RSS 1.0Fisheries
Recent Submissions
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Population characteristics of lake trout in Walker Lake, Gates of the Arctic National Park and Preserve, AlaskaThe population of lake trout in Walker Lake, southern Brooks Range, was investigated during summers. 1987 and 1988. Adults were most abundant at stream mouths after ice-out. Juveniles were most abundant in pelagic areas. Fingerlings preferred stream mouths. Ages ranged from 5 to 26 years. Lengths ranged from 203 to 924 mm; weights from 83 to 8,500 g. Both sexes had similar condition and matured at age 12. Fecundity increased with length and age. Females spawn every other year. Comparisons of growth curves and fecundity- at-length curves among populations in various Alaskan lakes suggested that lake trout in Walker Lake have not experienced heavy exploitation. The lake trout population in Walker Lake should be monitored in the future through angler surveys and selected studies of life history.
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Freshwater pressures on Pacific salmon in the coastal watersheds of AlaskaThis dissertation explores the implications of a warmer and wetter climate on the freshwater life stages of Pacific salmon (Oncorhynchus spp.) in the focal region of southern coastal Alaska. Recent trends and long-term climate change predictions support the notion that arctic and subarctic watersheds will be subject to warming air temperatures, increased rainfall in the autumn and winter, diminishing snowpack, and continued glacial recession. Such atmospheric and terrestrial changes will shift patterns of streamflow, water temperature, and habitat diversity that comprise the basic building blocks of freshwater ecosystems that support Pacific salmon. Alaska's Pacific salmon populations sustain a multi-billion-dollar economy and have supported Indigenous Peoples' way of life for millennia. The character of Alaska is defined, in part, by being one of the last places in North America to support a harvestable bounty of fishes and wildlife. Therefore, studies that describe and inventory current freshwater habitat diversity, predict future habitat change, and model the responses of Alaska Pacific salmon populations to a range of future habitat scenarios will not only advance general ecological understanding, but also provide valuable insights into the trajectory and range of Pacific salmon futures for the remainder of the 21st century. In Chapter 1, A classification of streamflow patterns across the coastal Gulf of Alaska, I classify and map 4,140 coastal Alaska watersheds according to 13 unique patterns of rain, snow, and glacier ice runoff. In Chapter 2, Hypoxia vulnerability in the salmon watersheds of Southeast Alaska, I demonstrate the utility of a mechanistic model of dissolved oxygen dynamics in streams based on low-flow channel hydraulics, water temperature, and spawning salmon density. In Chapter 3, Pacific salmon population responses to a warmer, wetter climate at northern latitudes, I apply a newly established life cycle model to quantify the population responses of chum (O. keta), pink (O. gorbuscha), and coho salmon (O. kisutch) to daily variation in discharge and water temperature patterns, including extreme floods and droughts. Taken together, these findings contribute to the growing body of knowledge on the impacts of a warmer and wetter atmosphere on high-latitude freshwater ecosystems and demonstrate the value of land and water management actions that conserve ecological functioning and promote Pacific salmon resilience.
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Implications of spatial population dynamics for abundance estimation and catch apportionment of Alaska sablefish (Anoplopoma fimbria)Spatial dynamics in fish populations are challenging to identify and incorporate into population dynamics models due to the large amount of data required and the uncertainty associated with spatial processes. However, ignoring spatial dynamics can result in biased population estimates and negatively affect population sustainability or the ability to meet fishery management goals. My research explored implications of spatial dynamics for the assessment and management of Alaska sablefish (Anoplopoma fimbria). Sablefish are highly mobile, targeted in commercial and recreational fisheries, and documented to have spatial variation in population dynamics such as abundance and biomass. However, gaps remain in understanding the drivers of these spatial dynamics and their effects on fishery management. Chapter 1 focused on sablefish population dynamics in Alaska by developing a spatial stock assessment model with movement between modeled areas. Chapters 2 and 3 detail the development (Chapter 2) and application of a simulation and estimation model framework (Chapter 3) to examine alternative management scenarios and inform fisheries management. The spatial stock assessment models developed in Chapter 1 showed that a combination of population processes (movement, recruitment) and fishing have resulted in spatial differences in sablefish spawning biomass and fishing mortality, and some management areas are likely below target biomass levels despite the population as a whole being at or near biomass targets. The implications of this apparent localized depletion are unknown, but could negatively impact recruitment success if depleted areas are crucial to population sustainability. Chapter 1 also highlights the complexity of spatial stock assessment models, which require large quantities of data and pose challenges for parameter estimation. In Chapters 2 and 3, sablefish spatial population processes were simulated based on parameters estimated in the spatial stock assessment developed for Chapter 1 then assessed using a single-area, panmictic stock assessment model. Chapter 2 focuses on the simulation framework development and tests a suite of alternative population assumptions regarding movement and recruitment, which were found to be very influential in preliminary analyses. The analyses also revealed the challenges associated with a simulation framework that relies on a relatively complex stock assessment model and cannot rely on human scientists to monitor and tweak assessment model estimation processes during the automated simulations. In Chapter 3, five alternative methods for apportioning harvest opportunity among management areas were examined through the simulation to understand whether there were unexpected consequences of how catch opportunities were apportioned across space, given the assumed underlying population dynamics. We found that recruitment was poorly estimated by the single-area stock assessment model, and recruitment and movement rates between areas were drivers of population dynamics in each modeled region. We also found that no method for apportioning sablefish resulted in long-term population declines under the simulation and management assumptions, but recommended an apportionment method that used data from an annual survey so that catch opportunities are relational to observed spatial biomass. Each apportionment method resulted in different levels of catch for management areas and different year-to-year stability in catch, and these differences may be meaningful to stakeholders. This research highlights the challenges and benefits of incorporating spatial population dynamics in assessment of a relatively data-rich species with high movement rates. For species with known processes that could create spatial dynamics but insufficient data for development of spatial stock assessment models, the development and implementation of monitoring and research plans to close data gaps could be a long-term strategy for improving understanding of the species' dynamics. However, monitoring can be logistically challenging and economically prohibitive in some situations, so simulation analyses such as those conducted here may help understand which data are most important to collect or inform the development of management procedures which are robust to the most plausible hypothetical population dynamics or future environmental conditions.
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Evaluating the viability of the use of two tag types on prespawn Arctic lampreyArctic Lamprey Lethenteron camtschaticum are harvested by subsistence and commercial fisheries in the Yukon-Kuskokwim region of Alaska; however, there is little to no baseline population data available for this species. For mark-recapture and telemetry studies to be effectively utilized to collect information on Arctic Lamprey abundance, migratory and dispersal patterns, and spawning locations, the tags and transmitters used must not impact fish survival, physiology, or behavior. For this laboratory evaluation, survival, incision healing, tag retention, changes in body size, and short- (24 hours) and long-term (43 days) swim endurance were examined for prespawn Arctic Lamprey (N = 216) collected from the lower Yukon River. A total of six treatment groups were evaluated: control, sham surgery, external t-bar anchor tag, and small (0.30 g; 0.1-0.4% tag burden [the ratio of transmitter weight to Arctic Lamprey body weight]), medium (0.57 g; 0.2-0.8% tag burden), and large (1.50 g; 0.6-1.9% tag burden) internal radio transmitters. While all Arctic Lamprey survived tagging and surgical procedures, the mortality hazard of Arctic Lamprey was significantly greater for the large transmitter treatment group compared to the control, t-bar, and sham surgery treatments. Internal scar tissue production, displacement of eggs, and breaks in male testes were found in individuals in all internal transmitter treatment groups. Over the 14-week experimental period, only one t-bar anchor tag and one small transmitter were shed by tagging-evaluation Arctic Lamprey. While no significant differences in healing were found among surgical treatment groups, persistent inflammation was observed at surgical incision sites as well as erosion of the skin at antenna protrusion locations. Most Arctic Lamprey declined in total length (mean relative change = -5.02%) and wet weight (mean relative change = -9.65%) over the experimental period, with no differences among treatments. While treatment group was not a significant predictor of swim endurance, higher tag burden resulted in reductions in swim duration at 24-hours, but not 43-days post-treatment. My results indicate that t-bar anchor tags and internal radio transmitters (maximum tag burden = 1.3%) do not impact survival, changes in body size, or swimming endurance of prespawn Arctic Lamprey and can be used to monitor spawner abundance and migratory patterns in the Yukon River.
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Predicting stream attractiveness to stray hatchery-origin chum salmon to aid in understanding salmon dispersal and informing hatchery managementUnderstanding the processes underlying dispersal propensity in animal populations is a fundamental goal of ecologists. In metapopulations of wild Pacific (Oncorhynchus spp) and Atlantic salmon (Salmo salar, hereafter collectively referred to as "salmon"), it is recognized that dispersal, or straying, exists in tandem with philopatry and provides benefits such as gene flow and colonization of new habitat. However, straying by hatchery-produced salmon into streams can negatively affect the genetic integrity and reproductive success of wild salmon populations. Straying by hatchery-origin salmon may also confound fishery management procedures around assessing wild spawner escapement, given the difficulty in identifying hatchery salmon in the field. A first step in mitigating and managing the consequences of straying by hatchery salmon is to understand where and why hatchery salmon stray. In this study, I described the relationship between the number of hatchery-origin strays received by streams and the characteristics of those streams based on the hypothesis that certain characteristics are attractive to hatchery strays. An extensive dataset documenting the number of stray hatchery-origin chum salmon (Oncorhynchus keta) that spawned in 57 streams in Southeast Alaska was produced from hundreds of field surveys conducted over a 10-year period 2008-2019. I used these data in a generalized linear mixed effects modeling framework to predict how "attractive" a given stream was to hatchery strays based on hypothesized influential stream characteristics, such as streamflow, distance and numbers of hatchery releases, and conspecific density. I found that some streams were more attractive than others to hatchery strays: 10 of 57 streams surveyed had mean observed attractiveness indices of 39 recipient strays over time (range: 12-115) in a given survey, while the remaining 47 sites only attracted two recipient strays on average (range: 0-8). Furthermore, stream attractiveness to hatchery strays was predicted to increase by 44% with a 1-SD (27.6 million) increase in the number of hatchery-origin chum salmon released near the stream and increase non-linearly with elevated levels of intra-annual variability (CV > 0.55) of stream discharge. These results corroborate results from other studies that distance to a source population (e.g., a hatchery release site) influences the number of dispersing immigrants, or strays, received by the stream. However, additional ecological factors such as streamflow also affect the distribution of hatchery strays, indicating that inclusion of distance is necessary but not sufficient for accurate prediction. In the second part of this study, I expanded predictions to 558 additional streams throughout Southeast Alaska in 2008-2019 and in a hypothetical future year given increased hatchery releases. Only a small subset of streams (~10%) was predicted to be attractive, with mean predicted attractiveness indices of 57 recipient hatchery strays (range: 9-600). Bootstrapped coefficients of variation described uncertainty around predictions. Uncertainty was modest for predictions for streams in 2008-2019 (CV range: 0.21-0.62) but high for predictions of hypothetical future stream attractiveness (CV range: 0.70-1.15). These results suggest that the predictive modeling framework may be useful in describing patterns of stream attractiveness beyond the spatial range of the observed data, but not beyond its temporal range. Taken together, the results of this study elucidate the role of stream ecology and spatial location in attracting dispersing hatchery-origin salmon and provide insight into how predictions of stream attractiveness may be incorporated into hatchery management.
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Physiological regulation of annual life history events in adult female Weddell sealsPredicting the impacts of environmental changes on animal populations requires a comprehensive understanding of the life history and physiological ecology of organisms in the wild, including the precise timing and regulation of annual biological events. In this dissertation, I assess how intrinsic factors including serum hormone concentrations and nutritional status relate to the critical annual events of reproduction, seasonal foraging, and pelage molt in an Antarctic marine predator, the Weddell seal (Leptonychotes weddellii). A large component of these assessments are comparisons between female Weddell seals that pupped in the current season (postpartum females) and females that have pupped in the past but did not give birth in the most recent pupping period (skip females). First, I examine how reproductive hormone profiles (serum progesterone, estrogen, prolactin, luteinizing hormone and follicle-stimulating hormone) vary between postpartum females and skip females across the austral summer. I found that skip females ovulated earlier than postpartum females and had higher serum estrogen and progesterone concentrations during early pregnancy. I also report a distinct midsummer decline in serum prolactin concentrations in both skip and postpartum seals. This decline may be due to seals becoming photorefractory at the time that the breeding period ends. Second, I characterize patterns in body mass changes and associated metabolic hormones and serum binding proteins (cortisol, growth hormone, insulin-like growth factor-1 (IGF-1), total and free thyroxine, total triiodothyronine, and IGF binding proteins 2 and 3) in Weddell seals across summer. I found that endocrine profiles of lactating seals reflected their depleted nutritional states, though their serum cortisol remained low. Postpartum females rapidly gained lean mass after weaning, which was likely supported by high serum growth hormone concentrations, while skip females lost body mass, probably due in part to their low serum concentrations of growth hormone. Next, I detail the Weddell seal hair cycle and molt, using histology to determine the timing of hair follicle activation, hair growth, and shedding of old fur, and the relationship between molt and wound healing. Hair follicle activity began at a similar time (~October) in all seals but proceeded significantly faster in skip females; the full molt process took 131±23 days in postpartum seals and 86±11 days in skip females. Seals that spent more time hauled out molted more quickly, indicating behavior likely drove the variation in molt timing between postpartum and skip females by affecting their exposure to different thermal conditions. Finally, I examined differential gene expression in skin across the Weddell seal hair cycle using next generation RNA sequencing (RNA-Seq). I report large shifts in the skin transcriptome between hair cycle phases, including changes in expression of genes related to hormone signaling. Together, my findings provide an in-depth examination of annual life history events in adult female Weddell seals. Findings identify physiological drivers and reflections of critical seasonal processes, which may be applied to predict future life history outcomes for Weddell seals and similar species.
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The influence of acclimation on the organismal and molecular thermotolerance parameters in two Arctic teleostsThe nearshore Beaufort Sea is a highly dynamic thermal environment that is faced with climate change-driven increases in temperature. Analyzing the thermotolerance of important Arctic subsistence and prey fishes, such as broad whitefish Coregonus nasus and saffron cod Eleginus gracilis, will provide an understanding of the relative species specific responses to current and future temperature changes. The objectives of this study were to determine if acclimating broad whitefish and saffron cod to two different temperatures (5 and 15°C) affected their critical thermal maximum (CTmax) and their HSP70 protein and mRNA transcript concentrations in brain, muscle, and liver tissues. Following acclimation, fish were exposed to a thermal ramping rate of 3.4°C · h-¹. The CTmax temperature was recorded when the fish expressed a loss of equilibrium. Tissue samples were then collected and analyzed via western blotting and transcriptome sequencing. Broad whitefish and saffron cod acclimated to 15°C had a significantly higher mean CTmax (27.3°C and 25.9°C, respectively) than 5°C fish (23.7°C and 23.2°C, respectively). Broad whitefish had a significantly higher CTmax than saffron cod at 15°C in addition to significantly higher HSP70 protein concentrations in liver and muscle tissues at both acclimation temperatures. Brain and muscle tissues had the highest and lowest HSP70 protein concentrations, respectively, for both species and acclimation temperatures. The only significant difference in protein concentration between acclimation temperatures was in saffron cod liver tissues where 5°C samples had a significantly higher concentration than 15°C. Brain and liver tissues for broad whitefish acclimated to 15°C had significantly higher HSP70 mRNA transcript concentrations than the control group that remained in lab-acclimation conditions of 8°C. Transcript B expressed a higher quantity of transcripts than transcript A, but both transcripts followed similar expression profiles and there were no differences in transcript concentration between tissues. The molecular data from this study demonstrates the cellular mechanisms that are, in part, responsible for the observed shifts in broad whitefish and saffron cod organismal thermotolerance, and this elasticity could be used to respond to changing thermal conditions in the nearshore Beaufort Sea in the future.
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Intraspecific variation and the leaping ability of northern pike (Esox lucius): implications for invasion ecology and managementAlthough biological invasions are a leading threat to global biodiversity they provide opportunities to study factors that mediate invasion success from ecological and evolutionary perspectives and inform management efforts. The invasion of Northern Pike (Esox lucius) throughout southcentral Alaska has provided a useful case study, where invasive Northern Pike may benefit relative to native individuals due to high habitat suitability, abundant fish prey, and adaptive or plastic selective forces of invasion. Northern Pike continue to spread throughout the highly interconnected river and lake systems of southcentral Alaska; however, hypothesized differences in Northern Pike and native salmonid leaping abilities make selective vertical drop barriers a potential management option. Here, I build upon previous work by comparing physiological and morphological traits of invasive and native Northern Pike from river and lake habitats in Alaska that may influence their invasion success and leaping ability. Then, I used leaping experiments to determine how physical (abiotic) factors and individual biological traits influenced the maximum leaping ability of Northern Pike and developed a model to characterize these relationships. I found that invasive Northern Pike stomachs were two times more likely to contain energy-rich vertebrate diet items relative to native individuals, which was associated with two-fold faster growth rates, earlier ages-at-maturity, and 30% greater lipid content. Diet and physiological benefits were greater in lake habitats for invasive individuals, while native individuals experienced improved metrics in river habitats, potentially explained by thermal regimes, metabolic demands, and food availability. Leaping experiments proved that Northern Pike could ascend barrier heights four-times greater than previously assumed; pool depth, body size, and standardized growth rate also influenced individual leap success. Northern Pike leaping ability was significantly lower than salmonids. However, model predictions suggest that faster growth rates of invasive Northern Pike in Alaska may marginally enhance their leaping ability, and barriers should be tested in-situ before implementation. Insights into Northern Pike physiology and leaping behavior that result from this work can help managers determine if Northern Pike-selective barriers are a viable option in southcentral Alaska and elsewhere Northern Pike are invasive, and supports the importance of intraspecific variation in invasive species ecology and management.
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Marine debris in the Bering Sea: combining historical records, toxicology, and local knowledge to assess impacts and identify solutionsMarine debris, particularly plastic marine debris, has numerous impacts on the environment, wildlife, and human communities. This research examines dimensions of marine debris in the Bering Sea and Aleutian Islands, Alaska, including impacts of marine debris pollution on wildlife and the environment; the history of marine debris research, monitoring, and cleanup activities; and community perspectives on local to global solutions. The first chapter of this dissertation is an integrative literature review to better understand the current status of marine debris knowledge in the Bering Sea region and identify critical knowledge gaps. We synthesized the depth and breadth of research, monitoring, and cleanup activities to better understand the sources, prevalence, and impacts of marine debris on wildlife and coastal communities. Our review revealed several knowledge gaps, including two that were a focus of the final chapters of the dissertation: measuring the extent of plastic-associated contaminants in the Bering Sea and capturing community perspectives and concerns about marine debris in the Bering Sea. The second chapter examined variation in phthalates, a class of plastic-associated chemicals, in Aleutian Islands seabirds, to refine hypotheses regarding ecological and environmental factors that affect phthalate exposure in marine wildlife. We quantified phthalates in seabirds collected across >1700 km of the Aleutian Islands, Alaska, and measured six phthalate congeners in seabirds representing ten species and four feeding guilds. Phthalates were detected in 100% of specimens (n = 115) but varied among individuals (range 3.64 - 539.64 ng/g). Total phthalates did not vary geographically, but differed among feeding guilds, with significantly higher concentrations in diving plankton-feeders compared to others. Our findings suggest feeding behavior could influence exposure risk for seabirds and lend further evidence to the ubiquity of plastic pollutants in marine ecosystems. The final chapter of the dissertation explored perspectives and concerns of St. Paul Island community members regarding marine debris and plastic pollution. This component of the research aimed to catalyze the inclusion of local knowledge in marine debris solutions for St. Paul Island, Alaska, by documenting community members' perceptions of marine debris, including its origin, impacts, and proposed solutions. We interviewed thirty-six St. Paul Island community members from 2017 to 2020 about the types, amount, distribution, and impacts of marine debris they have observed on the island and its surrounding waters over recent decades. Research participants reported increases in plastic debris since the 1980s, particularly plastic bottles. Nearly 80% expressed concern about impacts to subsistence resources, including entanglement and ingestion of plastic particles by marine mammals and fishes. St. Paul Island community members' experiences highlight that solving the problem of marine debris cannot rely on local efforts alone but requires broader policies and mitigation strategies to address the sources of debris and advance environmental justice for coastal communities. Overall, this dissertation contributes an improved understanding of the social and ecological impacts of plastic pollution in the Bering Sea region and the potential science and policy solutions that can stem the tide of marine debris.
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Assessing the demographic and genetic contributions of precocial males in a naturally spawning population of coho salmonDespite the importance of alternative life history strategies to population productivity, little is known about the mating structure of precocial ('jack') males in Pacific salmon. The number of successful matings obtained by jacks in the wild is not well characterized and the impact of including or excluding jacks in the management of Pacific salmon populations is unknown. This study aims to fill knowledge gaps in the understanding of jack life history by 1) determining the typical contribution of jacks to the next generation in a natural mating population; and 2) estimating the impact of jacks on genetic diversity. The study capitalizes upon 11 years of demographic and genetic data from a naturally spawning population of Coho Salmon from Auke Creek, in Juneau, Alaska. Individuals returning over this time period (~8,000 individuals) were genotyped at ~250 single-nucleotide polymorphism (SNP) loci. Using these genotypes, we quantified the adult-to-adult reproductive success of different male types using parentage analysis for each of seven return years and compared genetic and demographic estimates of effective population size. We demonstrated that although jacks were less successful than full-size males on a per individual basis, they contributed substantially to the population and influenced population and evolutionary dynamics.
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Spatial and temporal variability of fish and mussel distributions revealed through eDNA metabarcodingUnionid mussels (order Unionida) are freshwater bivalves distributed worldwide and are among the world's most endangered taxonomic groups. Unionid mussels utilize various fish species as obligate hosts for their parasitic larval stage, and as a result, native fish species are vital to unionid persistence. One of the primary conservation needs for both unionids and fishes is more complete distributional data. However, these data are labor and resource intensive to collect using traditional survey methods. Here, we utilized an eDNA metabarcoding approach to detect unionid mussels and fishes within a large portion of the lower peninsula of Michigan, USA, with the goal of validating this method for the paired detection of these two groups of taxa. We investigated whether communities of fishes and mussels varied between the tributaries of Lake Michigan and the Grand River watershed, between early- and late-summer sampling events, and between areas of high and low mussel diversity. We detected 21 unique mussel taxa and 46 unique fish taxa within the Grand River watershed and 20 Lake Michigan tributaries. We detected differences in fish and mussel communities across different sampling regions and between sampling events. We also found fish taxa associated with areas of high and low mussel diversity. Notably, we detected more mussel taxa within the Grand River watershed compared to Lake Michigan tributaries, more fish in the August sampling event compared to June, three fish taxa more frequently at areas of high mussel diversity, and four fish taxa more frequently at areas of low mussel diversity. This study demonstrates the utility of combining unionid and fish metabarcoding primers to efficiently describe the co-distribution of these interdependent taxa within the Great Lakes region.
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The effect of sea otter predation and habitat structure on nearshore crab assemblages in Southeast AlaskaSea otter Enhydra lutris predation has resulted in conflict with humans for shared marine resources, as sea otters reduce the abundance and size of nearshore crabs. Several species of crab in Southeast Alaska are prey for sea otters including Cancer magister, a highly valued commercial and subsistence species, as well as Cancer gracilis, Cancer productus, and Telmessus cheiragonus, species that are abundant in the nearshore and of ecological and subsistence importance. Understanding the influence of sea otters and habitat structure on valuable crab species is of particular importance in Southeast Alaska as the abundance and range of sea otters expands across important crab nursery habitat. We 1) conducted breakpoint analyses to identify sea otter density thresholds that affect the abundance and biomass of nearshore crab species, 2) used a two-factor type III Analysis of Variance (ANOVA) to test the impact of sea otter presence and year on crab size, and 3) used general linearized models (GLM) to test the impacts of sea otter density and habitat structure on crab species abundance and size distribution. We found evidence of sea otters decreasing crab species' abundance, biomass, and size. C. magister, C. gracilis, and C. productus experienced a significant decline in size in the presence of sea otters, while T. cheiragonus size did not differ as a function of sea otter presence. We found a significant decrease in biomass in C. magister and in biomass and abundance in C. productus, associated with increasing sea otter density. Different responses across crab species are likely attributed to size distributions and sea otter foraging behavior. Habitat characteristics, such as eelgrass biomass and shoot density, had a small influence on crab abundance and size that depended on the species of crab. These results suggest that populations of large crabs do not persist in the presence of sea otters, small crabs may co-occur with sea otters, and eelgrass biomass and density marginally influence crab abundance and size.
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The effects of ocean acidification and warming on the metabolic physiology of juvenile northern spot shrimp (Pandalus platyceros)Northern spot shrimp (Pandalus platyceros) support important commercial, subsistence, sport, and personal use fisheries in Alaska. This species is currently experiencing population declines in Southeast Alaska, mandating fishery closures in previously productive regions. Northern spot shrimp are harvested as adults and declining populations may be a result of limited recruitment into the fishery. Very little is known about the physiology of P. platyceros early life history stages and no known data exists on how early life history stages may be affected by environmental stressors such as ocean acidification (OA) and ocean warming (OW). OA is a result of increased anthropogenic carbon dioxide (CO₂) input into the ocean. Increased pCO₂ affects both the physical and chemical properties of the ocean, which, in turn, affects the marine biota. In addition to OA, ocean warming (OW) is another environmental stressor associated with ocean change. The Intergovernmental Panel on Climate Change (IPCC) predicts an oceanic pH decrease of 0.2-0.4 units and an increase in ocean temperatures up to 5°C by the year 2100. The goal of this thesis is to characterize potential individual and interactive effects of increased pCO₂ and increased temperature on the metabolic rate (MO₂), gene expression of heat shock protein 70 (Hsp70), and gene expression of carbonic anhydrase (CA) in juvenile P. platyceros. In order to assess the individual and interactive effects of these environmental stressors on juvenile P. platyceros physiology, I built a low-cost open hardware OA and OW system in the seawater lab at the University of Alaska Southeast. This pH-stat system, based on open-source Arduino platform, allowed manipulation of pH and temperature in line with the IPCC's future predicted ocean conditions. Juvenile P. platyceros are a model organism for this type of research due to predictions that early developmental stages, the requirement of calcification for growth, and cold-water marine organisms may be most susceptible to OA and OW stressors. Understanding how this ecologically and economically important species may be affected by environmental stressors can highlight the capacity of P. platyceros to withstand ocean change.
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Spawning site selection of coho salmon Oncorhynchus kisutch in Susitna River tributaries, AlaskaCoho Salmon Oncorhynchus kisutch are the most widely distributed Pacific salmon species across Alaska. The lack of knowledge surrounding the habitat requirements of this species results in challenges for conservation and management due to natural and anthropogenic pressures. Tributaries of the Susitna River drainage in Alaska support many small and distinct Coho Salmon populations. Heterogeneity of in-stream spawning habitat is an ecological concept known to promote resiliency of salmonid populations. The goal of this study was to investigate the best habitat predictors of spawning site selection and the scale by which spawning habitat should be evaluated for management insights. Scale is particularly important when measuring, assessing, and predicting potential impacts to species from development activities because habitat research at the stream rather than the reach scale can overestimate the amount of available spawning habitat. I investigated a suite of field-measured stream habitat variables paired with empirical Coho Salmon spawning survey data in five tributaries during 2013 and 2014. Physical data was defined as biotic and abiotic surroundings of an organism or population that have an influence on survival, development, and evolution. Mixed-effects modeling results indicated that Coho Salmon spawning-site selection was positively related to gravel substrate and the presence of groundwater flux, and that spawning Coho Salmon avoided cobble substrate. Physical data were analyzed at both the stream and reach scales, and mixed-effects modeling results further concluded that variation in spawning activity at the reach scale (variance = 1.34, SD = 1.16) accounted for more variability and was more predictive than at the stream scale(variance = 0.04, SD = 0.19). This is important because fish habitat-associations identified at the reach scale were not identified at the stream scale. These results highlight the need for multi-scale habitat data collections and analyses to identify the most meaningful fish-habitat associations.
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Otolith derived hatch dates, growth rates, and microchemistry of Arctic cod (Boreogadus saida) support the existence of several spawning populations in Alaskan watersThe changing climate in the Arctic is resulting in increased air and water temperatures as well as a reduction in sea ice, affecting native species that evolved to live in the unique habitats of the Arctic Ocean. One species of significant importance to Arctic marine ecosystems is the Arctic Cod (Boreogadus saida), a keystone species that serves as vital prey for many marine mammals, seabirds, and fishes. Arctic Cod have a strong association with sea ice for spawning and for much of their early life history. In the Pacific Arctic, little is known about their early life history, especially with regards to hatch timing and locations. To address these gaps, I estimated the hatch timing and growth rates of Arctic Cod during their first year by examining incremental growth patterns in their otoliths. Specifically, I counted daily growth increments to estimate age, and used those estimates to describe the relationship between length and age. Using this relationship, length measurements of age-0 Arctic Cod were converted to estimated daily ages and subtracted from the day of capture to estimate hatch date distributions for multiple sampling regions. Results suggest that fish caught during spring in the northern Bering Sea and southern Chukchi Sea hatched near their capture location over a relatively short period that coincided with the timing of local sea ice recession. Hatch dates from summer samples over multiple sampling regions indicated a prolonged hatching event that lasted from early winter (December) through early summer (July). Summer aggregations in the northeast Chukchi Sea likely represented a mix of different hatching populations that had been transported from the south and retained in the northern regions. Within each sampling region, mean hatch dates differed between pelagic and demersal caught Arctic Cod, which supports the existence of multiple hatching populations mixing within each region during the summer. In general, hatching occurred earlier the further south they were captured for summer captured fish, whereas their growth rate declined as one moved northward, possibly due to the higher average temperatures during the larval stage in southern hatching locations. By analyzing the elemental composition of otoliths, I was able to infer environmental conditions such as salinity near the time of hatching of age-0 Arctic Cod. Regional differences in elemental concentrations at the time of hatching suggest a stronger freshwater influence in the eastern Beaufort Sea compared to the Chukchi Sea and western Beaufort Sea and support the existence of separate hatching populations. This study expands the understanding of the early life history of Arctic Cod and informs managers and policy makers to better protect critical life stages of this key species in a changing environment.
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Habitat analysis of major fishing grounds on the continental shelf off Kodiak, Alaska"The continental shelf and upper slope of the Gulf of Alaska support diverse and commercially important communities of demersal fishes. Twenty-eight video-strip transects conducted from a research submersible, together with habitat maps based on interpreted multibeam sonar data, were used to classify distribution and abundance patterns of fishes relative to seafloor substrate type and water depth on Albatross and Portlock Banks on the Kodiak Shelf in the Gulf of Alaska. These associations were examined across spatial scales: ranging from tens of kilometer centimeters in size. A total of 5,778 fishes were recorded from 33 taxa. Fish community distribution patterns were largely correlated with depth and to a lesser extent with substrate type. Individual fish species habitat associations were also influenced by depth and substrate type; however, the spatial scale at which these factors were relevant varied by fish species. There was strong regional concordance among observed fish species habitat associations and those previously documented in studies from central California to the northern Gulf of Alaska. Although integrating substrates classified at different scales was challenging, the resulting information of scale specific habitat associations provides a more comprehensive understanding of how demersal fishes utilize benthic habitats"--Leaf iii
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Age, growth and productivity of juvenile sockeye salmon in two high latitude lakes, Alaska"The growth of Seward Peninsula sockeye salmon (Oncorhynchus nerka) from Salmon and Glacial lakes is related to their physical environment. Dermal scales collected over many years were measured to document the annual age specific growth of smolts and adults. The effect of fertilization on fry growth was examined using the first year of growth. The growth histories of Salmon Lake sockeye salmon were compared to Glacial Lake sockeye salmon through smolting and in the marine environment. Annual age specific fry growth had no direct relationship to fertilization; however, there were interactions between biomass of salmon prey and fertilization, and between prey biomass and age of smolting. Glacial Lake age-1 smolts are the same size as Salmon Lake age-1 smolts, but age-1.3 Salmon Lake juveniles after their first year in the ocean are smaller than age-1.3 Glacial Lake juveniles suggesting lower size based mortality. The differences in growth histories show each population's response to lake production and mortality experienced by smolt between the rearing lake and the ocean"--Leaf iii
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Analysis of adult sport fishing lesson choices and their application to post-secondary curriculum development"Post-secondary angler education offerings have increased nationally, but little is known about what sport fishing skills anglers desire. I noticed variations in such curricula while developing the University of Alaska Fairbanks course, Fundamentals of Fly Fishing. My study objectives were to 1) determine what fly-fishing skills potential students desire so they invest both time and money attending my education events; 2) refine my offerings; and, 3) determine if students gained angling-related knowledge. I developed a questionnaire gauging the public's fly-fishing educational desires and requirements, and distributed it from 2003 to 2005. After analyzing the results, I revised my class to include more science-based angler knowledge and practical skills. The target audience for my classes is people under 55 years of age with less than three years angling experience who fish less than twice monthly. They want preparatory topics that allow them to continue with the sport once they complete the educational event. After incorporating the results into my offerings, enrollments more than doubled from 2003 to 2008. Students made measurable advances in understanding the sciences behind sport fishing. By surveying potential participants' educational desires and needs, adult educators should be able to build sustainable personal enrichment programs as demonstrated here"--Leaf iii
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Environmental gradients and prey availability relative to glacial features in Kittlitz's murrelet foraging habitat"The goal of this study was to characterize Kittlitz's murrelet (Brachyramphus brevirostris) foraging habitat relative to prey availability and oceanography in Kenai Fjords National Park, a glacial-marine system. I conducted oceanographic, hydroacoustic, trawl, beach seine, and marine bird surveys monthly from June-August in 2007 and 2008. High sediment load from glacial river runoff shaped the marine ecosystem, and this appeared critically important to Kittlitz's murrelets at sea. Submerged moraines influenced inner fjord habitat that was characterized by cool, fresh, stratified, and silt-laden waters. This silty glacial runoff limited light availability to chlorophyll near tidewater glaciers, but zooplankton abundance was enhanced in the surface waters, perhaps due to the absence of a photic cue for vertical migration. Zooplankton community structure was influenced by glacial features and varied along an increasing temperature gradient over the summer. Acoustic measurements suggested that low density aggregations of fish and zooplankton were available in the surface waters near glacial river outflows where murrelets typically forage. Dense fish aggregations moved into the fjords by August. Kittlitz's murrelets were more likely to occur in areas with higher acoustic biomass near glaciers, making these birds more susceptible to climate change than the congeneric marbled murrelet (B. marmoratus), which was most associated with shallow, ice-free areas"--Leaf iii
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Balancing biological sustainability with the economic needs of Alaska's sockeye salmon fisheries"The total revenue of the Bristol Bay, Alaska sockeye salmon, Oncorhynchus nerka, fishery has continued to decline despite strong run sizes. This decline is primarily attributed to increases in production of farmed Chilean rainbow trout O. mykiss and coho salmon, O. kisutch. Although wild salmon managers have less control over production than salmon farmers, there may be some opportunity to regain value to the fishery by altering management strategies. To explore this potential, we first simulated three management strategies for sockeye salmon: a fixed escapement range strategy, a fixed harvest strategy and a fixed harvest rate strategy. Yields from these simulations were then combined with a forecast of farmed Chilean trout and salmon production and a model of international trade flows for Alaskan sockeye and Chilean coho salmon and rainbow trout to generate forecasts of exvessel price and total revenue for 2010. All three management strategies were able to achieve a run size equilibrium indicating biological sustainability. The highest median yield resulted from the fixed escapement strategy and the lowest median yield was generated by the fixed harvest strategy. Exvessel prices and total revenue were highest under the fixed harvest strategy. These results demonstrate a switch to an inelastic market environment and reveal the need to modify current management strategies to improve the economic health of the fishery"--Leaf iii
