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Until recently, the Kara Sea was a stable ecosystem unaffected by alien species invasions. However, at the beginning of the twenty-first century, the snow crab (Chionoecetes opilio) was detected. Studies conducted between 2013 and 2022 in Blagopoluchiya Bay (Novaya Zemlya Archipelago, Kara Sea) provided an opportunity to observe the establishment of a population of this species and its influence on benthic communities. Various sampling methods, such as trawl and grab surveys, as well as video observations, were used to study two main seabed habitats, one in the deep inner basin and the other at the sill at the bay's exit. The study revealed significant changes in benthic ecosystems, including declines in integral benthic characteristics such as abundance, biomass, diversity, and shifts in dominant species. The response of megabenthos and macrobenthos varied between habitats, but in general, there was a sharp decline in the abundance of large bivalves and brittle stars. The observed changes were not related to environmental variability but most likely to the abundance and size structure of the snow crab. The taxonomic and size structure of the benthos changed as crab individuals increased in size, and the changes were faster and more pronounced in the area with higher crab abundance. These findings raise concerns about the potential long-term effects of the snow crab invasion on the Kara Sea ecosystem, including reduced biodiversity and changes in food webs. [ABSTRACT FROM AUTHOR]

The snow/pink crab (Chionoecetes opilio) and Northern shrimp (Pandalus borealis) are widely distributed in the North Atlantic Ocean. During processing/consumption, about 80% of the harvest is discarded as processing waste, which is a rich source of protein, chitin, minerals, and carotenoids. This study, for the first time, investigated the proximate composition and individual amino acids, minerals, and carotenoids from different body parts (carapace, shoulder, claw, tip, and leg) of snow crabs and shrimp shells. Shrimp proteins were found to be abundant and well-balanced in their amino acid composition. Compared to shrimp shells, a lower content of amino acids was found in the snow crab, depending on the part of the shell used. Moreover, crab shells, mainly crab claws, contained a higher (p < 0.05) level of chitin compared to shrimp shells. Seven micro-elements (Mn, Fe, Cu, Zn, As, Ba, and Ce) and six macro-elements (Ca, Na, K, Mg, P, and Sr) were identified using inductively coupled plasma-mass spectrometry (ICP-MS). Among them, calcium and iron were higher in crab carapaces (p < 0.05), followed by shrimp shells and other crab shell segments. Additionally, shrimp and crab carapaces contained a significant level of carotenoids, and these were mainly composed of astaxanthin and its mono- and diesters, along with zeaxanthin, astacene, canthaxanthin, and lutein. Thus, this investigation provides detailed information to allow upcycling of shellfish waste and addresses the knowledge gap concerning the availability of various nutrients in different crab sections and shrimp shells. [ABSTRACT FROM AUTHOR]

The snow/pink crab (Chionoecetes opilio) and Northern shrimp (Pandalus borealis) are widely distributed in the North Atlantic Ocean. During processing/consumption, about 80% of the harvest is discarded as processing waste, which is a rich source of protein, chitin, minerals, and carotenoids. This study, for the first time, investigated the proximate composition and individual amino acids, minerals, and carotenoids from different body parts (carapace, shoulder, claw, tip, and leg) of snow crabs and shrimp shells. Shrimp proteins were found to be abundant and well-balanced in their amino acid composition. Compared to shrimp shells, a lower content of amino acids was found in the snow crab, depending on the part of the shell used. Moreover, crab shells, mainly crab claws, contained a higher (p < 0.05) level of chitin compared to shrimp shells. Seven micro-elements (Mn, Fe, Cu, Zn, As, Ba, and Ce) and six macro-elements (Ca, Na, K, Mg, P, and Sr) were identified using inductively coupled plasma-mass spectrometry (ICP-MS). Among them, calcium and iron were higher in crab carapaces (p < 0.05), followed by shrimp shells and other crab shell segments. Additionally, shrimp and crab carapaces contained a significant level of carotenoids, and these were mainly composed of astaxanthin and its mono- and diesters, along with zeaxanthin, astacene, canthaxanthin, and lutein. Thus, this investigation provides detailed information to allow upcycling of shellfish waste and addresses the knowledge gap concerning the availability of various nutrients in different crab sections and shrimp shells.

The quantity of snow crabs (Chionoecetes opilio) harvested in Korea is subject to seasonal restrictions; therefore, snow crabs are imported from Russia. Metabolites in snow crabs from two geographic origins were compared. The metabolites were subjected to metabolomic analysis to prevent fraudulent sales of marine products from a particular country. Capillary electrophoresis time-of-flight mass spectrometry was used. Seventy-seven target metabolites were identified using a mass spectral library. Through orthogonal partial least squares discriminant analysis, the top 25 biomarker candidates were evaluated based on p -values and fold changes. A total of 246 peaks (187 and 59 in the cation and anion modes, respectively) were identified. Among the biomarker candidates, 2-oxovaleric acid, asymmetric dimethylarginine, hypotaurine, and allo-threonine were selected as final biomarkers to unequivocally determine the geographic origin. Overall, metabolic analyses allowed us to differentiate snow crabs from different geographic origins. This method could also be extended of other marine products. [Display omitted] • Metabolomics revealed distinct characteristics of Korean and Russian snow crabs. • 2-Oxoisovaleric acid best explained differences in snow crabs between two regions. [ABSTRACT FROM AUTHOR]

The snow crab (Chionoecetes opilio) fishery has great economic importance for Nova Scotia, contributing $263 million to fisheries and more than one-fifth of Canadian snow crab revenues in 2021. Being a stenothermic species, snow crabs can only live within a narrow range of temperatures between −1 to 6 °C. The Scotian Shelf holds the southernmost populations of snow crab in the Atlantic and snow crab catch-per-unit-area (CPUA) in the Scotian Shelf. Trawl survey data from Ocean, because these cold-temperature requirements are a limiting factor for its distribution. This study investigates the relationship between bottom ocean temperature Fisheries and Oceans Canada from 2012 to 2021 were used. Through nonlinear modelling, CPUA (mt/km2) was regressed with respect to bottom ocean temperature along Northwest Atlantic Fisheries Organization divisions N-ENS, CFA 23, CFA 24, and CFA. The temperature-vs-CPUA relationship was unimodal for all studied years. The best-fit models explained a limited amount of variation, but CPUA consistently decreased to zero towards the highest recorded temperatures. Due to the ongoing global warming, bottom ocean temperatures across the Scotian Shelf will likely continue to increase, which thus might harm the Scotian Shelf snow crab fishery. In conclusion, this study underscores the potential impact of global warming on the economically significant snow crab fishery in the Scotian Shelf. The findings serve as a critical alert to the possible consequences of rising ocean temperatures, thereby contributing to our understanding and preparation for the future of marine ecosystems and industries. • Data were used from snow crab trawl surveys conducted along the Scotian Shelf off Nova Scotia, Canada, from 2012 to 2021. • Attributes of location, timestamp, bottom ocean temperature, snow crab biomass, and trawled surface area were considered. • Catch Per Unit Area (CPUA) in mt/km2 was regressed with respect to temperature. • CPUA decreased towards high temperatures in the Scotian Shelf for all studied years. [ABSTRACT FROM AUTHOR]

Macro- and meiobenthos of the Blagopoluchiya Bay (Novaya Zemlya, Kara Sea) have undergone significant changes in their quantitative distribution from 2013 to 2020. During this period, meiobenthos abundance has increased greatly, whereas macrobenthos abundance has decreased. Mean meiobenthos density has tripled (from 702 to 2293 ind./10 cm2), while mean macrobenthos density decreased by more than a half (from 1530 to 645 ind./m2). The observed growth of meiobenthos density was mainly due to an increase in the abundance of free-living nematodes. We suggest that the invasion of snow crab Chionoecetes opilio is one of the most important drivers of changes in benthos distribution. Following the crab invasion, there was a reduction of macrobenthic density and biomass and a compensatory increase in those in meiobenthos in the Blagopoluchiya Bay. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome of Chionoecetes opilio is a 16,067 bp long, circular molecule which contains 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and 2 ribosomal RNA genes (rRNAs). Its gene contents and organization are generally similar to other majoid mitogenomes. However, the mitogenome shows unique characteristics; long terminal amino acids, loss or addition of 3 PCGs, a 1216 bp long putative D-loop region, and peculiar secondary structures of 5 tRNAs. The concatenated amino acid sequences of 13 PCGs were used to analyze the phylogenetic tree, which well supported the monophyly of brachyuran clades of Majoidea, Heterotremata, Thoracotremata, and Eubrachyura.

Expanding human activities alongside climate change, the introduction of invasive species and water contamination pose multiple threats to the unique marine ecosystems of the Pechora Sea in the Russian Arctic. Baseline data on biodiversity and responses to environmental change are urgently needed. Benthic decapod crustaceans are globally distributed and play an important role in fisheries, yet their roles in food webs are less understood. In this study, we used an integrated approach combining stomach content analysis and stable isotope analyses (δ13C and δ15N) to examine the trophic niches of three decapod species in the Pechora Sea including the invasive snow crab Chionoecetes opilio and two species of native decapods, the spider crab Hyas araneus and the hermit crab Pagurus pubescens. Stomach contents of 75 decapods were analysed (C. opilion = 23; H. araneusn = 9; P. pubescensn = 43), and 20 categories of prey items were identified with the most frequently occurring prey items being bivalve molluscs (Ciliatocardium ciliatum, Ennucula tenuis, Macoma calcarea), polychaetes, crustaceans and plant debris. Bayesian ellipse analyses of stable isotope signatures (n = 40) revealed that C. opilio displays an overlapping trophic niche with the two native decapods, providing direct evidence that the invader likely competes for food resources with both H. araneus and P. pubescens. As such, the presence of this invasive species could hold important consequences for trophic interactions, benthic ecosystem functioning and biodiversity. Microplastics were also found to be a likely stressor on this ecosystem, as 28% of all stomachs contained digested microplastics among other items. Long-term studies of benthic ecosystem structure and functioning are now needed to more fully understand the extent to which this new competitor may alter the future biodiversity of the Pechora Sea alongside the additional stressor of digested plastics. [ABSTRACT FROM AUTHOR]

This study investigated the behaviour and commercial catchability of snow crab (Chionoecetes opilio) in response to different low-powered LED lights under laboratory and field conditions. We created a novel choice-experiment in a laboratory setting in which we investigated the behaviour of snow crab in response to coloured LED lights. The results showed that snow crab movement was dependent on light colour, with animals choosing to move toward blue and white lights, away from purple lights, and no detectable effect for green and red lights. We then conducted two field experiments to investigate the effect of the same LED lights on the catch rates of commercial traps during the 2016 snow crab fishery on the east coast of Newfoundland and Labrador. Results from the first field experiment showed that adding white and purple LED lights into baited traps significantly improved Catch Per Unit Effort (CPUE) by 77% and 47% respectively. Results from the second field experiment showed that unbaited traps equipped with only LED lights (no bait), could also catch snow crab in comparable amounts to traditional baited traps, with soak time and depth explaining some of the variation in CPUE. Taken together, these experiments suggest that fishing enterprises can improve their catching performance and profitability by adding LED lights to their traps, or by using LED lights as a bait replacement.

The snow crab (Chionoecetes opilio) is one of the most important commercial crabs in the world; it is heavily exploited in Atlantic Canada, Alaska, the Sea of Japan and the Barents Sea. Catches in the Barents Sea north of Norway have increased dramatically in the last decade. Most of the world's catch is processed, frozen and exported overseas. However, recently there has been considerable interest in exporting live snow crab, particularly in Norway. The stress of capture and live transport can result in significant mortalities. In order to establish a live export industry for snow crab, the welfare of the animal must be monitored throughout all the steps of the live transport process. In this study the reactions of snow crabs exposed to increasing periods of air exposure were measured in terms of reflex indicators, incidence of mortality, blood lactate levels and blood protein and haemocyanin. Although this is not a specific live holding or live transport process the aim was to test the suitability of reflex indicators to reflect vitality (stress) and not just to predict mortality. This would be compared with traditional blood biochemistry techniques for measuring crustacean stress. The study demonstrated that the reflex index score (RIS) is suitable to assess the vitality of snow crab. Longer air exposure periods render higher mortality rates and less vital individuals. The authors believe using vitality reflex indicators would be a suitable way of measuring crab welfare during the live holding and transport process. [ABSTRACT FROM AUTHOR]

In this study, the effects of feeding (F) and starvation (S) on survival, injury, and weight of captive male snow crab were examined. The experiment was carried out with three replicates of each treatment. Each replicate had 11 individually tagged crabs (average weight of 650 g ± 37 SE) per tank (replicate) in a total of six circular tanks (500 L), with stocking densities of 14 kg/m. The experiment ran for 100 days and the animals were exposed to ambient seawater temperatures ranging from 4.4ºC to 5.4ºC during the trial period. There were no significant differences in wet weight between the groups at the start or at the end of the experiment. However, the hepatopancreas index (HI) significantly decreased in both groups from 6.1% at the start to, respectively, 4.6% (F) and 3.2% (S) at day 100. The S group had a significantly lower HI than the F group. Only one animal died during the experiment (day 100, F). The frequencies of injuries were similar in all groups. The results show that adult male snow crab can be stored for minimum 100 days (with or without feeding) with relatively low risk of physical injury, or mortality due to social interactions. [ABSTRACT FROM AUTHOR]

• We developed a high-resolution spatiotemporal state-space model for the snow crab (Chionoecetes opilio) population in the Eastern Bering Sea (EBS). • The model was used to refine the representation of spatial processes in integrated population models, facilitate understanding of the drivers of spatiotemporal population dynamics, and provide new insights for management advice. • The model implicitly accounts for seasonal movement between the time of the survey and that of fishery to estimate fine-scale spatial population dynamic and fishing impacts, including potential environmental drivers. • We quantify spatiotemporal variation in exploitable abundance, fishing mortality, recruitment, and mature and immature abundance. • The model estimated declines in exploitable abundance and in fishing mortality with variable spatial distributions, and sporadic recruitment, spatially concentrated in the northeast EBS. Considering spatial processes in population dynamics models can be difficult because of data limitations and computational costs. We adapted a high-resolution spatiotemporal assessment framework to better address fine-scale spatial heterogeneities based on theories of fish population dynamics and spatiotemporal statistics. Specifically, we developed a size-based state-space model for the snow crab (Chionoecetes opilio) population in the Eastern Bering Sea (EBS) to refine the representation of spatial processes in integrated population models, facilitate understanding of the drivers of spatiotemporal population dynamics, and provide new insights for management advice. The model fits to spatial survey and fishery-dependent catch data. It implicitly accounts for seasonal movement between the time of the survey and that of fishery to estimate fine-scale spatial population dynamic and fishing impacts, including potential environmental drivers. We quantify, for the first time, spatiotemporal variation in exploitable abundance, fishing mortality, recruitment, and mature and immature abundance. The model estimated declines in exploitable abundance and in fishing mortality with variable spatial distributions, and sporadic recruitment, spatially concentrated in the northeast EBS. Few spatial assessments have been used as the basis for management advice and we consider this study as a step towards the integration of spatial dynamics in stock assessment. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome of Chionoecetes opilio is a 16,067 bp long, circular molecule which contains 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and 2 ribosomal RNA genes (rRNAs). Its gene contents and organization are generally similar to other majoid mitogenomes. However, the mitogenome shows unique characteristics; long terminal amino acids, loss or addition of 3 PCGs, a 1216 bp long putative D-loop region, and peculiar secondary structures of 5 tRNAs. The concatenated amino acid sequences of 13 PCGs were used to analyze the phylogenetic tree, which well supported the monophyly of brachyuran clades of Majoidea, Heterotremata, Thoracotremata, and Eubrachyura. [ABSTRACT FROM AUTHOR]

Milky hemolymph syndrome (MHS) has been observed in both reared and wild populations of the snow crab Chionoecetes opilio from the Sea of Japan. The virus presumably associated with MHS and detected with electron microscopy was designated ' Chionoecetes opilio bacilliform virus' ( CoBV), but little is known about its infectivity or pathogenicity in the snow crab. In this study, we performed an infectivity experiment in which snow crabs were injected with a viral inoculum prepared from MHS-affected crabs and then maintained at 2 °C or 2-8 °C. Cumulative mortality increased more rapidly at 2 °C than at 2-8 °C, reaching approximately 80% in both groups at the termination of the experiment. This result demonstrates the temperature-dependent pathogenicity of CoBV in the snow crab. CoBV-infected crabs displayed the clinical and histopathological signs of MHS. Mortality tended to increase as the viral load in the hemolymph increased at both 2 °C and 2-8 °C. The viral load in the hemolymph was significantly higher in dead crabs than in surviving crabs and was also elevated in various other organs. We conclude that CoBV is the causative agent of MHS and that severely affected crabs develop viremia that leads to death. [ABSTRACT FROM AUTHOR]

A nonlinear thermodynamic Sharpe-Schoolfield-Ikemoto (SSI) model has been applied to temperature-dependent development of some arthropods and other ectotherms. The most important parameter estimated by the SSI model is the intrinsic optimum temperature (Φ), which is the temperature at which the probability of an enzyme being in its active state is maximal. It has been also suggested that Φ authentically represents the optimal ambient temperature for fitness in ectotherms. We applied the SSI model to larvae of four aquatic decapod crustacean species distributed in cold, temperate, and tropical waters for understanding thermal adaptation in decapods. As a result, TΦ's estimates for the larvae corresponded to the optimum temperatures for larval survival/growth. The estimates also changed in accordance with the geographical distribution of the stages, species, and populations studied, i.e., 6.91-9.06 °C for cold-water species and 19.68-27.00 °C for temperate and tropical species. It would be useful to examine the relationship between changes in geographical distribution with temperature Φ and population size for a better understanding of population fluctuations under global climate change. Additionally, stable aquaculture production could be enhanced if the temperature conditions of each life history stage were controlled at Φ. [ABSTRACT FROM AUTHOR]

In this study the effects of different stocking densities on survival, injury and weight of captive male snow crab were examined. The first experiment (I) was carried out in square plastic tanks (700 L) with stocking densities of 100 (L), 150 (M) and 200 kg m−3 (H) for 30 days. In a second experiment (II) snow crabs were kept at a stocking density of 50 kg m−3 and were either fed (F) or not fed (S) for the same period of 35 days. The last experiment (III), was carried out with stocking densities of 25 kg m−3 for 21 days with two groups, one with inactivated claw and one without rubber bands, with three replicates per treatment. In the first experiment mortality (H = 27, M = 26 and L = 36%) and occurrence of injuries (H = 27, M = 20 and L = 16%) were high in all groups. The weight loss during the experimental period was; H = 15.3, M = 10.9 and L = 15.5 g, and was not significant different between the groups. In experiment II the mortality (F = 13% and S = 14%) and injuries were lower (F = 12% and S = 17%). The average weight increased in the fed treatment and decreased in the starved treatments. In the last experiment there was no mortality in any of the groups and the levels of injury were low (5% and 7%). The results show that adult male snow crab cannot be stored at densities equal to or higher than 25 kg m−3 for 3 weeks without risk of mortality. [ABSTRACT FROM AUTHOR]

Growth and moulting of wild-born immature snow crabs (Chionoecetes opilio (Fabricius, 1788)) were investigated by laboratory culture experiments. Crabs with 16.2-42.9 mm carapace width caught from the Sea of Japan were cultured at a temperature of their natural habitat (approximately 1°C). The growth indices (size increments at moulting in mm and in % of premoult carapace width) and intermoult period were significantly affected by premoult carapace width, but sex did not affect these variables. Furthermore, we demonstrated that premoult carapace width and days after moulting significantly affected moulting probability and we developed a moulting probability model based on these variables. From this model, the number of days of intermoult periods when moults occurred in 50% of crabs of instars VI, VII and VIII was estimated at 234, 284 and 346 days, respectively. [ABSTRACT FROM AUTHOR]

The food consumption pattern in megalopae of the snow crab Chionoecetes opilio (Fabricius, 1788) was investigated in the laboratory. Ten megalopae were individually cultured and given an excess of Artemia nauplii each day. All megalopae moulted into first-instar crabs 28-34 days after metamorphosis. The mean total number and total weight of Artemia consumed during the megalopal stage were 1920 individuals and 5.2 mg, respectively. Hence, the food requirement of snow crab megalopae was estimated as ~190% of the dry body weight of the first-instar crab. Initially, the number of Artemia consumed was nearly constant or decreased only slightly but, later, Artemia consumption decreased with development days. Two-segmented regressions provided good fits to the relationship between the number of days after metamorphosis and the cumulative number of Artemia consumed by individual megalopae. The mean value of the time after metamorphosis of the breakpoint in the rate of food consumption was estimated as 69% of the stage duration, which corresponds to the intermediate of late premoult. Crab sizes (carapace width, wet and dry body weight) were not significantly dependent on the number of Artemia consumed during the entire megalopal period although a positive correlation between these variables was observed. These results provide useful information on the appropriate feeding schedule and management practice for culturing snow crab megalopae and contribute to the understanding of megalopal growth efficiency to the first-instar crab in their natural habitat. [ABSTRACT FROM AUTHOR]

Fish and invertebrates that are unintentionally captured during commercial fishing operations and then released back into the ocean suffer mortality at unknown rates, introducing uncertainty into the fishery management process. Attempts have been made to quantify discard mortality rates using reflex action mortality predictors or RAMP which use the presence or absence of a suite of reflexes to predict discard mortality. This method was applied to snow crab, Chionoecetes opilio, during the 2010-2012 fisheries in the Bering Sea. Discard mortality in the fishery is currently assumed to be 50% in stock assessment models, but that rate is not based on empirical data and is widely recognized to be in need of refinement. Over 19 000 crab were evaluated using the RAMP method. The estimated discard mortality rate was 4.5% (s.d. = 0.812), significantly below the rate used in stock assessment models. Predicted discard mortality rates from the 2010 to 2012 study were strongly correlated with the air temperature at the St Paul Island airport in the Pribilof Islands. Using this relationship, the discard mortality rate from 1991 to 2011 was estimated at 4.8% (s.d. = 1.08). [ABSTRACT FROM AUTHOR]

The snow crab population in the eastern Bering Sea is panmictic, but it is spatially structured by inferred ontogenetic migrations, and fishing pressure is often spatially restricted by sea ice. This spatial structure is ignored when stock assessments are conducted, yet it is unclear if this omission influences management outcomes. We describe a process for evaluating the influence of spatial structure on the performance of stock assessments. This involves developing a spatial model which includes spatially explicit trends in recruitment, fishing mortality and rates of movement. The model is over-parameterized but provides good fits to the data for snow crab. It was used to simulate data sets to test the ability of a non-spatially structured (aggregate) assessment method in terms of estimating trends in abundance and fishing pressure in the presence of spatial structure. The aggregate assessment method performed well if survey selectivity was well known, but was unable to reliably represent the dynamics of the population without data on survey selectivity. Additional data on movement from tagging studies or winter surveys would be useful to improve the understanding of the influence of spatial structure on snow crab in the eastern Bering Sea. [ABSTRACT FROM AUTHOR]

Hematodinium is a parasitic dinoflagellate of numerous crustacean species, including the economically important Atlantic snow crab, Chionoecetes opilio. The parasite was cultured in vitro in modified Nephrops medium at 0°C and a partial characterization of the life stages was accomplished using light and transmission electron microscopy (TEM). In haemolymph from heavily infected snow crabs two life stages were detected; amoeboid trophonts and sporonts. During in vitro cultivation, several Hematodinium sp. life stages were observed: trophonts, clump colonies, sporonts, arachnoid sporonts, sporoblasts and dinospores. Cultures initiated with sporonts progressed to motile dinospores; however, those initiated with amoeboid trophonts proliferated, but did not progress or formed schizont-like stages which were senescent artefacts. Plasmodial stages were associated with both trophonts and sporonts and could be differentiated by the presence of trichocysts on TEM. Macrodinospores were observed but not microdinospores; likely due to the low number of Hematodinium sp. cultures that progressed to the dinospore stage. No early life stages including motile filamentous trophonts or gorgonlocks were observed as previously noted in Hematodinium spp. from other crustacean hosts. All Hematodinium sp. life stages contained autofluorescent, membrane-bound electron dense granules that appeared to degranulate or be expelled from the cell during in vitro cultivation. [ABSTRACT FROM PUBLISHER]

Snow crabs, Chionoecetes opilio (Fabricius, 1788), have a complex mating system, and understanding their reproductive physiology is paramount to crab fishery management. Mating and molting are inextricably linked, so the energetically demanding molting process may compromise male mating potential for some period prior to and after the molt. Recently molted, new-shell males are targeted preferentially during the commercially valuable eastern Bering Sea (EBS) fishery. Old-shell males, or males that have not molted within the last year, are not as visually appealing, but may have greater reproductive capacity and can contribute disproportionately to the genetic stock. We measured a crustacean reproductive hormone, methyl famesoate (MF), and reproductive fitness, using gonadosomatic index (GSI) as a proxy, in EBS male snow crab to determine differences in reproductive potential between adolescents and adults. We compared these reproductive indices in new- and old-shell males as a broad estimate of the effect of molting biology on reproduction. Circulating MF was significantly higher in new-shell adolescent males compared to old-shell adolescent males and old-shell adult males, suggesting a juvenilizing rather than gonadotropic role for MF in C. opilio. New-shell males had a significantly lower GSI compared to old-shell males for both adolescent and adult males. The lower GSI measured in new-shell adults compared to the significantly higher GSI levels measured in old-shell adults suggests that new-shell males harvested during the commercial fishery lack the reproductive capacity of the old-shelled adults and therefore may not be contributing equally to the population. [ABSTRACT FROM AUTHOR]

Trichocyst morphology and development were explored using transmission electron microscopy in Hematodinium spp. isolated directly from Atlantic snow crab ( Chionoecetes opilio ) hemolymph and from in vitro cultures. Appearance of trichocysts defines the initiation of a morphological transition in the parasites life cycle from vegetative stage to the transmission stage. Trichocysts within sporonts were found in distinct clusters near the nucleus in close apposition to the Golgi. As cells transitioned to more mature dinospores however, trichocysts were found randomly distributed throughout the cytoplasm. Clusters contained both primordial and maturing trichocysts at various stages indicating an asynchronous development. The random distribution of mature trichocysts suggests deployment to the cell membrane for future extrusion. Mature trichocysts of Hematodinium spp. appeared structurally similar to trichocysts from photosynthetic dinoflagellates. Hematodinium spp. trichocysts differed by the presence of peripheral tubules associated with novel cuboidal appendages in the apical region rather than a network of central electron dense fibres as found in photosynthetic dinoflagellates. Additionally, the trichocyst membrane of Hematodinium spp. was in close apposition to the square crystalline core. Trichocyst expulsion was not observed during our study which along with features of development and maturation within Hematodinium life stages should provide insight into proposed roles in host attachment or defense that could further our understanding of the mechanisms of pathogenesis and transmission of the parasite. [ABSTRACT FROM AUTHOR]

Decreasing sea ice in the Arctic is expected to impact marine ecosystems, and to lead to increased human activity in the form of shipping traffic, fishing pressure, and mineral resource exploration and extraction. In the face of these pressures, we examine genetic population structure in the snow crab Chionoecetes opilio (Fabricius, 1788), throughout its distribution in Alaskan waters, to determine degrees of population connectivity between the Arctic and more southerly portions of the species' range. Snow crabs are widely distributed on the high-latitude continental shelves of North America, where they support a valuable commercial fishery in the United States and Canada. Fishing pressure in United States waters is currently concentrated in the Bering Sea, but large populations of snow crab also occur farther north in the Chukchi and Beaufort Seas. These northern stocks are not well studied, and not yet targeted by fisheries, although commercial- sized individuals were recently reported in areas of the Western Beaufort Sea. We used seven polymorphic microsatellite markers to examine tissue samples from 573 individual crabs collected at 12 sampling locations distributed across the Bering, Chukchi, and Beaufort Seas. These data indicate that Alaskan snow crabs constitute one large, panmictic population. Connectivity between fishery areas in the south and unexploited regions farther north thus appears to be substantial, perhaps due to a lengthy larval dispersal period and highly mobile adult population. [ABSTRACT FROM AUTHOR]

Shifts in climate regime are prominent features of the physical environment of the eastern Bering Sea and in recent years have been documented in approximately 1977 and 1989. Average snow crab ( Chionoecetes opilio) recruitment decreased sharply after the 1989 fertilization year. Models in which control of snow crab recruitment shifts between drivers dependent on climate 'regime' are presented. These models are evaluated using cross-validation and retrospective analysis, both of which indicate that the relationships are relatively robust to varying levels of information. Larval survival as influenced by food availability in the pelagic phase and advection to suitable nursery grounds are the hypothesized mechanisms driving recruitment dynamics. [ABSTRACT FROM AUTHOR]

Abstract: The fishery for snow crab in the eastern Bering Sea was declared overfished in 1999 and had by 2010 failed to rebuild in the time specified. A key component of the rebuilding plan for snow crab was the stock assessment on which management advice was based. In common with all stock assessments, there are numerous potential sources of uncertainty, but it is not clear which uncertainty is most influential, and hence how research should be focused to best reduce uncertainty. A simulation framework is used to explore the estimation ability of the assessment method when its assumptions are violated. The focus of this evaluation is on how well management quantities such as mature male biomass and the overfishing level can be estimated. Three categories of uncertainty are considered: mis-specification of pre-specified parameters, data quantity and/or quality, and assumptions in the assessment related to fishing mortality. Management quantities are estimated reasonably well when all assumptions of the stock assessment method are correct. Additional data on growth and natural mortality would be most beneficial. However, penalties on fishing mortality introduce bias into estimates, and survey selectivity patterns are poorly determined by the estimation method. [Copyright &y& Elsevier]

Milky hemolymph syndrome (MHS) is a previously undescribed disease in snow crab Chionoecetes opilio. Outbreaks of this disease occurred in reared and wild populations from the Sea of Japan when the water temperature was 2-3°C. The common symptom of the disease was a distinct milky or opaque coloration of the hemolymph. Some severely affected crabs also showed yellow or ivory discoloration on the ventral shell and uncalcification of the arthrodial membranes of walking legs. Histopathological changes consisted of widespread cellular degeneration characterized by enlarged nuclei with marginal hyperchromatosis and basophilic intranuclear inclusions in the interstitial connective tissues of various organs. Electron microscopy analyses of degenerated cells revealed a nonoccluded, enveloped bacilliform virus within the nuclei. The virus morphologically resembles white spot syndrome virus (WSSV) or unassigned intranuclear bacilliform viruses (IBVs) reported from other crustaceans. However, we could not detect WSSV from diseased tissues by PCR using WSSV-specific primers, and the tissues targeted by the virus differed from those targeted by IBVs. This is the first report of a virus from the genus Chionoecetes. Thus, we have tentatively designated the virus presumably associated with MHS as Chionoecetes opilio bacilliform virus ( CoBV) until its relationship with other crustacean viruses can be clarified. [ABSTRACT FROM AUTHOR]

Based on materials from plankton surveys carried out in 2004-2009, the period of occurrence, density, and distribution of larvae of three commercial species of crabs in the Peter the Great bay and adjacent areas of Sea of Japan were studied. The larvae of the horsehair crab Erimacrus isenbeckii (Brandt, 1848) occurred in the plankton from mid-March to early June, within the range of water temperature from −1 to 10.8°C. The larvae of the helmet crab Telmessus cheiragonus (Tilesius, 1812) appeared in the plankton in mid-April and occurred to the end of June within the temperature range from 2.8 to 13.0°C. The larvae of the snow crab Chionoecetes opilio (O. Fabricius, 1788) appeared in the plankton in mid-April as well, but some individuals sporadically occurred until early August. All the species of crabs produced one generation of larvae for their reproduction season. The terms of larval stay in plankton depended on water temperature and the duration of the pelagic period increased in colder years. In that area, the larvae of C. opilio were the most abundant (up to 41 ind./m) and the zoea density of horsehair and helmet crabs was significantly lower (no more than 2 ind./m). The larvae of C. opilio occurred over the entire area of the Peter the Great bay; the greatest aggregations of their early stages were observed in its southwestern open part. The maximum density of E. isenbeckii zoea was recorded in the south of the Amursky bay and in the Posyet bay. Individual larvae of T. cheiragonus occurred in the Posyet bay and in the southern part of the Amursky and Ussuriisky bays. The late-stage larvae of all crab species were concentrated in areas of the coastal circulation. [ABSTRACT FROM AUTHOR]

The article discusses the abundance of snow crab Chionoecetes opilio in the northwest Atlantic Ocean after the decrease in numbers of major groundfish stocks. Climate control, top-down control of snow crab and bottom-up control of cod were the three hypothesis created by the authors, which was later tested against analyzing time series data of cob and snow crab abundance. They concluded that temperature during the early postsettlement years and the top-down mechanisms before the fishery recruitment affected the abundance of snow crab in the region.

Sequential acidic precipitation followed by a single chromatographic step (gel filtration) allowed the recovery of a collagenolytic fraction containing several proteases from by-products of snow crab ( Chionoecetes opilio). The partial purification was particularly efficient to recover tryptic (purification fold = 1,352.5; yield = 110%) but also chymotryptic, elastolytic, and collagenolytic activities. A temperature of 40 °C and pH 8.0-8.5 were optimal for enzyme activity, which was stable for 2 h under these conditions. Calcium was not required for stability and thus activity. The isoelectric points of the protein components ranged from 3.7 to 4.6. Zymography revealed 29 and 48 kDa major components and others from 22 to 56 kDa. Enzymes were inhibited by PMSF and TLCK but were insensitive to TPCK. In view of these properties, the proteases likely belong to the serine collagenase group. Inhibition by EDTA could be due to a mechanism other than Ca chelation. Using a food system (ground fish), the fraction was more proteolytic than a commercial bacterial protease, suggesting potential applications in enzymatic hydrolysis processes. [ABSTRACT FROM AUTHOR]

Abstract: Chionoecetes opilio (snow crab) in Atlantic Canada is a valuable fishery. A key factor in the conservation and sustainability of C. opilio is the length of its reproductive cycle, which in different regions has been observed to be ca. 1 or 2 years and temperature dependent. Ten years of embryo colour (a proxy for embryo development) data from the Scotia Shelf (SS) is analyzed using a binomial Generalized Linear Model. The influences of temperature and time variations upon the transition of early developmental stages are described. Over 80% of the females were estimated to follow a ∼1 year reproductive cycle, corresponding to the relative proportion of springtime SS bottom temperatures greater than 1°C. As an upper bound, total annual larval production is expected to have ranged from 280 billion and 32 trillion since 1997 with an associated female mortality from larval stage to maturity of 63–81% per annum (Z =1–1.65). Climate variability can therefore have a large influence upon the total potential reproductive output. Global Circulation Models predict that there will be more positive North Atlantic Oscillation years for the North Atlantic, assuming this to be the case we speculate that the associated warmer bottom temperatures along the central and west SS would lead to even greater percentages of the C. opilio females entering a 1 year reproductive cycle, whereas cooling along the eastern shelf (where the majority of the population resides) would shrink the warm water habitat available and potentially force more females into a two year cycle. If the magnitude of warming extends beyond C. opilio''s preferred range, the entire population may shift north-east. [Copyright &y& Elsevier]

Aged female snow crabs Chionoecetes opilio, 9 or so years old after their final molt, were collected sporadically from artificial reefs established off the coast of Wakasa Bay, Sea of Japan. In order to clarify the degenerative changes that occur in spent ovaries, the ovaries of these crabs were examined histologically. The ovaries were found to be reduced in both size and volume, with most showing significant oosorption by follicular epithelial cells. Reserve fund eggs and unspawned eggs were rarely detected, with the exception of some in atretic follicles. One to dozens of orange to black nodules scattered over the ovary consisted of masses of degenerative ova in various stages of oolysis. Since nodular formation was recognized in 26% of these aged individuals, it seems very likely that such crabs are unable to spawn healthy eggs. [ABSTRACT FROM AUTHOR]

Abstract: An experiment was carried out during September of 2001 to estimate the relative catching efficiency of the NAFC''s (Northwest Atlantic Fisheries Centre) standard survey bottom trawl, the Campelen 1800 shrimp trawl, for Snow Crab (Chionoecetes opilio). Secondary trawls were mounted underneath the main trawl directly behind the footgear to estimate escapement of crab passing underneath the main trawl. Overall, the capture efficiency of the survey trawl was found to be much lower than 1.0 and highly variable, with variability being strongly related to substrate type and Snow Crab size. The probability of capture monotonically increased with crab size, and was higher on soft than on hard substrates. Three substrate-specific capture efficiency functions were defined; (1) efficiency was highest (about 0.73–0.95), and least dependent on crab size, on the softest mud substrate; (2) efficiency was lower (about 0.39–0.70) and linearly related to crab size throughout a soft mud–sand substrate; and (3) efficiency was lowest (about 0.05–0.33) on a variety of hard substrates within relatively shallow water. Our models over-estimated true efficiency because secondary trawls were not fully efficient, i.e., crab escaped underneath their footgear. Nevertheless, our experiment demonstrated that substrate type can affect capture efficiency and annual changes in trawl configuration or in Snow Crab distribution in relation to substrate type will affect survey biomass estimates. Additional studies using various approaches could provide a basis for standardizing survey catches for varying capture efficiency effects and refining survey-based estimates of biomass and exploitation rates of Snow Crab. [Copyright &y& Elsevier]

Terminal molting probability (TMP) of snow crab Chionoecetes opilio was estimated using instar- and state-structured model incorporating the terminal molt in the waters off the Pacific coast of northern Honshu, Japan. TMP is defined as the probability that terminal molt occurs within a year in an instar and is an important parameter for stock assessment. TMP was estimated from the model and the rate of terminal molted crabs (RTM) for instars, which means carapace widths over 30 mm. Carapace widths at RTM of 0.5 were 81 mm for males and 66 mm for females. TMP was estimated as 0.23 and 0.29 for these carapace widths, respectively. Carapace widths at TMP of 0.5 were 94 mm for males and 71 mm for females, and for these carapace widths 57% of male and 50% of female crabs were considered as old-shell which had survived 1 year or more from terminal molt. Changing the fishing or natural mortality by ±0.1, the maximum difference of TMP was less than 0.1 from default estimates. [ABSTRACT FROM AUTHOR]

The recent identification of uridine diphosphate (UDP) as the female sex-pheromone in the European shore crab Carcinus maenas demonstrated not only the link between moult and pheromone production, but also how it may have evolved from a ‘simple’ metabolic byproduct. Consequently, it is expected to be present in other moulting crustaceans, thus raising issues involving species specificity of the female pheromone. Bioassays were conducted using synthetic pheromone (UDP, 10–3–10–4 M) to examine if it induced sexual behaviour in other crustacean species that are neither closely related nor occur in the same ecosystem. The snow crab, Chionoecetes opilio, and the yellowline arrow crab, Stenorhynchus seticornis, both belonging to a different superfamily (Majoidea) and occurring in different habitats than C. maneas (Portunoidea), displayed significant sexual behaviour towards UDP treated objects (p < 0.005). These and other examples demonstrate that the female sex-pheromone UDP is not species-specific but is present and active in some other decapod crustaceans. [ABSTRACT FROM AUTHOR]

Abstract: A total of 12,755 adult male snow crabs (Chionoecetes opilio) were tagged with spaghetti–Carlin tags in 33 sites throughout the southern Gulf of St. Lawrence (sGSL) and eastern Nova Scotia (eNS) between 1993 and 2003. Of the 1971 tag returns obtained between 1994 and 2004, 1703 had accurate geographical recapture positions. The average distance travelled was 16.7km for sGSL (maximum 165km) and 61.5km for eNS (maximum 368km). The release site and the number of days at liberty before recapture were significant factors affecting the distance travelled by the crabs. Size had no significant effect on the distance travelled or the direction of movement. The present observations support the sedentary nature previously reported for the sGSL snow crab stock, but not the eNS stock, where the movement of snow crab was more dynamic. In both regions, there were movements between management areas, which indicates that managing the fisheries in discrete units is not warranted. [Copyright &y& Elsevier]

Catch forecasting and the relationship between water temperature and catch in the snow crab Chionoecetes opilio in the western Sea of Japan were investigated. Catch was used as an index of abundance on the basis of high correlations between catch per unit effort for the period when the latter data were available. The pattern of fluctuations in catches and index coincided well with each other. Therefore, catch data were regarded as an index of abundance and the correlation coefficient between catch and water temperature was calculated at several depths from 1964 to 1999. Catch forecasting models were composed using significantly correlated variables with the following results: (i) in April and September, the catch showed high positive correlation with water temperatures (depth 50, 100, and 200 m, time lag 4–6 years); and (ii) a model using water temperatures in April alone (depth 100 m, time lag 4–7 years) forecasted the catches with a coefficient of determination of 0.504, where models using more variables (water temperatures in the 2 months and catches) showed a coefficient of 0.587 at most. Environmental conditions during the early life stages of the snow crab are thought to deeply influence the fluctuations in abundance. [ABSTRACT FROM AUTHOR]

Larval rearing experiments were conducted to examine the potential for mass seed production of the snow crab Chionoecetes opilio using a total of eight 20-kL tanks. Tanks were equipped with agitators, which move the water using a rectangular blade to prevent the zoeas sinking to the bottom of the tank. Larval rearing water was treated with sodium nifurstyrenate once a week to reduce the chance of larval infection by pathogenic bacteria. Zoeas were fed with rotifers and Artemia nauplii. A total of 122 830 megalops and 16 660 first-stage crabs were produced. Thus, the potential for mass seed production of snow crab was determined. Survival rates up to the megalopal stage were high in tanks with a feeding regime that fed rotifers to larvae through an entire zoeal stage. This study also describes the fatty acid composition of snow crab larvae. It revealed that the first zoeas had a high DHA content and DHA/EPA ratio, but these values significantly decreased in the second stage zoeas and megalops. Improving the DHA content and/or DHA/EPA ratio of larvae should be important in studies on mass seed production technology of the snow crab. [ABSTRACT FROM AUTHOR]

Abstract: The success with which Alaska''s groundfish stocks have been managed is not matched by management of its crab stocks, several of which have been declared overfished. It is unlikely that all species will be sampled equally well in a generic, multispecies trawl survey with a uniform distribution of sampling effort. We evaluated the relative sampling tractability of six species targeted by the eastern Bering Sea stock assessment survey conducted annually by the U.S. National Marine Fisheries Service to see if there were differences that might explain the dichotomy in management success observed for groundfish and crabs. Using relative niche breadth, Green''s Index of spatial patchiness, heterogeneity of variance and abundance-estimate precision, we analyzed 22 years of survey data to conclude that three major crab species, red king crab (Paralithodes camtschaticus), snow crab (Chionoecetes opilio) and Tanner crab (Chionoecetes bairdi), were less tractable than three major fish species, walleye pollock (Theragra chalcogramma), Pacific cod (Gadus macrocephalus) and yellowfin sole (Pleuronectes asper). In particular, our analysis established red king crab as the species for which abundance-estimate precision, niche breadth and sampling efficiency were lowest, patchiness was highest and heterogeneity of variance was the most severe. As a consequence, Bering Sea multispecies sampling is not likely to achieve the same degree of abundance-estimation success for red king crab as it might for other crab or fish species. [Copyright &y& Elsevier]