Now showing items 1-15 of 15

    • Evaluating the Accuracy of Unmanned Aerial Systems to Quantify Glacial Ice Habitats of Harbor Seals in Alaska

      Pegus, Courtney; Atkinson, Shannon; Quinn, Terry; Pyare, Sanjay (Wiley-Blackwell, 2021-11-17)
      Long-term monitoring programs to evaluate climate-driven changes to tidewater glaciers, an important habitat for harbor seals (Phoca vitulina) in Alaska, are primarily carried out by costly, weather-dependent aerial surveys from fixed-winged aircraft. Unmanned aerial systems (UAS) can be an alternative cost-effective solution for gathering image data to quantify, monitor, and manage these habitats. However, there is a paucity of information related to the accuracy of using imagery collected by UAS for purposes of measuring floating icebergs. We evaluated the accuracy of using a UAS with a built-in 20 megapixel (MP) camera as well as a consumer-grade digital 16 MP camera to capture images of floating and stationary icebergs for the purpose of collecting vertical height measurements. Images (n=869) were captured of simulated icebergs (Cuboidal foam boxes) “Cb” (n=5) and real icebergs (n=5) that were either grounded or floating. The mean error ratios obtained were less than 10% and derived by comparing the mean calculated measurements of heights of Cb obtained from images captured by UAS with the physical measured heights of these Cb. The mean error ratio for height measurements of grounded icebergs (n=4) and one floating iceberg was also less than 10%. Within an object-image distance range of 6-25 m, the cameras captured images that were suitable to accurately calculate the heights of floating and grounded objects, and drift or uncontrolled movement of the UAS caused by wind or temporary loss of GPS did not appear to have any significant effects on measurement error. Our study provides substantial evidence of the high accuracy associated with using images captured by UAS for measuring dimensions of structures positioned on water and land surfaces. Ultimately, accurate surveys of glacial ice used by harbor seals will improve our understanding about the role of decreasing habitat in explaining population variability between different tidewater glaciers.
    • Pacific herring juvenile winter survival and recruitment in Prince William Sound

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

      Tibbles, Marguerite; Seitz, Andrew C.; Falke, Jeffrey A.; Prakash, Anupma; Robards, Martin D. (2018-12)
      Lagoons are zones of habitat transitions between freshwater and marine ecosystems, providing safe and productive feeding habitats for whitefishes in Northwest Alaska, important to subsistence users in the region. However, many important lagoon processes are not understood. Therefore, the goal of this thesis was to gain a baseline understanding of two important seasonal processes of lagoons in Northwest Alaska. First, I attempted to identify environmental processes correlated with Arctic lagoon breaching for three indicator lagoons that represent a range of environmental characteristics using generalized linear models (GLM) in an information theoretic approach and model averaging. Second, I developed a habitat suitability (HS) model to identify the range of physical conditions that whitefishes may experience if overwintering under ice of these lagoons during the Arctic winter, for the same three lagoons. The GLM model suggested that lagoon breaching day of year was slightly negatively related to day of year of river break-up, but other unconditional confidence intervals for the covariate parameters overlapped zero indicating considerable uncertainty in these estimates. Further data collection and monitoring in the region is needed to improve and verify lagoon breaching modelling results. The HS model indicated that lagoons have reduced suitability as whitefish habitat in winter due to loss of habitat due to the presence of bottomfast ice and a reduction of liquid water quality due to cold temperatures, high salinities and low dissolved oxygen levels. Importantly, small lagoons without freshwater inputs were potential sinks for fish populations. The results from this research will help the National Park Service and the Native Village of Kotzebue in a joint effort to understand and manage these important habitats that are critical for subsistence fisheries as the Arctic faces an uncertain future with climate change, oil spill threats, and increased coastal development.
    • Biochemical and microbiological assessments of dried Alaska pink salmon, red salmon and Pacific cod heads

      Biceroglu, Huseyin; Smiley, Scott; Crapo, Charles; Bechtel, Peter J. (2012-05)
      Fish heads are generally considered as unsuitable byproducts for human consumption in the United States. The initial objective was to compare the moisture content and water activity levels on dried pink salmon (Oncorhynchus gorbuscha) and dried red salmon (O. nerka) using different temperature and time integration. The secondary objective was to compare shelf life characteristics, rancidity and mold growth, between dried pink dried salmon and dried Pacific cod (Gadus macrocephalus) heads stored for up to 180 days at the ambient temperature (21°C) for East African seafood markets. The third objective was to assess the antioxidant effects for frozen and dried pink salmon heads stored for up to 60 days. In a preliminary experiment, dried red salmon heads were found unsuitable due to the water activity levels above 0.6. The critical moisture contents were detected around 10% for pink salmon heads and were around 15% for Pacific cod heads to reduce water activity levels below 0.6 in these products. The applicable drying temperatures of 50°C lasting over 50 hours for pink salmon heads and 50°C for over 24 hours followed by 30°C for over 24 hours for Pacific cod heads were found optimal. Dried Pacific cod heads showed shelf stability as a potential dried seafood product. Frozen pink salmon heads had 60 days shelf life, while heads with antioxidant glazing retarded oxidation levels (p <0.05). The antioxidant treatment in dried pink salmon heads kept oxidation levels lower than the acceptable limit up to 60 days. This study provided essential information to improve the utilization of these Alaskan seafood byproducts.
    • Feeding ecology of maturing sockeye salmon (Oncorhynchus nerka) in nearshore waters of the Kodiak archipelago

      McIntosh, Bruce Charles (2001-08)
      The diet and feeding behavior of maturing sockeye salmon (Oncorhynchus nerka) were investigated during the final marine phase of the spawning migration, prior to reentering natal streams. The stomach contents of commercially caught sockeye salmon, migrating within the nearshore waters of the Kodiak Archipelago during 1998 and 1999, were examined to determine the level of feeding activity and taxa of dominant prey items. Samples were collected throughout the majority of the migration (early June to late August) from areas known to be used principally as migration corridors, and from areas proximate to several natal streams. Dominant prey of sockeye salmon were decapod larvae, Pacific sandlance (Ammodytes hexapterus), and the pteropod Limacina helicina. Feeding activity levels and dominant prey taxa varied both between areas and within areas over time. Feeding activity levels for the population appear to gradually diminish, rather than abruptly ceasing, as sockeye approach their natal streams to spawn.
    • Diets of juvenile flatfishes near Kodiak Island, Alaska

      Holladay, Brenda A. (2001-12)
      Flathead sole, Pacific halibut, rock sole, and yellowfin sole were found co-existing near Kodiak Island as juveniles (<200 mm) during late summer. Dietary differences were attributed to fish species, size, and depth-sediment characteristics of their habitat. Two to three size classes were assigned within each species. Across all habitats, significant differences in dietary composition, stomach fullness, and diet diversity were found between size classes of different flatfish species. Within a single depth-sediment habitat, flatfishes of different species and size classes ate similar prey. Seven of nine species size classes had similar prey composition across multiple habitats. Significant differences in dietary composition across habitats were detected only for small Pacific halibut and small rock sole. The juvenile flatfishes near Kodiak were opportunistic feeders, and appeared to select habitat based on parameters other than the presence of specific prey taxa.
    • Seasonal reproductive endocrinology and anatomy of Steller sea lions (Eumetopia jubatus)

      Harmon, Heather Louise (2001-08)
      The decline of western Alaskan Steller sea lions (SSLs) may be related to changes in reproductive rates. However, our understanding of SSL reproductive biology is poor. My objectives were to determine if saliva samples are a valid alternative to plasma samples for measurements of peripheral progesterone and testosterone, to describe annual cycles of steroid concentrations, and to provide anatomical verification of reproductive endocrinology. Samples were collected from adult, captive and wild SSLs. Progesterone and testosterone concentrations in paired plasma and saliva samples were highly correlated (96% and 84%, respectively). Captive SSLs had seasonal variations in these steroids that did not follow typical pinniped patterns, suggesting that reproductive activity may be sensitive to social cues. The wwild SSLs exhibited steroid patterns similar to other seasonal breeders. Vaginal cytology could not be evaluated for detecting estrus because no samples were obtained during estrus. Testes volume was correlated to plasma testosterone concentrations (71%).
    • A protocol for assessing the impacts of urbanization on coho salmon with application to Chester Creek, Anchorage, Alaska

      Whitman, Matthew S. (2002-08)
      Coho salmon (Oncorhynchus kisutch) abundance has declined in many urban streams. The causes of these declines can be hard to identify because urban impacts on stream ecology are complex and can vary between watersheds. This makes it difficult to develop appropriate and effective strategies for stream rehabilitation or mitigation aimed at increasing coho productivity. To improve this situation I developed a habitat quality assessment protocol for urban coho salmon to help identify significant habitat degradation as a prelude to restoration planning. To evaluate the protocol I used it to assess coho habitat quality in Chester Creek, Anchorage, Alaska, an urban stream that once supported a large population of coho salmon but now only supports a remnant population. I compared habitat characteristics from one non-urban and two urban study reaches to 'healthy' standard guidelines. This application of the protocol showed that the most significant adverse effects of urbanization on coho salmon habitat in urbanized reaches were increased flood intensity, barriers to adult and juvenile migration, reduced physical habitat complexity, siltation of spawning gravels, stressful water quality conditions, and stocking of potential predators and competitors. These results provide useful information for prioritizing rehabilitation and mitigation efforts in Chester Creek.
    • Effects on fitness traits of intercrossing three geographically separate populations of southeast Alaska coho salmon (Oncorhynchus kisutch)

      Granath, Karla Louise (2002-08)
      Adaptive differences among three geographically separate populations of coho salmon (Oncorhynchus kisutch) were investigated by forming first generation intercrosses (hybrid lines) and comparing them to parental types (control lines). Survival, development time, size at ponding, and first year growth were measured as indicators of locally adapted fitness traits. Significant differences (p <0.05) were found between mid-hatching times for control and hybrid groups. Effects of intercrossing on development time are consistent with additive genetic variation, indicating that important genetic divergence exists between the populations. Growth studies were broken down into four different experiments; a 'common garden' experiment, containing all possible controls and reciprocal crosses between pairs of populations, and three 'hybrid' experiments which contained one of the three control lines and all reciprocal crosses associated with the control. Effects of intercrossing on growth were more apparent in the hybrid experiments where there were fewer interactions between different lines.
    • Outbreeding depression in hybrids between spatially separated pink salmon (Oncorhynchus gorbuscha) populations: marine survival, homing ability, and variability in family size

      Gilk, Sara E. (2003-05)
      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.
    • Spawning habitat characteristics of pacific herring (Clupea pallasii) in Prince William Sound, Alaska

      Gerke, Brandee Lynn (2002-12)
      Spawning habitats of Pacific herring in Prince William Sound, Alaska were analyzed to determine the importance of habitat features including vegetation type, percent vegetative cover, substrate type, water depth, and shoreline slope in the importance of herring spawning ground selection. Sidescan sonar data were used to compare bottom habitat characteristics of herring spawning areas vs. non-spawn areas. No significant differences in vegetation or substrate type were detected between areas where herring do and do not spawn. Generalized linear models and analysis of variance models were constructed to predict the probability of herring spawn and estimate egg densities given habitat information collected by the Alaska Department of Fish and Game during herring egg deposition surveys. Habitat characteristics explained 31 % of the deviance in spawn presence and absence and 28% of the variability in egg densities. Vegetation type was the most important variable in determining the presence of spawn and vegetative percent cover was the most important variable in determining the intensity of herring spawn. Herring spawned most often on brown and red filamentous algae and red foliose algae. Egg densities increased with increasing percent vegetative cover. Spawning occurred most frequently in the shallow subtidal zone from 0 - 4 m.
    • Maturity, fecundity, growth, and sustained yield of coastal cutthroat trout at Florence Lake, Southeast Alaska

      Foster, M. Birch (2003-08)
      The resident coastal cutthroat trout Oncorhynchus clarki clarki population in Florence Lake, Southeast Alaska was sampled from July through October, 1997 to assess its maturity, fecundity, growth and sustained yield. Maturing female cutthroat have significant gonad development between mid September and late October. A gonadosomatic index threshold was established for female cutthroat trout. A logistic model for maturity estimated asymptotic percentages by age and length: 92% and 100% for males and 86% and 80% for females, indicating presence of skip spawning. Male cutthroat trout matured earlier and at smaller length than females, but females matured more rapidly. An allometric model fitted fecundity data well. Schnute's growth model indicated that growth was relatively slow. An ll-inch (279 mm) minimum size limit allows a high proportion of trout at Florence Lake to spawn at least once. Age-based and length-based per recruit analyses performed comparably and established sustainable fishing mortality estimates.
    • The ecology of eulachon (Thaleichthys pacificus) in Twentymile river, Alaska

      Spangler, Elizabeth Ann Kitto (2002-12)
      The ecology of eulachon (Thaleichthys pacificus) was studied at Twentymile River, a tributory of Turnagain Arm located in southcentral Alaska. In 2000 and 2001, we investigated the environmental factors associated with the migration of adult eulachon and downstream drift of larval eulachon. We assessed run timing, freshwater duration, length, weight, age, presence or absence of teeth, fecundity, and gear selectivity for dip and gill nets. Catch per unit effort of migrating adult fish were correlated with water temperature, tide height, river discharge, light intensity, and the density of bald eagles (Haliaeetus leucocephalus). Water temperature, river discharge, tide height, and light intensity were related to downstream drift intensity of larvae. Radio telemetry was used successfully to study the migratrion movements of adult eulachon. Clusters of the upstream limits of migration identified four common spawning areas in both years.
    • Growth, foraging behavior and distribution of age-0 Arctic grayling in an Alaskan stream

      Dion, Cheryl Ann (2002-12)
      I evaluated the ability of three models to relate habitat characteristics to habitat quality for age-0 Arctic grayling Thymallullus arcticus in an Alaska stream. A temperature-based growth model made accurate predictions, showing it can reliably assess thermal habitat quality. Deviations between predicted and observed growth were useful because they identified the timing of possible critical periods, when competition for food or space may cause density-dependent mortality and emigration. A foraging model consistently overestimated the mean prey size of fish, showing that such models need further work before then can accurately assess food availability from invertebrate drift. A habitat selection model accurately predicted small fish would occupy the stream margins and the ontogenetic shift into faster, deeper water, but its detailed predictions for larger fish were not very precise. These models were useful tools for assessing habitat quality and gave insight into possible interactions between habitat characteristics and population dynamics.
    • Transport of dungeness crab (Cancer magister) megalopae into Glacier Bay, Alaska

      Herter, Heidi L.; Eckert, Ginny L.; Shirley, Thomas; Taggart, Spencer (2007-05)
      Areas of high Cancer magister larval recruitment and transport mechanisms were identified in the lower portion of Glacier Bay, Alaska. Megalopae were collected at three sites in 2004 and 2005 using light traps positioned within 1 m of the surface and bottom at 10 m depth. Surface traps captured 96.5 - 99.4 % of megalopae collected. Megalopae abundances were highly pulsed and decreased with increasing distance from the mouth of Glacier Bay. Spatial variation was similar between years with significant differences among all sites in 2005. Half of the total annual megalopae supply occurred over just two nights in September or October, the dates of which varied by location. Megalopae abundance in Bartlett Cove was negatively cross-correlated with tidal amplitude at -3 to + 1 d lags and positively cross-correlated with maximum wind speed at a 0 d lag. Megalopae abundance in the South Beardslee Islands was positively correlated with tidal amplitude and negatively correlated with maximum wind speed at +2 to +3 d lags. Abundance in the North Beardslee Islands was low and not correlated with tides or winds. Spatial variation in megalopae abundance and correlations between abundances and transport processes suggests that Dungeness crab megalopae are transported into Glacier Bay.