• 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.
    • Pacific sleeper sharks in the Northeast Pacific Ocean: relative abundance, plausible incidental exploitation rates, trophic ecology, and habitat use

      Courtney, Dean Louis; Adkison, Milo D.; Foy, Robert; Sigler, Mike; Criddle, Keith R.; DiNardo, Gerard (2017-12)
      Pacific sleeper shark relative abundance indices in the eastern Bering Sea and Gulf of Alaska were developed from sablefish longline surveys and the sustainability of a plausible range in Pacific sleeper shark incidental exploitation rates in the Gulf of Alaska was evaluated with a risk analysis using Monte Carlo simulation for use in fisheries management. A significant increase in Pacific sleeper shark relative abundance was identified in the Gulf of Alaska during the years 1989-2003. The aggregate risk of ending in an overfished condition in the Gulf of Alaska increased from 0% under a low exploitation rate scenario to 59% under a high exploitation rate scenario. Baseline information about Pacific sleeper shark trophic ecology and habitat utilization in the eastern Bering Sea and Gulf of Alaska was developed for use in ecosystem-based fishery management. Analysis of stable isotope ratios of nitrogen (δ¹⁵N) and lipid normalized carbon (δ¹³C′) identified significant geographic and ontogenetic variability in the trophic ecology of Pacific sleeper sharks in the eastern Bering Sea and Gulf of Alaska and revealed wider variability in the feeding ecology of Pacific sleeper sharks than previously obtained from diet data based on stomach contents alone. Time series analysis of Pacific sleeper shark electronic tag data from the Gulf of Alaska identified a simple autoregressive relationship governing short-term movements (hours) throughout the time series which included substantial variation in longer time period movement patterns (months) and demonstrated that statistical inference about habitat utilization could be drawn from simultaneous analysis of an entire time series depth profile (six months of data) stored on an electronic archival tag.
    • Pacific walrus use of higher trophic level prey and the relation to sea ice extent, body condition, and trichinellosis

      Seymour, Jill-Marie; Horstmann-Dehn, Lara; Atkinson, Shannon; Barboza, Perry; Rosa, Cheryl; Sheffield, Gay; Wooller, Matthew (2014-05)
      The changing Arctic ecosystem may prompt Pacific walruses (Odobenus rosmarus divergens) to change their usual diet of lower trophic level prey (e.g., benthic invertebrates) by increasing the consumption of higher trophic level prey (HTLP). Prey-switching may have consequences to walrus populations through increased energetic costs, increased stress response, declines in body condition, and exposure to diseases, including the zoonotic parasite Trichinella spp. Trichinella is possibly transmitted to walruses via predation or scavenging on seals. The goal of this study was to quantify reliance on HTLP using stable carbon and nitrogen isotope ratios, and assess potential correlations among consumption of HTLP and sea ice extent, sex, Trichinella infection, body lipid stores, and cortisol concentrations used as an index of the stress response. Walrus diet is comprised of ~1-22% HTLP and reliance on HTLP may be correlated with sea ice extent in a complex way. Trichinella was present in ringed seal (Pusa hispida, 1/57), Arctic fox (Vulpes lagopus, 3-7/32), and polar bear (Ursus maritimus, 1/1), but was not detected in walruses (0/137) regardless of %HTLP in the diet. Walrus blubber and attached skin contained 44.6 ±12.4% lipid wet weight, which was lower than that found for other Arctic marine mammals; however, the inclusion of skin likely decreased our %lipid values. While the absolute value of %lipid from blubber and attached skin was not a suitable substitute for %lipid from blubber only, we were still able to detect the influence of biological factors, with sex-linked variability in walrus lipid stores observed. Cortisol analysis from full-thickness blubber resulted in a wide range of concentrations (2.77 to 34.04 ng/g), but showed that this stress hormone can be extracted from blubber. While neither %lipid nor blubber cortisol was correlated with the proportion of HTLP in walrus diet, they may serve as minimally-invasive methods for health monitoring of walruses. Overall, dietary plasticity of walruses is robust and switching to HTLP is not likely to have immediate adverse effects on the Pacific walrus population.
    • Paleoceanographic shifts in the Gulf of Alaska over the past 2000 years: A Multi-proxy perspective

      Boughan, Molly McCall; Finney, Bruce; Naidu, Sathy; Whitledge, Terry E. (2008-12)
      The Gulf of Alaska (GOA) is a dynamic region influenced by climate variability on time scales ranging from days to millennia. Recent regime shifts suggest interdecadal GOA primary productivity patterns, yet it is unclear whether such fluctuations extend beyond the instrumental record. This thesis examined the nature of prevalent climatic and oceanographic patterns before the twentieth century using several marine sediment core proxies for paleoproductivity and paleoceanography. Sediment cores were from two locations: Bay of Pillars, Kuiu Island, in southeast Alaska (56.63 ̊N, 134.35 ̊W), and a central midshelf location (GAK4) along the Global Ecosystem Dynamics (GLOBEC) Seward Line (59.25 ̊N, 148.82 ̊ W). Proxy data from these cores include: percentages of organic carbon, nitrogen and biogenic opal; organic carbon-to-nitrogen ratios; stable isotope ratios from sediment organic matter (δ13C and δ15N) and foraminifera tests (δ13C and δ18O); and foraminifera faunal analysis. Bay of Pillars proxy data suggest that the onset of the Little Ice Age (LIA) ca. 1200 AD coincides with pulses of decreased salinity and increased productivity. GAK4 proxy data indicate increased productivity and decreased terrestrial input over the past century; as well as fresher surface water was during the latter portion of the LIA (1716 – 1894) and positive Pacific Decadal Oscillation phases.
    • Paralytic shellfish poisoning: the relationship between Alexandrium abundance and psp toxins on Kodiak Island, Alaska

      Matweyou, Julie A. (2003-05)
      Paralytic shellfish poisoning (PSP) events have severe negative impacts on Alaska commercial shellfish fisheries as well as recreational and subsistence harvests. This study, designed to improve existing PSP monitoring programs, involved the use of a rapid sandwich hybridization assay to detect and quantify the relative abundance of Alexandrium catenella based on species-specific LSU rRNA targeted oligonucleotide probes. Blue mussel (Mytilus edulis) toxicity, expressed as saxitoxin equivalents, was determined using the ³H-Saxitoxin receptor binding assay. Shellfish toxicity was relatively low in both 2000 and 2001 compared to historically high values on Kodiak, but exhibited pronounced late spring and late summer peaks, in both years at four to seven sampling sites. Temporal and spatial variability in shellfish toxicity among sites, seasons, and years suggested dynamic, and possibly unpredictable, Alexandrium bloom events. Importantly, DNA probe data revealed a strong association between Alexandrium abundance and shellfish toxicity. The results also demonstrated that increases in Alexandrium abundance preceded elevated toxin levels in shellfish, indicating that this assay may prove useful as a monitoring tool to predict toxic events in shellfish before they are harvested. Water column nutrients and climate data were evaluated to determine if bloom-triggering mechanisms could be identified.
    • Particles in the Pacific: how productivity and zooplankton relate to particles in the deep sea

      Pretty, Jessica L.; McDonnell, Andrew; Johnson, Mark; Hopcroft, Russ (2019-05)
      The magnitude and spatio-temporal patterns of particulate material flux from the surface ocean through mesopelagic and bathypelagic depths determines sequestration of atmospheric carbon and the food supplied to deep-dwelling ocean life. The factors that influence how and where this organic material is exported from euphotic depths are poorly understood. Zooplankton are thought to play a key role in modulating the transport of surface-produced particles to depths through consumption, fragmentation, active diel vertical migration, and fecal pellet production, thus it is important to study both particulate matter and zooplankton in tandem. In this study, I use an in-situ optical instrument, the Underwater Video Profiler 5 (UVP5), to describe broad scale patterns of large (> 100 μm) particles and zooplankton across a longitudinal transect of the Pacific Ocean during April to June 2015. Satellite-derived surface chlorophyll-a was employed to describe the timescales over which particles arrive in meso- and bathypelagic depths after a productivity peak. High abundances and volumes of particles are noticeable beyond the euphotic zone across the Equator, transition zone, and the sub-arctic Pacific, indicating increased export in these high-nutrient low-chlorophyll (HNLC) areas. In two of these areas, the Equator and transition zone, large abundances and volumes of particles extend into bathypelagic depths. High abundances of zooplankton were seen in all areas where high abundances of particles are seen in bathypelagic waters. Rhizaria were revealed to be pervasive across all biogeographic regions, and appear to play a role in particle attenuation in the sub-arctic Pacific. The insight into patterns between particles, zooplankton, and productivity identify HNLC regions as deserving more detailed examination in future studies of biological pump efficiency.
    • Patterns and environmental drivers of juvenile sablefish movement in Southeast Alaska

      Ehresmann, Rhea K.; Beaudreau, Anne H.; Seitz, Andrew C.; Green, Kristen M. (2018-08)
      Sablefish Anoplopoma fimbria are a long-lived, deep-dwelling groundfish that inhabit the North Pacific Ocean, ranging from northern Mexico to the Gulf of Alaska to Japan, supporting one of Alaska's most valuable commercial fisheries. After decades of heavy fishing, declines in the Sablefish population led to significant fishing restrictions but few strong year classes developed in recent years. Most Sablefish research has focused on the larval, near-surface juvenile, or adult life history stages, but few studies have examined post-settlement juvenile Sablefish in nearshore areas. This study used acoustic telemetry to understand the presence and movement of juvenile Sablefish in a nursery area in Southeast Alaska. Throughout the summer and fall of 2015 and 2016, 40 juvenile Sablefish implanted with acoustic transmitters were monitored using an array of eight fixed receivers in St. John Baptist Bay, Baranof Island, Alaska. We quantified the movement patterns of 28 juvenile Sablefish using displacement from the head of the bay, daily distance traveled, daily duration within the bay, unique movement types among individuals, and movement in relation to environmental variables. From these analyses, we show that juvenile Sablefish exhibit fidelity to the middle-head region of the bay, display relatively high rates of daily movement and residence, demonstrate three distinct movement patterns, and are influenced by environmental variables like water temperature, diel state, moon phase, and day of year. Our results show that juvenile Sablefish exhibit seasonality in movements as they progressively emigrate from the bay throughout the summer and fall. Certain factors were found to increase the likelihood of movement for juvenile Sablefish, perhaps allowing them to remain in suitable environmental conditions. This study fills a gap in our knowledge of Sablefish early life history and reinforces the importance of nursery areas like St. John Baptist Bay for juvenile Sablefish prior to recruitment into commercial fisheries.
    • Patterns in size, growth, and condition of juvenile chum and pink salmon in the northeastern Bering Sea

      Prechtl, Melissa; McPhee, Megan; Beaudreau, Anne; Beckman, Brian (2014-12)
      The Bering Sea has alternated between warm and cool spring thermal regimes, as defined by May sea surface temperature, and in recent years has remained in a "cool" state. Differences in spring thermal regime influence the timing of sea ice extent in the southeastern Bering Sea (SEBS) region, with warm springs facilitating early ice retreats and cool springs resulting in later ice retreat. A recent conceptual model for relating production to higher trophic levels in the SEBS proposes that during years of early sea ice retreat, phytoplankton blooms occur in warm water and support small, lipid-poor species of zooplankton. Conversely, years of late sea ice retreat results in an ice associated bloom that supports large, lipid-rich species of zooplankton. As a consequence the energy density of prey sources available to higher trophic levels is reduced during warm years and enhanced during cool years. While the northeastern Bering Sea (NEBS) has consistently supported an ice-associated bloom, it is likely that productivity in the SEBS influences trophic-level connections in the NEBS. In order to examine this possibility, we extended this conceptual model to juvenile salmon and compared size and condition of juvenile chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon in the NEBS between spring thermal regimes of the SEBS. We hypothesized that juvenile salmon would be longer in warm years and more energy dense in cool years. In years with cool springs, pink salmon were shorter and chum salmon exhibited greater energy density, but no other aspects of size and condition differed significantly between spring thermal regimes. We further examined relationships of size, growth, and condition of juvenile salmon with environmental variables within the NEBS. For both species, length increased over the time of the surveys; longer individuals were caught at stations with greater bottom depths and in cooler sea-surface temperatures, while individuals with high length-corrected energy density were associated with cooler temperatures and shallower depths. We used insulin-like growth factor-1 (IGF-1) concentrations as an indicator of relative growth rate for fishes sampled 2009-2012 and found fish exhibited higher IGF-1 l concentrations between 2010-2012 than in 2009. IGF-1 concentrations were positively correlated with temperature for juvenile chum salmon and with depth and length for juvenile pink salmon. The consistent appearance of depth (indicating distance from shore) in the best size and condition models was interpreted to indicate that as juvenile salmon moved offshore, they were allocating more energy to growth than fat storage over the course of the surveys. The association of cooler temperatures with greater energy density and longer lengths may reflect direct effects of temperature on salmon physiology as well as indirect effects on food quantity or quality indirect. Overall, recent conditions of the NEBS appear to successfully contribute to the growth and condition of the juvenile chum and pink salmon. Finally, we compared indicators of energy allocation between even and odd brood-year stocks of pink salmon and found the even broodyear stocks were more energy dense while odd brood-year stocks exhibited higher growth rates. These results reflect differences in energy allocation between brood-year stocks of juvenile pink salmon and suggest that the two brood-year stocks may respond differently to changing climate.
    • Pelagic nitrogen cycle in an arctic lake

      Whalen, Stephen Charles (1986-05)
      A mass balance for nitrogen was developed for the water column of Toolik Lake and the isotope tracers 15N and 14C were used to examine the phytoplankton ecology with respect to dissolved in organic nitrogen (ammonium and nitrate). The nutrient budget showed an oligotrophic ecosystem with important flux terms few and small in magnitude. Nitrogen input was primarily from inflowing rivers and was dominated by the dissolved organic fraction. Ammonium release from sediment provided the only other major source of nitrogen to the lake water. Toolik acted as a nitrogen sink, trapping 18% of the annual input. Retention was almost exclusively (98%) as dissolved organic nitrogen. Tracer experiments suggested chronic nitrogen deficiency in the phytoplankton, but indigenous populations were well-adapted for utilizing characteristically low levels of nutrient. Phytoplankton showed a high affinity for both nitrate and ammonium as well as a lack of discrimination between the two forms of inorganic nutrient. The ambient concentration was the most important factor regulating uptake, with light and temperature of secondary importance. More than 66% of the dissolved in organic nitrogen supporting phytoplankton productivity was derived from local recycling, with the remainder from sediment efflux and riverine input. Dissolved organic nitrogen from inflowing waters probably provided an additional, important source of nutrient for the phytoplankton.
    • Penetrative convection in sediments

      Musgrave, David L. (1983-05)
    • Phosphorus metabolism of several aquatic microorganisms

      Lang, Douglas; Brown, E. J. (1980-12)
      Several taxonomically diverse aquatic microplankton were described growing at phosphorus (P) concentrations that limit growth in many natural aquatic systems. Because natural aquatic systems are subject to periodic fluctuations in P levels, both steady-state (via continuous culture) and transient (via batch culture) growth were described. Complete growth kinetic descriptions of Synechococcus Nageli (strain A) and Scenedesmus quadricauda were used to predict the relative competitive abilities of these species when P was the growth-limiting nutrient. These descriptions, coupled to their morphological characteristics, were used to construct partial physiological profiles for each organism. The profiles indicate that S. Nageli (strain A) (a small unicellular blue-green alga) is better suited for growth in P-limited oligotrophic niches than is S. quadricauda (a green alga). However, results from kinetic experiments with these and several other microplankton, show that such physiological profiles are not necessarily indicative of profiles for taxonomically related species.
    • Phylogenetic relationships and identification of juveniles of the genus Sebastes

      Li, Zhuozhuo (2004-12)
      The genus Sebastes is speciose and most members are distributed in the northeastern Pacific Ocean (NEP). Historically, morphology has been the basis for species identification and determination of phylogenetic relationships. However, because many Sebastes species overlap in range and are similar in morphology, especially during early life stages, morphological characters are often inadequate for species identification. This study examines the potential of using restriction site variation in the mitochondrial NADH-dehydrogenase subunits -3 and -4 and 12S and 16S ribosomal RNA genes to resolve the problems in species identification and phylogenetic relationships, particularly assignments to subgenera. Of the 71 species representing 16 subgenera examined, 58 species had species-specific mtDNA markers. The identity of the remaining species could be narrowed down to small groups. Forty-nine juveniles were tested for their identity. Twenty-four specimens were identified either to species or to a small group of species; the remaining specimens were not identified because of low quality of DNA. Analysis of the coherence of current sub generic assignments revealed that only the subgenus Sebastomus was monophyletic. Some consistent groups were formed by members from different subgenera. In particular, NEP members of the subgenus Pteropodus were monophyletic with three other NEP species in two subgenera.
    • The phylogeography and population genetic structure of least cisco (Coregonus sardinella) in Alaska

      Padula, Veronica M.; Causey, Douglas; Lopez, Andres; Gharrett, Anthony J. (2013-12)
      The least cisco (Coregonus sardinella) is a whitefish species broadly distributed across the Arctic regions of Russia, Alaska, and Canada, and little is known about the genetic relationships among groups within this species. We investigated the genetic relationships among least cisco on two landscape scales. On a broader landscape scale, we investigated the relationships among populations across the state of Alaska by comparing mitochondria) DNA (mtDNA) sequences. On a finer landscape scale, we investigated the relationships among least cisco populations in closely located lakes on the Arctic Coastal Plain by comparing microsatellite DNA haplotypes. Data from mtDNA suggest that least cisco are relatively diverse across Alaska, with 68 unique haplotypes found in 305 individuals and a large proportion of genetic variation is shared across Alaska, but this variation is not homogeneously distributed across all regions and for all haplotype groups. Interpretation of microsatellite data was limited. Overall, the data suggest that least cisco populations are currently isolated from one another. Isolation also occurred historically, accounting for divergence among major Glades. But general recontact events occurred as isolated populations migrated and colonized new habitats, accounting for the heterogeneity found across Alaska. Ultimately, Alaskan least cisco may have functioned as a metapopulation historically, but present populations are too isolated to be considered a metapopulation today.
    • Physical And Biological Factors Affecting The Diel Vertical Migration Of Walleye Pollock

      Adams, Charles F.; Kelley, John J.; Coyle, Kenneth O. (2007)
      The mechanisms underlying diel vertical migration (DVM) in marine fishes are unclear, although it is generally thought that this behavior is influenced by light, hydrography, food availability and predator avoidance. In the North Pacific Ocean, walleye pollock (Theragra chalcogramma) undergo DVM as juveniles, ascending to the surface at night and returning to the bottom at dawn. Adults are generally considered demersal. The objective of this research was to examine the effect of light, temperature and prey availability on the DVM of adult pollock. The work was undertaken to further our understanding of pollock biology, and the mechanisms underlying DVM in marine fishes in general. The study was conducted in the northern Gulf of Alaska in April, August and November 2003. Trawls < 80 m in April, and < 50 m in August, suggested that at least some portion of the pollock population was ascending to within 20 m of the surface in spring and summer. In November, acoustic data and targeted hauls > 100 m indicated that adults were not ascending to the surface at night, and that DVM behavior was occurring at depth. Euphausiids were the primary component of the diet in April and August. Decapods, primarily the shrimp Pandalus borealis, were the main component of the diet in November. Pollock passed through the thermocline during their ascent to the surface at night in August, and there was no relationship between the mean depth of pollock and the isolume (line of equal light intensity) necessary for visual foraging. In contrast, there was a significant relationship between the biomass of adult pollock above the 200 m isobath and the isolume necessary for visual foraging in November. Pollock did not pass through the thermocline at this time. It was concluded that in August adults ignore the isolume and thermocline, simply tracking the movements of euphausiid prey to feed upon them near the surface at night. In November, when euphausiids are no longer in patches, pollock shoals migrate up and down with the isolume necessary for visual foraging to feed on decapods.
    • Physical environmental and biological correlates of otolith chemistry of Arctic marine fishes in the Chukchi sea

      Gleason, Christine Marie; Norcross, Brenda; Brown, Randy; Horstmann-Dehn, Larissa; Trefry, John; Christie, David (2012-08)
      Life history movement patterns in marine fishes can be determined by otolith chemistry if environmental variables are reflected in the otoliths. Arctic cod (Boreogadus Saida), Arctic staghorn sculpin (Gymnocanthus tricuspis), and Bering flounder (Hippoglossoides robustus) are abundant Arctic fishes in the Chukchi Sea with overlapping distributions. Physical environmental data, demersal fishes, bottom seawater, and sediment interface seawater samples were collected from the Chukchi Sea Offshore Monitoring in Drilling Area (COMIDA) cruise on July 30, 2009 and the Russian American Long-term Census of the Arctic (RUSALCA) cruise from September 3 to 30, 2009 in the Chukchi Sea. Magnesium (Mg), strontium (Sr), barium (Ba), and calcium (Ca) were measured with an inductively coupled plasma mass spectrometer (ICP-MS) on the most recent growth edge of otoliths and in whole fish blood, as well as Ba in bottom and sediment interface seawater. Environmental variables and fish age correlated with Arctic cod and Arctic staghorn sculpin otolith signatures while only environmental variables correlated with Bering flounder signatures. Elemental correlations were not always consistent for the variables tested among species. The complexity of this multi-element tool suggests otolith chemistry may not be useful to determine life history movement patterns of these demersal Arctic fishes in offshore waters.
    • Physical Mechanisms For Variation In Pink Salmon (Oncorhynchus Gorbuscha) Survival Within The Upwelling And Downwelling Domains Of The Northeast Pacific

      Miller, Sara Elizabeth; Adkison, Milo; Criddle, Keith; Cokelet, Edward D. (Ned); Haldorson, Lewis J. (2011)
      Regional coastal conditions have a strong influence on juvenile salmon (genus Oncorhynchus) survival during their critical first months in the marine environment. Salmon survival has been thought to be favored within the downwelling domain if water column stabilities increase, whereas stability may have the opposite effect at lower latitudes. To explore this hypothesis at a local scale, we examined the relationship between stability and the characteristics of growth rate, condition, and marine survival of several stocks of pink salmon (O. gorbuscha) within Prince William Sound (PWS) and two water masses, Alaska Coastal Current and shelf, in the northern coastal Gulf of Alaska (GOA). While slower and weaker development of stratification with a deeper mixed layer depth may be more important for juvenile pink salmon survival in the Sound, earlier and stronger stratification with a shallower mixed layer depth may be more beneficial within the Gulf. As expected, stability within PWS did explain the growth rate of hatchery fish, although stability explained only a small amount of the variability and did not have the same relationship for each hatchery stock. Contrary to expectation, stability just prior to capture did not explain the variability in condition index for either hatchery or wild fish collected from within the Sound or from within either GOA water mass. When stability was below average just prior to capture within PWS, the relationship between condition index and year-class survival was positive; when stability was above-average just prior to capture, the relationship was negative. In a broader scale study, we explored the relationships between regional water column stabilities during early marine residence of pink salmon in both upwelling and downwelling domains of the northeast Pacific Ocean and marine survival rates the following year for hatchery stocks ranging from Vancouver Island, British Columbia, to Kodiak Island, Alaska. Contrary to expectation, our findings were similar between the upwelling and downwelling areas, but differed by the distance offshore. Marine survival rates of hatchery pink salmon from northern and southern stooks increased for salmon that experienced below-average stability on the inner shelf (luring early marine residence while stability effects from the outer shelf showed no consistent relationship to marine survival.
    • Physiological and behavioral responses of tanner crabs (Chionoecetes bairdi) to handling, emersion and temperature

      El Mejjati, Sonya Y. (2006-12)
      Commercially harvested Tanner crabs (Chionoecetes bairdi) are exposed to physical stressors during capture and sorting including changes in temperature and oxygen availability. This study characterizes the physiological and behavioral responses of Tanner crabs exposed to air (emersion) at 8 and -15°C for various durations. Concentrations of glucose and lactate in hemolymph measured between 30 and 120 min following emersion for 45 min differed between animals exposed to 8 or -15°C. Glucose concentrations were higher among animals emersed at 8°C than those exposed to -15°C within the intervals sampled. Lactate concentrations were unchanged at intervals following emersion at 8°C, while they were elevated at 120 min following emersion at -15°C. Rates of oxygen consumption (VO₂) increased immediately following 15, 30, and 45 min emersion at 8°C, whereas 30 and 45 min emersion at -15°C resulted in depressed VO₂. All crabs survived handling and emersion at 8°C, while exposure to -15°C resulted in increased mortality. Thus, differences among physiological parameters corresponded with differences in percentage survival between the two temperature treatments. While not providing a causal relationship between survival and physiology, the metabolic responses of Tanner crabs following a simulated capture protocol provide a predictive index of subsequent survival.
    • Physiological ecology of Porphyra sporophytes: growth, photosynthesis, respiration and pigments

      Lin, Rulong (2000-05)
      Growth, photosynthesis, respiration and photosynthetic pigments of the sporophytic stage for Alaskan Porphyra species were investigated in response to various environmental variables. Optimal conchocelis growth (7.6%) volume increase d⁻¹) of P. abbottae (Pa) occurred at 11C̊, 80 umol photons m⁻² s⁻¹ and 30ppt salinity. Porphyra torta (Pt) grew best (6.5%d⁻¹) at 15C̊, 80 umol photons m⁻² s⁻¹ and 30ppt. Porphyra pseudolinearis (Pi) generally had higher growth rates with optimal growth (8.8% d⁻¹) occurring at 7C̊, 160 umol photons m⁻² s⁻¹ and 30ppt. Salinities between 20 and 40ppt and irradiances between 20 and 40ppt and irradiances between 20 and 160 umol photons m⁻² s⁻¹ generally had little effect on growth rates, but there was virtually no growth at <10ppt. Plant hormones were shown to promote the growth of conchosporangia, which increased by 6.9-31.7% (for Pa), 4.7-25.7% for (Pe, P. pseudolanceolata) and 8.9-35.1% for (Pi). Concentrations between 0.4-1.6ppm of kinetin and indole-3-acetic acid at higher temperatures generally had higher stimulatory effects, but Pe had higher volume increase at lower temperatures. Irradiance, temperature and salinity influenced photosynthesis of the conchocelis. P-I curves, Pmax, Imax, and Ic varied with temperature and species. Higher photosynthesis generally occurred at 25-35ppt salinities. Pa had maximal photosynthesis at 11C̊ and 60 umol photons m⁻² s⁻¹, whereas Pi and Pt had maximal photosynthesis at higher temperatures and irradiances. The highest photosynthesis (240 umol O₂ production g dw⁻¹ h⁻¹) of Pa occurred at 11C̊, 60umol photons m⁻² s⁻¹ and 30ppt. Pi and Pt had optimal photosynthetic rates (200 and 210, respectively) at 15C̊, 120 umol photons m⁻2 s⁻¹ and 30ppt. Conchocelis had lower respiration rates (30-35) at 7C̊ than at 11 and 15C̊ (45-58 umol O₂ consumption g dw⁻¹ h⁻¹). All three species exhibited lowest respiration at salinities between 25-35ppt. Phycoerythrin (PE), phycocyanin (PC), carotenoid Ca) and chlorophyll a (Chl.a) contents were significantly affected by irradiance, nutrient concentration and culture duration. For Pa, Pi and Pt, maximal PE (63.2-95.1 mg/g.dw) and PC content (28.8-64.8 mg/g.dw) generally occurred at 10 umol photons m⁻² s⁻¹, f/4-f/2 nutrient concentration after 10-20 days, while Pe had highest PE (73.3 mg/g.dw) and PC content (70.2 mg/g.dw) at 10 umol photons m⁻² s⁻¹, f nutrient concentration after 60 days. For all four species, highest Ca (3.4 - 6.3) and Chl.a content (3.6 - 8.1 mg/g.dw) generally occurred at 0-10 umol photons m⁻² s⁻¹, f/4-f nutrient concentration. High irradiances, low nutrients and longer culture duration generally caused a decline of pigment content.
    • Physiological effects of the parasite ichthyophonus on spawning chinook salmon and their offspring in a Yukon River tributary

      Floyd-Rump, Theresa; Horstmann-Dehn, Larissa; Skaugstad, Calvin; Atkinson, Shannon; Sutton, Trent (2015-12)
      In recent years, Chinook salmon Oncorhynchus tshawytscha returns to the Yukon River, Alaska, have been substantially reduced. In summer 2010-2012, spawning Chinook salmon (n=51, 32, and 23, respectively) were collected from the Salcha River, a tributary of the Yukon River, to determine the effects of Ichthyophonus, a protozoan parasite, on salmon reproductive success. Eggs and milt from Ichthyophonus-infected and non-infected parents were collected in 2010 and cross-fertilized to investigate offspring survival and potential second-generation effects induced by the parasite. Proximate composition analysis of adult muscle, eggs, and alevins, and blood chemistry analysis of adult blood plasma and alevin whole body homogenates were analyzed to explore potential differences between Ichthyophonus-infected and non-infected salmon. Ichthyophonus infection prevalence was 7.8, 6.3, and 8.3 % in 2010, 2011, and 2012, respectively. Egg lipid content was significantly higher in eggs from Ichthyophonus-infected females, compared to eggs from Ichthyophonus-negative females. Survival of fertilized eggs to hatching was not significantly different between offspring from Ichthyophonus-infected parents (Mean±1SD: 24.4±29.8 % survival) and non-infected parents (41.0±24.8 % survival). Proximate composition (% lipid, % protein, kJ/g) of muscle from spawning adult salmon also did not differ, nor did total body composition or morphology of alevins produced by either Ichthyophonus-infected or non-infected parents. We found no significant differences in blood plasma cortisol concentrations (a stress indicator) between Ichthyophonus-positive and negative adults or their offspring. There were also no significant differences in blood chemistry parameters indicative of tissue damage between Ichthyophonus-positive and Ichthyophonus-negative adults or resulting alevins, with the exception of aspartate aminotransferase, which was unexpectedly higher in plasma of Ichthyophonus-negative adults. Overall, infection with Ichthyophonus does not appear to impact the spawning ability or spawning success of Chinook salmon in the Salcha River.