) herring. Towards this end, my dissertation addresses three specific objectives: 1) incorporate oceanographic and biological variables into a herring recruitment model, 2) describe patterns in growth and condition of PWS YOY herring and their relationship to winter mortality risks, and 3) compare the growth, condition, swimming performance, and mortality of YOY herring that experience different winter feeding levels. In the recruitment modeling study, annual mean numbers of PWS herring recruits-per-spawner were positively correlated with YOY walleye pollock (Gadus chalcogrammus) abundance in the Gulf of Alaska, hence including a YOY pollock index within a standard Ricker model improved herring recruitment estimates. Synchrony of juvenile herring and pollock survival persisted through the three-decade study period, including the herring stock collapse in the early 1990s. While the specific mechanism determining survival is speculative, size-based tradeoffs in growth and energy storage in PWS YOY herring indicated herring must reach a critical size before winter, presumably to reduce size-dependent predation. Large herring switched from growth to storing energy, and ate more high-quality euphausiid prey, which would delay the depletion of lipid stores that compelled lean herring to forage. Lipid stores were highest in the coldest year of the seven-year field study, rather than the year with the best diets. With diets controlled in a laboratory setting, spring re-feeding following restricted winter diets promoted maintenance of size and swimming ability, but had little effect on mortality rates compared to fish continued on restricted rations. Declines in gut mass, even among fully fed herring, and low growth potential suggest limited benefits to winter feeding. Mortalities due to food restriction compounded by disease were highest among herring that fasted through winter months, and among small herring regardless of feeding level. Taken together, these findings illustrate the importance of achieving a critical size and high lipid stores in the critical period before winter to promote YOY herring winter survival and ultimately recruitment.
    • 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.
    • 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.
    • Reproductive potential of female eastern Bering Sea tanner crab

      Knutson, Michael R.; Eckert, Ginny L.; Daly, Benjamin; Mueter, Franz; Webb, Joel (2020-05)
      Changes in abundance and sex ratio can contribute to variation in the reproductive potential of a population. The commercially important Bering Sea Tanner crab (Chionoecetes bairdi) are distributed throughout the north Pacific Ocean and display cyclical population dynamics. The goal of this study was to examine how fishing pressures and population dynamics affected the reproductive potential of Bering Sea Tanner crab to better inform sustainable fishery management. I quantified female stored sperm levels and fecundity for both primiparous (in their first reproductive cycle) and multiparous (in their second or later reproductive cycle) crab to examine spatial and temporal variation in reproductive potential. Multiparous female crab had higher spermathecal load than primiparous ones, but spermathecal load varied widely across female size. Higher sperm cell counts were associated with visual indication of fresh ejaculate for primiparous crab but not for multiparous crab. Sperm cell counts increased with increasing spermathecal load for both primiparous and multiparous crab, although the slope of the regression line varied for the two categories. Female fecundity was highest in crab in their second year after the terminal molt to maturity and was lower in the first year and in the third and subsequent years. Female fecundity (size-corrected) did not differ among management areas. Measures of mature female sperm storage and quantification of reproductive stage can provide fishery managers with an early warning of reproductive failures.
    • 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.
    • The use of aerial imagery to map in-stream physical habitat related to summer distribution of juvenile salmonids in a Southcentral Alaskan stream

      Perschbacher, Jeff; Margraf, F. Joseph; Hasbrouck, James; Wipfli, Mark; Prakash, Anupma (2011-12)
      Airborne remote sensing (3-band multispectral imagery) was used to assess in-stream physical habitat related to summer distributions of juvenile salmonids in a Southcentral Alaskan stream. The objectives of this study were to test the accuracy of using remote sensing spectral and spatial classification techniques to map in-stream physical habitat, and test hypotheses of spatial segregation of ranked densities of juvenile chinook salmon Oncorhynchus tschwytscha, coho salmon O. kisutch, and rainbow trout O. mykiss, related to stream order and drainage. To relate habitat measured with remote sensing to fish densities, a supervised classification technique based on spectral signature was used to classify riffles, non-riffles, vegetation, shade, gravel, and eddy drop zones, with a spatial technique used to classify large woody debris. Combining the two classification techniques resulted in an overall user's accuracy of 85%, compared to results from similar studies (11-80%). Densities of juvenile salmonids was found to be significantly different between stream orders, but not between the two major drainages. Habitat data collected along a 500-meter stream reach were used successfully to map in-stream physical habitat for six river-kilometers of a fourth-order streams. The use of relatively inexpensive aerial imagery to classify in-stream physical habitats is cost effective and repeatable for mapping over large areas, and should be considered an effective tool for fisheries and land-use managers.
    • A total environment of change: exploring social-ecological shifts in subsistence fisheries in Noatak and Selawik, Alaska

      Moerlein, Katie J. (2012-05)
      Arctic ecosystems are undergoing rapid changes as a result of global climate change, with significant implications for the livelihoods of arctic peoples. In this thesis, I use ethnographic research methods to detail prominent environmental changes observed and experienced over the past few decades and to document the impact of these changes on subsistence fishing practices in the Inupiaq communities of Noatak and Selawik in northwestern Alaska. Using in-depth key informant interviews, participant observation, and cultural consensus analysis, I explore local knowledge and perceptions of climate change and other pronounced changes facing the communities of Noatak and Selawik. I find consistent agreement about a range of perceived environmental changes affecting subsistence fisheries in this region, including lower river water levels, decreasing abundances of particular fish species, increasingly unpredictable weather conditions, and increasing presence of beaver, which affect local waterways and fisheries. These observations of environmental changes are not perceived as isolated phenomena, but are experienced in the context of accompanying social changes that are continually reshaping rural Alaska communities and subsistence economies. Consequently, in order to properly assess and understand the impacts of climate change on the subsistence practices in arctic communities, we must also consider the total environment of change that is dramatically shaping the relationship between people, communities, and their surrounding environments.