• Spatial variability in size at maturity and reproductive timing of golden king crab (Lithodes aequispinus) in Southeast Alaska

      Olson, Andrew P.; Eckert, Ginny L.; Kruse, Gordon H.; Siddon, Christopher E. (2016-08)
      Many crab fisheries around the world are managed by size, sex and season regulations, where male crabs are given at least one opportunity to reproduce before being harvested. Therefore, to set minimum legal size and fishing season for harvest, information on size at maturity and reproductive timing is needed. Lithodes aequispinus has supported a commercial fishery in Southeast Alaska since 1972, with an average annual harvest of 207 t. The current legal size and season for harvest are based L. aequispinus growth and maturity information from other parts of the range and limited information on reproduction. Additionally, evidence suggests that these life history parameters can vary spatially. Therefore, I investigated size at maturity, reproductive timing, and variation in harvest from the commercial fishery for L. aequispinus. I compared size at maturity estimates (males and females), mean spine contribution to legal size male crabs, and depth and bottom temperature among seven management areas in Southeast Alaska (Lynn Canal, Icy Strait, North Stephens Passage, Frederick Sound, Mid-Chatham Strait, Lower Chatham Strait, and Clarence Strait) and investigated reproductive timing of mature females in Frederick Sound. Male size of maturity estimates varied spatially, with an increasing trend with latitude and significant differences occurred among the majority of management areas. Female maturity estimates varied significantly among all areas, but showed no latitudinal pattern. The latitudinal pattern for size at male maturity in Southeast Alaska differed from published values in other parts of the range (Japan, Russia, the Bering Sea and from the Aleutian Islands to Canada), where size at maturity decreased with increasing latitude. When I investigated the ability of environmental factors to explain the patterns in Southeast Alaska, depth and temperature were not found to influence the spatial variation in male maturity estimates. Depth varied by management area, and males and females were distributed at similar depths. Temperature varied less than 1.0 °C among management areas, and monthly temperature measured at a mooring in the Gulf of Alaska also varied by less than 1.0 °C throughout the year at depths where L. aequispinus are found (250 m). Mean spine contribution to legal size varied spatially but did not influence calculated legal size. Reproductive timing was determined for eyed embryos, with projected hatching of embryos occurring from April to November, indicating that a distinct reproductive season does not exist. Management implications from this research are that the current legal size (177.8 mm/7.0 in carapace width (CW)) does not allow male crab to reproduce at least once before being harvested for all management areas. If legal size is increased to 196.5 mm/7.7 in CW, a higher proportion of male crab could reproduce at least once before being harvested. This size change could have negative economic impact to the commercial fishery with potential harvest lost in areas with smaller sizes at maturity. This study shows the importance of re-examining legal size and season based on an improved understanding of how life history characteristics change over space and the resulting implications for improved fisheries management.
    • Spatiotemporal variation of benthic communities on weathervane scallop (Patinopecten caurinus) beds with socioeconomic considerations of the commercial fishery off the coast of Alaska

      Glass, Jessica Rose; Kruse, Gordon; Jewett, Stephan; Miller, Scott; Mueter, Franz (2014-08)
      Weathervane scallops (Patinopecten caurinus [Gould, 1850]) off Alaska are commercially harvested in areas that contain commercially important groundfish and crabs. Using observer bycatch data collected during 1996-2012, we analyzed spatial and temporal patterns in community composition on weathervane scallop beds and explored whether observed patterns related to environmental variables (sediment, depth, bottom water temperature, and freshwater discharge) and anthropogenic variables (trawling and dredging effort). Significant (P<0.05) differences in community structure were observed at the scale of state fishery registration districts, as well as among individual scallop beds. Spatial differences were most strongly correlated with sediment, depth, and dredging effort. Sequential changes over time were also detected, as was a split between 1996-1999 and 2000-2012. Temporal changes were weakly yet significantly correlated with freshwater discharge and dredging effort. We also conducted a socioeconomic assessment of the commercial weathervane scallop fishery, structured within the framework of a SWOT (strengths, weaknesses, opportunities, threats) analysis. Specifically, we focused on five categories: social, technological, economic, environmental, and regulatory. Whereas the data-poor status of the stock appears to be the fishery's biggest weakness, the largest strengths are conservative management, industry self-regulation, and the fishery's small footprint. Impending threats include stock declines, effects of dredging, and changes in the structure of the fishery. These analyses provide a baseline of benthic community composition on weathervane scallop beds, as well as socioeconomic information to contribute to the environmental, economic, and social sustainability of the Alaska scallop fishery.
    • 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.
    • Sponges Dominant In The Alaska Intertidal: Biology, Ecology, And Genetic Diversity

      Knowlton, Ann Lynette; Highsmith, Raymond C. (2002)
      The role of the sponge, Halichondria panicea, in a Kachemak Bay, Alaska, intertidal community was investigated through field and laboratory experiments. The relationship between H. panicea and co-occurring macroalgae was studied and results indicate that removing macroalgae had no effect on sponge abundance. A laboratory feeding trial investigating H. panicea and its primary predator Archidoris montereyensis showed that nudibranchs consuming symbiotic sponge had higher feeding and egg production rates than individuals eating aposymbiotic sponge. In a simulated predation event, initial sponge growth rates into experimental feeding scars were high, indicating a response mechanism to tissue damage. A naturally occurring high nudibranch recruitment into a sponge population resulted in the local decline and extinction of both sponge and predator. Genetic studies revealed that at least two sponge species likely comprise the intertidal populations investigated, Halichondria panicea and H. bowerbanki. The reproductive cycle of H. panicea at exposed, hard-substrate habitats, and H. bowerbanki at sheltered, soft-sediment sites, exhibited seasonal peaks in oocyte production and maturation. H. panicea produced embryos 3--4 months earlier than H. bowerbanki. Six genomic DNA microsatellite loci were isolated and utilized in the characterization of two Halichondria panicea populations. The two populations were differentiated from one another with no significant inbreeding or bottleneck effect detected. All individuals were genetically unique, indicating little or no cloning. Sexual reproduction appears to be the dominant mode of reproduction maintaining the populations. DNA sequence analyses suggest that at least two species are likely present in Kachemak Bay. Distributions of ITS and CO1 haplotypes corresponded to habitat type. Analyses of the data grouped Alaska haplotypes separately from European samples of Halichondria panicea and H. bowerbanki , suggesting separate species may occur in Alaska. A re-examination of sponge systematics in southcentral Alaska is needed.
    • The status of Pacific Walrus (Odebenus rosmarus divergens) foraging habitat and diet around St. Lawrence Island

      Merrill, Tracie E.; Konar, Brenda; Hills, Susan; Bluhm, Bodil; Coyle, Kenneth (2008-12)
      With ongoing climate change, food resources may be reduced for Pacific walruses (Odobenus rosmarus divergens). Significant differences in walrus foraging habitat (benthic communities) or diet might indicate changes in prey quality or quantity. In this study, benthic infaunal biomass, abundance, and composition were compared between 1970-1974 and 2006 at stations southwest of St. Lawrence Island. Sediment grain size was compared because it strongly determines benthic community structure. Wet weights, counts, and species composition of prey items found in stomachs of walruses collected near the island were compared between the 1980s and 2007. Benthic invertebrate biomass and abundance increased mainly due to high Nuculidae biomass and abundance, although results may be skewed by low sample size. Silt fractions increased regionally. No significant dietary differences were detected in walruses. Walruses may have undergone a population redistribution or decline in response to benthic community changes that would be undetected in stomach content analyses.
    • Steller sea lion (Eumetopias jubatus) strandings and the role of pathogens in reproductive failure

      Esquible, Janessa A.; Atkinson, Shannon; Burek-Huntington, Kathy; Cox, Keith; Tamone, Sherry (2018-08)
      Steller sea lions (SSL, Eumetopias jubatus) have faced severe population fluctuations over the last five decades with a myriad of possibilities affecting their SSL population including disease, malnutrition, predation, climate change, entanglement in marine debris, and other factors. This thesis examined the effects that anthropogenic factors and disease may play in SSL strandings and reproductive failure. The goal of this study was to characterize long-term seasonality and spatial trends in SSL strandings and to investigate the role Brucella spp., Coxiella burnetti. Chlamydophila spp. and morbilliviruses may play in reproductive failure including spontaneous abortion and premature parturition. In Chapter 1, we utilized stranding data (n=1507) collected in Alaska, Oregon, and Washington from 1990-2015. We assessed temporal trends by identifying seasonality patterns across all years, analyzing sex, age class, body length, and characterizing signs of human interaction including factors contributing to mortality. Clear seasonality trends were evident, with the greatest number of reported strandings occurring during the spring and summer. Gunshot wounds and fishery interactions accounted for a large proportion (46%) of human interaction cases in strandings. Adult males were the most frequently stranded sex and age class in the Alaska and West Coast Regions. This study attempted to quantify efforts to monitor strandings and determined that the apparent increase in strandings following 2000 was likely due to increased stranding response effort resulting from increased federal grant awards. We encourage conducting further spatial analyses of strandings in addition to continued stranding surveillance monitoring with attempts to improve stranding response time. In Chapter 2 of my thesis, we analyzed archived lung, skin lesion and placenta tissues for the pathogens of interest in SSL fetuses (n=18) and neonatal pups (n=2) collected from 1998 2015 in Alaska. Associated pathological findings and morphometric data were examined to identify signs of pathology or abnormalities in all cases. Marine mammal Brucella was detected in the lung tissue of three cases. This is the first documented detection of Brucella in SSL by PCR methods. Phocine distemper virus was also detected in the skin lesion of two cases and in the placenta of one case, in which the cases with skin lesions exhibited abnormal pathology that included vesiculoulcerative dermatitis. Currently, there is very little available information on the significance of Brucella spp. and morbilliviruses in marine mammal populations inhabiting Alaskan waters. Therefore, this study demonstrates the clear need to continue disease surveillance programs and further investigate the role disease may play in SSL reproductive health, and more generally on cohort population stability.
    • Steller sea lion survivors: a retrospective on the impact of alternative research methods on an endangered species

      Shuert, Courtney; Mellish, Jo-Ann; Horning, Markus; Buck, C. Loren; Aguilar-Islas, Ana (2015-08)
      Two novel research approaches were developed to facilitate access to wild juvenile Steller sea lions. First, the Transient Juvenile Steller sea lion Project (TJ) facilitated numerous studies of physiology, behavior, and nutrition through temporary captivity (branded TJs, n=45) over the past decade. As a complement, a control group was sampled and released during capture events (FRs, n=35). Second, the Life History Tag (LHX) project was implemented within the TJ project to implant individuals (LHX-1, n=35) with internal transmitters to detect potential causes of mortality. Our goal was to evaluate the potential for long-term impacts of these two research programs on study individuals (Chapter 1) as well as identify potential metrics of survival for use in field efforts (Chapter 2). The first chapter used open-population Cormack-Jolly-Seber (CJS) mark-recapture models to project survival from resights of branded individuals in combination with demographic covariates in program MARK. TJ and FR groups were compared to identify the potential effect of temporary captivity on survival, while LHX-1 and non-implants were compared to examine a tagging effect on survival. Overall, our results mirror previous efforts to characterize survival in sea lions and indicate minimal long-term effects on mortality from research efforts, higher survival in females than males, and increasing survival rate with age. For the second chapter, a three-tiered approach to the decade of archived physiological data attempted to build links to survival in TJs through similar CJS modeling techniques. The first two levels looked at survival in relation to observed responses of handling stress through six a priori principle blood parameters measured at entry and exit. In addition, several condition indices were also incorporated into mark-recapture models, but separately considered when measured at entry and exit due to sampling inconsistencies. The third level evaluated the efficacy of single-point sampling to project similar trends for field use. Change in mass (kg) and white blood cell count (WBC, m/mm3) had the most support in predicting survival. Mass gains over captivity and slight increases in WBC resulted in a higher averaged survival rate. Minor support was identified for exit mass and entry WBC. A higher exit mass predicted a higher survival rate, while a higher entry WBC predicted a lower survival rate and may demonstrate the efficacy of single-point sampling as a management tool.
    • Stock Structure And Environmental Effects On Year Class Formation And Population Trends Of Pacific Herring, Clupea Pallasi, In Prince William Sound, Alaska

      Brown, Evelyn Dale; Norcross, Brenda L. (2003)
      Fluctuating forage fish populations trigger large ecosystem responses in the North Pacific. A representative species, Pacific herring, Clupea pallasi, was chosen to model environmental effects on population fluctuations and recruitment with a case example in Prince William Sound (PWS), Alaska. A unique approach was used to (1) develop a spatially-explicit, life history-based conceptual stock model, (2) quantify population level effects of climatic trends, and (3) model key environmental factors affecting recruitment. Framed as a simulation model, the stock model was compartmentalized by life-history stages based on shared habitats and environmental forcing. Initial model conditions impacting year-class formation were adult size-at-age, spawn timing, location and spawner density, and conditions during egg incubation, all impacting a two-stage larval mortality rate. Larval survival probably dictates the extremes in year-class strength. Age1 abundance should reflect recruitment levels 2--3 yrs later, unless a predator pit exists. A metapopulation structure was proposed with at least two local population groupings with spatial complexity required to maintain stock levels. Herring abundance correlated with long-term climate trends supporting hypotheses of bottom up environmental forcing. Adult growth was oscillatory over a 13 yr period in phase with zooplankton production and climatic trends. Spawn timing occurred progressively earlier over the last 30 yr period with a concurrent regional spawn allocation shift and decrease in recruits per spawner. Incorporating local stock structure and local environmental variables into nonlinear herring recruitment models improved explanatory power over traditional models. Best-fit variables were eastern PWS SST, salinity, SST variance, and salinity variance from spring to fall. Eight critical life stage periods were defined based on the season and lag of the best-fitting varibles. Examining other variables in these critical periods led to defining potential key processes affecting year class formation. Allocation of spawn and age-3 recruits to metapopulation regions also impacted recruitment to PWS as a whole and these results supported the metapopulation theory. The results led to formulation of a new theory, entitled "opposing response", explaining the mechanism producing the observed pattern of alternating strong and week year class strengths in northern Pacific herring.
    • Stock structure and environmental effects on year class formation and population trends of Pacific herring, Clupea pallasi, in Prince William Sound, Alaska

      Brown, Evelyn D. (2003-12)
      Fluctuating forage fish populations trigger large ecosystem responses in the North Pacific. A representative species, Pacific herring, Clupea pallasi, was chosen to model environmental effects on population fluctuations and recruitment with a case example in Prince William Sound (PWS), Alaska. A unique approach was used to 1) develop a spatially-explicit, life history-based conceptual stock model, 2) quantify population level effects of climatic trends, and 3) model key environmental factors affecting recruitment. Framed as a simulation model, the stock model was compartmentalized by life-history stages based on shared habitats and environmental forcing. Initial model conditions impacting year-class formation were adult size-at-age, spawn timing, location and spawner density, and conditions during egg incubation, all impacting a two-stage larval mortality rate. Larval survival probably dictates the extremes in year-class strength. Age-1 abundance should reflect recruitment levels 2-3 yrs later, unless a predator pit exists. A metapopulation structure was proposed with at least two local population groupings with spatial complexity required to maintain stock levels. Herring abundance correlated with long-term climate trends supporting hypotheses of bottom up environmental forcing. Adult growth was oscillatory over a 13 yr period in phase with zooplankton production and climatic trends. Spawn timing occurred progressively earlier over the last 30 yr period with a concurrent regional spawn allocation shift and decrease in recruits per spawner. Incorporating local stock structure and local environmental variables into nonlinear herring recruitment models improved explanatory power over traditional models. Best-fit variables were eastern PWS SST, salinity, SST variance, and salinity variance from spring to fall. Eight critical life stage periods were defined based on the season and lag of the best-fitting varibles. Examining other variables in these critical periods led to defining potential key processes affecting year class formation. Allocation of spawn and age-3 recruits to metapopulation regions also impacted recruitment to PWS as a whole and these results supported the metapopulation theory. The results led to formulation of a new theory, entitled 'opposing response', explaining the mechanism producing the observed pattern of alternating strong and week year class strengths in northern Pacific herring.
    • Straying, stress, and potential for reproductive interactions between hatchery-produced and wild chum salmon (Oncorhynchus keta) in Southeast Alaska

      McConnell, Casey John; Westley, Peter; McPhee, Megan; Atkinson, Shannon; Oxman, Dion (2017-12)
      Approximately 1.5 billion juvenile hatchery-produced Pacific salmon (Oncorhynchus spp.) are currently released each year into Alaskan waters with goals of enhancing important fisheries and minimizing detrimental impacts on wild stocks. As the abundance of hatchery-produced salmon has increased, so have concerns about hatchery-origin strays entering wild systems and interactions with wild individuals on the spawning grounds. The influx of non-native strays and their associated fitness-related traits can reduce the resilience and productivity of recipient wild stocks, and is likely to be most deleterious when disparities in population sizes and heritable phenotypic characteristics between wild and hatchery fish exist. Thus, understanding the ecological and life-history mechanisms that regulate gene flow between hatchery and wild populations is crucial for conservation and management strategies in areas where hatchery enhancement is common. Currently, the ecology of strays on the spawning grounds and proximate physiological factors associated with straying (e.g., stress) are not well known. In this thesis I examine, 1) differences and similarities in several fitness-related phenotypic traits between naturally produced (presumably wild local individuals) and stray hatchery-produced chum salmon (Oncorhynchus keta) that died on the spawning grounds of Sawmill Creek, a small watershed near Juneau, Alaska, and 2) physiological differences in cortisol concentrations and the frequency of crystalline (vaterite) structure of otoliths between straying and correctly homing salmon. Hatchery-strays comprised 51.4% of the adult chum salmon that returned to Sawmill Creek during the 2015 spawning season. Hatchery males and females returned approximately seven days later, were consistently smaller (10% for males, 6% for females) in length, and younger on average than their naturally-produced counterparts. Additionally, hatchery-produced females lived fewer days on the spawning grounds during the spawning season, and retained a higher proportion of their eggs than did naturally produced females. To explore the potential role of stress on straying, I compared cortisol samples and frequency of vaterite formation in otoliths among groups of hatchery-produced fish that homed to the hatchery, hatchery-produced fish that strayed to Sawmill Creek, and naturally produced chum salmon that presumably homed to Sawmill Creek. No significant differences in cortisol concentration were found among any groups, though differences between the sexes were detected. Males of all groups had significantly lower cortisol concentrations than did females. No differences in frequency of vaterite occurrence were found between hatchery-stray and hatchery-home groups, though both hatchery groups were higher than naturally produced groups, which is consistent with findings of other studies. Thermal marking while at the hatchery during early development was not associated with vaterite formation, and no difference in frequency of vaterite formation was observed among groups of varying mark intensities. Overall, these results revealed there was ample opportunity for reproductive interactions between stray hatchery-produced and naturally produced chum salmon in Sawmill Creek during the 2015 spawning season, and consistent differences in phenotypic traits suggests the potential for gene flow to alter population-level phenotypic variation. However, despite the potential for gene flow, these results also reveal potential barriers to introgression and indicate that at least some of the presumed locally adapted traits of the natural stock remain intact. It remains unknown what the characteristics of the wild stock were prior to regional hatchery production and the extent to which the traits of this population are reflections of genetic differences between the hatchery and wild groups or phenotypic plasticity. To the extent these results are generalizable, observed differences in fitness-related traits between naturally produced and stray hatchery-produced fish may underlie the reduced reproductive success often reported in the literature. There were no differences in cortisol concentrations and frequency of vaterite occurrence between hatchery chum salmon that strayed and those that homed correctly, and the frequency of vaterite occurrence of hatchery chum salmon did not change as thermal mark intensity increased, which suggests that thermal marking may not directly alter homing ability of adults or development of juveniles, at least via otolith formation. Despite not having an effect on straying, the consistent findings of higher frequency of vaterite occurrence in hatchery-produced fish compared to naturally produced counterparts highlight the need for future work to uncover the causal underlying mechanisms and implications of vaterite on survival of the 1.5 billion salmon released each year in Alaskan waters.
    • Structure of nearshore fish assemblages in relation to varying levels of habitat complexity

      Markis, Joel A. (2007-05)
      Complex kelp and rocky habitats can be beneficial to fishes, however, their use of these habitats is poorly understood in northern latitudes. This study examined nearshore kelp habitats to examine the potential effects of kelp density and substrate topography on nearshore fish communities in Kachemak Bay, Alaska. Fish were collected from multiple sand, understory kelp, and understory and canopy kelp sites, along with kelp and substrate complexity measurements. Standard Monitoring Units for the Recruitment of Fish (SMURFs), light traps, shrimp pots, and SCUBA visual surveys were all employed in these collections. Relative fish abundance and community composition varied temporally in all habitats. The dominant fish families were gadids, pleuronectids, hexagrammids, and sebastids. Habitat use differed significantly temporally and spatially in relation to size class. These differences were family specific. Community analysis of the dominant fish families showed that different habitat complexities supported distinct fish assemblages. Low complexity sand habitats were particularly important for juvenile pleuronectids in this region and complex nearshore kelp habitats may be essential fish habitat for juvenile Pacific cod. Although these high complexity nearshore environments may be challenging to sample, they support large fish assemblages and may be essential to a variety of fish families and species.
    • Structure, inter-annual variability, and long-term change in zooplankton communities of the Chukchi Sea

      Ershova, Elizaveta A.; Ершова, Елизавета А.; Hopcroft, Russell; Kosobokova, Ksenia; Gradinger, Rolf; Coyle, Ken; Winsor, Peter (2016-08)
      The Chukchi Sea is a complex transition zone between the Pacific and Arctic Oceans that has been experiencing dramatic change in recent decades due to shifting sea ice cover and increasing temperatures. We examine summer mesozooplankton communities of the Chukchi Sea in Alaskan and Russian waters during summers 2004, 2009, 2010 and 2012 within the scope of the RUSALCA (Russian-American Long Term Census of the Arctic) program. Community structure was highly variable between the study years, but was overall tightly correlated to water mass properties, with bottom temperature being the most significant factor influencing communities. Zooplankton biomass was dominated by the large copepod Calanus glacialis, while abundance was dominated by small shelf species of copepods, such as Pseudocalanus spp. and Oithona similis. The “cold" summers of 2009-2012 had nearly twice the biomass and abundance of zooplankton compared to the oceanographically “warm" summer of 2004. We discuss the implications of the inter-annual variability of planktonic communities within the Chukchi Sea, and the possible effects of longer-term climate change. We then look at distribution and population structure of an ecologically important species complex within the zooplankton, Pseudocalanus spp, and evaluate the implications of a warming climate for this group of copepods. While numerically dominating the communities, Pseudocalanus spp. has been historically understudied at the species level due to very subtle morphological differences between the species. Our approach used a combination of microscopic identification as well as a novel species-specific PCR identification method to discriminate between the four species found in the Chukchi Sea. Our results suggest that shifting oceanographic patterns and climate warming will have unequal impact on this group of organisms, arising from species-specific life histories and tolerance to environmental conditions. These recent observations on zooplankton are then placed into a historical context through comparison to data collected throughout the past half-century (1946-2012). Despite significant challenges associated with the highly variable spatial coverage and methodology of the available datasets, significant trends were detected. In addition to high levels of inter-annual variability, we demonstrate significant increases in zooplankton biomass and abundance in recent years compared to historical studies, as well as shifting distribution ranges for several key species. This signal was most pronounced within the copepods, particularly Calanus glacialis, which appears to be indirectly benefiting from warming of the region. While summer zooplankton communities of the Chukchi Sea have been primarily Bering-Pacific in character for as long as our records exist, continuing warming and ice loss are increasing the influence of Bering-Pacific fauna within the Chukchi region.
    • Studies on the ecological physiology of Porphyra abbottae and Porphyra torta (Rhodophyta): development of new species for mariculture in Alaska

      Conitz, Jan Marie (1999-12)
      Environmental factors affecting the distribution and growth of Porphyra abbottae and Porphyra torta were studied in a research project on the feasibility of nori mariculture in southeast Alaska. In situ abundance of Porphyra abbottae was compared at sites in Sitka Sound, Cross Sound and Chatham Strait. Growth of laboratory cultured Porphyra torta gametophytes was studied in response to nutrients, salinity, crowding and substrate. The seasonal progression of abundance in Porphyra abbottae varied between study sites, with associated differences in water motion and temperature. Double sampling techniques improved accuracy of in situ abundance estimates. Germination and initial growth of cultured Porphyra torta gametophytes were dependent on plant density, and substrate texture affected recruitment. Nitrate positively affected growth and pigment concentration at environmental levels; negative effects of low nitrate were reversible. Porphyra torta gametophytes tolerated low salinity and inorganic carbon at least to half of normal levels.
    • Subsistence salmon fishing in Beaufort Sea communities

      Cotton, Shelley S.D.; Carothers, Courtney; Craighead George, John (2012-12)
      Environmental change, combined with observations of increasing numbers of salmon in subsistence fisheries, has generated a need for more information about salmon use, abundance, and distribution in the Arctic. Ethnographic research was conducted in Barrow and Nuiqsut, Alaska, in 2010 and 2011 with 41 active fishermen and elders. Salmon catches were perceived to be increasing; however, perceptions about changing salmon abundance were mixed. While pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta) have been observed in subsistence fisheries in the central North Slope region for over 50 years, only within the last 10 to 20 years has local use of these resources begun to increase. In this region, salmon are less important as a subsistence resource compared to whitefish species (Coregonus spp.). However, many fishermen participating in the Elson Lagoon gill net fishery near Barrow have begun to target salmon. Harvest estimates for this fishery in 2011 indicated that chum salmon and pink salmon catches comprise the majority of all fish caught (42% and 23%, respectively). Chinook salmon (O. tshawytscha) have been increasingly targeted, but catches are generally low. While sockeye salmon (O. nerka) numbers were perceived to have increased on the North Slope, catches of this species are rare. Only a few stray coho salmon (O. kisutch) have been captured in this region. Informants identified new stream systems where salmon are present and spawning, suggesting possible distribution shifts. Fishermen in both communities reported developing knowledge of salmon and are increasing their use of salmon as a subsistence resource.
    • Successional changes in the hydrology, water quality, primary production, and growth of juvenile Arctic grayling of blocked Tanana River sloughs, Alaska

      Wuttig, Klaus G. (1997-08)
      A comparative stream study was conducted to assess the influence of development and blockage on the hydrology, water quality, primary production, and Arctic grayling of Badger Slough, Alaska. Data collected showed that Badger Slough exhibited stable, clear flows throughout the summer, and higher total and total dissolved phosphorus, orthophosphate, alkalinity, pH, conductivity, and average temperatures, and lower winter dissolved oxygen concentrations than both Piledriver and 23-Mile Sloughs. Mean algal biomass (3.3 mg m-3) and primary production (6.9 g O2 m-2 d-1) are greater than that recorded for any other interior Alaska streams and percent fines in riffle substrates have increased. However, growth of age-0 grayling remains high. Badger Slough has eutrophied due to increased nutrients and stable flows, and the quality of rearing habitat for age-0 fish remains good. However, an annual flushing flow of 8.0 m3 s-1 is recommended for controlling accumulations of fines and maintenance of grayling habitat.
    • Summer distribution and habitat characteristics of fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) off Northeast Kodiak Island, Alaska

      Baraff, Lisa Susan (2006-12)
      Summer distributions of fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales were examined relative to bathymetry, oceanography, and zooplankton composition and density in Marmot and Chiniak Bays (Kodiak Island, AK) during 2002 and 2003. Habitat use and habitat partitioning were assessed using Monte Carlo and randomization tests, logistic regression analyses, and kernel density probability contours of high-use areas. Fin whales associated with deeper, cooler waters near areas of maximum slope and consistently used Marmot Bay. Fin whale spatial-temporal distribution likely coincided with Neocalanus copepod concentrations during early summer and adult euphausiids later in summer. Fin whale associations with Pseudocalanus copepods may relate more to that copepods' prevalence than to relevance as prey. Humpback whale site fidelity and association with shallow waters was evident in 2002, but not in 2003. Variability in humpback whale distribution was likely related to their exploitation of forage fish aggregations and threshold foraging needs. High densities of adult euphausiids may promote spatial overlap and shared resource use by fin and humpback whales. This mesoscale snapshot of a dynamic nearshore marine environment and the whales foraging there is an integral step toward identifying and characterizing important habitats for endangered fin and humpback whales.
    • Surface water connectivity of Arctic lakes drives patterns of fish species richness and composition, and food web structure

      Laske, Sarah M.; Wipfli, Mark S.; Rosenberger, Amanda E.; Verbyla, David; Zimmerman, Christian E. (2017-08)
      Hydrological processes regulate fish habitat, largely controlling availability and suitability of habitat for freshwater fishes. Seasonal fluctuations in surface water distribution and abundance on the Arctic Coastal Plain, Alaska, influence individual fish species occupancy in lentic habitats. On low-relief tundra, permafrost processes and climate are chiefly responsible for lake formation and surface water dynamics, such as the timing, duration, and availability of water that affects fish species distributions. However, it is unclear how these relationships scale up to influence fish community richness and composition, or food web structure. Further, each of these processes is also likely to change with rapid climate warming occurring in the Arctic. By observing patterns of fish species occupancy, we examined how fish species richness and composition in Arctic lakes varied with surface water connectivity at coarse and spatial fine scales. Through experiments and observation, we determined the structure of food webs as they related to surface water connectivity and foraging habits of associated fish species. We found surface water connectivity was a driver of fish species richness and assemblage patterns. Permanently connected lakes contained nearly twice as many species as disconnected lakes; and the most strongly connected lakes contained an average of four additional species compared to isolated lakes. Functional traits of fishes, like life history or body morphology, likely dictate their ability to colonize habitats. Given reduced colonization potential, isolated lakes either never supported or could not retain larger predatory fishes. In isolated systems only one fish predator occurred consistently, and this species showed strong top-down control of invertebrate prey in experimental systems. Yet, in natural environments single-predator systems have fewer trophic links than multi-predator systems, and therefore, less trophic redundancy across species. The loss of species due to isolation reduced the total number of trophic links and shortened food chains. However, I argue that the complexity and addition of top-predators in surface water connected lakes adds trophic redundancy, stabilizes energy flow, and potentially enhances persistence within in food webs and across the meta-community of food webs. Changes to fish species richness, composition, or food web structure from climate warming may be dampened by the resilience of food webs locally, but across the broader landscape it is likely that some food webs will be restructured due to changes in colonization potential regulated by surface water connectivity.
    • Survival and development of pink salmon (Oncorhynchus gorbuscha) embryos and fry as related to egg size and quantitative genetic variation

      Malecha, Patrick William (2002-08)
      The effect of egg weight on survival and development of pink salmon (Oncorhynchus gorbuscha) embryos, alevins, and fry was analyzed; in addition, embryo survival was investigated in relation to additive genetic variation. Embryonic survival to eyeing, development time to hatch, yolk weight, somatic tissue weight, yolk use rate, somatic tissue growth rate, and the survival of first-feeding fry was recorded relative to egg weight. The analyses demonstrated significant egg weight effects on development time to hatch, yolk weight, somatic tissue weight, yolk use rate, and somatic tissue growth rate on alevins. Weight and length of post-emergent fry (17 weeks post-ponding) were also significantly affected by initial egg weight. However, egg weight did not affect survival of eyed eggs or fry. Differential family-specific survival of eyed eggs indicated the presence of significant additive genetic variation.
    • A synopsis of the marine prosobranch gastropod and bivalve mollusks in Alaskan waters

      Foster, Nora Rakestraw (1979-12)
      This study presents information on the taxonomv and distribution of the marine prosobranch gastropod and bivalve mollusks from the waters surrounding Alaska. Three hundred fifty-two species of prosobranch gastropods and 202 species of bivalves are reported from these waters. Over 3,000 lots of specimens, representing 330 species and literature sources form the basis of this study. References, synonymy, geographic and bathymetric ranges are provided for each species. Characteristics used to identify the species of 66 genera are presented in tabular form. The greatest number of species is reported from the southern Bering Sea, the fewest from the Beaufort Sea. Most of the species have wide ranges in the eastern or western Pacific. New collecting records reported here extend the known ranges of 27 species. Eight species were previously unknown from Alaskan waters.
    • Synthesis and modelling of zooplankton at pan-Arctic scales

      Rutzen, Imme; Hopcroft, Russel R.; Huettmann, Falk; Coyle, Kenneth O.; Gradinger, Rolf R.; Weingartner, Thomas J. (2017-05)
      Zooplankton are an important link between primary producers and higher trophic levels. They are sensitive indicators of change in the Arctic ecosystem due to their relatively short lifespan. To date, the greatest impediment to detect changes in the Arctic zooplankton community at pan-Arctic scales is the absence of a reference baseline. To contribute to baseline data, I taxonomically analyzed zooplankton samples from the Canada Basin collected during August and September of 2003-2006. Over 50 taxonomic groups were identified, but copepods dominated abundance and biomass. Non-copepod abundance was dominated by larvaceans, while non-copepod biomass was dominated by chaetognaths. I applied multivariate analysis to look at patterns in community similarity, finding a tendency to separate the years sampled. The sample analysis served the larger goal of my research: collation of zooplankton data from online databases, reports, papers, and through scientific cooperation with scientists throughout the Arctic. In total, 13,014 zooplankton samples were assembled, containing over 200,000 individual taxonomic records spanning the period from 1921 to 2012. I also assembled 25 environmental layers for variables of possible influence on zooplankton distribution. Using these data, I employed the Geographic Information System ArcMap, as well as the data mining approaches TreeNet and RandomForests to predict the climatological mean distribution and abundance of seven ecologically and numerically important epipelagic copepod species (Calanus finmarchicus, C. glacialis, C. hyperboreus, Metridia longa, M. pacifica, N. cristatus, and P. glacialis) on a pan-Arctic scale from 60° - 90°N. The model predicted the overall distribution and abundance characteristics of each species well, but it also predicted potential niches for these or sibling species in areas where they are known to be absent. The model correctly associated species advected to the Arctic with corresponding water masses, while Arctic endemic species were more strongly associated with geographic variables. Continued assimilation of new data, plus rescuing and consolidating older datasets, are critical pathways toward both enhancing this baseline, and building the observational time-series necessary for studying changes in the Arctic zooplankton community.