• Arrowtooth flounder Atheresthes stomias diet and prey consumption near Kodiak Island, Alaska

      Knoth, Brian Anthony (2006-12)
      The arrowtooth flounder Atheresthes stomias (ATF) population in the Gulf of Alaska has increased dramatically over the past 25 years and the resulting ecosystem impacts are unclear. Arrowtooth flounder diet and prey consumption was studied to more accurately assess the predator-prey relationships of this key predator near Kodiak Island, Alaska. Temporal and ontogenetic diet trends were quantified from the analysis of 742 ATF stomachs sampled from annual bottom trawl surveys conducted in May and August from 2002 to 2004. Several significant dietary trends were found, most notably: 1) euphausiids decreased in dietary importance from May to August whereas the importance of capelin Mallotus villosus increased and 2) smaller ATF consumed more capelin and larger ATF consumed more walleye pollock Theragra chalcogramma and Pacific sand lance Ammodytes hexapterus. A bioenergetics model was used to estimate ATF prey consumption. Within the study area, the ATF population was dominated by large individuals ([great than or equal to] 50 cm total length) that accounted for> 75 % of the population's total prey biomass consumption. Arrowtooth flounder were significant predators and consumed an estimated 339 t of fish prey including Pacific sand lance and walleye pollock and 222 t of invertebrate prey such as euphausiids and shrimps.
    • Assessing a macroalgal foundation species: community variation with shifting algal assemblages

      Metzger, Jacob Ryan; Konar, Brenda; Edwards, Matthew; Beaudreau, Anne (2018-08)
      Foundation species provide critical food and habitat to their associated communities. Consequently, they are disproportionately important in shaping community structure, promoting greater biodiversity and increased species abundance. In the Aleutian archipelago, once extensive kelp forests are now relatively rare and highly fragmented. This is due to unregulated urchin grazing shifting the majority of nearshore rocky-reefs from kelp forests to either urchin barrens or "transition forests" - kelp forests devoid of understory algae. The algal communities within kelp forests, transition forests, and urchin barrens represent a stepwise loss in fleshy algal guilds, a regression from a full algal community, to having only canopy kelp, to areas largely denuded of all fleshy algae. This stepwise loss of algal guilds was used to test the designation of the resident canopy-forming kelp, Eualaria fistulosa, as a foundation species--a species that has strong, positive effects on communities where it occurs. Therefore, I assessed the impact that E. fistulosa's occurrence had on faunal community structure (in terms of species diversity, abundance and biomass, and percent bottom cover)and invertebrate size-structure. This study found that the presence of E. fistulosa does not correspond to strong differences in invertebrate size-structure or faunal community structure. However, in kelp forests where E. fistulosa exists in tandem with a variety of subcanopy macroalgae, faunal communities are more species rich, have significantly different community structures with notably higher abundance, biomass, and percent cover of filter feeding taxa, and support sea urchin populations containing significantly higher proportions of larger individuals. Consequently, this study stresses the context dependent role of foundation species and suggests their strong, positive effects on associated communities may change with perturbations to ecosystems. To that end, this study suggests that we may need to reconsider the designation of E. fistulosa as a foundation species following the extensive fragmentation and range restriction that has occurred throughout much of the Aleutian Archipelago.
    • Assessing juvenile sockeye salmon (Oncorhynchus nerka) energy densities and their habitat quality in the Chignik watershed, Alaska

      Finkle, Heather (2004-05)
      The Chignik watershed, on the southern side of the Alaska Peninsula, supports a large salmon fishery vital to the local economy. Recent morphological changes to the watershed generated concern regarding the sockeye salmon (Oncorhynchus nerka) stock that rears in Black Lake, at the head of the system. Studies of the Chignik watershed to date have not incorporated energy density data to explain the life history strategies of Chignik sockeye salmon. Re-estimated condition factor parameters improved our understanding of the length-weight relationships to fish health that isometric models described in Chignik sockeye salmon. Subsequent comparisons of age, length, weight, location, and temperature data to energy density indicated that Black Lake fish, which were all age 0 fish, were significantly affected by temperature and had energy densities greater than did fish from other areas of the watershed. Sockeye salmon captured in Chignik Lake, Chignik River, and Chignik Lagoon were only energetically different from one another based on age. Observed seasonal trends suggested juvenile sockeye salmon emigrate from Black Lake before the onset of winter due to forage and temperature limitations. A constant downstream migration occurred in the watershed during the summer, which suggested smoltification and osmoregulation processes in Chignik Lagoon fish.
    • Assessment and application of DNA metabarcoding for characterizing Arctic shorebird chick diets

      Gerik, Danielle Elizabeth; López, J. Andrés; Lanctot, Richard; Gurney, Kirsty; Wipfli, Mark (2018-12)
      Climate change in the Arctic is affecting the emergence timing of arthropods used as food by nesting shorebirds and their young. Characterizing the diets of shorebird young is a prerequisite to evaluate the potential for asynchrony to occur between the timing of arthropod emergence and when shorebird young hatch, an example of trophic mismatch. In this study, DNA metabarcoding was used to identify arthropod remains in feces collected from wild-caught Red Phalarope (Phalaropus fulicarius), Pectoral Sandpiper (Calidris melanotos), and Dunlin (Calidris alpina), young in Utqiaġvik, Alaska between 2014 and 2016. Arthropod specimens were collected at the field site to generate DNA reference sequences from potential prey items. The newly generated sequences in combination with publicly available sequences served as a reference set for species determinations. I assessed the ability of two mitochondrial markers (CO1 and 16s) to detect arthropods in the feces of captive pre-fledged young in controlled feeding experiments. After combining information from both markers, experimental prey taxa were detected in chick feces 82-100% of the time, except for Trichoptera which was never detected. I used the same strategy to characterize the diets of wild-caught shorebird young. The technique detected nearly all prey families documented in historical gut content analyses, as well as 17 novel families. Some of the novel prey diversity may be the result of detecting the prey of prey, known as secondary consumption. We observed that the diets of shorebird young shifted over the course of a summer. Changes in diet generally reflected arthropod composition in the environment estimated from collection of arthropods in pitfall traps. Evidence of diet flexibility by shorebird young suggests that chicks can shift their diets to take advantage of intra-seasonal changes in prey availability. Here, I provide an evaluation and application of DNA metabarcoding to characterize prey resource use by shorebird young for assessing the presence and impacts of trophic mismatch.
    • Assessment and prediction of electroshocked-induced injury in North American fishes

      Holliman, Farland Michael (2003-05)
      Electrofishing has served as an efficient method for scientific sampling of freshwater fishes since the mid-1900s, but it has become apparent since the 1990's that electroshock can cause fish injury. Electroshock-induced fish injury (damage to hard or soft tissues), which is primarily manifested as vertebral fracture or hemorrhage (broken blood vessels) along the backbone, can be a critical determinant of fish survival. The ability to predict factors influencing fish injury rate (the proportion of. injured fish in a sample) would be very useful to biologists. To test the null hypothesis of no effect of electrical waveform (W), voltage gradient (E), and fish size (S) on injury rate, I conducted controlled electroshock experiments on chinook salmon Oncorhynchus tshawytscha, rainbow trout O. mykiss, channel catfish Ictalurus punctatus, largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and hybrid striped bass Morone saxatalis x M. chrysops. Data collected included electrical stimulus, fish behavioral response (R), length (L) and weight (W), and injury status (present/absent). Vertebral injury was determined using radiography, and hemorrhage by bilateral filleting. My model selection criteria, which was based on Akaike's Information Criterion (AIC), indicated that risks for both types of injury in chinook salmon and channel catfish were best represented by the (W, E, S) model, the (W, S) model for both types of injury in rainbow trout, the (W, E) model for hemorrhage and the (W, E, S) model for vertebral injury in largemouth bass, the (W) model for both injury types in hybrid striped bass, and, that risk for injury in bluegill injury was best described by the null model (no effect of W, E, S). A mechanistic model relating electrical stimulus, the force of contraction, and the resistance to contraction to electroshock-induced injury, using (R) as a surrogate for electrical stimulus, (L) as a surrogate for force of contraction, and vertebral count (V) as a surrogate of resistance to injury, was explored. Application of the mechanistic model (R, L, V) to the pooled data set demonstrated a strong predictive relationship. This model offers guidance for the reduction and prevention of electroshock-induced injury for all species in all situations.
    • Assessment of the benthic environment following offshore placer gold mining in Norton Sound, northeastern Bering Sea

      Jewett, Stephen Carl; Smith, Ronald L. (1997)
      The effects of placer gold mining on the benthic environment of Norton Sound in the northeastern Bering Sea were assessed. Research focused on red king crab Paralithodes camtschaticus, a species with commercial and subsistence importance in the Sound and seasonal occurrence in the mining area. The study addressed mining effects on: (1) benthic macroinvertebrates, many serving as food for this crab, (2) crab relative abundance, distribution, and food, and (3) heavy metal concentrations in crabs. Mining on variable substrates in $<$20 m water depths occurred between 1986-90 during ice-free months when crabs were further offshore. Sampling nearly a year subsequent to mining revealed moderate substrate alteration. Benthic community parameters and abundance of numerically predominant families (e.g., owenid, spionid, and capitellid polychaetes and echinarachniid sand dollars) were reduced in mined areas. Many reduced taxa are known crab prey. Although young individuals of opportunistic taxa predominated, taxa were generally smaller at mined areas. Multi-year surveys of a once-mined area showed continued smoothing of bottom relief. Ordination of taxon abundance from mined (1 yr after mining), recolonizing (2-7 yrs after mining), and unmined stations reflected decreasing station disturbance. At least four years were required for benthos to recover from mining. Mining had a negligible effect on crabs. Crab catches, size, sex, and most prey groups in stomachs were similar between mined and unmined areas. Concentrations of eight heavy metals in muscle and hepatopancreas tissues were generally not different in mined areas. Furthermore, these metals were not different in sediments upcurrent and downcurrent of mining. Concentrations of most metals in tissues showed no temporal trend. Elemental concentrations in muscle tissues were below or within the range of concentrations in red king crabs from other North Pacific locations. Most metals from Norton Sound crabs were well below federal guidance levels for human consumption. Effects from mining were apparent for benthic macrofauna with virtually no effects observed for king crabs. Absence of any demonstrable effects of mining on this crab is primarily a result of the high natural dynamics of the Sound and opportunistic feeding behavior and high mobility of the crab.
    • Assessment of the reproductive ecology of harbor seals (Phoca vitulina) and northern sea otters (Enhydra lutris kenyoni) in Alaska using subsistence biosampling programs

      Hutchinson, Emily A.; Atkinson, Shannon; Hoover-Miller, Anne; Kruse, Gordon; Wynne, Kate (2014-08)
      Harbor seals (Phoca vitulina) and northern sea otters (Enhydra lutris kenyoni) in Alaska have experienced extreme fluctuations in abundance in recent decades. The purpose of this study was to examine growth and determine the age and size at sexual maturity in populations of these two species, as spatial and temporal variations in environmental conditions and changes in ecological constraints as a result of population fluctuations can influence growth and reproductive characteristics of individuals. All samples for this research were collected via biosampling, the collection of measurements and biological tissue samples, as a component of subsistence harvesting by Alaska Natives. In Chapter 1, morphometric measurements and reproductive tracts were collected by the Alaska Native Harbor Seal Commission's Biosampling Program from female harbor seals harvested throughout the Gulf of Alaska from 1998 through 2005. Seals attained an asymptotic standard length (SE) of 147.7 ± 2.6 cm and body mass of 82.2 ± 4.8 kg. Female harbor seals did not mature until a minimum age of 3 yr, a standard length of 122 cm, and a weight of 48 kg. The average age of sexual maturity was 4.2 ± 0.7 yr (95% CI). Fetal growth was measured by standard length, curvilinear length, axillary girth, the cube root of fetal mass, skull length, condylobasal length, zygomatic width, and skull width against the day of the year the mother was harvested. The x-intercept of the linear regression of each fetal growth measurement against the day of the year produced estimates of the implantation date that ranged from September 22nd to October 17th, with a mean date of September 30th ± 8 d (SD). Harbor seals from this study are smaller in length, have a later implantation date, and are larger at sexual maturity compared to harbor seals in the Gulf of Alaska from the 1960s. In Chapter 2, morphometric measurements and reproductive tracts were collected by a Native Alaskan subsistence hunter from 40 male sea otters near Gustavus, in Southeast Alaska. The maximum recorded standard length and axillary girth were 160 cm and 78.7 cm, respectively. Sexual maturity was assessed by the histological examination of the testes and epididymides and the subsequent measurement and characterization of the seminiferous tubules. Male sea otters in the region reached sexual maturity at 3 to 4 yr of age, after attaining a standard body length of 130 cm., a mean seminiferous tubule diameter of 140 µm, and a baculum length of 14 cm. Sea otters outside Gustavus, Alaska exhibit increased body size and lower ages of sexual maturity compared to sea otters in other regions of Alaska, suggesting that resources are abundant and are not limiting maturation rates of male sea otters near Glacier Bay. In the future, as anthropogenic influences continue to increase and environmental conditions fluctuate, biosampling programs will be an invaluable tool for continued monitoring of marine mammals in Alaska.
    • An assessment of trap efficiency to estimate coho salmon smolt abundance in a small Alaskan stream

      Eskelin, Anthony Alexander (2004-08)
      Smolt abundance is commonly estimated using trap efficiency-based methods; however, few studies have investigated the accuracy of trap efficiency estimates. The objectives of this study were to: (1) test the hypotheses that (i) trap efficiency is not affected by release timing nor release distance, (ii) trap efficiency-based estimates of smolt abundance are concordant with smolt-adult mark-recapture estimates, and (2) evaluate if water level and turbidity influence trap efficiency. In Deep Creek, Alaska, during 2001 and 2002, coho salmon Oncorhynchus kisutch smolt abundance was estimated using trap efficiency-based methods and compared to independent smolt-adult mark-recapture estimates. Marked smolts were released at two times of day (1200 hours and 0000 hours) and two release distances upstream of the trap (400 m and 1500 m) every 2 to 4 d throughout each year. Trap efficiency estimates were highly variable (range 0%-55%) and trap efficiency-based estimates of abundance were not concordant with smolt-adult mark-recapture estimates. Release timing and turbidity significantly influenced trap efficiency, whereas release distance did not. Several assumptions of the trap efficiency approach were not met, which produced biased estimates and conflicting results among years when comparing estimation techniques. These results suggest that assumptions of the trap efficiency-based methods be fully assessed to accurately estimate smolt abundance.
    • Back to the future: Pacific walrus stress response and reproductive status in a changing Arctic

      Charapata, Patrick Maron; Horstmann, Larissa; Misarti, Nicole; Wooller, Matthew (2016-08)
      The Pacific walrus (Odobenus rosmarus divergens) is an iconic Arctic marine mammal that Alaska Natives rely on as a subsistence, economic, and cultural resource. A decrease in critical sea ice habitat and uncertain population numbers have led to walruses being listed as a candidate for the Endangered Species Act. However, there is no clear understanding of how walruses might be affected by climate change. The first objective of this study was to describe how bone steroid hormone concentrations relate to commonly used blubber and serum steroid hormone concentrations (i.e., cortisol, estradiol, progesterone and testosterone), because steroid hormones have not been extracted from marine mammal bone until now. Bone, blubber, and serum were collected from individual adult walruses (n = 34) harvested by Native Alaskan subsistence hunters during 2014 and 2015. Complete turnover of cortical bone in a walrus skeleton was estimated as ~33 years, approximately the lifetime of a walrus. Results showed bone and blubber steroid hormone concentrations were similar (P = 0.96, 0.51, 0.27 for cortisol, estradiol, and progesterone (males only), respectively), but not testosterone (males and females, P = 0.003) nor progesterone in blubber of female walruses (P = 0.007). Progesterone concentrations in males were significantly correlated between bone and blubber (R² = 0.51, P < 0.001). Estradiol measured in bone had high interannual variability (P < 0.001), indicating a shorter reservoir time in cortical bone compared with other hormones in this study, possibly due to local production of estradiol in walrus bone. Overall, bone serves as a long-term reservoir of steroid hormone concentrations compared with circulating serum concentrations. Progesterone measured in blubber can be compared with bone progesterone, but local production of estradiol in bone should be taken into account when interpreting these concentrations in cortical bone. The second objective of this study was to understand the physiological resiliency of walruses to the current warming in the Arctic. Steroid hormone concentrations were measured in walrus bone collected from archaeological (n = 38, > 200 calendar years before present (BP)), historical (n =135, 200 – 20 BP), and modern (n = 47, 2014 – 2015) time periods, but were also analyzed at a finer decadal (1830s – 2010s) scale. Walrus bone cortisol concentrations measured in modern-day walruses were similar to other time periods (P = 0.38, 0.07, for archaeological and historical time periods, respectively) indicating no increase in the stress response of walruses as a result of current sea ice conditions in the Arctic. Estradiol (females only), progesterone, and testosterone were significantly negatively correlated with walrus population estimates (P = 0.008, 0.003, <0.001, respectively). A negative correlation indicates that walrus population numbers are low when reproductive hormone concentrations are high, and population numbers are high, possibly at carrying capacity, when hormone concentrations are low. Data from the current decade (2014–2015) show that the current walrus population has lower reproductive hormone concentrations compared to times of rapid population increase. These data indicate the present-day walrus population may not be increasing, but is either experiencing low calf production and / or is near its carrying capacity. Overall, these data provide walrus management with insights into the physiological resiliency of walruses in response to arctic warming, and validate bone as a valuable tissue for monitoring long-term physiological changes in the walrus population.
    • Bacteria associated with paralytic shellfish toxin-producing strains of Anabaena circinalis

      Raudonis, Renee Alaine (2007-12)
      Paralytic shellfish toxins (PSTs) are produced by dinoflagellates and cyanobacteria. There is growing evidence that bacteria associated with dinoflagellates play a role in the production of PSTs, however, no studies have examined the type of bacteria associated with toxic cyanobacteria or the role these bacteria could play in PST-production or metabolism. Further, there are no known axenic cultures of PST-producing cyanobacteria, suggesting that cyanobacteria are dependent on one or more bacteria for growth/survival. The research reported here examined the bacterial community associated with six Australian freshwater cyanobacterial strains of Anabaena circinalis obtained from the CSIRO, three toxic and three non-toxic. The goal was to identify bacteria that could be essential for cyanobacterial growth/survival and/or PST production/metabolism. Confirmation of cyanobacterial species identification was confirmed by molecular techniques; one species was found to be more closely related to Anabaena flos-aquae. PST-production by the three toxic strains was confirmed using HPLC. Bacterial communities associated with the cyanobacteria were dominated by the [alpha]-Proteobacteria, of which the Rhizobiales group was dominant. Two bacterial ribotypes were associated with only the toxic cyanobacteria, and could be important in PST-remineralization.
    • Barents Sea hydrographic variability (1975-1991)

      Zimmermann, Sarah Lukens (2003-12)
      Barents Sea temperature and salinity anomalies and their connection to the Arctic Oscillation (AO) are analyzed using a 16-year time-series of hydrographic data (1975-1991). Seasonal and inter-annual variations are investigated along two sections spanning the meridional and zonal length of the Barents Sea over two depth layers, 0 to 50m and 50 to 200m. Depending on location, mean seasonal differences in the deeper layer are as large as 3°C in temperature and 0.2 in salinity, whereas the upper layer differences are 6°C and 1.4. Inter-annual anomalies are 0.6°C and 0.07 in the deeper layer and 0.8⁰C and 1.2 in the upper layer. Temperature and salinity anomalies' leading EOFs explain 49% and 34% of the total variance, and are in-phase from 1975-1985 but out-of-phase for 1985-1991. Examination of the surface heat-flux suggests the temperature anomaly is advective before 1985 and locally formed after 1985. This is supported by the temperature anomaly's changing propagation pattern through the Barents Sea after 1985. The salinity anomaly's source appears to be advective throughout the period. The AO correlates with the temperature EOF suggesting the AO's influence on the temperature anomaly is stronger over the Norwegian Sea before 1985 and stronger over the Barents Sea after 1985.
    • Bathymetric and spatial distribution of echinoderms on seamounts in the Gulf of Alaska

      Underwood, Danielle Parker (2006-12)
      The bathymetric and spatial distribution of echinoderms was examined on five seamounts in the Kodiak-Bowie seamount chain in the northern Gulf of Alaska from video transects of 200 or 500 m length, conducted at approximately 700, 1700 and 2700 m depths with the DSV Alvin in August, 2004. Temperature and salinity varied significantly with depth, but not between seamounts; an oxygen minimum zone encompassed the shallowest depth sampled. Holothuroid (Pannychia and Psolus) and asteroid density for the shallower depth category was 19.94·100 m⁻² and 2.07·100 m⁻², significantly higher than at the deeper depths. Asteroid density generally decreased northwesterly along the seamount chain. Density of three ophiuroid genera (Asteronyx, Amphigyptis, and Ophiomoeris) was 139.6·100 m⁻² on Dickens Seamount, and was significantly less on the other three seamounts to a low of 31.19·100 m⁻² on Pratt Seamount. Ophiuroid density was significantly higher at the intermediate depth (141.07·100 m⁻²), and lower at the other two depths. Density of Pentametrocrinus and Guillecrinus crinoids was not significantly affected by seamount or depth, but was highest (3.15·100 mm⁻²) at the deepest depths. No echinoids were found on transects, but were observed on three of the seamounts. Many brittle stars and asteroids were found associated with paragorgid and primnoid corals.
    • Bathymetry of Alaskan arctic lakes: a key to resource inventory with remote-sensing methods

      Mellor, Jack C. (1982-05)
      Water depth is a major factor in predicting resources associated with tens-of-thousands of uninventoried Alaskan arctic lakes. Lakes were studied for physical, chemical, and biological resources related to water depth in 3 specific areas along a north/south transect extending from Pt. Barrow on the Arctic Ocean to the foothills of the Brooks Range. Side-Looking Airborne Radar (SLAR) imagery was acquired over the same study transect to investigate its application for determining lake depth. Ice thicknesses, necessary for the interpretation of depth contours from SLAR imagery, were measured along with other parameters in the study lakes throughout the winter 1978-79. This ice-thickness data and sequential SLAR images are used to illustrate a method of contouring water depths in arctic lakes. This is based on changes in intensity of SLAR signal return which define the zone at which ice cover contacts the bottom. This intensity is a function of physical and dielectric properties of the snow, ice, water, bottom substrates, and ice inclusions within these lakes. A computer program was developed to manipulate Landsat satellite digital data and compile a master file of lakes and their computer-calculated surface features (i.e. area, perimeter, crenulation, and centroid). The master file uniquely identifies each computer catalogued lake by latitude and longitude and stores the calculated features in a data base that can be retrieved for a specified geographic ABSTRACT area. Each lake record also provides storage space for resource data collected outside the computer generated data. The application of these remote-sensing tools and the knowledge of aquatic resources associated with bathymetry add to our ability for regional inventory, classification, and management of arctic lake resources.
    • Benthic community development in Boca de Quadra, Alaska

      Winiecki, Carol Irene (1986-05)
      The purpose of this experiment was to find ways of evaluating the community development in Boca de Quadra, a fjord in southeast Alaska, after a severe physical disturbance. Containers of defaunated sediment were used near the head of the fjord to simulate the benthic habitat after such a disturbance. Important features of community development were described, potential indicator taxa were selected, and the extent of community development was examined. Seasonal variations tended to mask the developmental trends. However, samples collected during the same season, but representing various lengths of colonization, allowed developmental trends to be observed in faunal composition, numbers of taxa, density, biomass, and diversity. Maldanidae, Nematoda, Lumbrineris luti. Leitoscoloplos pugettensis, Pholoe minuta. and Spionidae are potential indicators of community maturity.
    • 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.
    • Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites

      Chenoweth, Ellen M.; Atkinson, Shannon; McPhee, Megan; Criddle, Keith; Friedlaender, Ari; Heintz, Ron; Straley, Janice (2018-08)
      Since 2008, humpback whales have been documented depredating hatchery-produced juvenile salmon, a novel prey, at points of their release in Southeast Alaska. The objectives of this dissertation are to determine the spatial distribution, seasonal distribution, and frequency of humpback whale foraging at release sites, determine whether whale presence is affecting the economic productivity of hatchery operations, and compare the bioenergetic benefits for whales feeding on juvenile salmon at hatchery release sites relative to typical prey. Five hatchery release sites were monitored over six years during the spring release season for whale presence/absence, numbers, and behaviors. Linear models were used to determine that for coho salmon, cohorts with frequent humpback whale presence had lower marine survival than cohorts with less or no humpback whale presence, but this was not seen for chum or Chinook salmon. Over six years, these sites lost an estimated 23% of revenue from coho salmon totaling almost a million dollars per year in addition to increased rearing costs to mitigate whale predation. A process model was developed to compare the net energy gain for humpback whales foraging on krill, herring and juvenile salmon. Whales were found to feed profitably on krill and chum salmon where they occurred in dense enough distributions and on herring when large coordinated groups impeded the escape of prey. Coho salmon typically distributed too diffusely for humpback whales to recuperate the full energetic costs of engulfment, indicating that behaviors such as bubble net feeding may be essential for increasing prey aggregation to an energetically profitable level, or humpback whales may be feeding to mitigate energetic losses. As intraspecific competition increases due to recovery and or changes to prey resources, generalist humpback whales may expand feeding to exploit new and less profitable prey resources.
    • Biogeochemical tracers of change in Pacific walruses past and present

      Clark, Casey; Horstmann, Lara; Misarti, Nicole; Konar, Brenda; Severin, Ken; Lemons, Patrick (2019-05)
      Reduced sea ice and projected food web shifts associated with warming of the Arctic have raised concerns about the future of Arctic species. Pacific walruses (Odobenus rosmarus divergens) use sea ice as a platform for molting, giving birth, and resting between foraging bouts. Exactly how sea ice loss will affect walruses is difficult to predict, due to a lack of information about regional ecosystems and their responses to climate change. The objectives of the research in this dissertation were to 1) examine how walrus diet changed in response to shifting sea ice conditions over the last 4,000 years, with the goal of generating predictions about how current and future ice loss may affect the walrus population; 2) make it easier to directly compare the results of retrospective and contemporary stable isotope studies of walruses; and 3) generate new tools to assist wildlife managers in monitoring the walrus population in an uncertain future. Stable carbon and nitrogen isotope ratios of walrus bone collagen indicated that diet was similar during previous intervals of high and low sea ice; however, diet variability among individual walruses was greater when sea ice cover was low, suggesting decreased abundance of preferred mollusk prey. Modern walrus diet was different from both previous high and low ice intervals, meaning that food webs in the Arctic are still in a state of flux, or that recent changes are novel within the last 4,000 years. Tissue-specific stable isotope discrimination factors were generated for walrus muscle, liver, skin, and bone collagen to improve comparisons between retrospective and contemporary studies of walrus diet. Additionally, lipid normalization models were parameterized for walrus skin and muscle, thereby making future walrus stable isotope research more feasible by reducing analytical costs and allowing the use of non-lethal sample collection. Finally, a novel technique for estimating the age at onset of reproductive maturity using concentrations of zinc and lead in the teeth of female walruses was established. This new approach has the potential to become a powerful tool for monitoring the walrus population and may be applicable to other species. Use of this technique on archived specimens may make it possible to examine changes in wildlife population dynamics across thousands of years.
    • Biogeochemistry of a glaciated fjord ecosystem: Glacier Bay National Park, Alaska

      Reisdorph, Stacey; Weingartner, Thomas; Mathis, Jeremy; Hood, Eran; Danielson, Seth; Aguilar-Islas, Ana (2015-05)
      The burning of fossil fuels, coupled with land use and deforestation practices, has resulted in CO₂ being emitted into the atmosphere. As much as one third of the anthropogenic, or man-made, CO₂ that ends up in the atmosphere is absorbed by the oceans and has led to increases in marine dissolved inorganic carbon (DIC) concentrations and a decrease in ocean pH, a process referred to as ocean acidification (OA). Increased concentrations of DIC can reduce saturation states (Ω) with respect to biologically important calcium carbonate minerals, such as aragonite. However, CO₂ may not be the only factor in seasonal changes to calcium carbonate saturation states. With this project I was interested in understanding how glacial runoff impacts the seasonal changes to the marine biogeochemistry in a glaciated fjord. In addition to CO₂, glacial meltwater is low in alkalinity (TA) and may impact the seasonal biogeochemistry of the marine system, as well as how it influences the duration, extent, and severity of OA events in an Alaskan glacial fjord, Glacier Bay National Park (GLBA). Through this study, I found that glacial runoff heavily impacts aragonite saturation states, with the main drivers of Ω (DIC and TA) varying seasonally. In GLBA low Ω values were well correlated with the timing of maximum glacial discharge events and most prominent within the two regions where glacial discharge was highest. The influence of glaciers is not limited to just TA as runoff is also low in macronutrients due to a lack of leaching from the soil and rocky streambeds. This has the potential to greatly impact the efficiency and structure of the marine food web within GLBA, the lowest level of which can be estimated using net community production (NCP). Changes within the lowest level of the food web, as a result of seasonal OA events, may lead to bottom-up effects throughout the food web, though this project focused only on production and respiration signals within the lowest level. We estimated regional NCP values for each sampling season and found the highest NCP rates (~54 to ~81 mmoles C m⁻² d⁻¹) between the summer and fall of 2011, with the most marine influenced lower part of the bay experiencing the greatest production. As the climate continues to warm, further glacial volume loss will likely lead to additional modifications in the carbon biogeochemistry of GLBA. Understanding the dynamics that drive seasonal changes in Ω, NCP, and the associated air-sea CO₂ fluxes within glacially influenced Alaskan fjords can provide insights into how deglaciation may affect carbon budgets and production in similar fjords worldwide.
    • Biophysical factors associated with the marine growth and survival of Auke Creek, Alaska coho salmon (Oncorhynchus kisutch)

      Robins, Joshua Benjamin (2006-12)
      Correlation and stepwise regression analyses were used to investigate relationships between growth in four distinct marine habitats, marine survival, and biophysical indices for Auke Creek coho salmon, a coho salmon population in Southeast Alaska. Early marine growth of males and females were positively correlated, but neither was correlated with early marine growth of jacks. Regional biophysical indices had significant effects on early marine growth of jack, but not on early marine growth of adult coho salmon. Sea surface temperature and number of hatchery pink and churn salmon juveniles released had negative and positive effects on growth in strait habitat, respectively. Hatchery pink and churn salmon abundance and pink salmon catch in Northern Southeast Alaska were negatively related to the growth of Auke Creek coho salmon in the late ocean phase. The average length-at-return of males, but not females, was negatively related to the abundance of hatchery pink and chum salmon. Female and male size-at-return were positively correlated (r = 0.68) but within-year variation was less for females, indicating possible sex-specific differences in adult size requirements associated with reproductive success. Adult survival and jack return rate were significantly related to early marine growth of adults and jacks, respectively, indicating size-selective mortality. Hatchery pink and churn salmon abundance had positive effects on adult survival and jack return rate.