Now showing items 283-302 of 468

• #### Natural abundance of nitrogen(15) in a subarctic lake and biogeochemical implications to nitrogen cycling

Stable isotope ratios of nitrogen ($\delta\sp{15}$N) were employed to track the origin and fate of nitrogen in a subarctic lake, Alaska. The annual planktonic nitrogen cycle was dominated by N$\sb2$ fixation in spring and NH$\sb4\sp+$ assimilation in summer. In winter, microbial nitrification was the major sink for NH$\sb4\sp+$ and denitrification was accounted for most of the loss of NO$\sb3\sp-.$ The small isotope fractionation in nitrification is proposed as a result of substrate (NH$\sb4\sp+)$ limitation. The temporal and spatial homogeneity of the $\delta\sp{15}$N of dissolved organic nitrogen may be related to its large pool size and refractory nature. A stable isotope mass balance suggests that the winter phytoplankton was only composed of 10 to 20% of the suspended organic matter in water column due to low primary productivity during the ice cover period. A close correlation between $\delta\sp{15}$N of phytoplankton and $\delta\sp{15}$N of dissolved pools indicates that NH$\sb4\sp+$ was the predominant nitrogen source for non-N$\sb2$-fixing algae. The similarity of $\delta\sp{15}$N between a spring blue-green bloom and N$\sb2$ suggests an atmospheric origin for nitrogen. A mixing model estimated that the blue-green algal bloom derived approximately 70% of its nitrogen from molecular nitrogen. This fixed nitrogen was further transferred to higher trophic levels via the food chain and to other primary producers following mineralization. The $\delta\sp{15}$N of aquatic macrophytes indicates that non-rooted species obtained their nitrogen from the water column while rooted species obtained their nitrogen largely from the sediment. Evidence from dual isotope tracers ($\delta\sp{15}$N and $\delta\sp{13}$C) suggests that the zooplankton were supported by phytoplankton throughout the growing season despite an apparent abundance of detritus in the water column. Benthic fauna relied on either phytoplankton detritus or other organic matter in the sediment. The $\delta\sp{15}$N data exhibit only two to three trophic levels in both planktonic and the benthic communities in Smith Lake.
• #### Navigating the predator gauntlet: consumption of hatchery- and wild-born juvenile chum salmon (Oncorhynchus keta) by common nearshore marine fishes in Southeast Alaska

Juvenile chum salmon (Oncorhynchus keta) undergo extensive mortality at marine entry, a period which is believed to be a potential population bottleneck. Although this early mortality has been consistently observed, our understanding of the mechanisms responsible is limited. Furthermore, the implications of large-scale salmon hatchery releases for the ecology of juvenile chum salmon and their consumers is another important knowledge gap. To better understand the predation responses of abundant consumers to hatchery- and wild-born juvenile chum salmon, we examined the diets of Pacific staghorn sculpin (Leptocottus armatus) and Dolly Varden (Salvelinus malma) near Juneau, Alaska, in 2016 and 2017. Chum salmon composed 4.5% and 19.6% of the diets of staghorn sculpin and Dolly Varden by weight, respectively, and 88% of chum salmon individuals consumed were of hatchery origin. Chum salmon prey were shorter than average when compared to chum salmon concurrently collected by beach seine and hatchery releases of chum salmon. Regression analyses indicated that occurrence of juvenile chum salmon in diets varied primarily by date and site. Predation generally occurred more frequently at sites closer to hatchery release areas. The quantity of chum salmon in staghorn sculpin stomachs was related to predator length, chum salmon catch-per-unit-effort (CPUE), and the proportion of hatchery fish present; however, date was the only important predictor explaining quantity of chum salmon in Dolly Varden stomachs. To translate diet data into consumption rate, we experimentally determined gastric evacuation rate for staghorn sculpin and implemented a field-based consumption model. Average daily consumption of chum salmon was low relative to all other prey groups. Estimates of average seasonal consumption of juvenile chum salmon by staghorn sculpins suggest that predator populations would have to be implausibly large to consume even 1% of local hatchery chum salmon production. Together, these results yield new insights into the interactions between the predators of wild-born and hatchery-born salmon during the critical stage of marine entry.
• #### Nitrogen utilization during spring phytoplankton bloom development in the southeast Bering Sea

Interactions between a high latitude, continental shelf, spring phytoplankton bloom and water column physics and chemistry were studied using measured rates of nitrogen uptake. Peak bloom conditions commenced when the mixed layer shallowed and minimized respirational losses. Integrative light-mixing growth models were accurate during early bloom stages. An advection-diffusion model associated peak bloom nitrate uptake with pycnocline mixing rates of 2.1 m d * in an 18 m mixed layer. The accumulation of surface buoyancy was a reliable index of peak bloom temporal and spatial "patchiness" since mixing rates influenced both respirational losses and nutrient supply. Maximum nitrogen specific uptake rates (h r .- 1 ), unlike those of carbon, coincided with peak bloom conditions. Although species com positions among peak bloom periods were similar, particulate C/N ratios were not. Apparently, both intercellular factors and prevailing mixing conditions influence specific uptake rates and cell composition. A large proportion of new (nitrate) to total productivity was associated with the dominance of the early bloom forming diatoms in the mixed layer. In the absence of these net plankton the residual nanoplankton dominated community exhibited a greater dependence on regenerated nitrogen. Nitrate uptake averaged 700 mg-at m during the spring bloom and 1 g-at m-2 year-1 The yearly f factor was 0.40. Nitrogen uptake based carbon productivity was 188 g C m -2 year -1 A mass balance of the inorganic carbon system indicates that nitrate uptake alone cannot account for all the carbon leaving the surface layer. The correspondence between 1SN0~ uptake measurements and nitrate decreases suggests the diffusion of slope water into the middle shelf is slow. Large scale meteorological patterns may be responsible for the inter annual variability observed in production. Frequent May storm activity prolonged peak bloom periods, while calm conditions promoted extensive Chijl layers. The passage of atmospheric low pressure system s was also associated with the cross shelf "pumping" of water masses.
• #### Non-linear dynamics of marine ecosystem models

Despite a rapid trend towards more realistic Nutrient-Phytoplankton-Zooplankton (NPZ) models, in which zooplankton are presented with multiple nutritional resources, investigations into the fundamental dynamics of these newer models have been limited. The objective of this dissertation was to explore the dynamical behavior of such NPZ models parameterized for the coastal Gulf of Alaska. With alternative stationary forcing regimes and zooplankton grazing functions, the dynamics of one-dimensional NPZ models were investigated for a range of specific predation rates (h) and predation exponents (q), which together define the form of the predation (model closure) function. Oscillations in state variables are shown to be an intrinsic property of the NPZ models, not dependent on variable seasonal forcing for their existence. Increasing mixed layer diffusivity or reducing mixed layer depth increased model excitability; it is hypothesized that this is due to the resultant increase in flux of utilizable nutrient. Model behavior was also strongly influenced by the form of both the grazing and predation functions. For all of the grazing functions implemented, Hopf bifurcations, where the form of the solution transitioned between steady equilibrium and periodic limit cycles, persisted across the q-h parameter space. Regardless of the values of h and q, with some forms of the grazing function steady equilibrium solutions that simultaneously comprised non-zero concentrations for all model components could not be found. The inclusion of sinking detritus in the model had important implications for the composition and excitability of model solutions, generally increasing the region of q-h space for which oscillatory solutions were found. Therefore, in order to correctly simulate the depth-explicit concentrations of model components, or to have an accurate understanding of the potential excitability of the system, inclusion of this component is valuable. This dissertation highlights the importance of understanding the potential impact that choice of functional response may have on the intrinsic oscillatory nature of a model prior to interpreting results from coupled bio-physical simulations. As we come to rely more on ecosystem models as a tool to interpret marine ecosystem functionality it will be important to improve our understanding of the non-linear behavior inherent in these models.
• #### 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 )

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.
• #### Numerical investigations of the hydrography, dynamics, and ice distributions of Chukchi Sea shelf

Warm, moderately salty Bering Sea Water (BSW) carried into the Chukchi Sea through Bering Strait provides an oceanic heat flux for melting sea ice comparable to that of the solar heat flux. Intrusions of BSW transport heat and nutrients via intrapycnocline eddies vertically beneath the sea ice and laterally across structural fronts near the ice edge, setting up hydrographic features important to ice edge communities and the seasonal evolution of the ice melt-back. However, the intrapycnocline eddy dynamics and associated hydrography near the fronts have not previously been well described or characterized. Three numerical models using the Regional Ocean Model System (ROMS) are integrated to systematically investigate the importance of the intrapycnocline eddy field and the factors that affect its dynamics. The models suggest that the heat transported by eddies depends on frontal stratification, which is influenced primarily by the Bering Strait inflow discharge and salinity. The eddy field is also indirectly modified by the sea surface height, which varies with strong winds. Two frontal zones near the ice edge are identified according to the model-derived hydrographic structures and eddy dynamics: the Shelf Water Transition Zone (SWTZ) and the Melt Water Transition Zone (MWTZ). Improved understanding of these frontal zones will benefit future research of the ice edge ecosystem. Our models show a noticeable effect of strong wind events on ice edge displacement and vertical transports, both of which may be important to primary production in the frontal zones. Changing winds associated with increasing sea surface temperatures could alter the manifestation of the processes highlighted in this study.
• #### Numerical Method For Tsunami Calculation Using Full Navier -Stokes Equations And The Volume Of Fluid Method

A two-dimensional numerical model was developed to study tsunami wave generation, propagation and runup. The model is based on solving the Navier-Stokes (NS) equations. The free-surface motion is tracked using the Volume of Fluid technique. The finite difference two-step projection method is used to solve NS equations and the forward time difference method to discretize the time derivative. A structured mesh is used to discretize the spatial domain. The model has been conceived as a versatile, efficient and practical numerical tool for tsunami computation, which could address a comprehensive understanding of tsunami physics with the ultimate aim of mitigating tsunami hazards. The prediction capability of tsunami generation, propagation and runup is improved by including more accurately the effects of vertical velocity/acceleration, dispersion and wave breaking. The model has the capability to represent complex curved boundaries within a Cartesian grid system and to deal with arbitrary transient-deformed moving boundaries. The numerical model was validated using laboratory experiments and analytical solutions. The model was used as a tool to determine the adequacy of the shallow water (SW) approximation in the application of tsunami simulations. Numerical results were compared with experimental data, analytical solutions and SW results in terms of the time-history free surface elevations and velocity. Reasonable agreements were observed based on the spatial and temporal distributions of the free surface and velocity.
• #### Nutrient Dynamics In The Northern Gulf Of Alaska And Prince William Sound: 1998--2001

The northern Gulf of Alaska (GOA) shelf is a productive coastal region that supports several commercially important fisheries. The mechanisms supporting such high levels of productivity over this shelf are not understood, however, since it is a downwelling-dominated shelf. In an effort to understand the mechanisms underlying such high biological productivity, nutrient distributions were determined 25 times throughout 1998, 1999, 2000, and 2001 from over the northern GOA shelf and in Prince William Sound (PWS). Deep water (>75 m) nitrate, silicate and phosphate concentrations were positively correlated with salinity indicating an offshore nutrient source. The average annual cycle was established, in which nitrate, silicate and phosphate responded seasonally to physical and biological processes. Ammonium concentrations were generally low and uniform (<1.2 muM) with occasional patches of higher concentrations. During each summer, an onshore flux of dense nutrient-rich bottom water onto the shelf was evident when the downwelling relaxed. This seasonal flux created nutrient reservoirs over the deeper shelf regions that were eventually mixed throughout the water column during the winter months. This annual evolution may be vital to the productivity of this shelf. A large degree of interannual variability was found during the study, which included El Nino (1998) and La Nina (1999) years. Spring phytoplankton biomass over the shelf was highest in 2000 when the upper waters were nutrient enriched and strongly stratified. The highest phytoplankton biomass was measured in May 1999 during the passage of a slope eddy, which demonstrated the potential of these phenomena to greatly enhance primary productivity. A large degree of spatial variability was also found, both cross-shelf and along-shelf. Hinchinbrook Canyon was found to consistently have high salinity, nutrient-enriched bottom waters suggesting it plays an important role in the transport of slope waters onto the shelf and probably into PWS. Along-shelf trends were found in the upper coastal waters in the winter and spring, with higher salinities, temperatures, and nutrient concentrations upstream of PWS. The nutrient dynamics were similar in PWS and over the shelf/slope in 2001; however, nutrient drawdown, followed by depletion, and the spring bloom appeared earlier and stronger in PWS.
• #### Nutritional and behavioral aspects of reproduction in walruses

Walruses (Odobenus rosmarus) at Marineland, California consumed food in increasing amounts as they grew larger out ate less per unit of body weight. Adult males consumed the most food in November - December, then fasted throughout the breeding season. Females apparently fasted during ovulation and birth. Females consumed 50% more energy while pregnant or lactating than when not pregnant or lactating. Male walruses spent more time displaying, and their displays were more stereotyped, during the breeding season. Females initiated and terminated interactions with the males during the breeding season, and those interactions were preceeded by displays. Females vocalized to the calf to initiate suckling bouts, reassure the calf, and to call the calf. Calves vocalized to initiate suckling bouts and indicate danger. When the calf was threatened, the female responded quickly by tusk strikes, kinesic tusk threats, vocal threats, or calling the calf. The calf tended to follow the female.
• #### Ocean Wilderness In Theory And Practice

Wilderness preservation has been an important focus of resource conservation since the dwindling number of wild places was perceived by some as losing a valued part of our collective natural and cultural heritage. While wilderness preservation efforts have been almost entirely focused on the land, recently there has been growing interest in "ocean wilderness." However, implementation has been constrained by the lack of a common vision of how "wilderness" is applied to the ocean, and how such areas should be managed and preserved. The purpose of this work was to identify and evaluate potential definitions of ocean wilderness and the values and qualities such areas possess, and to determine how they might be effectively identified and managed to preserve their wilderness character. This research focused on articulating a robust definition for "wilderness waters," within the context of how wilderness is currently conceived and articulated in law and policy, as well as evaluating how such areas might be most appropriately identified and managed. Extensive inventories were conducted of existing ocean wilderness areas, focused on North America, to determine what currently exists, how these areas are managed, and how future ocean wilderness designations should be prioritized. A survey was conducted, targeting resource managers and scientists, to identify preferences and perceptions of ocean wilderness and its potential stewardship. The survey results suggested that coastal waters possessed considerable values and qualities of wilderness, particularly areas adjacent to existing designated wilderness, that certain human uses might be appropriately permitted, and that there was much support for expanding the area of coastal waters designated as wilderness. The research also suggested that the North American Arctic might offer many opportunities for preserving ocean wilderness, in close collaboration with the Indigenous communities in this region. A number of recommendations were offered including that priority should be given to evaluating and designating areas adjacent to designated coastal wilderness areas, that the existing legal and policy framework in North America can be effectively used to expand the "wilderness waters" system, and that more work needs to be done to build the constituencies of support essential to accomplish this task.
• #### Odors And Ornaments In Crested Auklets (Aethia Cristatella): Signals Of Mate Quality?

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.
• #### Optimal Inseason Management Of Pink Salmon Given Uncertain Run Sizes And Declining Economic Value

This is a comprehensive study on the fishery and management system (including the inseason stock abundance dynamics, the purse seine fleet dynamics and the inseason management) of pink salmon (Oncorhynchus gorbuscha) in the northern Southeast Alaska inside waters (NSE). Firstly, we presented a hierarchical Bayesian modelling approach (HBM) for estimating salmon escapement abundance and timing from stream count data, which improves estimates in years when data are sparse by "borrowing strength" from counts in other years. We presented a model of escapement and of count data, a hierarchical Bayesian statistical framework, a Gibbs sampling estimation approach for posterior distributions, and model determination techniques. We then applied the HBM to estimating historical escapement parameters for pink salmon returns to Kadashan Creek in Southeast Alaska. Secondly, a simulation study was conducted to compare the performance of the HBM to that of separate maximum likelihood estimation of each year's escapement. We found that the HBM was much better able to estimate escapement parameters in years where few or no counts are made after the peak of escapement. Separate estimates for such years could be wildly inaccurate. However, even a single postpeak count could dramatically improve the estimability of escapement parameters. Third, we defined major stocks and their migratory pathways for the NSE pink salmon. We estimated the escapement timing parameters of these stocks by the HBM. A boxcar migration model was then used to reconstruct the catch and abundance histories for these stocks from 1977 to 1998. Finally, we developed a stochastic simulation model that simulates this fishery and management system. Uncertainties in annual stock size and run timing, fleet dynamics and both preseason and inseason forecasts were accounted for explicitly in this simulation. The simulation model was applied to evaluating four kinds of management strategies with different fishing opening schedules and decision rules. When only flesh quality is concerned, the present and a more aggressive strategy, both of which are adaptive to the run strength of the stocks, are able to provide higher quality fish without compromising the escapement objectives.

• #### Organochlorines In Steller Sea Lions (Eumetopias Jubatus)

Existing populations of Steller sea lions (Eumetopias jubatus ) have declined precipitously over the last half-century. Investigations into the cause of this downward trend have focused on many different possible factors. Toxicity caused by the accumulation of organochlorines (OCs), such as polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or dichlorodiphenyltrichloroethane (DDT), has been demonstrated in marine mammals and was considered here as one possible factor that may have contributed to the decline of Steller sea lions or their failure to recover. The focus of this project was to investigate the relationship of contaminant loads to hormone levels, specifically thyroid hormones and cortisol in Steller sea lions. Two approaches were taken to this study. Firstly, baseline hormone concentrations were identified for the thyroid hormones, thyroxine (T 4) and triiodothyronine (T3), and cortisol. This involves comparison and extrapolation. Secondly, possible risk effects were examined by comparing levels of OCs in captive and free-ranging Steller sea lions to known effects in related species with known physiological thresholds. Serum concentrations of total T4 were highest in Steller sea lions followed by total T3 concentrations. Concentrations of free T4 and free T3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. Cortisol concentrations were similar in male and female pups. Cortisol varied with age but when considered in regards to time of year when sampled, followed a seasonal pattern. Cortisol was elevated in fall months in captive sea lions (non-pups), which is similar to what is seen in other marine mammals and is likely associated with the annual molt. Male pups from Alaska had lower levels of SigmaPCBs and SigmaDDT when compared to male pups from Russia. Female pups from Alaska were significantly lower in SigmaPCBs than Russian female pups as were female pups for SigmaDDT levels between areas. Anywhere from 12 to 64% (depending on rookery) of Steller sea lion pups investigated for contaminants had concentrations of SigmaPCBs that are high enough to cause physiological problems. Concentrations in blood taken monthly for 2 years in three captive Steller sea lions were similar at any given sampling time and followed a seasonal pattern with levels significantly higher in the summer months of July to September and lower in the three month winter period January to March. Concentrations of OCs in blubber samples collected quarterly for the captive females followed an analogous pattern to blood samples but the captive male sea lion was considerably lower and declined over the study period. A significant relationship between blubber contaminants and lipids was noted in the three captive Steller sea lions. Even though OC contamination has not been hypothesized to be the primary factor that precipitated the population decline, there is a potential for these chemicals to have a negative effect on the health of free-ranging Steller sea lions. These data suggest that concentrations of OCs in Steller sea lions may be high enough to cause endocrine or reproductive dysfunction and could potentially impact fertility or fecundity. Therefore, OC contaminants can not be dismissed as a contributing source to either the decline or the failure to recover of the Steller sea lion population.
• #### Otters, sea stars, and glacial melt: top-down and bottom-up factors that influence kelp communities

Kelp beds are important features of the Alaska coastline and provide habitat, protect coastlines, and support commercial and subsistence harvests. Kelp beds are affected by top-down and bottom-up factors, which are changing due to human and climate-related impacts. The influences of these top-down and bottom-up factors on kelp beds are investigated in three chapters. My first chapter investigated the influence of glacial discharge on recruitment and early community development in subtidal kelp communities by monitoring benthic sessile algae and invertebrates on cleared rocks across a glacial gradient along with various physical and biological parameters in the summers of 2013-2014. It has been predicted that Alaska's glaciers will lose 30-60% of their volume by 2100. The melt from glaciers increases sedimentation and lowers salinity, impacting important habitat-providing kelp. I found that sites upstream from glacial discharge had higher kelp recruitment than downstream sites, and that up to 72% of the variation in community development was related to mobile invertebrates and kelp in the surrounding community. Glacially-influenced environmental factors did not explain any variation that was not already explained by biological factors. My second chapter explored whether patterns in the recruitment of the dominant canopy kelp, Nereocystis luetkeana and the subcanopy kelp, Saccharina latissima were a result of dispersal limitation or failure to grow to macroscopic size. My goals were to determine 1) whether glacial melt conditions affect adult fecundity (spore production) of either species, 2) how sedimentation affects early gametophyte growth and survival in each species, and 3) whether competitive interaction between species at the gametophyte stage is altered by sediments. I found that glacial melt conditions did not affect the fecundity of either species, but sedimentation affected survival and competition. Saccharina latissima was the superior competitor under high sediment conditions. Because glacially-influenced coastal areas often have little exposed hard substrate and predation by sea otters and sea stars on clams can provide hard substrate for kelp colonization, my third chapter examined methods for determining predation on clams by these predators without direct observation. I found that foraging pits of sea otters and sea stars could not be distinguished using quantitative measurements. In contrast, shell litter proved useful in quantifying relative foraging rates. Clam consumption by sea otters and sea stars was equal at all but one site. Collectively, my thesis chapters provide information on the effects of glacial discharge on microscopic and early kelp life stages in Alaska which can be incorporated into management practices.
• #### Outbreeding depression and inheritance in three generations of geographically distinct southeast Alaska coho salmon (Oncorhynchus kisutch) populations

I observed no fitness losses among F₂ hybrids of three Southeast Alaska coho salmon (Oncorhynchus kisutch) populations relative to parental controls. Marine survival did not differ among groups in one generation, but was greater for hybrids than controls in another, although the power of these tests was low. Increases in fluctuating asymmetry, which can signal losses in fitness, were not observed. Line cross analyses of length suggested additive and additive plus dominance gene action, and two of three analyses suggested epistasis. In contrast, meristic characters exhibited little variability; and in most cases tests failed to reject a simple additive model. Half- and full-sib analyses provided no evidence of quantitative genetic variation for any trait although the power to detect these effects was low. Comparisons of population divergence measured by quantitative traits (Qst) and molecular markers (Fst) that length is an adaptive trait and that bilateral meristics are highly conserved. Although we did not observe losses in fitness, the power of our tests was low, the among-population differences were unique to our experiment and so results of this study should be interpreted with caution.
• #### Outbreeding depression in hybrids between spatially separated pink salmon (Oncorhynchus gorbuscha) populations: marine survival, homing ability, and variability in family size

Hybridization between distinct populations of salmon can cause fitness loss (outbreeding depression), and may result in reduced survival. The erosion of fitness-related traits such as homing ability and change in family size distribution may underlie reduced survival. Out breeding depression was investigated in two independent experiments that made hybrids between geographically separated and genetically divergent pink salmon populations. Control crosses were made from male and female Auke Creek (Southeast Alaska) pink salmon and hybrid crosses were between Auke Creek females and Pillar Creek (Kodiak Island, about 1000km away) males. Parentage assignment from microsatellite analysis improved estimates of survival and straying, and was used to examine variation in family size. The return rates of even-broodyear F 1 control and hybrid fish were similar, but the odd-broodyear F 1 control returns exceeded hybrid returns. The F 2 control returns exceeded hybrid returns in both the even- and odd broodyears. Hybridization did not impair homing ability; weekly surveys in nearby ( - lkm) Waydelich Creek revealed similar straying rates from Auke Creek by both hybrid and control fish in all years. Family data were available only for even-broodyear returns; hybridization did not increase the index of variability (ratio of variance to mean) in family size in these years. Outbreeding depression in hybrids of geographically separated populations demonstrates the potential for introgression of nonnative fish to erode natural production.
• #### Pacific herring juvenile winter survival and recruitment in Prince William Sound

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

Pacific sleeper shark relative abundance indices in the eastern Bering Sea and Gulf of Alaska were developed from sablefish longline surveys and the sustainability of a plausible range in Pacific sleeper shark incidental exploitation rates in the Gulf of Alaska was evaluated with a risk analysis using Monte Carlo simulation for use in fisheries management. A significant increase in Pacific sleeper shark relative abundance was identified in the Gulf of Alaska during the years 1989-2003. The aggregate risk of ending in an overfished condition in the Gulf of Alaska increased from 0% under a low exploitation rate scenario to 59% under a high exploitation rate scenario. Baseline information about Pacific sleeper shark trophic ecology and habitat utilization in the eastern Bering Sea and Gulf of Alaska was developed for use in ecosystem-based fishery management. Analysis of stable isotope ratios of nitrogen (δ¹⁵N) and lipid normalized carbon (δ¹³C′) identified significant geographic and ontogenetic variability in the trophic ecology of Pacific sleeper sharks in the eastern Bering Sea and Gulf of Alaska and revealed wider variability in the feeding ecology of Pacific sleeper sharks than previously obtained from diet data based on stomach contents alone. Time series analysis of Pacific sleeper shark electronic tag data from the Gulf of Alaska identified a simple autoregressive relationship governing short-term movements (hours) throughout the time series which included substantial variation in longer time period movement patterns (months) and demonstrated that statistical inference about habitat utilization could be drawn from simultaneous analysis of an entire time series depth profile (six months of data) stored on an electronic archival tag.
• #### Pacific walrus use of higher trophic level prey and the relation to sea ice extent, body condition, and trichinellosis

The changing Arctic ecosystem may prompt Pacific walruses (Odobenus rosmarus divergens) to change their usual diet of lower trophic level prey (e.g., benthic invertebrates) by increasing the consumption of higher trophic level prey (HTLP). Prey-switching may have consequences to walrus populations through increased energetic costs, increased stress response, declines in body condition, and exposure to diseases, including the zoonotic parasite Trichinella spp. Trichinella is possibly transmitted to walruses via predation or scavenging on seals. The goal of this study was to quantify reliance on HTLP using stable carbon and nitrogen isotope ratios, and assess potential correlations among consumption of HTLP and sea ice extent, sex, Trichinella infection, body lipid stores, and cortisol concentrations used as an index of the stress response. Walrus diet is comprised of ~1-22% HTLP and reliance on HTLP may be correlated with sea ice extent in a complex way. Trichinella was present in ringed seal (Pusa hispida, 1/57), Arctic fox (Vulpes lagopus, 3-7/32), and polar bear (Ursus maritimus, 1/1), but was not detected in walruses (0/137) regardless of %HTLP in the diet. Walrus blubber and attached skin contained 44.6 ±12.4% lipid wet weight, which was lower than that found for other Arctic marine mammals; however, the inclusion of skin likely decreased our %lipid values. While the absolute value of %lipid from blubber and attached skin was not a suitable substitute for %lipid from blubber only, we were still able to detect the influence of biological factors, with sex-linked variability in walrus lipid stores observed. Cortisol analysis from full-thickness blubber resulted in a wide range of concentrations (2.77 to 34.04 ng/g), but showed that this stress hormone can be extracted from blubber. While neither %lipid nor blubber cortisol was correlated with the proportion of HTLP in walrus diet, they may serve as minimally-invasive methods for health monitoring of walruses. Overall, dietary plasticity of walruses is robust and switching to HTLP is not likely to have immediate adverse effects on the Pacific walrus population.