Sablefish Anoplopoma Fimbria Research Articles

Establishment and characterization of novel spontaneously immortalized larval cell lines from sablefish Anoplopoma fimbria.

Sablefish Anoplopoma fimbria is a groundfish of the North PacificOceantypically found in sea floor habitat at depths to 2700m. Prized as a food fish with exceptionally high market value, sablefish aquaculture has been sought to provide a sustainable source of this fish to meet market demands. While commercial culture has successfully produced market-sized fish in Pacific coastal environments, production has been hampered by disease and the overall lack of information on sablefish health and immunology. To begin to address these knowledge gaps, herein we describe the isolation and characterization of spontaneously immortalized sablefish larval cell lines (AFL). Six sublines were established from pools of early yolk-sac larvae, while attempts to develop tissue-specific-derived cell lines were unsuccessful. The six yolk-sac larval cell lines each display two morphologies in culture, an elongated fibroblast-like cell type, and a rounded squamous or epithelial-like cell type. Cytogenetic characterization suggests that both cell types are diploid (2n = 48) with 24 pairs of chromosomes, 23 pairs of autosomes, and 1 pair of sex chromosomes. A small proportion (11%) of AFL cells display tetraploidy. Incubation temperature and medium composition experiments revealed HEPES buffered L-15 media containing 10-20% FBS at temperatures between 15 and 18° C yielded optimal cell growth. These growth characteristics suggest that sablefish larval cells display a robustness for varying growth conditions. The establishment of AFL cell lines provides a foundational tool to study the physiology, health, immunology, and cell and molecular biology of sablefish.

Automated species classification and counting by deep-sea mobile crawler platforms using YOLO

Edge computing on mobile marine platform is paramount for automated ecological monitoring. The goal of demonstrating the computational feasibility of an Artificial Intelligence (AI)-powered camera for fully automated real-time species-classification on deep-sea crawler platforms was searched by running You-Only-Look-Once (YOLO) model on an edge computing device (NVIDIA Jetson Nano), to evaluate the achievable animal detection performances, execution time and power consumption, using all the available cores. We processed a total of 337 rotating video scans (∼180°), taken during approximately 4 months in 2022 at the methane hydrates site of Barkley Canyon (Vancouver Island; BC; Canada), focusing on three abundant species (i.e., Sablefish Anoplopoma fimbria, Hagfish Eptatretus stoutii, and Rockfish Sebastes spp.). The model was trained on 1926 manually annotated video frames and showed high detection test performances in terms of accuracy (0.98), precision (0.98), and recall (0.99). The trained model was then applied on 337 videos.In 288 videos we detected a total of 133 Sablefish, 31 Hagfish, and 321 Rockfish nearly in real-time (about 0.31 s/image) with very low power consumption (0.34 J/image). Our results have broad implications on intelligent ecological monitoring. Indeed, YOLO model can meet operational-autonomy criteria for fast image processing with limited computational and energy loads.

Trends in predicted age at maturity of Sablefish from 22 years of surveys

AbstractObjectiveOur aim was to predict the maturity (will spawn or immature) of Sablefish Anoplopoma fimbria in Alaska for past years during a period when macroscopic data are not of utility and histological observations are not available.MethodsIn a previous study, female maturity was determined using histology and a model was developed that predicted maturity using maternal length, age, and relative condition. We used this published model to predict the maturity of individual Sablefish collected annually in the same area on the same dates. The maturity predictions were used to create predicted time series of maturity at age for surveys conducted over 22 years.ResultA k‐means cluster analysis of annual maturity parameters revealed that data should be split into two clusters. These groups were chronologically sequential (1998–2010 and 2011–2019), with two exceptions: 2015 and 2017 were assigned to the early time period. We created two chronological time blocks by incorporating the two outlier years into the late period post hoc, as we are not aware of mechanisms that may have caused these two outliers, and it is important for stock assessment to capture the signal and not the noise. Sablefish in the later period were predicted to mature later than fish in the earlier period; age at 50% maturity was 5.5 years in the early period and 6.8 years in the later period, and the slope was shallower in the later period.ConclusionThere are often gaps in reliable maturity data. This case study illustrates that limited histological data sets can be used to predict maturity in years without ovary samples and illustrates how these data can be grouped based on similarities and chronology for use in stock assessment. We recommend more histological studies in the future to test assumptions of the predictive model, and we recommend evaluations of other factors, such as environmental time series, that may be drivers of annual maturity.

Genetic analyses reveal a non-panmictic genetic structure in the sablefishAnoplopoma fimbriain the northern Pacific

AbstractThe sablefish Anoplopoma fimbria is distributed on the continental shelf of the North Pacific, has a high commercial value for both fisheries and aquaculture, and represents a shared resource between countries in the North Pacific basin. In the present study, we extend the geographic range surveyed in previous studies and reexamine the population’s genetic structure by integrating phylogeographic patterns of mitochondrial DNA and microsatellite DNA markers. Our results contradict the proposal that sablefish constitute a single population throughout their distributional range. We observed a signal of ancient divergence in mtDNA that differentiates the North Pacific West Coast from the rest of the sample sites, and microsatellite markers reveal a contemporary isolation of Mexican sablefish. Our findings show genetic differences between localities that should be explored in more detail to fully understand the interconnectedness that appears to exist between populations.

Sea-level index of recruitment variability improves assessment model performance for sablefish Anoplopoma fimbria

Environmental recruitment indices may improve the precision of stock assessments, allow hindcasting, and aid in near-term forecasting. We used Bayesian dynamic factor analysis (DFA) to find common trends in sea level from 16 tide gauges spanning the US West Coast. We then used these dynamic factors as predictors of sablefish Anoplopoma fimbria recruitment deviations from the 2021 assessment. We evaluated the ability of the resulting northern sea-level index (north of Cape Mendocino, ∼40°N) to inform recruitment estimates and its impacts on assessment model predictions by running two hindcast stock assessment models: (1) a catch-only model, which assumed average recruitment from the stock–recruit relationship, and (2) a catch plus sea-level model. In both cases, survey data were removed from 2011 forward. The model including sea-level index captured the observed increase in stock biomass from 2016 onwards, while the catch-only model did not, predicting a continued biomass decline. This work provides evidence of the potential to improve forward-looking stock projections by better capturing stock trends, providing an advance over average recruitment assumptions.

Advancing statistical models to reveal the effect of dissolved oxygen on the spatial distribution of marine taxa using thresholds and a physiologically based index

The rapid pace of ocean change has prompted a need to forecast likely future species distributions. Species distribution models are often categorized as either correlative (statistical) or mechanistic, and each has limitations both for advancing understanding and for prediction. Here we sought to benefit from mechanistic understanding of how and why low dissolved oxygen affects species' distributions by applying physiologically informed statistical models to the spatial distribution of sablefish Anoplopoma fimbria, a deep‐dwelling commercially important groundfish. We fit spatial models to trawl‐survey data on catch rate, local temperature and dissolved oxygen, and estimated parameters of the metabolic index, which provided a way to express the temperature‐dependence of oxygen tolerance. We fit generalized linear mixed effects models with Gaussian random fields to capture the latent spatially fixed variables, and included both linear and breakpoint functions for pO2 and the metabolic index. The best fitting models all included breakpoint effects of pO2, and the estimated threshold value of 0.05 atm is close to levels in laboratory studies where metabolism begins to decline. Models based on the metabolic index were not as well supported as those that included pO2, likely because of the decrease in temperature and slight increase in pO2 at deep (> 800 m) depths. These findings illustrate that statistical models of species distributions can be improved by incorporating knowledge of how physiological mechanisms operate. Furthermore, they illustrate that even species with high tolerance for low dissolved oxygen may undergo species distribution shifts in the face of growing oxygen depletion in coastal ocean ecosystems.

Long-term dynamics for stocks of sablefish Anoplopoma fimbria in the western Bering Sea and prospects for their fishery

Sablefish is an endemic species of the North Pacific. Its range extends from California Peninsula, along the Pacific coast of the US and Canada to Aleutian Islands and further, along the Pacific coast of Kamchatka and the Kuriles to the central part of Honshu Island. They dwell also in the Bering Sea and southeastern Okhotsk Sea. Sablefish are the most abundant in the southeastern Bering Sea and in the Gulf of Alaska, that is conditioned by favorable conditions for their larvae and juveniles. In the Asian part of the range, the environments are generally more severe, and reproduction of sablefish is rather risky. Following to the results of modern genetic studies, the sablefish stocks are distinguished by high genetic homogeneity that suggests a common population with the main spawning grounds in the southeastern Bering Sea, at the Pacific coasts of Aleutian Islands, in the Gulf of Alaska, and at the coasts of British Columbia, Washington, Oregon and California. Dynamics of the sablefish biomass is considered on the data of bottom and midwater trawl surveys conducted by TINRO in 2003–2020, fishery statistics, and accessible data of NOAA (USA). Sharp increasing of the biomass and annual catches is noted both in the eastern and western Bering Sea in the last few years because of appearance of several strong year-classes. Western Bering Sea stock depends on migration of recruits from the common spawning grounds in the southeastern Bering Sea. For the western Bering Sea, two main ways of such migration are possible: i) active migration of juveniles with benthic habitat; and ii) passive transfer of pelagic larvae and early juveniles across the Bering Sea through the system of surface currents. The latter mechanism supports the sablefish recruitment in the bays of the western Bering Sea and, to a lesser extent, at the eastern coast of Kamchatka. Sablefish in the West Bering Sea fishery zone were caught in 2010–2020 mostly as by-catch for trawling and longline fishery (93 %), other 7 % were landed by specialized longline fishery. The basic points for managing the sablefish fishery in the West Bering Sea zone are defined. About 400 t of sablefish is permissible to catch annually in the West Bering Sea fishery zone in conditions of modern high stock of this species. This value includes 100–120 t that will inevitably be caught as by-catch and the rest of 280–300 t is a foreseeable resource for organization of specialized fishery.

Temporal and Age‐Based Variation in Juvenile Sablefish Diet Composition and Quality: Inferences from Stomach Contents and Stable Isotopes

AbstractPrey communities in the North Pacific Ocean have been disrupted by marine heatwaves, and reductions in forage fishes have had notable impacts on upper‐trophic‐level consumers. Little is known about the potential effects of a changing prey base for some commercially valuable fishes, such as Sablefish Anoplopoma fimbria. The objectives of this study were to evaluate temporal and age‐based shifts in diets of juvenile Sablefish, with a focus on understanding their reliance on high‐quality forage fishes. We collected Sablefish from a bay in Southeast Alaska over 2 years (2017–2019) during their first autumn (September–October; age 0), in late winter (March; age 1), and during their second summer (July; age 1). Pacific Herring Clupea pallasii constituted the majority of the Sablefish diet by weight (82.1%) and by frequency of occurrence (40.7%), with variation among months, years, and age‐classes. Stable isotopes corroborated our interpretation of diet composition from stomach contents and indicated that age‐0 Sablefish sampled in October 2017 relied on more depleted carbon sources than other groups, potentially explained by consumption of adult salmon carcasses. Significant relationships between stable isotope ratios and Sablefish length indicated that size‐based diet composition differences were most prevalent during March and July. Sablefish exploited prey taxa of variable quality (0.02–5.3 kJ/g), but mean energy density of consumed prey differed little among years or months (3.62–4.48 kJ/g). Overall, 21% of stomachs sampled were empty, with the percentage of empty stomachs peaking in late winter (46%). Stomach content weights expressed as a percentage of body weight were highest in autumn 2018, when Pacific Herring comprised over 80% of the diets by weight. Consumption of high‐energy prey, such as Pacific Herring, may contribute to rapid growth of Sablefish during the critical prewinter period. If strong Sablefish year‐classes become more frequent with a warming ocean, they will require substantial prey resources to support their growth to adulthood.

First winter energy allocation in juvenile sablefish Anoplopoma fimbria, a fast growing marine piscivore

Understanding how energy allocation changes with ontogeny can provide insights about survival bottlenecks during early life stages for marine fishes. Energy allocation in juvenile fish before and during their critical first winter differs among species based on life history and foraging characteristics. To improve understanding of energy-size relationships in marine fish, we examined seasonal energy allocation in sablefish Anoplopoma fimbria, a species with unusually fast growth rates during early life. We assessed seasonal metrics of growth and energy storage in sablefish during their first 2 yr using field collections from 2016-2019. Based on growth rates estimated from length-frequency distributions, sablefish increased rapidly in size during autumn, and growth continued but slowed through their first winter as newly settled young-of-the-year. Mean energy density (ED, kJ g-1) declined over the winter, but total energy (TE, kJ ind.-1) increased significantly between October and March, reflecting positive overwinter growth. Relationships between energy storage and length were atypical for high-latitude marine fish in that they were steepest in March, indicating that relatively large fish grew during winter with minimal energy depletion, whereas relatively small fish grew but depleted their energy stores. We propose that improved foraging success for large fish may explain this pattern. Our results suggest that sablefish benefit from achieving large sizes prior to winter and support the hypothesis that the first winter can be a survival bottleneck for sablefish. This work informs our understanding of piscivore energy allocation during early life history and our understanding of possible sablefish recruitment drivers.

Adaptive Behaviors to Marine Ecosystem Shifts: Examining Fishermen’s Strategies in Response to Abundant Juvenile Sablefish (Anoplopoma fimbria) in Alaska

Over recent years there have been rapid changes occurring across marine ecosystems worldwide, with high latitude systems seeing ecosystem shifts emerging at unprecedented rates. The Gulf of Alaska and Bering Sea marine ecosystems have experienced substantial fluctuation in fish stocks, with some species experiencing considerable decreases while others thrive. Following the marine heatwave of 2014, sablefish (Anoplopoma fimbria) had a historically unparalleled juvenile recruitment class that is now dominating the stock composition. While this recruitment class bodes well for future fisheries, it is currently undermining the value of the fishery with limited incentives to retain the smaller and less valuable fish, compounding adverse effects on earnings in the fishery due to whale depredation that has been occurring for years. This study examines the well-being implications of fishermen’s adaptive strategies to these ecosystem conditions within the Alaska sablefish fishery using a socio-ecological system framework, operationalized as a qualitative network model (QNMs) and quantitative indicators. We examine the extent to which adaptation strategies, derived from a literature review and stakeholder interviews, are being utilized in the fishery with quantitative indicators. These strategies are then examined with QNMs that explore their impacts across the spectrum of well-being. By coupling quantitative indicators and QNMs, we were able to demonstrate how adaptive strategies can be examined to capture the multi-faceted well-being effects of fisheries participants’ adaptations to changing conditions. This study directly addresses several of the key guiding principles of the U.S. EBFM Road Map, including advancing our understanding of ecosystem processes, exploring trade-offs within an ecosystem, and maintaining resilient ecosystems, inclusive of community well-being. Thus this paper demonstrates how coupled socio-ecological models can elevate the inclusion of human adaptive behaviors, providing a framework for the development of policymaking that can mitigate adverse effects on both the participants and the resource by facilitating the mixture of adaptive strategies that maximizes desired well-being outcomes.

Spatio-temporal patterns in juvenile habitat for 13 groundfishes in the California Current Ecosystem.

Identifying juvenile habitats is critical for understanding a species’ ecology and for focusing spatial fishery management by defining references like essential fish habitat (EFH). Here, we used vector autoregressive spatio-temporal models (VAST) to delineate spatial and temporal patterns in juvenile density for 13 commercially important species of groundfishes off the US west coast. In particular, we identified hotspots with high juvenile density. Three qualitative patterns of distribution and abundance emerged. First, Dover sole Microstomus pacificus, Pacific grenadier Coryphaenoides acrolepis, shortspine thornyhead Sebastolobus alascanus, and splitnose rockfish Sebastes diploproa had distinct, spatially-limited hotspots that were spatially consistent through time. Next, Pacific hake Merluccius productus and darkblotched rockfish Sebastes crameri had distinct, spatially limited hotspots, but the location of these hotspots varied through time. Finally, arrowtooth flounder Atheresthes stomias, English sole Parophrys vetulus, sablefish Anoplopoma fimbria, Pacific grenadier Coryphaenoides acrolepis, lingcod Ophiodon elongatus, longspine thornyhead Sebastolobus altivelis, petrale sole Eopsetta jordani, and Pacific sanddab Citharichthys sordidus had large hotspots that spanned a broad latitudinal range. These habitats represent potential, if not likely, nursery areas, the location of which will inform spatial management.

Addition of the red macroalgae Turkish Towel Chondracanthus exasperates and taurine improves the performance of alternative plant‐based feeds for juvenile sablefish Anoplopoma fimbria

Turkish Towel Chondracanthus exasperates and taurine were added to alternative plant-based feeds for juvenile sablefish Anoplopoma fimbria to evaluate the effect of these ingredients, alone or combined, on fish growth, feed intake and efficiency, whole body nutrient composition, and liver histomorphology. Fish growth was significantly increased with the addition of taurine, and to a lesser extent, Turkish Towel to the experimental feeds. Feed efficiency and protein retention were significantly improved with the addition of taurine, but were unaffected by Turkish Towel addition. As expected, whole body taurine content was significantly affected by taurine addition. Increases in whole body lipid were observed with both taurine and Turkish Towel addition, with a significant interaction between the two factors. Liver histomorphology was generally normal; however, histopathologic changes were observed in some fish at the end of the experiment. The occurrence of hepatocellular nuclear pleomorphism and clear cell foci was less among fish that had received the Turkish Towel feeds. The addition of taurine had no effect on the number of fish with a histopathologic change. Overall, results from this study reaffirm taurine supplementation is beneficial to sablefish receiving plant-based feeds and indicate Turkish Towel may be a promising feed ingredient for this species.

Evolutionary history told by mitochondrial markers of large teleost deep-sea predators of family Anoplopomatidae Jordan & Gilbert 1883, endemic to the North Pacific

AbstractWe propose three calibration scenarios of to date contemporary divergence of Anoplopomatidae (skilfish Erilepis zonifer and sablefish Anoplopoma fimbria) for a data set of two mtDNA loci (СOI and Control Region). The first scenario is based upon a fossil record and the second and third ones upon major palaeogeological events 3.5 and 15 Mya. Estimated evolution speeds indicate that COI evolves faster in the skilfish mitochondrial genome. There is also evidence of skilfish going through a bottleneck event limiting its genetic diversity in the relatively recent past near Japan. Sablefish had two refugia on both sides of the Pacific Ocean. The contemporary haplotype divergence was formed ~450 thousand years ago during an ice age in the Pleistocene and contemporary populations display no apparent geographic differentiation.

Establishing genome sizes of focal fishery and aquaculture species along Baja California, Mexico

Genome size—the total haploid content of nuclear DNA— is constant in all cells in individuals within a species, but differs among species. Consequently, the genome size is a quantifiable genetic signature that not only characterizes a species, but it can reflect chromatin modifications, which play fundamental roles in most biological processes that are involved in the manipulation and expression of DNA. This characteristic makes the genome size a crucial parameter for genetic research on endemic aquatic species and for genetic manipulations in aquaculture species. Technologies for genetic assessments and improvements applied to fishery and aquaculture species use genome size values as a means by which hybrids, polyploids, and sex can be identified, when sex chromosomes exist. The objectives of this study were to determine genome sizes of aquatic species with economic and biological importance along the Pacific coast of Mexico, as well as to identify the appropriate reference standards for use in this study. Blood, hemolymph or milt were collected from 10 species occurring along the coast of Baja California: Sablefish Anoplopoma fimbria, Black Snapper Lutjanus novemfasciatus, California Halibut Paralichthys californicus, Pacific Sardine Sardinops sagax, Flag Rockfish Sebastes rubrivinctus, Starry Rockfish Sebastes constellatus, Totoaba Totoaba macdonaldi, Whiteleg Shrimp Litopenaeus vannamei and two Yellowtail Seriola lalandi and S. dorsalis. Nuclear DNA was stained with propidium iodide solution and the genome size was determined by flow cytometry, with results ranging from 0.61 pg (1.22 pg/diploid cell) to 2.59 pg (5.18 pg/diploid cell), with the smallest value in Sablefish and the largest in the Whiteleg Shrimp. No significant differences were detected (P ≤ 0.05) among individuals of the same species; the likely reason behind any dissimilar DNA content values with those from the literature were differences in methodologies or variations in genetics. Red-ear Slider Turtle Trachemys scripta elegans 2.65 pg (5.30 pg/diploid cell) and Red Junglefowl Gallus gallus 1.27 pg (2.54 pg/diploid cell) were chosen as the standards for reference values. These results establish the basis for the Mexican National Aquatic Genetic Resources project supporting genetic improvements for aquaculture and conservation status parameters for fisheries species.

Changes in Hematological Parameters and Heat Shock Proteins in Juvenile Sablefish Depending on Water Temperature Stress.

Juvenile Sablefish Anoplopoma fimbria were used to assess the effects of water temperature (8, 10, 12, 14, 16, 18, and 20°C) on hematological parameters and heat shock proteins 70 and 90 for 4months. Hematological parameters, including red blood cell count, hematocrit, and hemoglobin, were significantly decreased at 18°C. The inorganic plasma components calcium and magnesium were not altered by water temperature. The organic plasma components glucose and cholesterol were notably elevated at 18°C, whereas total protein was reduced. The enzymatic components, including aspartate aminotransferase, alanine aminotransaminase, and alkaline phosphatase, were notably elevated at 16°C or 18°C. The results of this study indicate that a temperature higher than the proper temperature affects the hematological parameters and heat shock proteins of juvenile Sablefish.

A Comparison of Methods for Classifying Female Sablefish Maturity and Skip Spawning Outside the Spawning Season

AbstractOvarian development in Sablefish Anoplopoma fimbria was classified using three methods for samples collected during July and August in the Gulf of Alaska, approximately 6–8 months prior to spawning. Although not an ideal time for predicting future spawning, this is when survey platforms, such as longline and trawl vessels, are available annually. The three maturity classification methods included (1) macroscopic classification at sea by trained scientists but with these personnel varying throughout the survey period, (2) macroscopic classification after the survey from photographs by a single, highly trained scientist (standardized macroscopic), and (3) a microscopic evaluation of ovarian structures from histological slides. Based on certain oocyte development characteristics, the second half of August was identified as the time period when maturity could be the most accurately classified in the Gulf of Alaska. Age and length at maturity were estimated to be earlier or smaller, respectively, on some portions of the survey, when macroscopic at‐sea methods were used as opposed to standardized macroscopic or microscopic methods. Skip spawning was documented throughout the survey but at a lower rate than was reported in other studies (2% versus 6% and 21%), indicating that the rate of skip spawning is likely variable. The results demonstrate that accurate maturity classifications may be determined from collections during nonpreferable months when histology or the standardized macroscopic method is used. Identifying skip spawning is likely reliant on microscopic analysis, and so a combination of the standardized macroscopic method along with limited histological sampling, to identify skip spawning rates or to classify maturity when there is uncertainty at sea, may be the most time‐ and cost‐effective option for species similar to Sablefish that skip spawn.

Temperature-dependent growth and consumption of young-of-the-year sablefish Anoplopoma fimbria: Too hot, too cold or just right?

Sablefish Anoplopoma fimbria are a highly valued, economically important groundfish in Alaska; however, estimated stock biomass has been in steady decline since the early 1990s, likely as a result of poor recruitment. Among several factors found to impact recruitment strength, ocean temperature often has been to affect early-life condition. Despite the importance of early-life condition in predicting cohort success, few studies have examined the thermal response of young-of-the-year (YOY) sablefish in regards to growth and development, and those focus on only a narrow size range. In this study, we measured the effects of temperature on growth and consumption rates of YOY sablefish (218–289 mm TL) in laboratory trials with fish held over 5 temperature treatments (5 °C, 8 °C, 12 °C, 16 °C and 20 °C) and maintained on ad libitum ration for 3 weeks. We compared growth, consumption, and body condition of fish between treatments. Specific growth rate (SGR; % wet weight gain (g) d−1) was used to derive a temperature-dependent growth model, and consumption rates were used to calculate species-specific parameters for the consumption function of a Wisconsin-type bioenergetics model. Daily growth in length varied from 0.13 mm d−1 to 1.74 mm d−1 and SGR ranged from 0.52 to 2.31. SGR peaked at 15.4 °C, remained high at 12 °C and 16 °C, and steadily declined as temperatures shifted outside this range. Residuals of length-weight regressions were positive at 12 °C and 16 °C, and negative at 5 °C, 8 °C, and 20 °C. Consumption rose sharply with temperature, peaking at 17.6 °C. The narrow thermal range facilitating higher than average condition and optimal SGR indicates that YOY sablefish growth and development may be dramatically influenced by relatively small shifts in water temperatures. Further, when compared to similar studies of smaller-sized sablefish, we observed a shift with size in thermal performance, with larger fish performing better at colder temperatures compared to smaller fish. The shift in thermal performance with size is an important consideration for understanding the result of environmental perturbation on recruitment. While traditional recruitment models rely heavily on information from a single life-stage, resource use and physiological requirements often change with development. Given the widespread occurrence of anomalous thermal events in the Gulf of Alaska, a life-stage specific understanding of the effects of varying temperatures is crucial.

Movement Patterns of Juvenile Sablefish within a Nursery Area in Southeast Alaska

AbstractThe Sablefish Anoplopoma fimbria is a commercially important species that inhabits waters of the Pacific Ocean from Baja California, Mexico, to the Bering Sea, Alaska. Most studies have focused on the larval, neustonic (near‐surface) juvenile, or adult stage of the Sablefish life cycle, while much less is known about the postsettlement juvenile stage (ages 0–2) in nearshore nursery areas, even though survival of postsettlement juveniles is thought to be important for determining year‐class strength. We used acoustic telemetry to monitor movement of postsettlement juvenile Sablefish in a nursery area in Alaska to better describe their period of nearshore residency. Forty juvenile Sablefish received surgically implanted acoustic transmitters and were monitored using eight fixed receivers throughout the summer and fall of 2015 and 2016 in a small bay (St. John Baptist Bay) in Southeast Alaska. We quantified movement patterns in terms of displacement from the head of the bay, distance traveled, and duration of time spent within the bay for 28 individuals. Sablefish showed fidelity to the bay during the summer, with relatively high rates of movement within the bay. Juvenile Sablefish traveled 9.4 km/d and spent 20.2 h/d within the bay on average in 2015 and traveled 13.0 km/d and spent 17.9 h/d within the bay on average in 2016. Tagged Sablefish showed the greatest affinity for a region near the head of the bay, perhaps indicating an area of preferred habitat, prey resources, or environmental conditions. In addition, we assessed variation in horizontal movements among individuals and identified three distinct movement types. This study fills a gap in knowledge of Sablefish early life history by characterizing movement during nearshore residency before out‐migration into deeper waters. Our results reinforce the importance of nearshore habitats like St. John Baptist Bay for juvenile Sablefish prior to recruitment into fisheries.

Preliminary observations of the skeletal development in pre-flexion larvae of sablefish Anoplopoma fimbria

Sablefish Anoplopoma fimbria support a lucrative fishery in the Gulf of Alaska, but their numbers have been declining despite a regulated fishery. Recruitment in A. fimbria is poorly understood due to its unusual early life history relative to many other deep-water fishes. Developmental patterns can identify critical periods during ontogeny that influence foraging and swimming abilities among individual larvae. External development in A. fimbria has been described, but the data presented here are the first examination of the skeletal development of A. fimbria during the transition to first feeding.

Oceanographic drivers of sablefish recruitment in the California Current

AbstractOceanographic processes and ecological interactions can strongly influence recruitment success in marine fishes. Here, we develop an environmental index of sablefish recruitment with the goal of elucidating recruitment‐environment relationships and informing stock assessment. We start with a conceptual life‐history model for sablefish Anoplopoma fimbria on the US west coast to generate stage‐ and spatio‐temporally‐specific hypotheses regarding the oceanographic and biological variables likely influencing sablefish recruitment. Our model includes seven stages from pre‐spawn female condition through benthic recruitment (age‐0 fish) for the northern portion of the west coast U.S. sablefish stock (40°N–50°N). We then fit linear models and use model comparison to select predictors. We use residuals from the stock‐recruitment relationship in the 2015 sablefish assessment as the dependent variable (thus removing the effect of spawning stock biomass). Predictor variables were drawn primarily from ROMS model outputs for the California Current Ecosystem. We also include indices of prey and predator abundance and freshwater input. Five variables explained 57% of the variation in recruitment not accounted for by the stock‐recruitment relationship in the sablefish assessment. Recruitment deviations were positively correlated with (i) colder conditions during the spawner preconditioning period, (ii) warmer water temperatures during the egg stage, (iii) stronger cross‐shelf transport to near‐shore nursery habitats during the egg stage, (iv) stronger long‐shore transport to the north during the yolk‐sac stage, and (v) cold surface water temperatures during the larval stage. This result suggests that multiple mechanisms likely affect sablefish recruitment at different points in their life history.