• Using otolith strontium isotopes to elucidate population structure and movements of Bering cisco (Coregonus laurettae)

      Padilla, Andrew John; Wooller, Matthew; Adkison, Milo; López, Andrés (2015-05)
      Methods for stock discrimination and tracking the movements and distribution of fishes have often involved expensive field logistics, a problem compounded in remote regions such as Alaska. An alternative approach is to use the chemical signatures preserved in otoliths, or ear bones, of teleost fishes to discriminate stocks or to track the movement history of fish. Currently, a commercial fishery targeting the anadromous Bering cisco Coregonus laurettae is occurring in the Yukon River, Alaska. There are only three known Bering cisco spawning rivers worldwide, the Yukon, South Fork Kuskokwim (Kuskokwim), and Susitna rivers. Managers and researchers believed that two of the three spawning-river populations (Yukon and Kuskokwim rivers) were being harvested in the fishery, due to major coastal currents linking two of the spawning rivers' deltas. To determine the likelihood of a mixed-stock fishery, in Chapter 1, I used the strontium isotope signature (⁸⁷Sr/⁸⁶Sr) preserved in the freshwater portion of otoliths to establish a baseline for the three natal rivers. The baseline data set was composed of otoliths from spawning adult Bering cisco of known origin (n=82). Subsequently, the baseline was used to classify commercially harvested Bering cisco (n=139) and determine the stock composition of the fishery. Greater than 97% of the commercial samples were classified as Yukon River origin. However, 0.7%, and 1.4% of the commercial samples were classified as originating from Kuskokwim and Susitna rivers, respectively. In Chapter 2, I used the baseline data to classify Bering cisco from three coastal rearing areas (Alaska Arctic coast, n=49; Y-K Delta, n=70; and the Alaska Peninsula, n=8). More than 96% of the coastal rearing Bering cisco had ⁸⁷Sr/⁸⁶Sr signatures consistent with a Yukon River origin. These data demonstrate the wide-spread coastal distribution of Bering cisco, with some travelling >4,900 km between coastal rearing and spawning habitats. This approach illustrates that ⁸⁷Sr/⁸⁶Sr can determine the natal river of Bering cisco. Subsequently, this method can be used for stock discrimination and elucidating migration patterns for unknown origin Bering cisco.
    • Using remote camera techniques to study black-legged kittiwake (Rissa tridactyla) productivity in Resurrection Bay in the northern Gulf of Alaska

      Tanedo, Sarah; Hollmén, Tuula; Winsor, Peter; Beaudreau, Anne (2016-05)
      Monitoring sentinel species in environments undergoing ecosystem change is essential to understanding how the organisms living in these habitats will respond. Seabirds are considered sensitive to shifts in their local environment and have been used as sentinels but many species occupy remote locations, posing logistical challenges for long-term studies. Remote camera techniques offer a possible alternative to other methods of monitoring seabirds during their breeding seasons. To investigate the use of remote camera techniques to study cliff-nesting seabirds and identify factors influencing their productivity, a remote video-camera system was used to collect 6 years (2010-2015) of reproductive data from a sub-colony of Black-legged Kittiwakes (Rissa tridactyla) in Resurrection Bay near Seward, Alaska. The first objective was to refine remote camera techniques by investigating the influence of 1) observation frequency and 2) observation type (video or still image) on estimates of productivity. Observation frequency from daily up to one week intervals did not have a significant effect on estimates of productivity. Observations made twice annually were found to be significantly different from estimates of productivity calculated using daily observation frequency. Still image and video methods of observation did not significantly affect estimates of productivity. The second objective was to identify factors that influence reproductive success of kittiwakes at Cape Resurrection by 1) determining the effect of nest characteristics on individual nest success, 2) identifying the effect of behavior of breeding adults during the incubation period on hatch success, 3) determining the effect of seasonal weather patterns on loss events, and 4) investigating the relationship between annual productivity and sea surface temperature (SST) over a 5 year period. Model analysis of nest characteristics on individual nest success indicated that mainland/island location and nest height above water influenced individual nest success. Behavior of breeding adults did not influence hatch success. Nest loss was influenced by average wind speeds. Annual SST was not correlated with annual productivity over a 5 year time period. Based on the results of this study, I recommend remote camera technologies for the purpose of studying cliff-nesting seabirds in remote locations and found them a useful tool for identifying and tracking factors that influence the breeding success of these populations over a multiyear time period.
    • Using remote sensing, occupancy estimation, and fine-scale habitat characterization to evaluate fall chum salmon (Oncorhynchus keta) spawning habitat usage in Arctic Alaska

      Clawson, Chelsea M.; Falke, Jeffrey; Westley, Peter; Prakash, Anupma; Martin, Aaron (2017-08)
      Groundwater upwellings provide stable temperatures for overwinter salmon embryo development and this process may be particularly important in cold, braided, gravel-bed Arctic rivers where rivers may freeze solid in the absence of upwellings. Aerial counts and remote sensing were used during 2013-2015 to estimate fall chum salmon (Oncorhynchus keta) spawner abundance states (e.g., low or high), classify river segments by geomorphic channel type (primary, flood, and spring), and map thermal variability along a 25.4 km stretch of the Chandalar River in interior Alaska. Additionally, I used on-the-ground examination of fine scale variation in physical habitat characteristics at 11 representative sites to characterize habitat variability, placed temperature loggers to assess overwinter thermal conditions in redds, and used a developmental model to predict hatching and emergence timing given known spawning dates and incubation temperatures. I delineated 330 unique river segments (mean length = 536 m) and used a multi-season multistate occupancy model to estimate detectability, occupancy, and local colonization and extinction rates. Triplicate surveys performed in 2014 allowed me to estimate detectability and the influence of observer bias. I found that detectability did not vary by observer, channel type, or segment length, but was better for high abundance (0.717 ± 0.06 SE) relative to low abundance (0.367 ± 0.07 SE) aggregations. After correcting for imperfect detection, the proportion of segments occupied by spawning fall chum salmon was highest in 2014 (0.41 ± 0.04 SE), relative to 2013 (0.23 ± 0.04) and 2015 (0.23 ± 0.04). Transition probabilities indicated unoccupied segments were likely to remain so from year to year (2013→2014 = 0.67; 2014→2015 = 0.90), but low abundance spawning segments were dynamic and rarely remained in that state. One-third of high abundance sites remained so, indicating the presence of high quality spawning habitat. Mean segment temperatures ranged from -0.5 to 4.4°C, and occupancy varied positively with temperature. I predicted a 50% probability of occupancy in segments with temperatures of 3°C. With my on-the-ground work, I found that habitat characteristics varied among the three channel types, with most significant differences between main channel and off-channel habitats. Dissolved oxygen and pH decreased with increasing temperature, and conductivity increased with temperature. Predicted hatching and emergence timing ranged from 78 and 176 days (December 11th and March 18th) to 288 and 317 days (July 8th and August 6th), respectively, post-spawning, and were highly variable within sites and among channel types owing to high habitat thermal heterogeneity. Because the Chandalar River supports 30% of the fall chum salmon run in the Yukon River Basin, information such as provided by this study will be critical to allow resource managers to better understand the effects of future climate and anthropogenic change in the region.
    • Using strontium isotopes to track Pacific salmon migrations in Alaska

      Brennan, Sean Reiss; Wooller, Matthew; Fernandez, Diego; Cerling, Thure; Zimmerman, Christian; McPhee, Megan; Weingartner, Thomas (2014-08)
      Pacific salmon (Oncorhynchus spp.) are an important cultural, ecological, and economic natural resource in Alaska. Not only do salmon maintain an important mechanism of nutrient transport between marine, aquatic, and terrestrial ecosystems, but they also provide a sustainable food and economic resource for human communities. A challenging issue in the management, conservation, and research of Pacific salmon is tracking their responses to perturbations across the multiple scales of population structure that characterize these species. Research has shown how the inherent biodiversity of Pacific salmon imparts resiliency to environmental change, and temporal stability to their overall productivity and the human systems dependent upon such productivity (e.g., fisheries). The vast biodiversity of salmon arises primarily via precise natal homing of adults to their rivers of origin, resulting in locally adapted populations. Thus, there have been considerable efforts to develop methods to effectively manage and monitor Pacific salmon biodiversity. One important example is using genetic differentiation among populations to discern the relative contributions of genetically distinct stocks in mixed stock fishery harvests. In the Bristol Bay region, sockeye salmon (O. nerka) harvests can be discerned at the watershed level (i.e., the nine major watersheds contributing to the fishery). However, tens to hundreds of locally adapted populations exist within each of these watersheds and methods to apportion fishery harvests to this finer scale population structure are lacking. This dissertation presents a new method in Alaska to discern fine-scale population structure (i.e., within watersheds) of Chinook salmon (O. tshawytscha) harvests using a naturally occurring geochemical tracer in rivers, strontium (Sr) isotopes (⁸⁷Sr/⁸⁶Sr). To this end, in Chapter 1, I characterize the statewide geographic variation on multiple spatial scales in ⁸⁷Sr/⁸⁶Sr ratios of Alaska's rivers and discuss the geochemical and geological controls of observed ⁸⁷Sr/⁸⁶Sr ratios. In Chapter 2, I approach the persistent problem of evaluating site-specific temporal variation, especially in remote Subarctic and Arctic regions, by employing the non-migratory behavioral ecology of slimy sculpin (Cottus cognatus). Finally, in Chapter 3, I demonstrate how the development of temporally and spatially robust ⁸⁷Sr/⁸⁶Sr baseline datasets within the Nushagak River was able to apportion a mixed stock fishery harvest of Chinook salmon conducted in Nushagak Bay back to natal sources at the sub-basin watershed level. Because of the conservative nature of the ⁸⁷Sr/⁸⁶Sr ratio during physical and biological processes, the development of this method is applicable not only to Chinook salmon, but also to other salmon species (e.g., sockeye and coho salmon, O. kisutch). Additionally, the development of baseline ⁸⁷Sr/⁸⁶Sr information (e.g., waters) and an overall research framework to employ this tracer in provenance studies, have statewide implications for the research and management of other migratory animals.
    • Utilizing Multi-Source Abundance Estimation And Climate Variability To Forecast Pacific Salmon Populations

      Shotwell, Stacey Anne Kaleinauialoha; Adkison, Milo D. (2004)
      Data limitation is a common property of many fisheries. Some Pacific salmon populations are a typical example of this situation because the monitoring of numerous tributaries within an area becomes logistically intractable. Fishery management often responds to this scenario with qualitative stock assessments in the form of harvest projections In some cases, fishery data, although limited, exists in a variety of sources and may be integrated to develop quantitative population estimates. The first objective of this investigation is to generate a modeling process that combines multiple data sources to estimate abundance and escapement estimates for data-limited salmon populations. Second, we consider the reliability of these estimates by testing for robustness to various simulated levels of measurement error in the data. Finally, we perform rigorous development and selection on an age structured spawner-recruit model that incorporates abundance and escapement estimates and identifies potential environment-recruit relationships. We demonstrate our technique with a case study on summer chum salmon from the Kuskokwim and Yukon Rivers, Alaska. Recent declines of summer chum returns to this salmon-dependent region have created hardships for the local area residents. We developed a maximum likelihood statistical framework that synchronously combined all available data sources from this management region to estimate abundance and escapement. Successful estimation was dependent on an independent estimate of abundance for a least a few years. We provide error estimates of the modeling process through bootstrap methods. Simulations showed that measurement error had negligible effect on abundance estimates, whereas performance for escapement estimation was tied to the sequence of abundance years. High explanatory power was attained by including environmental variables in the spawner-recruit relationship developed from these population estimates. We used a three-stage modeling process to maintain biological realism in the predictor variables. Recent changes in variables chosen for the best model were consistent with poor environmental conditions and estimates of forecasting error were much lower than models using no environmental information. Based on our findings, we recommend that managers consider the utility of multiple source estimation and environmental variability with our modeling approach for future regulatory decisions of Pacific salmon fisheries in data-limited regions.
    • Validation and application of infrared thermography for the assessment of body condition in pinnipeds

      Nienaber, Jeanette (2009-08)
      Infrared thermography (IRT) was used to collect baseline information on skin surface temperatures of two species of pinnipeds, the harbor seal (Phoca vitulina; n = 6) and the Steller sea lion (Eumetopias jubatus; n = 2). The IRT technique was validated against objects of known temperature and through post-collection software manipulation of environmental parameters that influence IRT output (emissivity, distance, relative humidity, ambient temperature and reflected temperature). From February 2007 to February 2008, biweekly measurements were taken of skin surface temperature (FLIR P25 infrared camera) with subsequent measurements of blubber depth (SonoSite Vet 180 portable imaging ultrasound system) on captive individuals at the Alaska SeaLife Center, Seward, Alaska. Once validated, skin surface temperatures in 10 defined regions (whole body, torso, head, eye, muzzle, shoulder, axillae, hip, fore and hind flipper) were used to determine seasonal variability as well as consistent hot or cold spots, and of those spots, which may act as thermal windows (defined areas of active heat loss and/or retention). Concurrent measurements of blubber depth were compared to skin surface temperatures at eight body sites to assess: a) the impact of insulation level on skin surface temperature on a site-specific scale, and b) the potential use of IRT as an alternative method for the non-invasive measurement of body condition. Both species varied seasonally in skin surface temperature from winter to reproductive and molt to winter, however, harbor seals had greater regional variation. Similar hot and cold spots were consistently recognized in both species with shoulder, axillae, fore and hind flipper identified as likely thermal windows. While some site-specific significant relationships were found between skin surface temperature and blubber thickness, insulation level alone explained a very small portion of the variance. Future studies to determine the factors influencing the variance on skin surface temperature (i.e., blood flow to the skin) warrant further exploration.
    • Variability in foraging by humpback whales (Megaptera novaenangliae) on the Kodiak, AK, feeding ground

      Wright, Dana Louise; Witteveen, Briana; Quinn, Terrance II; Wynne, Kate; Horstmann-Dehn, Lara (2014-12)
      The North Pacific humpback whale (Megaptera novaeangliae) population has been growing rapidly following a moratorium on commercial whaling in 1986. Knowledge of humpback whale foraging on feeding grounds is becoming increasingly important as the growing population consumes more prey, including economically important commercial fishes. The goal of this thesis is to better understand how marine resources are shared among the growing humpback whale population and sympatric apex predators, including western Steller sea lions (SSLs; Eumetopias jubatus), on the Kodiak, AK, feeding ground. To address this, we explored spatial and temporal (inter-annual and within-feeding season) variability in summer foraging by humpback whales along the eastern side of the Kodiak Archipelago as described by stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios of humpback whale skin (n = 118; 2004-2013). We found evidence for the existence of two sub-aggregations of humpback whales ('North', 'South') on the feeding ground that fed at different trophic levels (TLs) throughout the study period. Bayesian stable isotopic mixing models were applied to describe the proportional contribution of prey species to the diet of humpback whales for the two regions. The 'North' region humpback whale sub-aggregation consumed a mixed diet of euphausiids and forage fishes, whereas the 'South' region sub-aggregation foraged predominantly on euphausiids. Results from these analyses were compared to diet composition of Kodiak SSLs of the recovering western SSL population estimated from fecal samples (n = 656; 2000-2005), to explore spatial differences in the degree of overlap in trophic niche between these predators. Western SSLs underwent a marked population decline starting in the late 1970's and have shown slow and variable signs of recovery. Regional variability in SSL and humpback whale diets resulted in a higher degree of overlap in trophic niche, although not biologically significant (Ojk < 0.60), for individuals in the 'North' region compared with the 'South'. However, humpback whale consumption appears to overlap considerably with multiple piscivorous fishes that are prominent prey for SSLs, and thus, consumption by humpback whales may indirectly impact the prey resources of SSLs. Therefore, this study highlights the complexity of the Kodiak ecosystem and suggests consumption by an increasing population of humpback whales has the potential to indirectly impact the recovery of SSLs on a regional scale depending on the biomass of prey species and diet composition of humpback whales in the region.
    • Variability In Population Trends, Life History Characteristics, and Milk Composition Of Northern Fur Seals In Alaska

      Hayden, Alison Banks; Springer, Alan; Iverson, Sara; Castellini, Michael (2012)
      The northern fur seal population on the Pribilof Islands has been declining since the 1960s and is now less than 30% of its former size. Chapter 1 examines factors that might cause a population to decrease to such an extent and concludes that only nutritional limitation caused by climate change or commercial fisheries, predation by killer whales, or a combination of factors that includes conditions in the North Pacific during the winter were possible explanations. Chapter 2 reports the seasonal patterns in proximate composition of fur seal milk between St. Paul Island (one of the Pribilof Islands) and Bogoslof Island (an increasing population) to understand the energy requirements of lactation and the energetics of pup growth and body condition at weaning. Factors that caused variability in milk composition included days postpartum, time ashore, individual phenotype, island and preceding trip duration. Average milk lipid increased from 45.5+/-0.7% to 53.8+/-1.0% at St. Paul and from 45.8+/-0.7% to 57.3+/-0.8% at Bogoslof between July and October, while average milk protein remained relatively stable ranging between 10.0% and 10.5%. The lipid content of northern fur seal milk near peak lactation is the highest reported among otariid seals and among the highest known for all mammals.
    • Variability in Steller sea lion (Eumetopias jubatus) prey quality in Southeastern Alaska

      Vollenweider, Johanna Jill; Kelly, Brendan; Adkison, Milo; Stekoll, Michael (2005-05)
    • Variability In The Circulation, Temperature, And Salinity Fields Of The Eastern Bering Sea Shelf In Response To Atomospheric Forcing

      Danielson, Seth Lombard; Weingartner, Thomas; Aagaard, Knut; Coyle, Kenneth; Hedstrom, Katherine; Kowalik, Zygmunt (2012)
      Although the Bering Sea shelf plays a critical role in mediating the global climate and supports one of the world's largest fisheries, fundamental questions remain about the role of advection on its salt, fresh water, heat and nutrient budgets. I quantify seasonal and inter-annual variability in the temperature, salinity and circulation fields. Shipboard survey temperature and salinity data from summer's end reveal that advection affects the inter-annual variability of fresh water and heat content: heat content anomalies are set by along-shelf summer Ekman transport anomalies whereas fresh water content anomalies are determined by wind direction anomalies averaged over the previous fall, winter and early spring. The latter is consistent with an inverse relationship between coastal and mid-shelf salinity anomalies and late summer -- winter cross-shelf motion of satellite-tracked drifters. These advection anomalies result from the position and strength of the Aleutian Low pressure system. Mooring data applied to the vertically integrated equations of motion show that the momentum balance is primarily geostrophic within at least one external deformation radius of the coast. Local accelerations, wind stress and bottom friction account for < 20% (up to 40%) of the along- (cross-) isobath momentum balance, depending on location and season. Wind-forced surface Ekman divergence is primarily responsible for flow variations. The shelf changes abruptly from strong coastal convergence conditions to strong coastal divergence conditions for winds directed to the south and for winds directed to the west, respectively, and substantial portions of the shelf's currents reorganize between these two modes of wind forcing. Based on the above observations and supporting numerical model integrations, I propose a simple framework for considering the shelf-wide circulation response to variations in wind forcing. Under southeasterly winds, northward transport increases and onshore cross-isobath transport is relatively large. Under northwesterly winds, onshore transport decreases or reverses and nutrient-rich waters flow toward the central shelf from the north and northwest, replacing dilute coastal waters that are carried south and west. These results have implications for the advection of heat, salt, fresh water, nutrients, plankton, eggs and larvae across the entire shelf.
    • Variability Of Pink Salmon Family Size Has Implications For Conservation And Management Models

      Geiger, Harold Joseph, Iii; Gharrett, A. J. (2002)
      In several populations of pink salmon, the short-term dynamics population size was related to both the mean and variance of individual family sizes, because not all families were equally productive. In the marine lifestage, population increases came disproportionately from the most productive families, especially in populations with the highest average marine survival. Moreover, the trait of marine survival itself had a statistically detectable genetic component. This implies that the most favored phenotypes change from generation to generation, and that the marine environment is unpredictable and changing. These results, together with laboratory studies of freshwater survival and measurements of wild pink salmon in Prince William Sound, Alaska, seemed to indicate that family-specific variation in marine survival and variation in egg retention within the redd were the most important potential influences on variation of pink salmon family size in the studied populations, when density was controlled to intermediate levels. These results provide more justification for maintaining stock sizes at intermediate or high levels, and for protecting metapopulation structure. These results also show the importance of variation and instability in the recruitment process of Pacific salmon, and highlight the inadequacy of current models of salmon recruitment, which emphasize stability and long-term averages.
    • Variation in abundance and physiological status of juvenile chum salmon (Oncorhynchus keta) in relation to marine factors in Southeast Alaska

      Kohan, Michael L.; McPhee, Megan V.; Mundy, Phillip R.; Orsi, Joseph A.; Mueter, Franz J. (2015-08)
      Little is known about the mechanisms influencing the critical early life stages of juvenile chum salmon (Oncorhynchus keta) from coastal to offshore marine waters. There is mounting evidence to suggest that fluctuations in early marine conditions affect juvenile salmon physiological status and year class strength. We investigated relationships of a suite of marine factors at local, regional, and basin scales to the physiological status and abundance of juvenile chum salmon in northern Southeast Alaska (SEAK) from 1997-2013. Correlation analyses were used to identify potential mechanisms influencing year class strength. Marine factors at the local scale were correlated to the observed physiological status of juvenile chum salmon: average June/July wind speed was negatively correlated to weight-at-length residuals, sea surface temperatures in July were positively correlated with length, and the June mixed-layer depth was positively correlated to the energy density of juvenile chum salmon in July. Marine factors at the regional scale influenced juvenile chum salmon abundance: freshwater discharge was positively correlated whereas upwelling was negatively correlated with abundance, linking high abundance to characteristics of strong Aleutian Low (AL) climatic conditions. Comparisons of juvenile chum salmon physiological status were also made between: 1) SEAK habitats (Icy Strait and the Eastern Gulf of Alaska, EGOA), 2) stock groups (hatchery and wild), and 3) years 2010 and 2011 possible mechanisms influencing productivity of chum salmon. Between habitats, length of juvenile chum salmon did not differ. However, both weight-at-length residuals and energy density values were significantly higher in the EGOA, irrespective of year, indicating juvenile salmon allocate energy to somatic growth in Icy Strait, while the EGOA may serve as a habitat for juvenile chum salmon to store energy as lipids. Between chum salmon stocks, wild stocks were shorter and had higher weight-at-length residuals than hatchery stocks. Between years, the 2010 ocean year was associated with a strong AL that coincided with higher physiological status of juvenile chum salmon and relatively higher returning adult commercial harvests and ocean survival of hatchery fish compared to the 2011 ocean year. Our results suggest differences in juvenile chum salmon physiological status in 2010 and 2011 coincided with positive and negative anomalies of the coupled ocean-atmosphere system, which were linked to previous winter environmental conditions, and have the potential to be used as a predictive salmon management tool to forecast year class strength in SEAK.
    • Variation in age and size at maturity of Lake Clark, Alaska sockeye salmon

      Benolkin, Elizabeth B.; Margraf, Joseph; Woody, Carol Ann; Adkison, Milo (2009-12)
      Salmon returning to Lake Clark, Alaska are a valuable subsistence, commercial and ecological resource, and are an important component of the larger Kvichak River escapement. Average escapement to the Kvichak River declined sharply during 1996-2005, prompting studies to investigate age and size at maturity, key life history traits of salmon linked to reproductive success and survival. We examined potential factors which may influence sockeye salmon Oncorhynchus nerka age and size at maturity: spawning habitat and ocean environment, and examined variation in both traits over time. Sockeye salmon age and length at maturity differed among spawning locations and between brood years, but no consistent patterns were observed among habitat types. Age and length at maturity differed over time; the proportion of older marine age 3 fish was larger in recent brood years, while fish were smaller during 1997-2001 compared to 1976-1980. Sea surface temperatures and coastal upwelling appeared to be important indicators of fish length, highlighting the importance of the ocean environment in salmon growth. These results demonstrate the complexity and importance of both the freshwater and ocean ecosystems in variation in age and size at maturity, and indicate that trends may not necessarily be similar among systems or years.
    • Variation of agonistic behavior and morphology among juvenile chinook salmon (Oncorhynchus tshawytscha) of hatchery, wild, and hybrid origin under common rearing conditions

      Lang Wessel, Maria Elena (2004-05)
      Hatcheries play an important role in the enhancement of Pacific salmon (genus Oncorhynchus) as a resource, but genetic and phenotypic divergence trom wild populations may occur as a result of founder effects, genetic drift and/or domestication. In this study, agonistic behavior, ability to establish dominance, and morphology were compared among juveniles of chinook salmon (Oncorhynchus tshawytscha) that have experienced five generations of hatchery ranching culture, juveniles derived trom the wild founding stock, and second generation hybrids of the two lines. The parent generation of all lines was cultured in the same hatchery environment as the juveniles tested. Behavioral observations were conducted in replicate artificial stream tanks; hatchery and hybrid fish were significantly more aggressive than wild derived fish. No difference was detected in the ability of fish lines to win dyadic dominance contests. Thin-plate spline analysis was used to characterize morphometric variation; hatchery and wild derived juveniles differed significantly. Canonical discriminant analysis correctly classified 88% of hatchery fish and 90% of wild derived fish. Morphologically, hybrid fish were significantly different trom both hatchery and wild derived fish. These results suggest that the differences observed between lines are genetic in origin although the sources of the divergence were not conclusively identified.
    • Walleye Pollock (Theragra Chalcogramma) Distribution In The Eastern Bering Sea Related To Fishery And Environmental Factors

      Shen, Haixue (2009)
      Walleye pollock (Theragra chalcogramma) in the eastern Bering Sea (EBS) support the largest single-species fishery in the world. Pollock also play an important role in the EBS ecosystem as an important prey species. The decline of the western population of Steller sea lions during the 1980s and 1990s raised concerns about the potential competition between the pollock fishery and the sea lion population. My research focused on pollock distribution related to the fishery and physical environment at different temporal and spatial scales using fisheries acoustic data and observer data in the winter fishing season during 2002-2006. Temperature and wind played important roles in determining the pollock distribution in winter, especially from late February to March. The changes in spatial structure during the fishing season suggested that the fishery probably influenced pollock distribution by removing some portion of the local population and perhaps even smoothing out the aggregated distribution of pollock. At a small scale, pollock schools became smaller and denser. At the meso-scale, the distances between schools increased. At a larger scale, range estimates from variography increased which indicated that the spatial correlation among pollock extended to greater distances after fishing. Fishing behavior was also studied using Levy flight theory and its relation to pollock distribution in the EBS. Fishing behavior was significantly correlated to the fractal dimension of fish which measures the degree of pollock clustering, rather than to pollock spatial concentration or density in the EBS. The observer data were also included to analyze the effect of fish distribution on fishing behavior at the school scale. The results indicated that school density rather than the school size played an important role in fishing behavior. Finally, catch depletion analysis was used to examine the potential local depletion. While frequentist and Bayesian methods confirmed that the fishery caused slight local depletion in some areas in the EBS, the magnitude was less than that before sea lion protection measures were put into place in 1999 to spread out the fishery in space and time.
    • Wasting disease and environmental variables drive sea star assemblages in the northern Gulf of Alaska

      Mitchell, Timothy James; Konar, Brenda; Iken, Katrin; Kelley, Amanda (2019-05)
      Sea stars are ecologically important in rocky intertidal habitats. The recent (starting 2013) sea star die-off attributed to sea star wasting disease throughout the eastern Pacific, presumably triggered by unusually warm waters in recent years, has caused an increased interest in spatial and temporal patterns of sea star assemblages and the environmental drivers that structure these assemblages. This study assessed the role of seven potential static environmental variables (distance to freshwater, tidewater glacial presence, wave exposure, fetch, beach slope, substrate composition, and tidal range) influencing northern Gulf of Alaska sea star assemblages before and after regional sea star declines. For this, intertidal surveys were conducted annually from 2005 to 2018 at five sites in each of four regions that were between 100 and 420 km apart. In the years leading up to the regional mortality events, assemblages were different among regions and were structured mainly by tidewater glacier presence, wave fetch, and tidal range. The assemblages after wasting disease were different from those before the event, and there was a partial change in the environmental variables that correlated with sea star structure. In these recent years, the environmental variables most highly correlated with sea star assemblages were slope, wave fetch, and tidal range, all of which relate to desiccation, attachment, and wave action. This indicates that the change in sea star density and structure by wasting disease left an assemblage that is responding to different environmental variables. Understanding the delicate interplay of some of the environmental variables that influence sea star assemblages could expand knowledge of the habitat preferences and tolerance ranges of important and relatively unstudied species within the northern Gulf of Alaska.
    • Whale-watching in Juneau, AK: assessing potential effects on humpback whales and understanding passenger perceptions

      Schuler, Alicia Rinaldi; Pearson, Heidi C.; Atkinson, Shannon; Mueter, Franz J. (2019-08)
      The feeding grounds of the North Pacific humpback whale (Megaptera novaeangliae) in Juneau, Alaska have rapidly developed into a popular whale watch destination during the summer (May-September). The whale watch industry has tripled in size in the last 18 years, currently numbering approximately 65 vessels. The sustainability of this industry could be jeopardized if the health and dependability of the resource, the whales, is negatively affected by increasing vessel pressure. The aim of this project is to provide a holistic understanding of whale watch tourism in Juneau by assessing 1) humpback whale responses to whale-watching vessels and 2) passenger experiences as a conduit for conservation of whales and the environment. Data were obtained during 2016 and 2017, comprising observations of 201 humpback whale groups and collection of 2331 passenger surveys. To address the first objective, shore-based measurements and observations of humpback whales were conducted to assess potential impacts of whale-watching vessels on short-term movement and behavioral patterns of whales. Linear mixed effects models indicated that the presence (vs. absence) of vessels was related to significantly higher deviation in linear movement, increased swimming speed, and shorter inter-breath intervals (IBI). For each additional vessel present, deviation increased and IBI significantly decreased. Linear regression models also indicated that as time spent in the presence of vessels increased, respiration rate (breaths per minute) increased. Markov chain analyses indicated that feeding and traveling humpback whales were likely to maintain their behavioral state regardless of vessel presence, while surface active humpback whales were likely to transition to traveling in the presence of vessels. To address the second objective, surveys were administered to passengers before, immediately after, and six months after a whale-watching tour to measure knowledge, intentions, behaviors, and attitudes over time. Following a whale-watching tour, awareness of whale-watching guidelines/regulations doubled and support for guidelines/regulations significantly increased and remained high six months later. Binomial logistic regression models determined that strong support for guidelines/regulations was more likely if participants were aware of guidelines/regulations and less likely if participants disagreed that vessels have a negative impact on whales. Lastly, linear regression models revealed that participants that acknowledged human impacts on whales and their habitat had stronger pro-environmental attitudes. As vessel presence increases in this region, adherence to whale watching guidelines/regulations is likely to become increasingly important to mitigate cumulative effects that may arise from short-term changes in whale behavior in a changing environment. It is recommended that management revisit the current measures in place to better suit the industry today, and that education during whale watching tours be included as a potential management tool to encourage operator compliance. The results presented in this thesis indicate that both management and the industry itself can help to develop a mutually beneficial industry for the whale watching operators, the whales, and the people that come to watch them.
    • Zooplankton abundance, community structure, and oceanography northeast of Kodiak Island, Alaska

      Wang, Xian (2007-08)
      Zooplankton community dynamics and correlations with physical characteristics of the water were studied in the northwestern Gulf of Alaska. Zooplankton were collected systematically northeast of Kodiak Island, Alaska in March, May, August and November of 2002 to 2004. Species composition, total abundance and spatial community structure were correlated to physical variables. Small copepods (numerically>50%) dominated the zooplankton composition and were most abundant in August. Average biomass was 48.7 g WW m⁻² in May and 52.0 g WW m⁻² in August in Kodiak region. Interannual zooplankton abundance variations were large, with May 2003 having a dramatically higher abundance (2x10⁴ individual m⁻³ higher) than 2002 and 2004, probably due to the higher temperature (1° C higher) and lower salinity in May 2003. Small to moderate correlations (r<0.7) were found between temporal zooplankton abundance and selected physical variables. Spatial patterns in zooplankton composition among stations were more discernable in May than in August, likely due to water column stability in the spring and more dynamic influences in the summer, but revealed no consistent spatial patterns. The zooplankton community patterns in this region thus appear to arise due to complex oceanographic and bathymetric interactions, and suggest high variability can occur in the availability of prey for higher trophic levels.
    • Zooplankton ecology of Norton Sound, Alaska

      Neimark, Lee Michael (1979-12)
      The zooplankton distribution in Norton Sound was monitored for the Outer Continental Shelf Environmental Assessment Program. Salinity, temperature, and predation were investigated as factors controlling species composition and community structure. Sampling was concentrated along the eastern coast of Norton Sound during July and August, 1976. The copepod Acartia clausi and the cladocerans Evadne sp. and Podon sp. were numerically dominant in the samples. These species are able to tolerate the widely ranging salinities and temperatures of the coastal waters. The A. clausi population abundance was correlated with water temperature, while cladoceran and larval mollusc populations were correlated with salinity. No differences in species composition were discerned between stations along the shallow coast; however, the seaward community contained a greater diversity of organisms supporting a larger planktonic carnivore biomass. Zooplankton was a numerically dominant item in the diets of many fish species, although the epibenthic mysid community was volumetrically most important.