Diet and some ecological features of the most widespread commercial crab species in the northwestern Sea of Japan in early spring

Results of the study of feeding habits of the commercial crab species Chionoecetes opilio, Ch. japonicus, Paralithodes platypus, P. camtschaticus, and Erimacrus isenbeckii in early spring 2009 are presented. The composition, distribution, and quantitative characteristics of benthos in the areas of sampling are analyzed. The generalized pattern of distribution of the considered crabs is shown with the maximum and mean densities. These crabs were found to consume at least three to four single portions of food during 10–12 hours of daylight. The lowest feeding intensity was observed in the opilio snow crab in March and April. Cannibalism proved to be typical for all the studied crab species in the spring. It was most developed in the deepwater red snow crab, in whose diet representatives of the same species constituted a one-third share. It was also noted that the diet of the studied crabs included a major proportion of crabs and shrimps, which was unusual for the feeding habits of the same species in other Far Eastern seas.     

Genetic Variation and Population Structure of Hair Crab (<Emphasis Type="Italic">Erimacrus isenbeckii</Emphasis> ) in Japan Inferred from Mitochondrial DNA Sequence Analysis

Genetic variation and population structure of hair crab (Erimacrus isenbeckii) were examined using nucleotide sequence analysis of 580 base pairs (bp) in the 3′ portion of the mitochondrial cytochrome c oxidase subunit I gene (COI) of 20 samples collected from 16 locales in Japan (the Hokkaido and Honshu Islands) and one in Korea. A total of 27 haplotypes was defined by 23 variable nucleotide sites in the examined COI region. Pairwise population F _ST estimates and neighbor-joining tree inferred distinct genetic differentiation between the representative samples from the Pacific Ocean off the Eastern Hokkaido Island and the Sea of Japan, while others were intermediate between these two groups. AMOVA also showed a weak but significant differentiation among these three groups. The present results suggest a moderate population structure of hair crab, probably influenced by high gene flow between regional populations due to sea current dependent larval dispersal of this species.     

Isolation and characterization of polymorphic microsatellite markers in the red snow crab (Chionoecetes japonicus)

A total of 12 polymorphic microsatellite DNA loci were isolated from the red snow crab, Chionoecetes japonicus (Brachyura: Majidae), one of important fisheries resources in the Far East. The number of alleles observed at each locus ranged from two to 19, with the observed and expected heterozygosities of 0.125-0.875 and 0.156-0.949, respectively, suggesting these loci to be a useful molecular marker for population analysis in this species. Of the 12 loci, seven also were available for genotyping of the snow crab, Chionoecetes opilio, implying these loci as a useful molecular marker in the genus Chionoecetes.     

Development of microsatellite loci in red king crab (Paralithodes camtschaticus)

Polymerase chain reaction (PCR) primers for three trinucleotide and three tetranucleotide microsatellite loci were developed for red king crab (Paralithodes camtschaticus) to aid in studies of genetic population structure in Alaskan waters. Number of alleles ranged from six to 18 alleles (N = 562), and locus heterozygosities ranged from 0.505 to 0.839. Six primers were cross amplified with golden king crab (Lithodes aequispinus); five primers with blue king crab (P. platypus); and one primer with the splendid hermit crab (Labidochirus splendescens), the ‘missing link’ between pagurid and lithodid crabs. No cross amplification occurred with Tanner crab (Chionoecetes bairdi) or Aleutian hermit crab (Pagurus aleuticus).     

First observations of temperature tolerances of adult male snow crab (Chionoecetes opilio) from the Barents Sea population and the effects on the fisheries strategy

This study investigates the effects of temperature on the survival, food intake, oxygen consumption and growth during long-term live holding of captive male snow crab (Chionoecetes opilio) (average?=?0.7?kg). The crabs were held at three different temperatures, 3, 6 and 9°C. The trials were done using groups of snow crabs held in nine land-based holding tanks (three replicates per temperature treatment). The results showed that temperature had a significant effect on survival. The survival rate at 3°C (61%) was significantly higher than at 6°C (33%) and at 9°C (28%). Specific oxygen consumption rates of unfed crab at 6°C were significantly higher than at 9°C and 3°C. In summary, the current study shows that the Barents Sea snow crab have a narrow temperature range in which they thrive compared with the Barents Sea red king crab (Paralithodes camtschaticus). Barents Sea snow crab has similar metabolic and physiological attributes to other major snow crab populations. In conditions when ambient temperatures are approximately 6°C, it may prove beneficial for animal welfare and also be financially advantageous to reduce ambient water temperatures in live snow crab holding facilities on boat or on land.     

Metamorphosis season from megalopa to the first crab stage in snow crab Chionoecetes opilio and red snow crab C. japonicus (Crustacea,Decapoda, Majoidea) in the Sea of Japan,estimated from captive culture

ABSTRACT

Metamorphosis season of megalopae to the first crab stage in snow crab Chionoecetes opilio and red snow crab C. japonicus was inferred by culturing wild-born megalopae collected from the Sea of Japan. Metamorphosis occurred from late June to late July (mainly in July) in snow crab, and from early July to early October (mainly from August to September) in red snow crab. The number of days required from the time of collection to metamorphosis was less than the intermoult period previously reported for snow crab megalopae. However, the developmental period of the megalopae was estimated as substantially longer in red snow crab than in snow crab. Previous studies have shown that the hatching season and the period of the zoeal stage in both two species are similar. These results suggest that a different metamorphosis season between the two species would be due to a difference in their megalopal intermoult period.     

Potential for bowhead whale entanglement in cod and crab pot gear in the Bering Sea

Bowhead whales (Balaena mysticetus) of the western Arctic stock winter in ice‐covered continental shelf regions of the Bering Sea, where pot fisheries for crabs (Paralithodes and Chionoecetes spp.) and Pacific cod (Gadus macrocephalus) pose a risk of entanglement. In the winter of 2008–2009 and 2009–2010 the spatial distribution of 21 satellite tagged bowhead whales partially overlapped areas in which pot fisheries for cod and blue king crab (Paralithodes platypus) occurred. However, these fisheries ended before whales entered the fishing areas, thus avoiding temporal overlap. A fishery for snow crab (Chionoecetes opilio) typically runs from January to May and provides the greatest potential for bowhead whales to encounter active pot gear. Tagged whales did not enter the area of the snow crab fishery during this study and generally remained in areas with >90% sea ice concentration, which is too concentrated for crab boats to penetrate. Pack ice sometimes overruns active fishing areas, resulting in lost gear, which is the most likely source of entanglement. The western Arctic stock of bowhead whales was increasing as of 2004; as such, incidental mortality from commercial pot fisheries is probably negligible at this time. Regardless, entanglement may increase over time and should be monitored.     

A Review of Size at Maturity in Male Tanner (Chionoecetes bairdi) and King (Paralithodes camtschaticus) Crabs and the Methods Used to Determine Maturity

This paper reviews existing studies on the size of sexual maturityfor male Tanner or snow crab (Chionoecetes bairdi), a brachyuran,and the anomuran red king crab (Paralithodes camtschaticus).In this report the term sexual maturity is denned as the abilityto reproduce. A variety of indirect and direct methods thathave been used to determine maturity are reviewed. Examiningthe vas deferens for the presence of spermatophores was usefulin determining the size at which males first become mature.Breeding experiments in the laboratory demonstrated that mostmales, from both species, that produced spermatophores couldbreed with soft-shelled mates. Males of both species can breedat smaller sizes than do females. Morphometric techniques basedon reproductive tract weights and chela morphometry overestimatedthe sizes at which males mature in both species. Previous experimentsfor Tanner crab, which have internal fertilization, suggestsmall mature males can fertilize two to five females. Breedingexperiments showed recently matured red king crab do not appearto be able to fertilize more than one female per breeding season,while males nearing harvestable size can fertilize more thanone female. Breeding experiments and in situ observations of grasping pairsappear to be the most feasible methods for identifying malesize at maturity for these species. The value of morphometricestimations for determining when males mature is questionable.     

First record of the decapod-egg predator Ovicides paralithodis (Nemertea,Carcinonemertidae) from the snow crab Chionoecetes opilio (Decapoda,Brachyura)

The carcinonemertid monostiliferan Ovicides paralithodis Kajihara and Kuris, 2013 was originally described as an egg predator of the red-king crab Paralithodes camtschaticus (Tilesius, 1815) in the Sea of Okhotsk, the Bering Sea, and the Gulf of Alaska. In the present study, several carcinonemertid specimens were obtained from the egg mass of the snow crab Chionoecetes opilio (O. Fabricius, 1788) in the Sea of Japan. Partial sequences of the mitochondrial cytochrome c oxidase subunit I gene (COI) determined from two specimens of the carcinonemertid were identical with a barcode sequence from the holotype of O. paralithodis, indicating that the host range of the species covers at least the two decapod species, P. camtschaticus and C. opilio.     

On the growth of the blue king crab (<Emphasis Type="Italic">Paralithodes platypus</Emphasis>) population in the Peter the Great Bay of the sea of Japan

The causes of the appearance of large blue king crabs (Paralithodes platypus) in Peter the Great Bay for the last decade are discussed. This species is an important commercial resource in the waters of Russian Far Eastern seas, and its general concentrations are related mainly to the sublittoral and upper bathyal zones of the northwestern Bering Sea and the northern Sea of Okhotsk. Until recently, this species has been observed in areas along the continental coast of the northwestern Sea of Japan up to the Peter the Great Bay, where it incidentally showed up in red king crab (P. camtschaticus) and snow crab (Chionoecetes opilio) catches but was also commercially used. This area was considered as the southern periphery of the species range. Since the late 1990s, both male and female blue king crabs have been recorded in trawl and trap catches during research works conducted within the Peter the Great Bay. Since 2002, any commercial catches of shelf crab species are prohibited in the waters south of 47°20′ N because of a dramatic decline in their populations. Since then all the illegally caught crabs, including blue king crabs that are seized live from poachers, are released back into the water in certain places of the bay. In total, at least 29 503 blue king crabs, including egg-bearing females, were released within the period from 2002 to November 2009. At present, the overall blue king crab abundance in Peter the Great Bay, estimated based on the trap catches over an area of 7048 km², is 50500, the abundance of commercial-size males (with a carapace width over 130 mm) is 7500, and the male to female ratio is 1.00: 1.35. The increase in the blue king crab population observed in the bay is the result of the immigration of mature and viable individuals from other areas of its range. After this “uncontrolled introduction” blue king crabs adapted to new conditions, and then began breeding and spreading over the entire area of the bay.     

Characterization of enzymatic hydrolyzed snow crab (Chionoecetes opilio) by-product fractions: A source of high-valued biomolecules

Snow crab (Chionoecetes opilio) constitutes valuable and nutritional sources of components, such as proteins, lipids and chitin. The present investigation was undertaken to evaluate the feasibility of applying a pilot scale enzymatic hydrolysis process of snow crab by-products, followed by fractionation, in order to recover enriched high-valued compounds. The yield of snow crab by-products recovered after manual processing; on a dry weight was 87.4%. The by-products (raw materials) were mainly moist (approximately 78%), and contained 42.9% proteins, 14.8% lipids, 25.7% minerals, 16.2% chitin, all expressed on a dry weight. The fatty acid profile of snow crab by-products and all fractions obtained following processing showed a higher content in mono-unsaturated fatty acids (MUFAs; approximately 50%), followed by polyunsaturated fatty acids (PUFAs; approximately 20%) and saturated fatty acids (SFAs; approximately 15%). The n − 3/n − 6 ratio was approximately 10 and represents a good index of nutritional value for snow crab oil by-products. Most protein enriched fractions demonstrate a well-balanced amino acid composition, notably the most essential amino acids. These protein fractions are characterized by biomolecules having a relatively low molecular weight (35 kDa and less) range. The enzymatic hydrolysis process developed in this study shows that snow crab by-products should to be viewed as having the potential of being identified as high-valued products. Even though the process could be optimized, it is controllable, and depending on hydrolyses conditions, the products obtained are reproducible and well defined. Results presented in this study indicate that snow crab by-products may serve as excellent nutritional components for future applications in the health and food sectors.     

The period of occurrence,density, and distribution of larvae of three commercial crab species in Peter the Great Bay,Sea of Japan

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./m³) and the zoea density of horsehair and helmet crabs was significantly lower (no more than 2 ind./m³). 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.     

Crustacean resources are vulnerable to serial depletion – the multifaceted decline of crab and shrimp fisheries in the Greater Gulf of Alaska

The seas around Alaska support (or have supported) some of the most commercially significant crustacean stocks in the world, spread over an overwhelming array of extensive and diverse coastal and open shelf areas. Major resources include three species of king crab (Paralithodes spp. and Lithodes aequispina), Tanner and snow crab (Chionoecetes spp.), Dungeness crab (Cancer magister), and five species of pandalid shrimp (Pandalus spp. and Pandalopsis dispar). Excluding the Bering Sea, the resources from the Greater Gulf of Alaska (ranging from the Aleutian Chain to the state's south-eastern panhandle contiguous with British Columbia) supported rapid expansion of several crab and shrimp fisheries during the 20 year period 1960–1980. Since then, most of those fisheries have collapsed. While some of the stock declines have been well documented and discussed (most prominently the dethroning of red king crab on the shelf around Kodiak Island), it has been less apparent that the demise of Alaskan crustace an stocks is a process on a much larger scale, and is still unfolding. Here we examine trends in catch, recruitment and abundance (when possible) and discuss existing evidence of overfishing and management options. We emphasize the importance of recognizing the multi-scale spatial structure of crustacean stocks, and suggest the need to consider spatially explicit strategies, particularly the creation of reproductive refugia     

A new genus and species of monostiliferoidean nemertean (Nemertea: Enopla) found on an egg mass of the anomuran decapod Paralithodes camtschatica

A new genus and species of monostiliferoidean enoplan nemertean from Alaska is described and illustrated. The nemertean, Alaxinus oclairi gen. et sp. nov. , was found on the egg mass of a red king crab, Paralithodes camtschatica.     

Evidence for a permanent establishment of the snow crab (Chionoecetes opilio) in the Barents Sea

In the Atlantic the snow crab (Chionoecetes opilio) is naturally distributed on the northwestern side, i.e. eastern Canada and west Greenland. Until recently, there have been no observations of snow crab in eastern Atlantic. However, in 1990s single and occasional reports were made of crabs captured in the eastern part of the Barents Sea, presumably introduced through ballast water. Special attention during the annual bottom-trawl surveys in the Barents Sea during February 2004–2006 were given to include recordings of snow crab to evaluate if the introduced species has succeeded to establish a self-sustaining population in this region. Recordings of snow crabs were systematically noted and biological measurements carried out. The results confirm previous Russian observations of snow crabs in the northern region of Gåsebanken. In addition, a significant number of crabs were also found in the central region of the Barents Sea, mainly in deeper waters from 180 to 350 m depth. The sizes ranged from 14 to 136 mm carapace width. All females above 70 mm were berried with fertilised eggs. A major fraction (31% in 2005; 76% in 2006) of the crabs consisted of juveniles below 50 mm CW, providing evidence for successful recruitment. The small-sized crabs were exclusively found in Gåsebanken, identifying the main recruiting area at present for snow crab in the Barents Sea. The results obtained show that the snow crab is now adapted to the northeast Atlantic.     

The bitter crab syndrome in commercial crabs in the Western part of the Bering and Chukchi Seas

We studied the distribution of the “bitter-crab” syndrome, a disease caused by the parasitic dinoflagellate Hematodinium sp., in eight commercial species of crabs in the west of the Bering and Chukchi seas. The crabs (25 388 individuals) were sampled during bottom trawl surveys of July?September 2010 and October?November 2012. The disease was first identified visually by a color change of the exoskeleton and the hemolymph of the animals and then using microscope analysis of hemolymph samples. Infestation was detected in crabs of three species, Chionoecetes opilio, C. bairdi, and Paralithodes platypus. The prevalence of the disease (the percent of infected individuals relative to all of those examined) in C. bairdi and P. platypus was very low, 0.1 and 0.3%, respectively. Infestation was widespread among C. opilio, its peak in the Bering Sea was in the fall. The average prevalence of the crab disease in different areas of the Bering Sea ranged from 0.8 to 10.8%. A high rate of crab infection was recorded in the Korfa Bay. In the Chukchi Sea, the average prevalence was 2%. Infestation by Hematodinium sp. was not revealed in the deep-sea snow crabs Chionoecetes tanneri and C. angulatus, and in three species of lithodid crabs, Paralithodes camtschaticus, P. brevipes, and Lithodes couesi. This can be explained by the small sample volume and/or ecology of these species, since the disease was registered in other areas in four of them.     

The first demersal trawl survey of benthic fish and invertebrates in the Beaufort Sea since the late 1970s

This study represents the first demersal trawl survey of marine fishes and invertebrates in offshore waters of the Beaufort Sea since 1977. Species composition, distribution, and abundance of demersal fish and benthic invertebrates were assessed with standard methods and demersal trawl gear by the Alaska Fisheries Science Center. Fishes made up 6% of the total catch weight, and invertebrates made up the remaining 94% of the catch weight. A total of 32 species of fish were identified, two taxa were identified to genus and one to family, and 174 taxa of invertebrates were identified. The most abundant demersal fishes were polar cod (Boreogadus saida), eelpouts (Lycodes spp.), Bering flounder (Hippoglossoides robustus), and walleye pollock (Theragra chalcogramma). The most abundant invertebrates were notched brittle stars (Ophiura sarsi), snow crab (Chionoecetes opilio), mussels (Musculus spp.), and the mudstar (Ctenodiscus crispatus). We documented or confirmed extension to the known ranges of four species of fishes: walleye pollock, Pacific cod (Gadus macrocephalus), festive snailfish (Liparis marmoratus), and eyeshade sculpin (Nautichthys pribilovius). We also documented the presence of commercial-sized snow crab (Chionoecetes opilio), which has not previously been recorded in the North American Arctic.     

Population genetic analysis and origin discrimination of snow crab (Chionoecetes opilio) using microsatellite markers

Major habitats for the snow crab Chionoecetes opilio are mostly found within the northwest Atlantic and North Pacific Oceans. However, the East Sea populations of C. opilio, along with its relative the red snow crab (C. japonicas), are two of the most important commercial crustacean species for fisheries on the east coast of the Korean Peninsula. The East Sea populations of C. opilio are facing declining resources due to overfishing and global climate change. Thus, an analysis of population structure is necessary for future management. Five Korean and one Russian group of C. opilio were analyzed using nine microsatellite markers that were recently developed using next-generation sequencing. No linkage disequilibrium was found between any pair of loci, indicating that the markers were independent. The number of alleles per locus varied from 4 to 18 with a mean of 12, and allelic richness per locus ranged from 4.0 to 17.1 across all populations with a mean of 9.7. The Hardy–Weinberg equilibrium test revealed significant deviation in three out of nine loci in some populations after sequential Bonferroni correction and all of them had higher expected heterozygosity than observed heterozygosity. Null alleles were presumed in four loci, which explained the homozygosity in three loci. The pairwise fixation index (F _ST ) values among the five Korean snow crab populations did not differ significantly, but all of the pairwise F _ST values between each of the Korean snow crab populations and the Russian snow crab population differed significantly. An UPGMA dendrogram revealed clear separation of the Russian snow crab population from the Korean snow crab populations. Assignment tests based on the allele distribution discriminated between Korean and Russian origins with 93 % accuracy. Therefore, the snow crab populations around the Korean Peninsula need to be managed separately from the populations in Bering Sea in global scale resource management. Also, this information can be used for identification of snow crab origin which is problematic in worldwide crab trade.     

Isolation and Primary Structure of Trypsin from the King Crab Paralithodes camtschaticus

Trypsin from hepatopancreas of the crab Paralithodes camtschaticuswas isolated in homogeneous state by successive ion-exchange chromatography on DEAE-Sephadex, affinity chromatography on Agarose modified with peptide ligands from trypsin hydrolysate of salmin, and ion-exchange chromatography on a Mono Q column. The total yield of the protein was 64%. Its N-terminal amino acid sequence was determined (IVGGTEVTPG-). A sample of amplified total cDNA of hepatopancreas of king crab was obtained. A cDNA fragment containing the complete coding part of the gene was isolated on the basis of the known N-terminal amino acid sequence of the mature form of the trypsin. The polypeptide chain of the proenzyme consists of 266 aa. The mature trypsin involves 237 aa, which corresponds to its molecular mass of 24.8 kDa. A comparison of the amino acid sequence of the king crab trypsin with those of trypsins from other species of crustaceans demonstrated their high structural homology. The trypsin from the shrimp Penaeus vannamei appeared to be closest in primary structure to that of the king crab (65% identity).     

The Reproductive Biology of Snow Crab, Chionoecetes opilio: A Synthesis of Recent Contributions

The existing literature concerning reproduction of snow crab(Chionoecetes opilio) is critically reviewed and discussed inthe context of recent conceptual paradigms and ongoing research.The functional anatomy of the male and female reproductive systemsis presented and interpreted in terms of the various matingpathways available to this species. Hypotheses to account forimmediate and delayed fertilization are presented. The possibleadaptive values of spermatophore storage and a novel mechanismfor ensuring last male precedence are explored. In additionto critical gaps in our understanding of reproduction in snowcrab and other brachyurans, ambiguities in current conceptsand terminology are highlighted. Directions for future researchwhich addresses central problems of snow crab reproductive biologyare suggested.