• Effects of jet boats on salmonid reproduction in Alaskan streams

      Horton, Gregg E.; Reynolds, James; Kane, Douglas; Barry, Ronald; Kavanagh, Ross (1994-09)
      Freshwater angling has increased dramatically in recent years in southwestern Alaska, and jet boat operators serve some of these anglers. Resources agencies are under pressure to regulate use of jet boats in waters that support spawning populations of salmonids, but they need more information regarding these potential effects. This thesis describes the methods and results of experiments to determine the effects of water turbulence from passing boats on embryo mortality and behavior of spawning adults. Field experiments on sockeye salmon were conducted in American Creek (in the Naknek drainage in Katmai National Park and Preserve) in 1992 and 1993. Laboratory experiments on rainbow trout were conducted at Fort Richardson Hatchery. These two species were viewed as surrogates for all species of genus Onorhynchus.
    • The reproductive biology and management of walleye pollock (Gadus chalcogrammus) in the Gulf of Alaska

      Williams, Benjamin C.; Kruse, Gordon; Criddle, Keith; Dorn, Martin; Quinn, Terrance II (2018-08)
      Ecosystem-based fishery management (EBFM) entails treating resource allocation and management as elements of a comprehensive framework that accounts for ecological linkages. The goal of EBFM is to maintain ecosystem resiliency in a manner that provides for the services desired e.g., fishery catch, species abundance, economic viability. Historically fisheries have been managed on a per species basis with a general focus on increasing or decreasing harvest rates. This management strategy often excludes meaningful processes such as interactions with other species, environmental changes, and economic effects of management changes. One feasible path for implementation of EBFM is through enhancement of existing single-species fishery management models. Contemporary age-structured stock assessment models generally use an estimate of spawning stock biomass (SSB), i.e., the biomass of female spawning fish, to approximate stock reproductive potential (RP). This approximation inherently assumes a proportional relationship between SSB and RP. Maturity at age or at length is a key aspect of reproductive biology that is central to estimating both RP and SSB. As a sequential augmentation to a single species management model the relationships among body condition, population abundance, the probability of being mature, relative fecundity, and environmental correlates were examined for female walleye pollock Gadus chalcogrammus in the Gulf of Alaska. Maturity data were corrected for spatial sampling bias using a mixed-effects generalized additive model. Once corrected for spatial bias, relationships between maturity, ocean temperature, body condition, ocean productivity (in the form of chlrophyll-a), and population abundance were explored. Estimates of fecundity were updated through the processing of archived samples and were also examined with mixed-effects generalized additive models to explore relationships between the previously listed covariates. Multiple measures of RP were examined to explore differences between methods currently incorporated into the stock assessment and updated measures of total egg production and time varying maturity. Walleye pollock body condition is density-dependent, declining with population abundance. However, after accounting for the effects of length, age, location, year, chlorophyll-a concentrations, summer ocean temperature and sample haul, condition has a positive effect on the probability of a fish being mature. Similarly, condition has a positive effect on relative fecundity, after accounting for length, age, egg diameter, chlorophyll-a concentrations, winter ocean temperature and sample haul. A positive relationship is observed between depth-integrated summer ocean temperature and maturity and depth-integrated winter ocean temperature and fecundity. Chlorophyll-a concentrations have a dome shaped relationship with maturity, peaking at 2.3 mg/m⁻³, and a negative relationship with fecundity. Variations in body condition have a direct influence on the estimated RP of the fish stock through both differences in the maturation schedule and total egg production. Over some periods these updated estimates of RP differ from estimates of female SSB from the annual stock assessment. Alternative estimates of annual RP, particularly total egg production, may provide better estimates of annual reproductive output than spawning stock biomass. In addition, relationships to density-dependent and density-independent factors provide informative predictions that can be incorporated into stock assessment analyses. Inclusion of spatially explicit information for walleye pollock maturity has implications for understanding stock reproductive biology and thus the setting of sustainable harvest rates used to manage this valuable fishery. Additionally, because management decisions have economic as well as biological consequences a suite of management strategies were simulated to examine the economic viability of a proposed small-vessel walleye pollock fishery in Alaska state waters in the Gulf of Alaska. As a case-study for straddling stocks, an agent-based model was developed to examine a suite of available federal and state management strategies as they relate to the economic viability of a nascent Alaska state-waters trawl fishery for walleye pollock that may develop after a long history of parallel state and federal waters management. Results of alternative strategies were compared in terms of indicators, such as variance of catch and quasi-rent value. Given the input characteristics of these simulations, the management strategy that produces the best overall improvements relative to status quo involved a federal-waters management strategy that allows for community-based cooperatives and an open access strategy in state-waters. Agent-based models may be used to inform managers of the underlying dynamics of catches and revenues in order to avoid unintended consequences of management decisions and to improve the likelihood of attaining fishery management objectives. This dissertation provides incremental additions to our knowledge of walleye pollock reproductive biology its spatial and temporal dynamics, and environmental correlates that may serve as ecological indices. These indices, coupled with an improved understanding of the socio-economic examinations of fishery management changes through agent-based modeling, may assist in producing more holistic management strategies, such as EBFM.
    • Reproductive indices of male snow crab, Chionoecetes opilio, from the Eastern Bering Sea

      Zaleski, Marilyn Fox; Tamone, Sherry L.; Kruse, Gordon; Eckert, Ginny (2012-08)
      The reproductive success of male snow crab (Chionoecetes opilio) is complicated by two different life history stages; male C. opilio undergo a terminal molt prior to adulthood which is marked by an allometric change in chela size. While adolescent males can produce spermatophores, terminally molted males are most successful in mating and reproduction. Molting and mating are hormonally linked, with molting regulated primarily by ecdysteroids and mating regulated by the putative reproductive hormone methyl farnesoate (MF). Methyl farnesoate is structurally related to the insect juvenile III hormone and, in addition to reproduction, may have a role as a juvenilizing hormone in crustaceans. The purpose of this study was to determine how molting affects the reproductive biology of snow crab by comparing the gonadosomatic index(GSI) and concentrations of circulating MF in adolescent and adult males. I used shell condition as a rough estimate of time post molt to compare GSI and MF between new-shell males, those that had molted within one year, and old-shell males, those that had not molted for at least 1 year. I measured GSI as the ratio of gonad weight to whole crab weight and used GSI as a proxy for reproductive fitness; I quantified circulating MF using high performance liquid chromatography. New-shell adolescent and adult males had significantly lower GSI than old-shell males; thus molting compromises the reproductive physiology of male C. opilio. New-shell adolescent males had significantly higher MF levels than old-shell adolescent males, and MF levels remained low after the terminal molt, supporting a juvenilizing role for MF in C. opilio.
    • 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.
    • 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.