Dungeness Crab Cancer Magister Research Articles

Spatial and Temporal Characteristics of California Commercial Fisheries from 2005 to 2019 and Potential Overlap with Offshore Wind Energy Development

AbstractAs climate change accelerates and fisheries management continues to evolve, California's commercial fisheries are changing. To improve the understanding of recent California fisheries dynamics, we compiled and analyzed commercial landings receipts to characterize temporal and spatial variation in landing and value of key fisheries groups within the exclusive economic zone across the state from 2005 to 2019. We found that California fisheries continue a shift first observed in the 1980s from higher‐biomass, lower‐value species, such as coastal pelagic species and market squid, toward lower‐biomass, higher‐value species, such as Dungeness crab Cancer magister and groundfish. Over the 15‐year time series analyzed, total landings declined by nearly two‐thirds but total value remained relatively stable, likely due to a focus on higher value species and rising prices. The northern half of the state has become much more economically valuable, accounting for over 50% of total value across the state in 2019. A case study analysis found groundfish to be the dominant fisheries in the two areas that have been identified as priorities for potential offshore wind development in central and northern California. Our results elucidate the most recent status and trends of California's commercial fisheries, over time, across space, and among different fisheries groups, providing valuable information for informing fisheries management and marine spatial planning.

Assessing commercial fishery bait in Dungeness crab Cancer magister feeding ecology: δ13C and δ15N stable isotope and gut content analysis

Dungeness crabsCancer magistersupport the largest fishery in Oregon (USA), which inputs millions of pounds of bait into the coastal ocean every year. We assessed evidence for seasonal consumption of commercial Dungeness crab fishery bait off the Oregon coast by that target species through δ13C and δ15N stable isotope and gut content analysis. Using Dungeness crab samples collected on the Oregon inner to mid-continental shelf, variation in δ13C and δ15N values were assessed according to sex, size class, region, and season using nested ANOVA, Euclidean vector statistics, and Bayesian standard ellipse areas corrected for sample size (SEAc) in R. The isotopic signatures of sampled crabs showed statistically significant variation by sex, region, and season; the differences in the isotopic niches of large male versus female crabs (carapace width ≥159 mm) were especially pronounced. δ15N in female crabs peaked in spring and declined toward fall with similar mean δ13C, which could be indicative of higher trophic level bait consumption in the winter when the fishery is the most active, while δ13C varied seasonally in males with similar mean δ15N. The approximated trophic niches (based on SEAc) of both male and female crabs were greatest in fall, suggesting broader foraging in the absence of bait inputs. This work provides a step towards understanding the ecological role of fishery activities on one of the most economically valuable species on the US west coast.

A decade of modeled dispersal of Dungeness crab Cancer magister larvae in the California Current

Marine populations are often typified by large annual variations in the number of larvae that return to the adult population. The Dungeness crab Cancer (Metacarcinus) magister is an important economic and ecological species along the western seaboard of the continental USA. Research suggests larval returns of Dungeness crabs vary annually by a factor of 1000, strongly influencing the population dynamics of the species. To understand how hydrographic conditions affect population dynamics, a light trap in Coos Bay, Oregon, was monitored daily during the recruitment season (April to September) from 1997 to 2001 and from 2006 to the present. Using an individual-based biophysical model, we tested the hypothesis that more Dungeness crab larvae recruit during negative-phase Pacific Decadal Oscillation (PDO). The model uses the Regional Oceanic Modeling System to simulate circulation in the California Current and an offline Lagrangian particle-tracking algorithm (Larval TRANSport Lagrangian Model, LTRANS) to model larval dispersal. We validated our model by comparing the model data to the light trap data. Our findings support the hypothesis that more megalopae (pelagic postlarvae) recruit during the negative phase of the PDO. In addition, megalopae appear to spend longer in the water column during positive-phase PDO as a result of faster development rates likely due to warmer seawater temperature. Lastly, our model suggests that the population experiences more self-recruitment than previously thought, albeit not to an extent to suggest there are multiple metapopulations.

Do Gray Whales Count Calories? Comparing Energetic Values of Gray Whale Prey Across Two Different Feeding Grounds in the Eastern North Pacific

Predators must consume enough prey to support costly events, such as reproduction. Meeting high energetic requirements is particularly challenging for migrating baleen whales as their feeding seasons are typically restricted to a limited temporal window and marine prey are notoriously patchy. We assessed the energetic value of the six most common nearshore zooplankton species collected within the Oregon, United States range of the Pacific Coast Feeding Group (PCFG) gray whale (Eschrichtius robustus) feeding grounds, and compared these results to the energetic value of the predominant amphipod species fed on by Eastern North Pacific (ENP) gray whales in the Arctic. Energetic values of Oregon zooplankton differed significantly between species (Kruskal–Wallis χ2= 123.38, df = 5,p< 0.0001), with Dungeness crab (Cancer magister) megalopae displaying the highest mean caloric content of all tested species (4.21 ± 1.27 kJ g– 1). This value, as well as the mean energetic value of the mysidNeomysis rayii(2.42 ± 1.06 kJ g– 1), are higher than the mean caloric content ofAmpelisca macrocephala, the predominant Arctic amphipod. Extrapolations of these results to daily energetic requirements of gray whales indicate that lactating and pregnant gray whales feeding in the PCFG range would require between 0.7–1.03 and 0.22–0.33 metric tons of prey less per day if they fed on Dungeness crab megalopae orN. rayii, respectively, than a whale feeding onA. macrocephalain the Arctic. Yet, these results do not account for differences in availability of these prey species to foraging gray whales. We therefore suggest that other factors, such as prey density, energetic costs of feeding, or natal philopatry and foraging site fidelity play a role in the differences in population sizes between the PCFG and ENP gray whales. Climate change is implicated in causing reduced body condition and increased mortality of both PCFG and ENP gray whales due to decreased prey availability and abundance. Therefore, improved understanding of prey dynamics in response to environmental variability in both regions is critical.

Benthic video landers reveal impacts of dredged sediment deposition events on mobile epifauna are acute but transitory

The “beneficial uses” of dredged sediment are increasingly being explored for habitat restoration and beach nourishment, but beneficial uses must be tempered by evaluating impacts to organisms. We studied a subtidal nearshore deposition site intended to aid beach nourishment where a “thin-layer” sediment deployment method was employed to minimize mounding and disperse sediment within a proscribed area. Baited benthic video landers (BVLs) in a Before-After Control-Impact (BACI) experimental design were used to test the acute effects (within one hour of deposition) of sediment deposition on dominant epifaunal Dungeness crab (Cancer magister) and dog whelk (Nucella spp). The effects of sediment deposition depths and the lateral surge (the turbidity front transiting the seafloor) were both considered. Observations revealed sedimentation levels were limited to <4 cm and burial likely posed no direct threat to epifauna. However, video and instrument measurements showed the lateral surge to impact the BVLs as a 1 to 3 m/s sediment-laden front. Crabs were significantly impacted, while gastropods were more resistant to dislodgment. However, the high velocity impact was relatively brief (2 to 7 min). Further, crabs returned to forage at BVLs after a mean lag of about 20 min post-impact. These results indicate an acute but ephemeral impact effect on crab, and support use of the thin-layer deposition method to minimize burial. Our novel use of BVLs in a BACI experimental design were an effective means of evaluating sediment impacts to targeted mobile epifaunal species, and video observations were informative for understanding lateral surge dynamics and the behavioral interactions of organisms.

Examining the potential conflict between sea otter recovery and Dungeness crab fisheries in California

Human exploitation of marine mammals led to precipitous declines in many wild populations within the last three centuries. Legal protections enacted throughout the 20th century have enabled the recovery of many of these species and some recoveries have resulted in conflict with humans for shared resources. With legal protections and reintroduction programs, the southern sea otter (Enhydra lutris nereis) has returned to portions of its former range from which it had been extirpated for decades, causing concern that the Dungeness crab (Cancer magister) fishery could be negatively affected by increasing otter range and population size. The Dungeness crab fishery is one of the most valuable in California, and these crabs are a known prey item of sea otters. We examine sea otter population growth by port region in relation to Dungeness crab catch using landing receipts since the early 1980s. We find Dungeness crab landings and fishing success, as measured by landings per trip receipt, increased across all ports. In the most recent decade, we observed slower growth in fishing success in northern ports where otters were absent, relative to southern ports where sea otters exist and their populations have grown. In ports where otters were present, fishing success was positively correlated with otter population size over time. Further, an extensive dataset of 83,000 sea otter foraging dives identified Dungeness crab to be less than 2% of the total diet. Though we find no evidence that sea otter populations impact the Dungeness crab fishery in California, other potential conflicts could be considered before expanding reintroduction programs.

Fine-scale spatial and temporal genomic variation among Dungeness crab Cancer magister larval recruits in the California Current Ecosystem

Dynamic marine environments can shape complex spatial and temporal patterns in the population connectivity of marine species, and this is often exemplified in species with long larval phases. Here, we used a genotyping-by-sequencing (GBS) approach to examine fine-scale spatial and temporal genomic variation among Dungeness crabCancer magisterlarval recruits sampled in the California Current Ecosystem. Specifically, we compared samples collected during expected- and late-season recruitment time periods within 2 consecutive years (2017 and 2018) at 2 sites in Oregon, USA (Yaquina Bay and Coos Bay). Evidence was found for high gene flow between the expected- and late-season recruits within each year and at both sites based on 1389 neutral loci. In contrast, strong genetic differentiation was observed between these 2 groups within each year and at both sites based on variation at 2 putatively adaptive loci. Contrary to prediction, the magnitude of genetic differentiation between these 2 seasonal groups was greater in 2017 when the Pacific Decadal Oscillation was stronger, upwelling was weaker, and the spring transition was later. Spatial genetic variation was not observed within 2017 or 2018. Comparing across years, expected- and late-season groups were differentiated at putatively adaptive loci. Interestingly, strong genetic differentiation was also observed between late-season groups across years. We found no evidence for cohesive larval dispersal among recruits based on genetic relatedness estimates. Overall, our findings provide evidence for high connectivity within Dungeness crab, but suggest that selective pressures and ocean conditions influence the genetic composition of larval recruits both intra- and inter-annually.

Assessing the Relative Importance of Estuarine Nursery Habitats - a Dungeness Crab (Cancer magister) Case Study.

Estuaries serve as important nurseries for many recreationally and commercially harvested fisheries species. Recent conceptual approaches (i.e., seascape) for assessing the value of estuaries to fisheries have advocated for complex habitat-scale assessments that integrate multiple life-history responses (e.g., abundance, growth, reproduction) and ecological processes across heterogeneous landscapes. Although ecologically compelling, implementing seascape approaches may not be feasible for resource-limited management agencies. In such cases, we propose that resource managers can enhance the identification of fishery-important estuarine habitats by integrating attainable aspects of the seascape approach into a more traditional single response (e.g., abundance) model. Using Dungeness crab (Cancer magister) as a case study, we applied a spatially-explicit hybrid approach to assess the relative contribution of different estuarine habitats to that important fishery species within three Oregon estuaries (Tillamook, Yaquina, and Alsea bays). We measured the abundance of juvenile C. magister from low-tide trawls in estuarine channels and the mosaic of habitat characteristics within defined home-range distances for the crabs. After identifying and reducing strong intercorrelations among habitat variable data, we developed a best-fit model that associated crab abundance with the most influential habitat variables. We found that lower-estuary side channels supported the highest abundance of juvenile crabs; furthermore, crab abundance was positively associated with high salinity and burrowing shrimp (Upogebia pugettensis) density on adjacent unvegetated tidal flats. This hybrid method produced a habitat-specific model that better predicted juvenile C. magister abundance than did a model based on generalized habitat categories.

Connecting Crabs, Currents, and Coastal Communities: Examining the Impacts of Changing Ocean Conditions on the Distribution of U.S. West Coast Dungeness Crab Commercial Catch

Dungeness crab (Cancer magister) is one of the most lucrative fisheries on the U.S. west coast. There have been large spatial and temporal fluctuations in catch, which reflect the interconnected influences of the coupled natural-human fishery system. Changing ocean conditions are likely to further alter the magnitude and distribution of Dungeness crab catch, the impacts of which will propagate ecologically and through the social systems of fishing communities. Therefore, the effect of changing ocean conditions on U.S. west coast Dungeness crab catch per unit effort (CPUE) was used as an interdisciplinary case study to examine the susceptibility, a metric that integrates Dungeness crab reliance and social vulnerability indices, of coastal communities to changes in the fishery. Statistical models indicated that ocean conditions influence commercial CPUE three to five years later and that CPUE is likely to decline in the future as ocean conditions change. In particular, sea surface temperature scenarios for 2080 (+1.7 °C and +2.8 °C) reduced Dungeness crab CPUE by 30-100%, depending on fishing port latitude. Declines in Dungeness crab CPUE were greater for southern port communities than for northern port communities under both scenarios – demonstrating greater exposure at the southern end of the species range. We show that U.S. west coast communities are differentially susceptible to a decline in Dungeness crab catch, with Washington communities being at least five times more susceptible than California communities. Our overall assessment showed varying levels of risk (a combination of exposure and susceptibility) for Dungeness crab fishing ports that do not necessarily align with regional or fishery management boundaries.

The Effect of a Spatial Harvest Closure Area on the Abundance, Movement, and Demographics of an Intensively Fished Population of Dungeness Crabs (Cancer magister) Along Roberts Bank, British Columbia, Canada

In addition to regulating sex, size, and season of harvest, resource managers can implement spatial fishery closures as a management tool to protect Dungeness crab populations. Yet, we have little understanding of the role that spatial closures play in conserving crab populations, especially in fisheries management zones that are subject to intensive harvest. The primary purpose of this study was to evaluate the biological effectiveness of a crab closure area adjacent to an intensive fishery, by examining relative abundance, population demographics, and seasonal movement patterns within and outside of a closure area. Relative abundance and population demographics were assessed weekly from August to October, using standardized trap lines distributed at four locations, stratified by treatment (inside versus outside of closure area) and water depth. To obtain individual male crab movement data within and outside of the closure area, mobile acoustic tracking surveys were conducted one to three times per week in the autumn and winter. Male crabs were larger and in greater abundance inside the closure area than outside. The overall trend in male crab movement was southwest towards deeper water during autumn and winter. Our research supports the hypothesis that fisheries decrease the abundance and size of an exploited species, but closure areas may reduce these effects. Based on the observed seasonal movement patterns of crabs, it appeared that the closure area provided a temporary refuge from harvest. Resource managers should consider seasonal movement patterns, habitat use, and quality of available habitat when selecting closure area boundaries.

Nearly a half century of high but sustainable exploitation in the Dungeness crab (Cancer magister) fishery

The fishery for Dungeness crab (Cancer magister) is one of the largest and most valuable on the US West Coast. Though conventional wisdom holds that the fishery takes the large majority of legal-sized male crab coast-wide each year, this has not been demonstrated analytically. We use catch and effort data and a Bayesian depletion estimator to estimate pre-season abundance of the coastal population of legal-sized male Dungeness crab from 1970 to 2016 (California) or 1982–2016 (Oregon and Washington) and estimate that the fishery takes 9 %–98 % of the legal-sized male population each year, averaging 66 %. The percent taken has increased over time in all areas. We find that although fish tickets (landing receipts) have limited information on fishing effort, they lead to similar estimates of abundance compared to the more detailed logbook data. Fish ticket estimates of abundance tend to be slightly lower than logbook estimates. Logbooks also show evidence that catchability is time-varying or density-dependent (i.e., catch rates exhibit hyperdepletion), which is not evident in the fish ticket data. Pre-season abundance of legal-size males appears to be stable or increasing in all areas over the period considered in spite of the high rate of exploitation and large year-to-year fluctuations. In Central California, pre-season abundance has shown a particularly rapid increase during the past decade after a long period of low abundance, likely due to changing oceanographic conditions.

Big Fishery, Big Data, and Little Crabs: Using Genomic Methods to Examine the Seasonal Recruitment Patterns of Early Life Stage Dungeness Crab (Cancer magister) in the California Current Ecosystem

The California Current Ecosystem (CCE) is a dynamic marine ecosystem from which many socioeconomically-important fisheries species are harvested. Here, a genotyping-by-sequencing (GBS) approach was used to examine genomic variation in an early life stage (megalopae) of the Dungeness crab (Cancer magister), which constitutes the most valuable single-species commercial fishery in the CCE. Variation in abundance and timing of megalopae recruitment has been extensively studied for over two decades in Coos Bay, Oregon, USA. Within the CCE, documented timing of Dungeness crab life history events indicates that coastal megalopae recruitment is expected to occur April through July; however, long-term studies in Coos Bay have observed late-season recruitment from August to October. Based on variation at 1,913 presumably neutral loci, evidence was found for weak, yet significant differentiation (FST estimate = 0.0011) between the 2014 expected-season recruits (n=47) and late-season recruits (n=47) collected in Coos Bay. However, two putatively adaptive loci with a high FST estimate (0.2036) between expected-season and late-season recruits were identified. These findings support the hypothesis that expected-season and late-season megalopae recruiting to Coos Bay within the same year may have originated from different locations or from different breeding groups. Understanding marine species connectivity between ecosystems is important when considering how future changes in ocean conditions may impact fishery harvests.

Uncovering mechanisms of global ocean change effects on the Dungeness crab (Cancer magister) through metabolomics analysis

The Dungeness crab is an economically and ecologically important species distributed along the North American Pacific coast. To predict how Dungeness crab may physiologically respond to future global ocean change on a molecular level, we performed untargeted metabolomic approaches on individual Dungeness crab juveniles reared in treatments that mimicked current and projected future pH and dissolved oxygen conditions. We found 94 metabolites and 127 lipids responded in a condition-specific manner, with a greater number of known compounds more strongly responding to low oxygen than low pH exposure. Pathway analysis of these compounds revealed that juveniles may respond to low oxygen through evolutionarily conserved processes including downregulating glutathione biosynthesis and upregulating glycogen storage, and may respond to low pH by increasing ATP production. Most interestingly, we found that the response of juveniles to combined low pH and low oxygen exposure was most similar to the low oxygen exposure response, indicating low oxygen may drive the physiology of juvenile crabs more than pH. Our study elucidates metabolic dynamics that expand our overall understanding of how the species might respond to future ocean conditions and provides a comprehensive dataset that could be used in future ocean acidification response studies.

Video sleds effectively survey epibenthic communities at dredged material disposal sites

This research assessed the effectiveness of benthic video sleds for monitoring the impacts of dredged material disposal on epifauna at shallow and deep water disposal sites near the mouth of the Columbia River, USA. Video sleds collected visual transects at the two disposal sites and comparable reference areas during 2014 and 2015 within a Before-After, Control-Impact (BACI) experimental design. These flat, soft-bottom habitats are populated by demersal fish and benthic invertebrates, including the economically important Dungeness crab (Cancer magister). At the shallow site, results from multivariate Similarity Profile Analysis (SIMPROF) and univariate ANOVA tests on prominent species did not detect any significant differences between disposal and reference communities. At the deep site, the multivariate and univariate analyses detected differences in communities and abundances between years, rather than between disposal and reference locations. At the scale of this research, there was no detectable impact of dredged material disposal on the epifauna communities at these two Pacific Northwest disposal sites. While the species resolution of cryptic or small organisms was found to be limited, the video sled technique had sufficient power to detect potential differences in most epifaunal species densities with a BACI statistical design. We found the video sleds were an effective tool to assess potential impacts of dredged material disposal on epifauna.

Classification of Hemocytes from Four Crustaceans and Cross-Reactivity of Their Antisera

Common antigens and analyzed the hemocytes of the lady crab (Charybdis japonica) were studied. Chinese mitten crab (Eriocheir sinensis), Dungeness crab (Cancer magister), and red king crab (Paralithodes camtschaticus) using a laser scanning confocal microscope (LSCM), flow cytometry (FCM), Western blotting (WB), and transmission electron microscopy. In this paper analyzed hemocyte classification and immunological characteristics of the whole proteins in these species and their antisera. Four antisera positively cross-reacted, to varying degrees, with hemocytes of the four species. Two subpopulations were classified in C. japonica, P. camtschaticus, and E. sinensis and three in C. magister. The LSCM results showed that four antisera were positive with the hemocytes of the four crustacean species, respectively. Dot fluorescent signals on the hemocyte membranes show a cricoid intensive distribution. FCM analysis showed a positive rate of cross-reaction, in which the reaction of the antisera with its own hemocytes was higher than that with other species' hemocytes. The positive rate of granulocytes was always higher than that of hyalinocytes. Western blotting results showed that the four antisera mainly recognized antigens with molecular weights of about 75 or 80 kDa in the hemocytes of C. japonica, 80 or 90 kDa in the hemocytes of P. camtschaticus, 30 and 82 kDa in the hemocytes of E. sinensis, and 43 or 70 kDa in the hemocytes of C. magister. More lanes reacted between hemocytes of E. sinensis and C. magister and their antisera. The results indicate antigenic similarities among the hemocytes of the four crustacean species.

A comparison of laboratory-holding and tag-return methods for evaluating delayed mortality of Dungeness crab (Cancer magister) discarded in Oregon fisheries

A comparison of laboratory-holding and tag-return methods for evaluating delayed mortality of Dungeness crab (Cancer magister) discarded in Oregon fisheries

Evidence for interannual variation in genetic structure of Dungeness crab (Cancer magister) along the California Current System.

Using a combination of population- and individual-based analytical approaches, we provide a comprehensive examination of genetic connectivity of Dungeness crab (Cancer magister) along ~1,200km of the California Current System (CCS). We sampled individuals at 33 sites in 2012 to establish a baseline of genetic diversity and hierarchal population genetic structure and then assessed interannual variability in our estimates by sampling again in 2014. Genetic diversity showed little variation among sites or across years. In 2012, we observed weak genetic differentiation among sites (FST range=-0.005-0.014) following a pattern of isolation by distance (IBD) and significantly high relatedness among individuals within nine sampling sites. In 2014, pairwise FST estimates were lower (FST range=-0.014-0.007), there was no spatial autocorrelation, and fewer sites had significant evidence of relatedness. Based on these findings, we propose that interannual variation in the physical oceanographic conditions of the CCS influences larval recruitment and thus gene flow, contributing to interannual variation in population genetic structure. Estimates of effective population size (Ne ) were large in both 2012 and 2014. Together, our results suggest that Dungeness crab in the CCS may constitute a single evolutionary population, although geographically limited dispersal results in an ephemeral signal of IBD. Furthermore, our findings demonstrate that populations of marine organisms may be susceptible to temporal changes in population genetic structure over short time periods; thus, interannual variability in population genetic measures should be considered.

Indigenous knowledge as data for modern fishery management: a case study of Dungeness crab in Pacific Canada

ABSTRACTIntroduction: Fisheries management is often data-limited, and conducted at spatial scales that are too large to address the needs of Indigenous peoples, whose cultures depend upon the local availability of marine resources.Outcomes: We combined Indigenous ecological knowledge with simulation modelling to inform modern fishery management. Semi-structured interviews with Indigenous fishers in coastal British Columbia, Canada, uncovered severe declines in the abundance and catches of Dungeness crab (Cancer magister) since the 1990s. We modelled the current probability of “successful“ crab harvesting trips—as defined by expectations from past catches by Indigenous fishers—using fishery-independent data from nine sites. These probabilities were very low (<20%) for all sites except one.Discussion: Our study highlights that local depletions, which Indigenous fishers attribute to commercial and recreational fisheries, have been widespread and undetected by federal managers who manage Dungeness crab at regional scales without fishery-independent data. Further, local depletions impacted the ability of Indigenous fishers to access traditional foods.Conclusion: Integrating Indigenous knowledge with scientific research is crucial to inform locally-relevant fisheries management and conservation.

Genetic Connectivity of the Dungeness Crab (Cancer magister) Across Oceanographic Regimes

Limited approaches exist for studying population connectivity in widely dispersing marine benthic invertebrates. Genetic techniques can provide important insights toward identifying recruitment trajectories. Here, 10 microsatellite loci were used to examine connectivity among Oregon Dungeness crabs (Cancer magister, Dana, 1852) in the California Current System (CCS) (n = 801) as well as between Oregon and two British Columbia populations, Alison Sound (n = 54) and Boundary Bay (n = 48). Using population-based methods (F-statistics), evidence for weak genetic differentiation was found among 12 sites in Oregon that did not conform to a pattern of isolation by distance.Whereas individual-based methods (kinship analyses) indicated higher than expected relatedness in two Oregon sites, this finding did not help interpret the pattern of genetic differentiation observed among sites in the CCS. Extending our analyses to British Columbia, it was determined that genetic diversity within the Boundary Bay population was comparable to that observed for Oregon, whereas genetic diversity within Alison Sound was considerably lower. Furthermore, genetic connectivity between Oregon and British Columbia was reduced as Alison Sound was genetically distinct from all Oregon sites, whereas Boundary Bay was genetically differentiated from several Oregon sites. In accordance, a Bayesian clustering approach provided support for two genetic groups: (1) Oregon and Boundary Bay and (2) Alison Sound. Kinship analysis revealed a high degree of relatedness within Alison Sound which helps explain the observed pattern of population differentiation. By combining population-based and individual-based approaches, these results demonstrate that connectivity between ocean and fjord-like areas is reduced and may lead to elevated kinship in isolated populations.

Comparing genetic connectivity among Dungeness crab (Cancer magister) inhabiting Puget Sound and coastal Washington

Understanding connectivity of marine organisms is necessary for determining the appropriate scale of conservation and management strategies. For species that inhabit both the coastal ocean and partially enclosed water bodies (i.e., estuaries or fjords), this information is even more critical since estuaries and fjords are often characterized by hydrological complexities which can limit dispersal potential and promote population subdivision. In this study, genetic connectivity of Dungeness crab Cancer magister in Puget Sound and coastal Washington, USA, was examined to test the hypothesis of genetic structure in partially enclosed versus open environments. Dungeness crab that were sampled at five sites in Puget Sound in 2015 and three sites in coastal Washington in 2014 were genotyped at ten microsatellite loci. We observed similar levels of heterozygosity and allelic richness within Puget Sound and coastal Washington. Pairwise F ST estimates indicated that Hood Canal was significantly differentiated from other Puget Sound sites, except Nisqually, suggesting larval retention within the Hood Canal basin. No evidence for significant genetic differentiation was found among the four remaining Puget Sound sites or among the three coastal sites. Analysis of molecular variance indicated that, in aggregate, Puget Sound sites significantly differed from coastal sites. On a site by site basis, we found evidence for significant differentiation between three sites in Puget Sound and coastal Washington. Based upon the observed patterns of genetic differentiation, our findings did not support our hypothesis of restricted genetic connectivity within Puget Sound, with the exception of Hood Canal. However, our results demonstrate that there is stronger genetic connectivity within Puget Sound and coastal Washington than between these two areas.