• A Multiple Stable Isotope Study Of Steller Sea Lions And Bowhead Whales: Signals Of A Changing Northern Environment

      Dehart, Pieter Andrew Philip; Wooller, Matthew J. (2006)
      The North Pacific and Arctic marine realm is currently experiencing dramatic environmental changes as a result of global climate change. Stable isotope analysis of western arctic bowhead whales (WABW, Balaena mysticetus ) and Steller sea lions (SSL, Eumetopias jubatus) were conducted to examine the influence of these changes on life history characteristics (migration and foraging) of these marine mammals. WABW baleen plates were analyzed for their stable oxygen and hydrogen isotope composition (delta 18O and deltaD) and were compared to the delta18O and deltaD in water and zooplankton prey along their seasonal migratory route. The delta18O and deltaD varied along the baleen (8 to 18�; -180 to -80�, respectively) and corresponded to stable isotopic differences in zooplankton from the winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW. Baleen delta18O and deltaD confirmed the seasonal annual migration of WABW and were subsequently compared to historical sea ice concentrations (SIC). This illustrated that WABW migration patterns appeared to have altered concomitant with changes in SIC. Years with a higher SIC (colder climate regimes) correlated with the largest difference in deltaD between winter and summer in WABW baleen during the period from 1972 to 1988. For a similar time period (1955 to 2000), the feeding ecology of SSL was also examined by analyzing the stable carbon and nitrogen isotope compositions (delta13C and delta 15N, respectively) of archived SSL bone and tooth collagen. Both delta 15N and delta13C varied greatly with location and sample year (14.6 to 20.5�; - 16.7 to -11.8�, respectively), with a significant change in delta13C observed around the 1976 regime shift. Bottom-up processes may have limited growth of SSL populations throughout this region over time, with animals focusing their foraging on offshore regions to mitigate this environmental change. Stable isotope analyses of historical samples of WABW (baleen) and SSL (bone and tooth collagen) both illustrated that recent environmental changes influenced the ecology (migration and feeding) of these marine mammals in the recent past.
    • Abundance, Recruitment, And Environmental Forcing Of Kodiak Red King Crab

      Bechtol, William R.; Kruse, Gordon H. (2009)
      Commercial harvests of red king crab Paralithodes camtschaticus around Kodiak Island, Alaska increased rapidly in the 1960s to a peak of 42,800 mt in 1965. Stock abundance declined sharply in the late 1960s, moderated in the 1970s, and crashed in the early 1980s. The stock has not recovered despite a commercial fishery closure since 1983. To better understand the rise, collapse, and continued depleted status of the red king crab stock around Kodiak Island, I conducted a retrospective analysis with three primary objectives: (1) reconstruct spawning stock abundance and recruitment during 1960-2004; (2) explore stock-recruit relationships; and (3) examine ecological influences on crab recruitment. A population dynamics model was used to estimate abundance, recruitment, and fishing and natural mortalities. Three male and four female "stages" were estimated using catch composition data from the fishery (1960-1982) and pot (1972-1986) and trawl (1986-2004) surveys. Male abundance was estimated for 1960-2004, but limited data constrained female estimates to 1972-2004. Strong crab recruitment facilitated increased fishery capitalization during the 1960s, but the high harvest rates were not sustainable, likely due to reproductive failure associated with sex ratios skewed toward females. To examine spawner-recruitment (S-R) relationships for the Kodiak stock, I considered lags of 5-8 years between reproduction and recruitment and, due to limited female data, two currencies of male abundance as a proxy for spawners: (1) all males ?125 mm carapace length (CL); and (2) legal males (?145 mm CL). Model selection involved AICc, the Akaike Information Criterion corrected for small sample size. An autocorrelated Ricker model using all males and a 5-year lag, with the time series separated into three productivity periods corresponding to different ecological regimes, minimized AIC c values. Depensation at low stock sizes was not detected. Potential effects of selected biotic and abiotic factors on early life survival by Kodiak red king crab were examined by extending the S-R relationship. Results suggested a strong negative influence of Pacific cod Gadus macrocephalus on crab recruitment. Thus, increased cod abundance and a nearshore shift in cod distribution likely impeded crab stock rebuilding.
    • Competition And Recruitment In Southeast Alaskan Subtidal Kelp Communities

      Okamoto, Daniel Kenji (2009)
      Shallow subtidal rocky reefs in the Northeast Pacific host frequent physical and biological disturbances as well as multiple competing algal species, including kelps and algal crusts. Kelps serve a critical role in local ecosystems by generating primary productivity and essential fish habitat. While kelp forests rank among the best understood ecosystems in the marine environment, protected and subarctic systems remain largely ignored. Because of the importance of kelp habitat in Southeast Alaska, and the susceptibility of kelps to both disturbance and competition, I estimated the variability in kelp community structure of subtidal, kelp dominated reefs in the Lynn Canal and quantified kelp recruitment in response to both competing algae and bare space which included clearings, artificial reefs, and settlement tiles installed at different periods. Surveyed communities varied most within rather than among reefs. Kelps exhibited strong, rapid, variable and apparent taxa specific colonization potential to clearings, artificial reefs and settlement tiles installed from summer to late fall. Algal crusts imposed a near 100% inhibition of kelp recruits in the field and lab; however the strong colonization potential of kelps facilitated recruitment in the face of strong inhibition by algal crusts.
    • 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.
    • Ecology Of Juvenile Pink Salmon In The North Gulf Of Alaska And Prince William Sound

      Boldt, Jennifer Lynn; Haldorson, Lewis J. (2001)
      Increased production of salmon in Alaska has been accompanied by a decrease in average body size and decreased wild stocks, indicating a possible density-dependent response to increases in salmon populations and hatchery releases. Pink salmon have a short two-year life cycle and most post-hatch mortality is thought to occur during their first months at sea; therefore, processes in the early marine residence period may determine abundance. Geographic and seasonal patterns in distribution, growth, and condition of juvenile pink salmon during their first months at sea were examined in Chapter 1. The migration of pink salmon from Prince William Sound (PWS) occurred over several months. Fish lengths, weights, and energy contents varied geographically and seasonally. Pink salmon energy content was highest on the Gulf of Alaska (GOA) shelf in July and August and lowest in PWS in July, indicating that growth conditions were better on the GOA shelf. Spatial and temporal variation in growth and condition is indicative of disparate feeding opportunities for juvenile pink salmon. An unusual aspect of this study was the concurrent collection of zooplankton and fish in PWS and on the GOA shelf. Geographic and seasonal changes in juvenile pink salmon diets were examined during their first six months at sea in Chapter 2. Pink salmon diets varied geographically and seasonally, and prey size increased as fish grew. A unique opportunity existed to compare the energy content of thermally marked hatchery pink salmon to their wild counterparts in PWS (Chapter 3). Fish condition varied geographically, however, there were no differences among hatchery groups and/or wild pink salmon at any one location. This indicates that fish were staying together as a group. In Chapter 4, pink salmon consumption was estimated to represent a small fraction of the production but potentially a large proportion of the available standing stock of zooplankton in PWS. Geographic variations in fish condition, diet, and zooplankton densities were observed in this study. This supports the hypothesis that local processes, including food depletion and/or zooplankton availability are important to juvenile pink salmon.
    • Effects Of Adult Salmon Carcasses On The Energy Allocation Strategies Of Juvenile Salmonids

      Heintz, Ron A. (2009)
      When adult salmon return to their natal streams to spawn they deliver energy in the form of carcass tissues and eggs. Currently, the effect of this marine-derived energy on the growth and energy allocation strategies of juvenile salmonids is unknown. This thesis examined the effects of marine-derived energy on the growth and energy allocation strategies of juvenile coho salmon and resident Dolly Varden. Fatty acid analysis was developed as a tool for monitoring the flow of marine-derived lipids and hence energy from carcass tissues to consumers in laboratory and field settings. Fish in these settings were examined before and after the arrival of adult salmon carcasses in their respective habitats. The allocation of protein and lipid was monitored in concert with the fatty acid analysis. In addition, the effect of different diets on fasting of wild coho salmon was studied to determine how marine-derived diets might influence over winter survival. Marine-derived energy was acquired by juvenile salmonids through both direct and indirect processes. Direct acquisition entailed consumption of marine-derived lipids or short trophic linkages between carcass tissues and consumers. Indirect acquisition was typified by long trophic linkages between consumers and carcass tissues in which marine lipids were incorporated by consumers after marine-derived lipids permeated food webs. The benefits of consuming marine-derived lipids depended on the method of acquisition. Fish that directly acquired marine-derived lipids altered their energy allocation strategies by storing greater amounts of lipid; allowing them to maintain elevated metabolic rates over winter and start spring in a high nutritional state. In contrast, indirect acquisition of marine-derived lipids afforded fish few benefits. These fish survive winter by down regulating metabolic rates and start spring in a low nutritional state. The ubiquity of direct acquisition by coho salmon and variable routes of acquisition in Dolly Varden suggest that the presence of carcass tissues may serve to reinforce anadromy among juvenile salmonids rearing in streams.
    • Effects Of Glacial Discharge On Kelp Bed Organisms In An Alaskan Subarctic Estuary

      Sparkland, Tania Marie; Iken, Katrin; Braddock, Joan; Gradinger, Rolf; Himelbloom, Brian; Konar, Brenda; Whitledge, Terry (2011)
      Global climate warming is having large-scale, pronounced effects on the physical environment of Arctic and subarctic nearshore marine ecosystems, such as the widespread melting of glaciers. The purpose of this study was to determine how changing environmental conditions due to glacial melting affect subarctic kelp bed community structure and organism fitness. This study compared kelp bed community structure under disparate environmental conditions on a glacially-influenced and an oceanic shore in the same subarctic Alaskan estuary. Laboratory tests assessed the effects of varying salinity and irradiance on growth and physiological competence (as maximum quantum yield ( Fv/Fm)) of the dominant kelp, Saccharina latissima. Reciprocal in situ shore transplant studies examined seasonal growth, Fv/Fm, morphology and storage product levels (mannitol) in S. latissima. This study showed that kelp communities were distinctly different in these two nearshore regions within the same subarctic estuary. In addition, the kelp S. latissima from these two environments, exhibited phenotypic plasticity in terms of growth to varying levels of salinity and light availability, while both populations maintained high physiological competence year-round. However, this phenotypic plasticity was constrained within different seasonal growth patterns in the populations from the two shores, which likely are genetically fixed. This is the first time that phenotypic plasticity within a genetically fixed seasonal growth cycle has been described for macroalgae and especially for two populations in such close proximity. However, the ability to elicit plastic responses and seasonal adaptations in S. latissima may be limited and concerns remain about the long-term persistence of this and other important foundation species and nearshore habitats with continued climate change.
    • Endocrine And Immune Profiles Of Immature Pinnipeds

      Keogh, Mandy Jean; Atkinson, Shannon; Castellini, Michael; Hellman, Tuula; Ortiz, Rudy; Runstadler, Jonathan (2011)
      There is increasing interest in assessing the health of individuals and populations of pinnipeds found in the North Pacific, primarily due to population declines leading to conservation concerns. This study assessed the "health" of animals by quantifying hormones associated with fat mass (leptin), lipid and water metabolism (cortisol and aldosterone), and growth and metabolism (thyroxine and triiodothyronine) as well as circulating total and differential leukocyte counts and in vitro proliferation of peripheral blood mononuclear cells (PBMC). Body mass and condition are influenced by an individual's disease and nutritional state. Glucocorticoids are known to affect the immune system and may be stimulated by a multitude of factors. I hypothesized that age or body mass would influence leukocyte counts, PBMC proliferation, and hormone concentrations in Steller sea lion (Eumetopias jubatus) pups and that the response of cortisol to an acute stressor would impact immune parameters in juvenile harbor seals (Phoca vitulina ). Further, given the inherent requirements of disturbance and animal handling necessary for sampling pinnipeds, the impact of these activities on endocrine and immune profiles was assessed. Total white blood cell (WBC) counts, neutrophil counts and T cell proliferation decreased with increasing age in Steller sea lion pups. However, no relationship between body condition index and circulating concentration of hormones quantified was detected. Circulating concentrations of cortisol, thyroxine, and triiodothyronine were influenced by the rookery disturbance. However, the variation attributed to the disturbance was low and did not alter total or differential WBC counts or in vitro proliferation of PBMC. In harbor seals, cortisol and aldosterone concentrations increased following an acute stressor which resulted in a stress leukogram. Total WBC decreased driven primarily by the decrease in neutrophil counts with simultaneous increase in lymphocytes leading to an overall decrease in neutrophil to lymphocyte ratio. These findings highlight the endocrine system's influence on the immune system in immature pinnipeds.
    • Feeding ecology of larval and juvenile walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) in the Southeastern Bering Sea

      Strasburger, Wesley Wayne; Hillgruber, Nicola; Pinchuk, Alexei; Mueter, Franz (2012-08)
      Poor recruitment success during warm years (e.g., 2001-2005) was hypothesized to lead to reduced gadid recruitment in the southeastern Bering Sea. These groundfishes are of particular importance, both commercially and ecologically in the southeastern Bering Sea. The spatial and temporal overlap of early life stages of walleye pollock and Pacific cod may explain their strongly correlated recruitment trends in the southeastern Bering Sea. The goal of this study was to compare feeding patterns of larval and juvenile walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) in the southeastern Bering Sea, and to assess the possibility of prey resource competition. Larvae and juveniles from both species collected between May and September 2008, an exceptionally cold year, were used to analyze stomach contents. Fish body size was most consistently related to diet composition within species, however, spatial and depth factors also had an influence. Feeding success and diet composition of these two gadid species were consistently different throughout the spring, summer, and especially fall seasons. Pacific cod larvae and juveniles consistently consumed larger prey items in every season and progressively fewer prey items, especially in the fall. This data suggests that competition for prey resources was unlikely during cold 2008.
    • Fifty years of Cook Inlet beluga whale ecology recorded as isotopes in bone and teeth

      Nelson, Mark A.; Wooller, Matthew J.; Iken, Katrin; Quakenbush, Lori T. (2017-12)
      Beluga whales (Delphinapterus leucas) are found across the Arctic and Subarctic in seasonally ice covered waters. Five stocks of beluga whales are associated with the waters near Alaska for at least part of the year and four of those five stocks are abundant and commonly hunted by Alaskan Natives. The belugas resident in Cook Inlet are also an important cultural and subsistence resource to Alaskan Natives in the area, but a ~50% decline in abundance in the 1990's led to the stock being designated as depleted under the Marine Mammal Protection Act in 2000 and listed as endangered under the Endangered Species Act in 2008. Numerous studies of beluga whales in relation to stranding events, predation (killer whales), parasitism, disease, contaminants, and other potential population threats have not identified the reason for their inability to recover. Changes in diet have been considered, but are difficult to study because observations of feeding in muddy water and beluga stomachs are difficult to obtain. To investigate the past feeding ecology of beluga whales from Cook Inlet I sampled bone and teeth for isotopic analyses. I sampled bone from 20 individuals that died between 1964 and 2007 for stable carbon and nitrogen isotope analysis (values expressed as δ¹³C and δ¹⁵N values). I also micro-sampled annual growth layer groups in the teeth of 26 individuals representing the years from 1962 to 2007. Bone and tooth data showed a general decrease in δ¹³C and δ¹⁵N values over time. The δ¹³C values from analyses of growth layer groups declined from -13.4‰ to -16.2‰ and δ¹⁵N values declined from 17.2‰ to 15.4‰. Although these values are consistent with a change in feeding ecology over time, the magnitude of the decrease in δ¹⁵N values (~2‰) is insufficient for a full trophic level shift (~3‰).The relatively large decrease in the δ¹³C values over the same time period (~3‰), however, is much greater than a full trophic level shift (~1‰) and suggests an increase in prey associated with freshwater, which typically have lower δ¹³C values than prey associated with marine water. To test this hypothesis I analyzed the strontium isotope composition (⁸⁷Sr/⁸⁶Sr ratios) of growth layer groups in teeth from a sub-set of individuals. The resulting ⁸⁷Sr/⁸⁶Sr ratios trended away from the global marine signature (0.70918) over time and toward the more freshwater signatures measured in rivers flowing into the upper reaches of Cook Inlet. These results indicate that the diet of Cook Inlet beluga whales has changed over time. This could be from feeding on different, more freshwater derived prey species, or from feeding on the same species, but on individuals from locations with a more freshwater influence. Both of these interpretations are consistent with population survey data indicating a retraction in beluga range into the upper reaches of Cook Inlet. This study presents the first evidence of a long term (~50 years) change in Cook Inlet beluga whale feeding ecology. The consequences of this change toward more freshwater-influenced prey, and how this change relates to Cook Inlet beluga whales' decline or recovery remains unknown. However, to better examine this change in feeding ecology a follow-up study will; 1) develop a strontium isoscape for the Cook Inlet watershed; 2) analyze more teeth to better analyze changes in feeding ecology by demographic group (sex, age); and 3) analyze growth layer groups from Bristol Bay beluga teeth for a comparison with Cook Inlet belugas to determine if the changes represent an ecosystem change within Cook Inlet or a broader scale change affecting another region. This study builds towards a better understanding of the changes in Cook Inlet beluga feeding ecology and will help to determine if changes in diet could be a factor in their recovery.
    • Growth Of Western Alaska And Asian Chum Salmon (Oncorhynchus Keta) In Relationship To Climatic Factors And Inter- And Intraspecific Competition

      Agler, Beverly Ann; Smoker, William; Hagen, Peter T.; Kruse, Gordon H.; Mueter, Franz J. (2012)
      Ocean climate shifts and interspecific interactions with Russian pink salmon and Asian chum salmon are all believed to influence the growth of chum salmon in the North Pacific Ocean. Stepwise generalized least squares regression and Mantel's tests were used to examine factors influencing mean annual growth from adult scales collected during 1962-2008. First-year scale growth was affected by warmer regional temperatures, the North Pacific Index (NH), and reduced ice cover. Significant negative effects of Asian chum salmon abundance were found on third-year growth of five of six age 0.3 populations and three of four age 0.4 populations examined, indicating intraspecific competition. I found a negative correlation with third-year growth, North Pacific annual sea surface temperature (SST), and NM. Effects of interspecific interactions on third-year growth due to Russian pink salmon abundance were smaller than effects of Asian chum salmon abundance and SST. Warmer large-scale SSTs associated with reduced third-year growth contradicted the original hypothesis and suggested that the abundance of Asian chum salmon created a masking effect overwhelming other factors promoting growth. Strong correlations among third-year growth suggested that chum salmon experienced similar environmental conditions in the North Pacific and had overlapping distributions. More synchronous growth was observed among populations from close rivers than distant ones, indicating the importance of regional scale versus oceanwide studies. In the first year, intercircular distance declined then rapidly increased at circuli 5-9, Intercircular distance was similar by gender until the third year when male growth exceeded female growth for all populations except Japan. Back-calculated lengths indicated that fish reach ~494 mm fork length by the third year before returning as age 0.3 adults. Smolts entering the ocean during odd years had greater distances between adjacent circuli the next year, indicating reduced growth in the first year and compensatory growth during the second and third years. Overall, these results suggested possible effects on chum salmon growth due to abundance of Asian chum salmon, and this effect led to a reduction in length of approximately 42 mm, potentially affecting fecundity by 3%. These results contribute to growing evidence of competition among conspecific salmon.
    • Habitat Function In Alaska Nearshore Marine Ecosystems

      Pirtle, Jodi L.; Eckert, Ginny; Reynolds, Jennifer; Quinn, Terrance II; Tissot, Brian; Woodby, Doug (2010)
      This research demonstrates how habitat structures subtidal communities and supports individual species in Alaska nearshore marine ecosystems. This was accomplished through a case study of southeast Alaska coastal regions, and an in-depth investigation of red king crab Paralithodes camtschaticus early life stage ecology and nursery habitat. How subtidal communities reflect variation in the marine environment of southeast Alaska is poorly understood. The purpose of the first part of this body of research was to identify and compare patterns of community structure for macroalgae, invertebrate, and fish communities at shallow subtidal depths between inner coast and outer coast regions, and link patterns of community structure to environmental variability in southeast Alaska. The major hydrographic gradient of decreasing salinity and increasing temperature from the outer coast to the inner coast affected regional community structure, with greater species diversity at the outer coast. Species distribution for invertebrate communities was linked to variation in benthic habitat at local scales among sites within regions. This study improves understanding of processes that structure marine communities to better predict how environmental change will affect Alaska marine ecosystems. Many Alaska red king crab populations have collapsed and continue to experience little recovery, even for areas without a commercial fishery. Several aspects of red king crab early life stage ecology were investigated because reasons for the lack of recovery may be related to the early life history of this species. Field experiments were conducted in southeast Alaska. Settlement timing was consistent between study years (2008--09) and with historical data for this region. Local oceanographic processes that influence larval transport may be responsible for spatial variation in larval supply. In laboratory and field experiments, early juvenile crabs (age 0 and 1) demonstrated refuge response behavior to a predator threat that changed with crab ontogeny. When predators were absent, juvenile crabs preferred highly structured biogenic habitats due to foraging opportunities, and associated with any structural habitat to improve survival when predators were present. This research shows how availability of high quality nursery habitat affects red king crab early life stage success and potential for population recovery.
    • Interrelationships of Pacific herring, Clupea pallasi, populations and their relation to large-scale environmental and oceanographic variables

      Williams, Erik Hamilton; Quinn, T. II (1999)
      Recruitment estimates for Pacific herring, Clupea pallasi, populations in the Bering Sea and Northeast Pacific Ocean are highly variable, difficult to forecast, and crucial for determining optimum harvest levels. Age-structured population models for annual stock assessments of the sac-roe fisheries rely on fishery and survey age composition data tuned to an auxiliary survey of total biomass. In Chapter 1, the first age-structured model for Norton Sound herring was developed similarly to existing models. Estimates of variability from age-structured stock assessment models for Pacific herring are often not calculated. In Chapter 2, a parametric bootstrap procedure using a fit of the Dirichlet distribution to observed age composition data was developed as a quick and easy method for computing error estimates of model estimates. This bootstrap technique was able to capture variability beyond that of the multinomial distribution. This technique can provide estimates of variability for existing population models with age composition data requiring little change to the original model structure. Recruitment time series from Pacific herring stock assessment models for 14 populations in the Bering Sea and Northeast Pacific Ocean were analyzed for links to the environment. For some populations, recruitment series were extended backward in time using cohort analysis. In chapter 3, correlation and multivariate cluster analyses were applied to determine herring population associations. There appear to be four major herring groups: Bering Sea, outer Gulf of Alaska, coastal SE Alaska, and British Columbia. These associations were combined with an exploratory correlation analysis of environmental data in chapter 4. Appropriate time periods for environmental variables were determined for use in Ricker type environmentally dependent spawner-recruit forecasting models. Global and local scale environmental variables were examined in forecasting models, resulting in improvements in recruitment forecasts compared to models without environmental data. The exploratory correlation analysis and best fit models, determined by jackknife error prediction, indicated temperature data corresponding to the year of spawning resulted in the best forecasting models. The Norton Sound age-structured model, parametric bootstrap procedure, and recruitment forecasting models serve as enhancements to the decision process of managing Pacific herring fisheries.
    • Juvenile Bristol Bay Sockeye Salmon Ecology

      Farley, Edward V., Jr.; Adkison, Milo (2008)
      Predicting annual returns of Bristol Bay sockeye salmon (Oncorhynchus nerka) has been difficult due to large, unexplained variations in return strength. Ocean conditions, particularly during the first few months after salmon leave freshwater, are believed to have a strong influence on their early marine growth and survival. Limited historical and present research suggests that sea temperature can affect juvenile Bristol Bay distribution. During years with cool spring sea temperatures, juvenile sockeye salmon are distributed nearshore along the Alaska Peninsula, whereas they are found further offshore during years with warm spring sea temperatures. Juvenile sockeye salmon are larger, in better condition, and have higher marine stage survival after the first year at sea when they are distributed further offshore than when they are distributed nearshore along the Alaska Peninsula. Juvenile sockeye salmon stomach contents also shift from primarily Pacific sand lance ( Ammodytes hexapterus) and euphausiids to age 0 walleye pollock ( Theragra chalcogramma) when their distribution changes from nearshore to further offshore. Annual averages of juvenile sockeye salmon growth rate potential (GRP) were generally lower among years and regions with cool spring sea temperatures. In addition, juvenile sockeye salmon GRP was generally higher in offshore regions than nearshore regions of the eastern Bering Sea shelf. A sensitivity analysis indicated that juvenile sockeye salmon GRP was more sensitive to changes in observed (August to September) sea surface temperatures during years when prey densities were lower. The results of the dissertation suggest that variability in early marine survival is primarily due to bottom-up control of the trophic structure of the eastern Bering Sea ecosystem.
    • Life History, Demography, And Ecology Of The Spiny Dogfish "Squalus Acanthias" In The Gulf Of Alaska

      Tribuzio, Cindy A.; Kruse, Gordon; Fujioka, Jeff; Gallucci, Vince; Hillgruber, Nicola; Lowe, Chris; Woodby, Doug (2010)
      The spiny dogfish (Squalus acanthias) is a small, cosmopolitan shark species, common in sub-tropical and sub-arctic waters. The species is often targeted commercially in most areas of the world throughout its range, and in some cases it is overfished or the subject of conservation concern. In the Gulf of Alaska, spiny dogfish are not targeted and not generally retained, but incidental catches can be high for this schooling species. Previously, biological parameters for spiny dogfish in the Gulf of Alaska were assumed from estimates for this specie's neighboring areas, including British Columbia and Washington State. The purpose of this study was to examine spiny dogfish in the Gulf of Alaska and estimate important parameters for stock assessment in four stages: (1) general biology, distribution, and life history; (2) modeling age and growth; (3) population demographic modeling; and (4) ecological interactions revealed by diet analysis. Spiny dogfish are similar in length in the Gulf of Alaska to neighboring regions, but mature at larger sizes and have a greater fecundity than reported elsewhere. There is high natural variability in estimated ages for the species, which is reflected in the poor fit of the growth models, possibly owing to measurement error from using the dorsal fin spine as the aging structure. A two-phase growth model provided the statistical best fit. However, questions were raised about the biological interpretation of the model and whether more traditional models (e.g., von Bertalanffy and Gompertz) may be more appropriate. Using the life-history and growth data, Leslie matrix type age- and stage-based demographic models were created to estimate sustainable fishing mortality rates and to examine the risk of harvest scenarios. Female Gulf of Alaska spiny dogfish can support up to a 3% annual harvest rate; fisheries that target juveniles have the greatest risk of population decline below threshold levels. Spiny dogfish are generalist opportunistic feeders that feed on whichever prey is available, however shrimp are the most important prey type, followed by cephalopods. Results of this study will be used in future ecosystem modeling and stock assessments for this species. Taking into account the history of targeted fisheries for the species on the U.S. east coast and in British Columbia and Washington, as well as the susceptibility of the species to overfishing, fishery managers will need to take a cautious approach should a target fishery develop in the Gulf of Alaska.
    • Multispecies Age-Structured Assessment Modeling As A Tool Of Fisheries Management In The Gulf Of Alaska

      Van Kirk, Kray F.; Quinn, Terrance J. II; Collie, Jeremy; Criddle, Keith; Kruse, Gordon; Mueter, Franz (2012)
      A multispecies age-structured assessment model (MSASA) for the Gulf of Alaska (GOA) is developed to examine the effects of integrating predation mortality into stock assessment efforts. Age-specific predation mortality is modeled as a flexible function of predator and prey abundances, constructed from species-preference and size-preference parameters and fitted to stomach-content data. Modeled species include arrowtooth flounder ( Atheresthes stomias), Pacific cod (Gadus macrocephalus), walleye pollock (Theragra chalcogramma), Pacific halibut (Hippoglossus stenolepis) and Steller sea lion ( Eumatopias jubatus). Recruitment, residual natural mortality, full-recruitment fishing mortality, and fishery/survey selectivities are estimated for pollock, cod, and flounder; abundances for apex predators sea lions and halibut are input. Estimated trophic structures and predation links show significant changes as a result of the inclusion of higher trophic level predators, and model results are highly sensitive to assumptions regarding sea lion diet. Simulation exercises suggest that model performance degrades more due to model misspecification and data scarcity than assumptions regarding data weighting and variance. Estimates of predation mortality work in tandem with survey data, constraining predation estimates in the face of incomplete diet data and potentially improving estimates of cohort structure. Exploration of predator functional responses (PFR) shows the default GOA MSASA Holling Type II PFR to be more flexible than initially thought, and that explicitly modeling predator competition for the same prey can improve model fit to stomach-content data. Median parameter estimates and their respective variances from the fitted MSASA model are used to construct management strategy simulations. Reducing fishing pressure on pollock during periods of high predator biomass is less effective at preserving pollock stocks than raising fishing pressure on flounder, and multispecies harvest control rules and biological reference points are shown to be more conservative and more efficient at preserving stock abundance while maintaining catch levels than their single-species counterparts.
    • Nucleic Acid Ratios As An Index Of Growth And Nutritional Ecology In Pacific Cod (Gadus Macrocephalus), Walleye Pollock (Theragra Chalcogramma), And Pacific Herring (Clupea Pallasii )

      Sreenivasan, Ashwin; Smoker, William (2011)
      Pacific cod (Gadus macrocephalus), walleye pollock (Theragra chalcogramma), and Pacific herring (Clupea pallasii) are among the most ecologically and commercially important species in the North Pacific Ocean. In spite of their importance, little is known about larval and juvenile growth strategies in these fish. Since larval and juvenile fish growth may determine future growth, possibly affecting recruitment success, assessments of growth strategies might improve predictive growth models. Nucleic acid ratios (RNA/DNA) can have applications as a sensitive growth index in larval and juvenile Pacific cod, walleye pollock, and Pacific herring, and can potentially be used to determine growth responses and energetic assessments at the cellular level. Determining physiological growth responses in these fish after exposure to different temperatures and nutritional states can help in understanding growth strategies and condition. Nucleic acid ratios from white muscle of juvenile Pacific herring and whole-body Pacific cod and walleye pollock larvae were used as a cellular growth index to provide energetic assessments in these species. Growth responses were studied in these fish across a range of temperatures and nutritional states. Growth was compared between fed, starved/fed and terminally starved Pacific herring cultured at 6.5�C, 8.5�C, and 12.5�C. Relative to fed controls, starved/fed fish showed similar RNA/DNA ratios and soluble protein concentration, but reduced mass. Nucleic acid ratios in starved/fed fish during the starvation phase, and in terminally starved fish, indicated incipient terminal starvation. Also, a seasonal variation of RNA/DNA, protein concentrations and total body lipid concentrations was seen in fed fish, reflecting changes in resource allocation. Early growth was compared in yolk-sac Pacific cod and walleye pollock larvae cultured at 5�C and 8�C, and in yolk-sac Pacific cod larvae cultured in two nutritional states (fed and starved). Growth responses in Pacific cod and walleye pollock larvae were affected by small differences in temperature. Exposure to the lower temperature resulted in higher RNA/DNA in both Pacific cod and walleye pollock larvae. Based on nucleic acid patterns with larval development, it was possible to identify distinct growth stanzas in Pacific cod larvae.
    • Odors And Ornaments In Crested Auklets (Aethia Cristatella): Signals Of Mate Quality?

      Douglas, Hector D., Iii; Springer, Alan M. (2006)
      Crested auklets (Aethia cristatella) are small colonial seabirds that display an ornamental feather crest and emit a citrus-like odorant during the breeding season. In this study odors and ornaments were investigated as possible signals of mate quality. Crest size was negatively correlated with the stress hormone corticosterone in males, but this was not the case in females. Body condition was negatively correlated with corticosterone in females, but this was not the case in males. Corticosterone levels were interpreted as an index of physiological condition, and it was concluded that males with longer crests were more competent at meeting the social and energetic costs of reproduction. I hypothesized that the crested auklet odorant: (1) functions as a chemical defense against ectoparasites, (2) is assessed as a basis for mate selection, (3) is facilitated by steroid sex hormones. Laboratory and field experiments showed that synthetic replicas of the crested auklet odorant repelled, impaired, and killed ectoparasites in a dose-dependent fashion. Chemical concentrations in plumage were at least sufficient to repel and impair ectoparasites. Chemical emissions from breeding adult crested auklets peaked at the time of egg hatching when young are most vulnerable to tick parasitism. In males, chemical emissions were correlated with crest size, a basis for mate selection. Presentation of synthetic aldehydes elicited behaviors similar to those that occur during courtship. Captive crested auklets responded preferentially to synthetic replicas of their odor, and the highest frequency of response occurred during early courtship. These results show that the chemical odor could be a basis for mutual mate selection. Production of the chemical odorant may be facilitated by steroid sex hormones since octanal emission rates were correlated with progesterone in males. Finally it was determined that the chemical composition of odorants in crested auklets and whiskered auklets (A. pygmaea) differed in three key respects. This suggests that an evolutionary divergence occurred in the odorants of the two species similar to what has been suggested for ornamental traits. In conclusion, crested auklets appear to communicate with odors and ornaments, and these signals may convey multiple messages regarding condition, quality, and resistance to parasites.
    • Organic matter accumulation and preservation in Alaskan continental margin sediments

      Ding, Xiaoling; Henrichs, Susan M. (1998)
      Continental margin sediments provide a historical record of the sources and fate of organic matter (OM) originating both from the continents and from primary productivity in the overlying water column. However, since this record can be altered by microbial decomposition within the sediment, the history cannot be interpreted without understanding how decomposition can affect OM composition. Also, the margins accumulate much of the OM buried in ocean sediments; hence, knowledge of processes influencing preservation of OM in these sediments is essential to understanding the global carbon cycle. OM preservation was examined using two approaches. First, I studied sediments in the northeastern Gulf of Alaska to determine sources of OM and temporal changes in carbon accumulation. A large amount of OM, 45--70 x 104 tons/yr, accumulated in this region, about 50% from terrestrial sources. Most of the sediment cores showed little evidence of change in TOC, TN, or C and N stable isotope compositions due to decomposition within the sediment. Second, I investigated the processes that control OM preservation, focusing on the role of the OM adsorption to mineral surfaces. Because proteins are major constituents of sedimentary OM, I examined factors controlling their adsorption, decomposition, and preservation. Three hydrophilic proteins were strongly adsorbed by two clay minerals, an iron oxide, sub-oxic sediments from Resurrection Bay (RB), Alaska, and anoxic sediments from Skan Bay (SB), Alaska. The partition coefficients were large enough to lead to their preservation provided that the proteins did not decompose while adsorbed. Generally, adsorption of proteins to solid phases decreased decomposition rates, suggesting that adsorption is important in protecting these compounds from microbial attack. Greater protein decomposition rates were found in SB than in RB sediments, indicating that anoxia did not inhibit protein biodegradation. Naturally-occurring adsorbed proteins were extracted from SB and RB sediments using a detergent solution. Most of these adsorbed proteins were small (<12 kDa), indicating that only the proteins adsorbed within the micropores of particle surfaces are preserved long-term.