• Quantifying fisher responses to environmental and regulatory dynamics in marine systems

      Watson, Jordan T.; Mueter, Franz; Haynie, Alan C.; Sigler, Michael F.; Sullivan, Patrick J. (2017-12)
      Commercial fisheries are part of an inherently complicated cycle. As fishers have adopted new technologies and larger vessels to compete for resources, fisheries managers have adapted regulatory structures to sustain stocks and to mitigate unintended impacts of fishing (e.g., bycatch). Meanwhile, the ecosystems that are targeted by fishers are affected by a changing climate, which in turn forces fishers to further adapt, and subsequently, will require regulations to be updated. From the management side, one of the great limitations for understanding how changes in fishery environments or regulations impact fishers has been a lack of sufficient data for resolving their behaviors. In some fisheries, observer programs have provided sufficient data for monitoring the dynamics of fishing fleets, but these programs are expensive and often do not cover every trip or vessel. In the last two decades however, vessel monitoring systems (VMS) have begun to provide vessel location data at regular intervals such that fishing effort and behavioral decisions can be resolved across time and space for many fisheries. I demonstrate the utility of such data by examining the responses of two disparate fishing fleets to environmental and regulatory changes. This study was one of "big data" and required the development of nuanced approaches to process and model millions of records from multiple datasets. I thus present the work in three components: (1) How can we extract the information that we need? I present a detailed characterization of the types of data and an algorithm used to derive relevant behavioral aspects of fishing, like the duration and distances traveled during fishing trips; (2) How do fishers' spatial behaviors in the Bering Sea pollock fishery change in response to environmental variability; and (3) How were fisher behaviors and economic performances affected by a series of regulatory changes in the Gulf of Mexico grouper-tilefish longline fishery? I found a high degree of heterogeneity among vessel behaviors within the pollock fishery, underscoring the role that markets and processor-level decisions play in facilitating fisher responses to environmental change. In the Gulf of Mexico, my VMS-based approach estimated unobserved fishing effort with a high degree of accuracy and confirmed that the regulatory shift (e.g., the longline endorsement program and catch share program) yielded the intended impacts of reducing effort and improving both the economic performance and the overall harvest efficiency for the fleet. Overall, this work provides broadly applicable approaches for testing hypotheses regarding the dynamics of spatial behaviors in response to regulatory and environmental changes in a diversity of fisheries around the world.
    • Quantity and quality of freshwater rearing habitat in relation to juvenile Pacific salmon abundance in the Kulukak River, Alaska

      Coleman, Jesse M.; Sutton, Trent; Zimmerman, Christian; Adkison, Milo (2012-12)
      Monitoring of freshwater habitat and its influence on stream-rearing fish is essential for recognizing and mitigating the impacts of human- and climate-induced changes. For the purposes of developing a monitoring program in the U.S. Fish and Wildlife Service Togiak National Wildlife Refuge, densities and habitat relationships of juvenile coho salmon Oncorhynchus kisutch and sockeye salmon O. nerka were estimated in two tributaries of the Kulukak River, Alaska, in July 2010. Multiple-pass depletion electrofishing was used to estimate density in a random sample of habitat units belonging to one of four categorical habitat classes. Regression methods were also used to quantify the physical habitat associations of juvenile coho and sockeye salmon density in the study areas. Densities of juvenile coho and sockeye salmon ranged from 0.22 fish-m⁻² in West Fork riffles and 0.05 fish·m⁻² East Fork riffles to 2.22 fish M⁻² and 1.32 fish-m⁻² in East Fork eddy drop zones (EDZ), respectively. The largest proportions of freshwater habitat were comprised of run (71 %) and EDZ habitats (44%) in the East Fork and West Fork, respectively. Regression coefficients for coho and sockeye salmon densities were positive with respect to proportional areas of in-stream overhanging vegetation (0.78 and 0.74, respectively), large wood (0.99 and 0.97, respectively), and undercut banks (0.99 and 0.02, respectively). Conversely, coho and sockeye salmon density was negatively related to depth ( -1.45 and -0.52, respectively) and velocity ( -2.45 and -1.67, respectively). Although substrate size was negatively related to sockeye salmon density ( -0.40), this variable had a weak positive relationship with coho salmon density (0.08). These findings suggest that EDZ habitats are important for juvenile coho and sockeye salmon during summer rearing and in-stream cover is an essential component of these rearing habitats.
    • Quikscat measurements of the wind field over the Bering and Chukchi Seas

      Mull, Jeremy M.; Johnson, Mark; Weingartner, Tom; Simmons, Harper (2008-12)
      The purpose of this study is to investigate the dynamic wind field and resulting ocean circulation patterns in the Bering and Chukchi Seas. This region forms an important link in global ocean circulation as Bering Strait is a major conduit for water flowing into the Arctic Ocean. The Arctic has been identified as an area sensitive to climate change; thus it is vital to understand how water and energy flow through this region. We first quantify the differences between the winds measured in this region by the Quik Scatterometer (QuikSCAT) and those modeled by the National Centers for Environmental Prediction (NCEP). Although the data sets are well correlated, we find significant discrepancies between these data sets and use linear regressions to correct the NCEP data. The magnitudes of the NCEP wind components are greater than the magnitudes of the QuikSCAT wind components. This creates directional differences between the two data sets at low wind speeds and NCEP speeds that are greater than QuikSCAT speeds at high wind speeds. We next challenge the assumption that the wind field is spatially uniform over the Bering and Chukchi shelves. We produce mean monthly maps of the wind field, surface Ekman transport, and wind variance based upon the 12-hourly QuikSCAT data from July 1999 – May 2007. These maps reveal that the winds are spatially and temporally dynamic in this region. There are several areas and times in which surface Ekman transport is onshore or offshore near the coasts and may engender coastal downwelling and upwelling, respectively. There are also several instances when surface Ekman convergence and divergence may lead to Ekman pumping and suction. We use the entire NCEP record (January 1948 – May 2007) to examine patterns of surface Ekman transport across the shelf break. There was a significant increase in the amount of onshelf surface Ekman transport that coincided with the regime shift that occurred in the Bering Sea in the mid-1970s. We attempt to correlate the time series of surface Ekman cross-shelf transport with several climate indices but find only very weak correlations. The annual surface Ekman freshwater fluxes across the shelf break are iii calculated and found to be very small compared to the total annual freshwater fluxes calculated by Aagaard et al. (2006) and Kinney et al. (2008). To resolve the dominant modes of wind variability we compute hourly, monthly, and annual Complex Empirical Orthogonal Functions (CEOFs) with the QuikSCAT and NCEP data sets. The first modes in each analysis account for more than 60% of the variance. Different aspects of the mode amplitude time series are cross-correlated with climate and indices to produce small but significant correlation coefficients. Finally we calculate Ekman pumping and suction at four locations in the Bering Sea during the spring and summer months of seven years (2000 – 2006). We identify regions and times when Ekman pumping and suction were particularly strong, and perform several runs of a one-dimensional Price-Weller-Pinkel (PWP) vertical mixing model with the QuikSCAT winds, the QuikSCAT winds and a wind-stress-curl term, and the NCEP winds. The results suggest that Ekman suction might facilitate subsequent vertical mixing while Ekman pumping might inhibit subsequent vertical mixing when the winds are generally weak and wind-stress-curl is moderate or strong. The temporal resolution of the QuikSCAT data set is too low to resolve inertial motions at high latitudes. The NCEP data set has higher temporal resolution and is adequate for running the model within this region. We propose interpolating the hourly NWS data collected at St. Paul Island (station PASN) to the QuikSCAT grid using the complex amplitudes and phases from the complex cross-correlations between the two data sets to produce a data set of high temporal and spatial resolution. This would enable researchers to accurately resolve inertial motions and compute wind-stress-curl.
    • A rapid assessment method to estimate the distribution of juvenile chinook salmon (Oncorhynchus tshawytscha) in an Interior Alaska river basin

      Matter, Allison N.; Falke, Jeffrey; Sutton, Trent; Savereide, James; Lopez, J. Andres (2016-08)
      Identification and protection of water bodies used by anadromous species in Alaska are critical in light of increasing threats to fish populations, yet challenging given budgetary and logistical limitations. Non-invasive, rapid assessment sampling techniques may reduce costs and effort while increasing species detection efficiencies. I used an intrinsic potential (IP) habitat model to identify high quality Chinook Salmon Oncorhynchus tshawytscha rearing habitats and select sites to sample throughout the Chena River basin for juvenile occupancy using environmental DNA (eDNA) and distribution within tributaries using snorkel surveys. Water samples were collected from 75 tributary sites in 2014 and 2015. The presence of Chinook Salmon DNA in water samples was assessed using a quantitative polymerase chain reaction (qPCR) assay targeting that species. Snorkel surveys were conducted and physical habitat was measured for a subset of tributaries examined with the eDNA approach. Juvenile salmon were counted within 50 m reaches starting at the tributary confluence and continuing upstream until no juvenile salmon were observed. The IP model predicted over 900 stream km in the basin to support high quality (IP ≥ 0.75) rearing habitat. Occupancy estimation based on eDNA samples indicated that 80.2% (± 4.3 SE) of previously unsampled sites classified as high IP and 56.4% of previously unsampled sites classified as low IP were occupied. The probability of detection of Chinook Salmon DNA from three replicate water samples was high (0.76 ± 1.9 SE) but varied with drainage area. A power analysis indicated power to detect proportional changes in occupancy based on parameter values estimated from eDNA occupancy models. Results of snorkel surveys showed that the upper extent of juvenile Chinook Salmon within tributaries was from 200 to 1,350 m upstream of tributary confluences. Occurrence estimates based on eDNA and snorkel surveys generally agreed, but care should be taken to ensure that little temporal gap exists between samples as juvenile salmon use of tributary habitats is likely often intermittent. Overall, the combination of IP habitat modeling, occupancy estimation based on eDNA, and snorkel surveys provided a useful, rapid-assessment method to predict and subsequently quantify the distribution of juvenile salmon in previously unsampled tributary habitats. These methods will provide tools for managers to rapidly and efficiently map critical rearing habitats and prioritize sampling efforts to expand the known distribution of juvenile salmon in interior Alaska streams.
    • Recruitment mechanisms of tanner crab in the eastern Bering Sea

      Richar, Jonathan; Kruse, Gordon; Mueter, Franz; Eckert, Ginny; Zheng, Jie (2014-08)
      Influences of biophysical conditions on survival of zoeal and early stages of eastern Bering Sea Tanner crab, Chionoecetes bairdi, were investigated using simple linear regression modeling, and a combination of hydrodynamic modeling and spatial and geostatistical methods. Linear regression analyses indicated that estimated reproductive female crab abundance, age 3-7 Pacific cod (Gadus macrocephalus) abundance and flathead sole (Hippoglossoides elassodon) total biomass were statistically related to estimates of recruitment to the 30-50 mm carapace width size interval of juvenile crab. Analysis of output from a Regional Ocean Modeling System simulation model indicated considerable capacity of the Bering Sea oceanography to retain zoeae at regional and local scales. Major transport patterns corresponded to long-term mean flows, with a northwesterly vector. Retention may be a significant recruitment process, particularly in Bristol Bay, which is effectively oceanographically isolated from other source regions of crab larvae. Periods during which conditions may have favored juvenile crab survival were observed at the model-estimated larval endpoints during the early 1980s and mid to late 1990s. While environmental conditions at model-estimated endpoints were highly variable, crab recruitment was positively correlated with endpoint locations either within the periphery of the cold pool, or outside of it, and SST >2° C after allowing for autocorrelation in the juvenile recruitment series. However, limitations of the model, gaps in knowledge of Tanner crab life history and ecology, and the possibility of spurious correlations complicate interpretation of these results.
    • Red King Crab Hatchery Culture And Ecological Requirements: Applications For Stock Enhancement

      Daly, Benjamin J.; Eckert, Ginny; Konar, Brenda; Kruse, Gordon; Stoner, Allan (2012)
      The ecologically and commercially important red king crab (Paralithodes camtschaticus) is depleted throughout much of the North Pacific and thought to be recruitment limited, making it an appropriate candidate for stock enhancement efforts. This research addresses bottlenecks associated with hatchery production and lays the groundwork for developing release strategies. I investigated effects of diet, stocking density, and size grading on survival, growth, and shell coloration of recently-settled juvenile red king crabs in large-scale hatchery experiments. I also conducted laboratory experiments with fish predators to determine if red king crab predator responses could be enhanced with experience. Finally, I tethered hatchery-cultured red king crabs of two sizes in the field for 24 h trials and used underwater video cameras to identify predators and predation susceptibility. In hatchery experiments, dietary astaxanthin supplementation improved survival and shell coloration suggesting that red king crab coloration is plastic and that astaxanthin may provide nutritional or immune system benefits. Size grading strongly influenced survival and growth in the hatchery. Generally, small crabs had higher survival than large and ungraded crabs, but large and ungraded crabs had higher growth, likely from cannibalism. In laboratory experiments, halibut exposure enhanced red king crab crypsis and survival suggesting that cryptic behavior is plastic and may be enhanced with experience. In the field experiment, I identified specific predators of recently-settled red king crabs in a nearshore habitat and showed that survival did not vary with body size or deployment month during the first juvenile instar stages. My research provides an important step for developing a responsible red king crab stock enhancement program by demonstrating that hatchery production can be improved with specific advances in rearing technology, hatchery-cultured red king crabs are morphologically and behaviorally plastic, hatchery-cultured red king crabs tethered in the field show no obvious behavioral deficiencies that may exacerbate predation, and that differences in predation susceptibility during the first juvenile instar stages are subtle and may be ecologically inconsequential for post-release survival. As bottlenecks in hatchery production and survival of released juveniles are overcome, stock enhancement will become increasingly feasible for red king crabs in Alaska.
    • Regional distribution, life history, and morphometry of spawning stage Capelin Mallotus villosus

      Ressel, Kirsten N.; Sutton, Trent M.; Bell, Jenefer L.; Seitz, Andrew C. (2019-12)
      Capelin Mallotus villosus is a forage fish that is integral to many Arctic and subarctic marine food webs, but is less thoroughly studied outside the Atlantic Ocean. The goal of this research was to study spawning Capelin in data-poor areas, particularly in waters off the coast of Alaska and the western Canadian Arctic, to enrich baseline data and allude to intraspecies diversity. Chapter one examined the distribution and life history of spawning Capelin in Norton Sound, Alaska, by conducting aerial surveys, collecting sediment samples to characterize beach spawning habitats, and identifying biological attributes of spawners (e.g., body size, age, fecundity, etc.). Chapter two used a geometric morphometric approach (i.e., relative warps) and multiple statistical techniques (i.e., relative warp analysis, Procrustes analysis of variance, estimates of morphological disparity, and canonical variates analysis) to differentiate among and within putative populations of spawning Capelin in the western Canadian Arctic, Newfoundland, Canada, and Alaska. Spawning Capelin in Norton Sound portrayed similar behaviors, occupied similar beach habitats, and encompassed a similar range in biological attributes as fish observed in other regions throughout this species' geographic distribution. However, average spawner body size, age, fecundity, and morphometry differed among regions. These results suggest that Capelin exhibit some similarities in spawning behavior and habitat use across their geographic distribution, but may exhibit population-specific differences in biological attributes among and within regions.
    • Regulation of ecdysteroid and vitellogenin levels during the molt and reproductive cycles of female dungeness crab, Cancer magister

      Thomton, Jamie David (2005-12)
      The reproductive cycle of Dungeness crabs is complicated by the requirement for molting prior to mating. The temporal requirements for molting and ovarian maturation may prohibit an annual reproductive cycle in a proportion of crabs. The goal of this study was to quantify temporal concentrations of circulating ecdysteroids and vitellogenins in female crabs during an annual cycle. Hemolymph in laboratory maintained crabs was sampled to assess physiological state (molting or reproduction). In laboratory crabs, ecdysteroid concentrations were low during intermolt (20.3 ng/ml), increased to maximal levels 15 days before ecdysis (1,886.5 ng/ml), and declined to low concentrations (<90 ng/ml) 5 days before ecdysis. Premolt duration was 150 days, with peak molting in November. Vitellogenin concentrations increased 6-fold during induced (via eyestalk ablation) ovarian maturation over a 90 ± 7.4 day vitellogenic period, and 4-fold for natural ovarian maturation over a 75 to 100 day period. The capability to predict ecdysis 150 days before molt and spawning 100 days before egg extrusion through hemolymph analysis is useful in molt and reproductive assessment of Dungeness crab populations. Additionally, in a preliminary study, reproductive failure and shell-disease were induced by physiological stress due to captive environmental conditions
    • The relationship between the depth to the 0°C isotherm of the Arctic Ocean and atmospheric forcing

      Moon, Sookmi (2004-05)
      Empirical Orthogonal Function (EOF) analyses of the depth to the 0°C isotherm of the Arctic Ocean were performed to determine the variability of the depth to the 0°C isotherm in the Arctic Ocean. The data are from the 'Environmental Working Group - Joint US. Russian Atlas of the Arctic Ocean.' The first three modes explain 99% of the total variance with each mode explaining 51 %, 26%, and 23%, respectively. Mode 1 shows the pattern of the outflow through Fram Strait and the Lincoln Sea. Mode 2 shows the variability of the inflow from the Barents Sea and the variability of the outflow through the Canadian Archipelago as well as the variability of the Transpolar Drift. Mode 2 has a close relationship with atmospheric conditions (Arctic Oscillation or North Atlantic Oscillation index). Mode 3 is significantly correlated with the annual mean vorticity index, when the vorticity index leads by 1 year. Composite analyses of the data using the AO, NAO, and vorticity index confirm that the EOF analyses of this study are valid. This study shows that the variability of the 0°C isotherm of the Arctic Ocean is significantly correlated with atmospheric conditions.
    • Relationships between anadromous lampreys and their host fishes in the eastern Bering Sea

      Siwicke, Kevin A.; Seitz, Andrew; Sutton, Trent; Murphy, James (2014-08)
      Arctic Lamprey Lethenteron camtschaticum and Pacific Lamprey Entosphenus tridentatus are ecologically and culturally important anadromous, parasitic species experiencing recent population declines in the North Pacific Ocean. However, a paucity of basic information on lampreys feeding in the ocean precludes an incorporation of the adult trophic phase into our understanding of lamprey population dynamics. The goal of this research was to provide insight into the marine life-history stage of Arctic and Pacific lampreys through lamprey-host interactions in the eastern Bering Sea. An analysis of two fishery-independent surveys conducted between 2002 and 2012 in the eastern Bering Sea revealed that Arctic Lampreys were captured in epipelagic waters of the inner and middle continental shelf and were associated with Pacific Herring Clupea pallasii and juvenile salmonids Oncorhynchus spp. In contrast, Pacific Lampreys were captured in benthic waters along the continental slope associated with bottom-oriented groundfish. Consistent with this analysis of fish assemblages, morphology of recently inflicted lamprey wounds observed on Pacific Cod Gadus macrocephalus was similar to morphology of Pacific Lamprey oral discs, but not that of Arctic Lamprey oral discs. Examination of 8,746 Pacific Cod, of which 4.9% had lamprey wounds, showed recent wounding rates positively increased with fish length up to 78 cm, and penetrating lamprey wounds were less likely to heal compared with superficial lamprey wounds, suggesting lamprey-related mortality. This study elucidates differences in the oceanic ecology between Arctic and Pacific lampreys and suggests a native lamprey can negatively impact hosts, which increases our understanding of lamprey ecology beyond traditional freshwater studies.
    • A remote sensing-GIS based approach for assessment of chinook salmon rearing habitat in the Unuk river floodplain

      Smikrud, Kathy M. (2007-05)
      Remote sensing offers an alternative method to managers in mapping and monitoring the habitat within large rivers. Large rivers are not accommodating for traditional (foot) fish habitat surveys due to their size and typically complex habitat. This study investigates the use of digital aerial photos and thermal infrared images acquired in spring 2003-2005 to map and quantify juvenile chinook salmon (Oncorhynchus tshawytscha) habitat in a 12-river km section of the Unuk River floodplain in Southeast Alaska. Images were processed and analyzed to produce a fluvial landscape classification (7 landcover classes with an overall classification accuracy of ~84%) using a combination of aerial and thermal images. Change detection of large woody debris (LWD) was also examined and revealed both quantitative and distributional changes during the 3 years. A GIS-based habitat suitability analysis was used to identify potential chinook salmon rearing habitats including: river channel edges, sloughs, braids, pools associated with LWD and primary river channels. Overall 77.82 hectares of potentially medium/high chinook rearing habitats were identified. Results from this study provide a promising foundation towards mapping and monitoring salmon habitat in large river systems for purposes of protection, conservation and monitoring to ensure sustainable stocks of salmon.
    • Reproductive and larval biology of northern shrimp, Pandalus borealis Kroyer, in relation to temperature

      Nunes, Pepsi (1984-05)
      The northern shrimp, Pandalus borealis Kr^yer, is an important fishery resource in Alaska. However, a drastic decline in the commercial catch since 1978 poses a serious problem for the fishery. This study examined the effects of temperature on reproduction and larval survival of P. borealis. These are factors though to be vital to the determination of year class strength. P. borealis was found to have narrow thermal requirements for egg production with moderate (6°C) to low (3°C) temperatures generally more favorable than high (9°C) temperatures. In contrast with egg production, larval survival was enhanced by higher (6 and 9°C) temperatures. This study provides useful information for management of the fishery by demonstrating that temperature can trigger flucuations in the commercial catch from 5-50% through its effects on rates or reproduction and larval survival, and thereby population size. In warm water areas averaging >6°C, temperature exerts its main influence on reproduction, causing fecundity to vary by as much as 50%. While in colder areas average <3°C, fecundity and larval survival can vary with temperature by as much as 20 and 40%, respectively. Use of the information derived here requires monitoring temperature in the major fishery areas to detect changes in abundance of ovigerous females, egg number and larval mortality. Changes in these parameters are valuable indicators of stock condition when combined with abundance surveys and fishing intensity estimates.
    • 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 cycle of the dungeness crab, Cancer magister, in Southeastern Alaska

      Swiney, Katherine Marie (1999-12)
      This study examined if female Dungeness crabs in Alaska reproduce annually. Crabs (287) were reared in flow-through tanks for one year and gonadosomatic indexes (GSI) and oocyte areas were calculated for seven months. Non-reproducing females had higher GSI and oocyte areas than reproducing females (<0.0001); resorption of gonads was observed. Male GSI varied significantly over the year. Crabs (27,506) were sampled with commercial pots and scuba in April and September in Glacier Bay, Alaska from 1992 to 1998. A large percentage (86%) of non-ovigerous females were observed in the spring when females should be brooding eggs. Molting probability is reduced as females become larger and they rely on stored sperm to fertilize eggs. A tagging study confirmed some females skip at least one mating season and extrude eggs in another season without ecdysis. This study demonstrated not all mature female Dungeness crabs in Alaska, especially larger females, reproduce annually.
    • 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.
    • Reproductive potential of female eastern Bering Sea tanner crab

      Knutson, Michael R.; Eckert, Ginny L.; Daly, Benjamin; Mueter, Franz; Webb, Joel (2020-05)
      Changes in abundance and sex ratio can contribute to variation in the reproductive potential of a population. The commercially important Bering Sea Tanner crab (Chionoecetes bairdi) are distributed throughout the north Pacific Ocean and display cyclical population dynamics. The goal of this study was to examine how fishing pressures and population dynamics affected the reproductive potential of Bering Sea Tanner crab to better inform sustainable fishery management. I quantified female stored sperm levels and fecundity for both primiparous (in their first reproductive cycle) and multiparous (in their second or later reproductive cycle) crab to examine spatial and temporal variation in reproductive potential. Multiparous female crab had higher spermathecal load than primiparous ones, but spermathecal load varied widely across female size. Higher sperm cell counts were associated with visual indication of fresh ejaculate for primiparous crab but not for multiparous crab. Sperm cell counts increased with increasing spermathecal load for both primiparous and multiparous crab, although the slope of the regression line varied for the two categories. Female fecundity was highest in crab in their second year after the terminal molt to maturity and was lower in the first year and in the third and subsequent years. Female fecundity (size-corrected) did not differ among management areas. Measures of mature female sperm storage and quantification of reproductive stage can provide fishery managers with an early warning of reproductive failures.
    • Reproductive Potential Of Pacific Cod (Gadus Macrocephalus) In Alaska

      Ormseth, Olav Aleksander; Norcross, Brenda L. (2007)
      The reproductive potential of female fishes, which results from the number of eggs they produce and the quality of individual eggs, is a critical factor in fisheries biology. Reproductive potential is important to individuals because maternal fitness is the product of the number of offspring produced and how many offspring survive. The growth rate of populations and their capacity for supporting commercial fisheries also depend on the number of viable offspring that females produce. I studied the reproductive potential of female Pacific cod (Gadus macrocephalus) in the North Pacific Ocean. Pacific cod is an important ecological and economic resource, yet much of its reproductive biology remains unexplored. I used several different approaches to investigate whether egg number or egg size are more important in determining reproductive potential, and to evaluate factors that influence reproduction. An analysis of life history variation among Pacific cod in Canada and Alaska demonstrated that despite differences in life history strategies, females from different populations had similar lifetime reproductive success (a proxy for individual fitness). I also collected Pacific cod in the Gulf of Alaska, eastern Bering Sea, and western Aleutian Islands from 2002 to 2005. Biochemical analyses of Pacific cod eggs revealed that Pacific cod produce low-energy eggs that are adapted for rapid development on the seafloor. Larger females produce eggs with less arachidonic acid (a fatty acid that has been linked to egg quality) than smaller females, suggesting that they may sacrifice egg quality to maintain fecundity. Determination of fecundity and egg size in 590 females from different areas and years revealed that maternal length and weight are excellent predictors of fecundity, but that variability in egg size is not related to the age or size of females, The greatest difference in reproductive potential among years and areas was reduced egg size in the eastern Bering Sea in 2003, which may have been due to changes in ocean temperature or prey availability that impacted the ability of females to store energy. These results suggest that female Pacific cod maximize their fitness through increased egg production, not egg quality, and that their reproductive success is under strong environmental control.
    • Reproductive potential of snow and tanner crab in Alaska

      Webb, Joel Benjamin; Kruse, Gordon; Eckert, Ginny; Woodby, Douglas; Sainte-Marie, Bernard (2014-12)
      Fisheries for snow (Chionoecetes opilio) and Tanner (C. bairdi) crab in Alaska are managed with large male only harvest regulations. Management of sex-selective crab fisheries could be enhanced by improved understanding of the functional relationship between male harvest and female reproductive potential. This research advances knowledge of factors associated with variation in reproductive potential by characterizing factors influencing female sperm reserves for Tanner crab, identifying factors associated with variability in fecundity for female snow crab in the eastern Bering Sea (EBS), and developing refined indices of egg (embryo) production and recruitment for snow crab that revealed a positive functional relationship that has not been previously described for this stock. Sperm reserves of female Tanner crab varied with mature female ontogeny, sex ratio, and harvest. Increasing exploitation rate is associated with decreased average sperm reserves of primipara (first reproductive cycle) while increased availability of large, sexually-dominant, adult males, was associated with increased cumulative sperm reserves for multipara (second or greater reproductive cycle) among Tanner crab stocks. A white-layer of fresh ejaculate in the spermathecae (sperm-storage organ) was a robust indicator of increased sperm reserves in both primiparous and multiparous females and is likely a useful tool for evaluating risk of sperm limitation in Chionoecetes. Fecundity of female snow crab in the EBS was influenced by both intrinsic and extrinsic factors. Fecundity increased with increasing female size and decreased for older multipara likely due to senescence. Variability in fecundity-at-size was higher among multipara than primipara and this may be associated with contrasting mating dynamics, tempo of reproduction, maternal age, or environmental influences on maternal condition. Mating success may also influence fecundity of multiparous females; females with fresh ejaculate had higher fecundity (~10%) than those that did not. Substantial embryo loss during brooding was not observed for snow crab, and embryo quality did not vary with female size or age relative to maturity. Refining indices of female reproductive potential with demographic and fecundity information resulted in reduced estimates of reproductive output. A positive functional relationship between reproductive potential and recruitment was detected at a lag of four years due to coherence between high reproductive output in the late 1980s and strong recruitment in the early 1990s. Stock productivity reached a minimum thereafter, preceding a rapid decline in mature abundance.
    • Resource competition, space use and forage ecology of sea otters, Enhydra lutris, in southern southeast Alaska

      Hoyt, Zachary N.; Eckert, Ginny; Siddon, Chris; Mueter, Franz; Tinker, M. Tim (2015-12)
      The growing sea otter population in southern Southeast Alaska is impacting commercial shellfish, through foraging and expanding in range and abundance except where hunted for subsistence. Sea otters and their prey have coexisted in the North Pacific Ocean for approximately 750,000 years, but due to exploitation of sea otters from the 1770s until 1911, the species became extinct over much of its range, including southern Southeast Alaska. Subsequently, invertebrate species flourished and were commercially targeted in the late 1900s. Sea otters were relocated (n = 106) to southern Southeast Alaska in 1968. In this dissertation, I evaluated this marine mammal-fisheries conflict through multiple approaches. In Chapter 1, I analyzed geoduck clam and red sea urchin abundance surveys (1994-2012) and catch and effort data from commercial Dungeness crab fisheries (1969-2010) to identify interactions between sea otters and commercial shellfish. In Chapter 2, I collected geo-locations from 30 instrumented sea otters (2011-2014) to identify space use and range expansion. In Chapter 3, I collected sea otter abundance and distribution data from fixed wing aircraft (2010-2014) and observational forage data from sea otters (2010-2013) to determine contemporary population growth and consumption of commercially important shellfish by sea otters. The sea otter population in southern Southeast Alaska has grown from 106 to an estimated 13,139 individuals between 1968 and 2011 with an annual growth rate of 12% and expansion of its range by 117 km2 y-1. Results from a before-after, control-impact analysis indicate that sea otters are rapidly impacting red sea urchin and significantly reducing geoduck clam densities. Further, breakpoints predicted from regression models of Dungeness crab catch are correlated with known sea otter colonization timing. Forty-six percent of the population level diet of sea otters represented commercially important prey. Sea otters targeted commercially important species, specifically red sea urchins and Dungeness crab, when first colonizing an area, after which the diet of sea otters became more diverse as colonization durations increased. Using habitat models based on a bivariate normal probability distribution function, environmental covariates and subsistence hunting pressure on sea otters, I determined that sea otter range expansion was limited by subsistence hunting. Further, female and non-territorial males segregated based on habitat and likely prey preferences. I conclude that sea otter populations will likely continue to grow, and that current shellfisheries cannot coexist with sea otters under existing management. Further, conservation and management of sea otter populations, whether to increase the distribution through translocation efforts or reduce the distribution to avoid human conflicts, could benefit from insights gained from spatially explicit modeling at the landscape level.
    • Resource Partitioning Among Sympatric Stellar Sea Lions And Northern Fur Seals On Lovushki Island, Russia

      Waite, Jason N.; Andrews, Russel; Castellini, Michael; Atkinson, Shannon; Rea, Lorrie; Trumble, Stephen (2010)
      The competitive exclusion principle maintains that one of two non-interbreeding species occupying the same ecological niche and geographical territory will be displaced if population growth is not the same between species. Steller sea lions (Eumetopias jubatus; SSL) and northern fur seals (Callorhinus ursinus; NFS) breed sympatrically on four rookeries in the Russian Far East, creating the potential for inter-specific competition for limited prey resources. Approximately 1,000 SSL and 14,000 NFS breed on Lovushki Island in the Kuril Island chain. An additional 13,000--14,000 juvenile NFS are present during the breeding season. The partitioning of forage resources among breeding SSL and both breeding and non-breeding NFS from 2003--2008 was examined through analysis of prey remains recovered from scats and spews, stable isotope (SI) analysis of vibrissae, fatty acid (FA) analysis of blubber, and analysis of foraging behavior through satellite-linked telemetry. Analysis of prey remains indicated a biologically significant overlap in the prey species and size selection of SSL and juvenile NFS and significant differences between the diets of SSL and breeding NFS. SSL fed primarily on Atka mackerel, while breeding NFS fed primarily on cephalopods and northern smoothtongue. SI analysis indicated significant differences in the trophic level and relative foraging location. SSL foraged at a higher trophic level, nearshore, and benthically, while NFS foraged at a lower trophic level, offshore, and pelagically. Analysis of FA signatures also suggested significant differences in the relative diets of breeding NFS and SSL. Foraging behavior analysis also indicated that SSL foraged nearshore and benthically and breeding NFS foraged offshore and pelagically. The combination of these four methodologies suggests breeding NFS and SSL partition their forage resources by prey type and prey size, as well as spatially. This partitioning of resources between breeding animals currently allows both species to coexist within the same geographical region and likely reflected the differences in foraging abilities and provisioning strategies of the adults, as well as the fasting abilities of their pups. However, continued growth of the non-breeding NFS population on Lovushki Island may lead to the competitive exclusion of SSL due to inter-specific competition for food resources.