Crab Populations Research Articles

Saving the horseshoe crab: A synthetic alternative to horseshoe crab blood for endotoxin detection.

Horseshoe crabs have been integral to the safe production of vaccines and injectable medications for the past 40 years. The bleeding of live horseshoe crabs, a process that leaves thousands dead annually, is an ecologically unsustainable practice for all four species of horseshoe crab and the shorebirds that rely on their eggs as a primary food source during spring migration. Populations of both horseshoe crabs and shorebirds are in decline. This study confirms the efficacy of recombinant Factor C (rFC), a synthetic alternative that eliminates the need for animal products in endotoxin detection. Furthermore, our findings confirm that the biomedical industry can achieve a 90% reduction in the use of reagents derived from horseshoe crabs by using the synthetic alternative for the testing of water and other common materials used in the manufacturing process. This represents an extraordinary opportunity for the biomedical and pharmaceutical industries to significantly contribute to the conservation of horseshoe crabs and the birds that depend on them.

Evaluation of Florida stone crab life history and management scenarios using spawning potential ratios

The stone crab, Menippe mercenaria, supported the third most valuable fishery in Florida in 2016. Declining catch per unit effort (CPUE) and a negative trend in landings since 2000 have raised concerns among fishermen, researchers, and fishery managers as to the fishery’s sustainability. The Fish and Wildlife Research Institute of the Florida Fish and Wildlife Conservation Commission estimates that the state’s stone crab fishery has been overexploited since 1997. This stock status determination, however, is based largely on trends in total landings and CPUE and does not account for the life-history parameters that describe stock productivity, such as size at maturity, fecundity, and survivorship. In this study, an age-structured per-recruit model was developed to evaluate how alternative biological parameters and management scenarios might affect reproductive output, calculated as the spawning potential ratio (SPR), of a theoretical stone crab population. The model incorporated new estimates of size at maturity, fecundity, and temperature-dependent release mortalities. Spawning potential ratios increased with decreasing size at sexual maturity and were sensitive to increasing natural mortality. The largest contributor to changes in SPR was mortality associated with the declawing and release of stone crabs. We also assessed various management scenarios including regulations governing minimum claw length, requiring the use of juvenile trap excluder devices, and institution of temperature-dependent season openings. Increasing the minimum claw length and excluding small juveniles from traps provided moderate protection to the spawning stock. The model suggests that adaptive management strategies that allow fishing only when water temperatures are below 24 °C (the temperature at which modeled survival is improved) could greatly reduce mortality and increase SPR. We examined a suite of management scenarios on the effect of SPR, but additional research should be conducted to determine the socioeconomic impact of changes in regulations in this valuable fishery.

A review on fisheries and conservation status of Asian horseshoe crabs

Horseshoe crabs are the only extant xiphosurans and are believed to be morphologically unchanged for more than 200 million years. Of the four extant species namely, Limulus polyphemus, Tachypleus tridentatus, Tapinauchenius gigas and Carcinoscorpius rotundicauda, the latter three are found in Asian waters. Recent evidences showed that Asian horseshoe crabs are facing serious threats such as degradation of their spawning grounds and habitat, environmental pollution, overexploitation as a culinary delicacy and biomedical bleeding practices. Baseline data on the distribution and existing population of the wild horseshoe crabs remain poorly known in several Asian regions. Several studies have clearly revealed that pressure due to over-fishing of wild stock has increased tremendously in the last decade. Due to an increase in demand for Tachypleus Amebocyte Lysate (TAL) analogous to Limulus Amebocyte Lysate (LAL) in the United States, there is an urgent need to comprehensively address their fishing and conservation measures in the Asian region. This review addresses the overall studies on three species of Asian horseshoe crabs in relation to their fishing practices, local exploitation of their wild stock either for human consumption (or) by biomedical industries. The authors have structured the discussion on an international scale to address the existing problems in fishing and conservation of horseshoe crabs. Since no specific regulatory force or legislative protection act or a policy to preserve their natural stock are available to this date, this paper strongly recommends representative countries to include horseshoe crabs under their wildlife protection act to avoid further unsustainable exploitation of their wild populations.

Functional responses of a cosmopolitan invader demonstrate intraspecific variability in consumer-resource dynamics.

BackgroundVariability in the ecological impacts of invasive species across their geographical ranges may decrease the accuracy of risk assessments. Comparative functional response analysis can be used to estimate invasive consumer-resource dynamics, explain impact variability, and thus potentially inform impact predictions. The European green crab (Carcinus maenas) has been introduced on multiple continents beyond its native range, although its ecological impacts appear to vary among populations and regions. Our aim was to test whether consumer-resource dynamics under standardized conditions are similarly variable across the current geographic distribution of green crab, and to identify correlated morphological features.MethodsCrabs were collected from multiple populations within both native (Northern Ireland) and invasive regions (South Africa and Canada). Their functional responses to local mussels (Mytilus spp.) were tested. Attack rates and handling times were compared among green crab populations within each region, and among regions (Pacific Canada, Atlantic Canada, South Africa, and Northern Ireland). The effect of predator and prey morphology on prey consumption was investigated.ResultsAcross regions, green crabs consumed prey according to a Type II (hyperbolic) functional response curve. Attack rates (i.e., the rate at which a predator finds and attacks prey), handling times and maximum feeding rates differed among regions. There was a trend toward higher attack rates in invasive than in native populations. Green crabs from Canada had lower handling times and thus higher maximum feeding rates than those from South Africa and Northern Ireland. Canadian and Northern Ireland crabs had significantly larger claws than South African crabs. Claw size was a more important predictor of the proportion of mussels killed than prey shell strength.DiscussionThe differences in functional response between regions reflect observed impacts of green crabs in the wild. This suggests that an understanding of consumer–resource dynamics (e.g., the per capita measure of predation), derived from simple, standardized experiments, might yield useful predictions of invader impacts across geographical ranges.

Effects of mangrove rehabilitation on density of Scylla spp. (mud crabs) in Kuala Langsa, Aceh, Indonesia

The density of mud crabs (Scylla spp.) in 2016 is described in three mangrove habitats: one rehabilitated 2007, one in 2013, and one not subject to any rehabilitation (a control site). We report the effects of mangrove rehabilitation on mud crab density, and correlations between mud crab density, mangrove density, mangrove stem diameter and tree height, and environmental parameters in the Kuala Langsa mangrove rehabilitation area, Aceh, Indonesia. Rehabilitation sites had significantly higher dissolved oxygen (DO), lower temperature, and greater mud depth than the control site. Mangrove density, stem diameter, and tree height were greater significantly in rehabilitation sites than at the control site. Mud crab density was significantly higher in the two rehabilitation sites than at the control site. Based on data from 140 sampling plots per site, stepwise multiple regression analysis revealed mangrove density to be the best predictor of mud crab density at all sites; correlations were positive. Tree height was the second predictor of mud crab density; correlations were positive at rehabilitated sites. Mud depth correlated positively with mud crab density at one rehabilitation site, and the control site. Multiple regression analysis for data combined for the three sites demonstrated mangrove density to be the best predictor of mud crab density (with positive correlation); a weak, positive correlation was also apparent for tree height and DO. Results support the view that mangrove rehabilitation enhances densities of mud crabs. Manipulative experimentation is required to determine the mechanisms of the ecology of mangrove ecosystems affect mud crab populations.

Spatial and temporal settlement patterns of blue crab (Callinectes sapidus and Callinectes similis) megalopae in a drought-prone Texas estuary

The Mission-Aransas Estuary is the wintering ground for the only sustained wild population of the endangered whooping crane (Grus americana), and blue crabs (Callinectes sapidus) are an important component of their diet as well as being a major food source for important sport fishes such as the red and black drum. Blue crabs also support a commercial crabbing industry, and fisheries data indicate that blue crab populations have been declining since the 1980s. Possible factors leading to decline in blue crab populations include overfishing, increased populations and predation by regulated sport fishes, reduced freshwater inflows into estuaries, and reduced larval recruitment. Little is known about blue crab recruitment dynamics in this region, but restricted passes between coastal estuaries and the Gulf of Mexico along with extended periods of drought that often lead to hypersaline conditions in coastal bays may limit larval recruitment from the Gulf into the bays. To investigate blue crab larval recruitment patterns, citizen scientist volunteers used hogshair settlement collectors to sample five monitoring sites over a four year period. Results show that large numbers of blue crab megalopae are common in nearshore waters of the Gulf of Mexico, but only a small fraction (∼1%) recruit into the estuary. Peak periods of ingress into the estuary occur during fall and winter months, with C. sapidus primarily contributing to the fall peak and C. similis dominating the winter peak. Increased salinity in the estuary during droughts may reduce the ability of blue crab larvae to detect and enter passes into the estuary.

Dramatic decline and limited recovery of a green crab (Carcinus maenas) population in the Minas Basin, Canada after the summer of 2013.

This paper reports the results of a ten-year monitoring program of an Atlantic Canadian population of green crabs, Carcinus maenas, in the Minas Basin of the Bay of Fundy. Intertidal densities, sex and reproductive ratios, juvenile recruitment, subtidal catch-per-unit-effort (CPUE), and sizes of crabs in this population were recorded from 2008 to 2017. In 2013 intertidal densities, mean crab sizes, subtidal CPUE, and proportions of crabs mature and reproducing all dramatically decreased to all-time lows, and large crabs virtually disappeared from the population. From 2014 to 2017 the population partially recovered but remained in an altered state. Potential causes of interannual changes to this population were investigated by correlating intertidal densities to 257 monthly environmental variables and performing stepwise multiple regression analyses. Crab densities in a given year were best explained by potential settlement during the summer and the maximum sea-surface temperature during March of the same year. However, potential roles of other factors (e.g., autumn winds, summer temperatures, North Atlantic Oscillation index) could not be ruled out. Changes in abundances of other species in the area, particularly predators and prey of green crabs, have also been observed and present possible alternative causative agents that should be investigated. Populations of other marine species in the Gulf of Maine-Bay of Fundy region within which the Minas Basin is situated have also been reported to have undergone dramatic changes in and after 2013, suggesting the occurrence of some oceanographic event or regime shift in the region. Declines to the monitored crab population in this study may have resulted from this same 2013 event. These observations have implications for recruitment to marine populations in this region.

Genetic variation in Irish Sea brown crab (Cancer pagurusL.): implications for local and regional management

AbstractUnderstanding demographic processes over multiple spatial scales is vital for the optimization of conservation/management strategies, particularly for commercially harvested taxa such as the brown crab (Cancer pagurusL). Brown crab population genetic structure was investigated at (i) a local scale within the Irish Sea, which included comparisons with the Lundy No Take Zone (NTZ) and (ii) across the NE Atlantic. The results indicate that the brown crab does not exhibit strong spatial structure either within the Irish Sea or at the regional level, suggesting high gene flow within and among the Irish Sea, English Channel and North Sea. Comparisons between the Lundy NTZ and harvested areas revealed similarly high levels of genetic diversity. An intriguing result was that the Lundy NTZ sample exhibited a degree of genetic patchiness (ephemeral geographically unpatterned differentiation) which may indicate elevated recruitment skews within the NTZ. Overall, the results support the view that brown crabs within the sampled area belong to a single genetically panmictic stock and that if breeding stock sizes are maintained genetic drift will not be strong enough to reduce neutral genetic diversity. The highly connected nature of this species requires international cooperation for sustainable management, an important component of which will be the application of more powerful population genomic approaches to assess finer scale aspects of stock structure as well drivers of genetic patchiness reported for the species. This is a timely consideration in light of potential future misalignments between biological and geopolitical stock boundaries in the Irish Sea following Brexit.

Biological Analysis of Blue Swimmer Crab (Portunus pelagicus) from Collectors in Lamongan, Tuban, Pasuruan, and Rembang, Java, Indonesia

Blue swimmer crab ( Portunus pelagicus ) can increase the country’s incomes due to its high demand of export. This study aims to determine biological analysis on the population of blue swimmer crab in Lamongan, Tuban, Pasuruan, and Rembang. The sampling location was based on the fishing area and the method used survey method from collectors in each location. The blue swimmer crab’s biological characteristics which observed are the correlation on wide of carapace and blue swimmer crab weight, sex ratio, and gonad maturity level. The results showed the correlation between the wide and weight of carapace in Lamongan (male: 113.80-122.99 mm and 87.98-121.60 g then female: 108.21-117.27 mm and 71.80-99.74 g), Tuban (male: 113.26-117.74 mm and 89.63-102.76 g g then female: 114.36 mm and 106.51 g), Pasuruan (male: 87.66-94.43 mm and 39.68-49.90 g then female: 101.94-110.89 mm and 66.98-82.89 g), and Rembang (male: 120.30-126.69 mm and 93.53-118.43 g then female: 125.30-132.13 mm and 134.42-157.47 g); sex ratio (male: female) in Lamongan (1.4: 1), Tuban (1: 1.5), Pasuruan (2.8: 1), and Rembang (1: 1.46); and also gonad maturity level in Lamongan (dominant male at level III was 30.29%, female at level II and III was 30.40%), Tuban (dominant male at level II was 41.93%, female at level III was 33.33%), Pasuruan (dominant male at level III was 25.79%, female at level III was 48.10%), and Rembang (dominant male at level II was 32.35%, female at level II was 33.33%). These results indicate that the total of Portunus pelagicus which was being caught had fulfilled the standards rules by No.1/PERMEN-KP/2015. However, it requires continuous direct monitoring and counseling to maintain the stock of blue swimmer crab resources. Keywords: Blue swimmer crab ( Portunus pelagicus ), gonad maturity level, sex ratio, wide and weight.

Native predators control the population of an invasive crab in no‐take marine protected areas

Abstract The resistance of an ecosystem to species invasion is considered to be related to the abundance and diversity of native species (i.e. biotic resistance hypothesis). Theory predicts that the high native diversity in pristine systems can hinder the establishment and/or the spread of non‐native species through direct and indirect mechanisms (e.g. through competitive and/or predatory interactions). Here we tested whether predation provides higher resistance to invasion by the Percnidae crab Percnon gibbesi (H. Milne Edwards, 1853) in protected native communities, compared with exploited ones. Specifically, this study aimed to compare: (i) the abundance and diversity of potential predator assemblages of P. gibbesi; (ii) the predation pressure on P. gibbesi; and (iii) the density of this species in two protected and two unprotected sites along the northern Sicilian coast (Italy). The relative predation rate was assessed by manipulative tethering experiments conducted on two size classes of P. gibbesi using long and short tethers, both at protected and unprotected sites. The abundance and diversity of the predators of P. gibbesi and the relative predation rate on tethered crabs were higher at protected than at unprotected sites, independent of crab size and tether length. The density of P. gibbesi was significantly lower in protected compared with unprotected sites. These results suggest that the diversity and abundance of native predator assemblages directly affect the invasion success of P. gibbesi in the Mediterranean Sea. We provided experimental evidence that the restoration of predator assemblages confers ‘biotic resistance’ to no‐take marine protected areas (MPAs) against P. gibbesi invasion. Our study confirms that no‐take MPAs are effective in combating non‐indigenous species (NIS) invasion, and that it is crucial to establish a long‐term monitoring programme to limit the introduction of NIS and to control the spread of existing ones.

Prevalence of the pathogenic crustacean virus Callinectes sapidus reovirus 1 near flow-through blue crab aquaculture in Chesapeake Bay, USA

Understanding the ecology of diseases is important to understanding variability in abundance, and therefore management, of marine animals exploited commercially. The blue crab Callinectes sapidus fills a crucial benthic-pelagic niche in Atlantic estuarine ecosystems and supports large commercial fisheries in both North and South America. In the USA, pre-molt blue crabs are typically held in short-term shedding (ecdysis) facilities to produce soft-shell crabs of increased value. However, mortality rates in these facilities are high and commonly associated with the pathogenic C. sapidus reovirus 1 (CsRV1). To assess whether crab mortalities in these facilities might increase CsRV1 prevalence in wild crab populations, tissue sampled from crabs collected over 2 summers either near to or far from shedding facilities using flow-through water systems were tested by reverse transcription quantitative PCR (RT-qPCR) for the presence of CsRV1 RNA. In support of our hypothesis, PCR data identified the probability of detecting CsRV1 in wild crabs sampled close to shedding facilities to be 78% higher than in crabs sampled from far sites. PCR detections were also 61-72% more probable in male crabs and 21% more likely in male and female crabs over the minimum landing size. As the prevalence at which CsRV1 was detected varied within seasons, among locations and between years, blue crab migration and/or population fluctuations appear to also be involved.

Pendugaan Growth Overfishing Rajungan (Portunnus pelagicus) di Teluk Banten

This research was conducted in February-March 2018 at Banten Bay. The purpose of research is to determine to presence of growth overfishing of crab ( Portunus pelagicus ) , to cover width-weight relationships, sex ratio, Gonad Maturity Rate (GMR), Length at First Capture (Lc) and Length at first maturity (Lm). The method used is market survey (observation on crab collectors). Temporary research result showed that width-weight relationships are allometrically positive. Sex ratio show a balance value. GMR is the dominant GMR III. Lc 11,26 cm male; 11,38 cm female and Lm 11,82 cm male; 9,30 cm female. Based on the data, it can be seen that the population of the male crabs more quickly decreased compared to the females. If these fishing conditions continue to happen in the long time. It will cause the growth overfishing, result the temporary loss of population and change the food chain.

Infestation and morphological identification of the stalked epizoic barnacle Octolasmis on the blue crab Portunus pelagicus from the Red Sea

The intensity of infestation of the epizoic stalked barnacle Octolasmis on the blue crab was calculated for a total of 180 individuals collected around Jeddah, the western Red Sea Saudi coast. More than 90% of the crabs were found bearing the Octolasmis at a prevalence rate of 92% and mean intensity of 18.5 ± 18.6 (0–127 epibiont per host). The intensity of infestation increased with host size in the range 90–135 mm. Generally, females were more infested (69%) than the males (31%). Octolasmis angulata occurred mostly on the gills, and the lower side of the gill chambers was more infested (84%) than the upper side (16%) and the left side of gills was also more infested than the right side in both males and females. Further studies are still needed to examine the commensal relationship and its impact on the fishery market of the Red Sea blue crab populations.

Acute thermal effects in an inland freshwater crab Austrothelphusa transversa (von Martens, 1868) occupying seasonal, tropical rivers

Crustaceans occupying drying waterholes in seasonal tropical rivers can access terrestrial areas to regulate hyperthermia. An experiment tank filled with water and containing a mesh ramp and dry platform was designed to determine the terrestrial locomotion response of the tropical inland freshwater crab Australothelphusa transversa (von Martens, 1868) when exposed to increasing water temperatures. A thermoline controller increased water temperature (acclimation 25 °C, ± 0.5) at two rates, 18 °C h–1 (commonly employed in other studies) and 3 °C h–1 (reflecting measured regional river conditions) to determine the acute effects temperature (AET50) threshold for the crab. Random movement was minimal in the 18 °C h–1 experiment, with crabs accessing and remaining on the platform until the experiment ended (AET50 = 40.2; maximum = 41.69 °C). Crabs exhibited more random movement in the 3 °C h–1 experiment, visiting the platform for 3–21 min before returning for 3–131 min (AET50 = 34.2, maximum = 37.25 °C). Crabs collected from a second, more arid, geographical location in northern Australia had a similar AET using 3 °C h–1 increase (AET50 = 35.3; maximum 37.60 °C) and a similar AET using 18 °C h–1 increase (AET50 = 39.3; maximum 41.7 °C) to the coastal crab results (ANCOVA interaction location and ramp rate F = 1.88, P > 0.15). A temperature rate altering AET estimates by several degrees (regardless of where crab population was collected: ANCOVA location, F = 0.668, P > 0.4; rate increase factor, F = 4.31, P < 0.001) highlights the need for laboratory experiments to be underpinned by relevant field data. These data outline that crab avoidance responses could include accessing river banks, as a response necessary to regulate temperature during critical periods.

The Role of Horseshoe Crabs in the Biomedical Industry and Recent Trends Impacting Species Sustainability

Every year the Atlantic horseshoe crab (Limulus polyphemus) arrives on shore to spawn, a sight once taken for granted. However, in addition to the gradual climate changes impacting all ecosystems, commercial demand from the widespread application of Atlantic horseshoe crab blood in industrial endotoxin testing and steady use as eel and whelk bait has brought the future of this enduring species into question. In response, regulations have been adopted to enhance the traceability and record keeping of horseshoe crab harvest, which has historically been difficult to track. However, these regulations do not restrict or limit LAL harvest in any significant manner. Still, sometimes-lethal biomedical bleeding process and associated behavioral changes pose a risk to horseshoe crab viability after bleeding and once returned to the waters. As a result, regulators and environmentalists are concerned that current trends and overfishing of this marine arthropod will significantly impact the surrounding ecosystem. This review examines their role and recent trends in the biomedical industry that are impacting these ancient creatures and the derivative effect on shorebirds, while considering emerging alternatives where feasible, as well as ways to ensure sustainable and pragmatic harvesting strategies. Ultimately, healthy populations of horseshoe crabs are vital to restoring and maintaining ecosystems while balancing the need for medical and research applications entirely dependent on these unique creatures.

In the middle of the road, there was a swamp: the social and environmental impacts of the Bragança-Ajuruteua highway, Pará, Brazil

The article investigates the social and environmental impacts of construction of Highway PA-458, which turned 26km of mangrove swamp into a landfill between the municipality of Bragança and Ajuruteua beach in northeastern Pará. Working with official documents, newspapers, photographs, and oral accounts, it analyzes politicians', local residents', and crab harvesters' representations of the significance of the highway. It is concluded that officials have disregarded the environmental impact both on the mangrove swamps and on the daily lives of crab harvesters. While the latter may even view the road as positive, they have been confronted with a progressively dwindling crab population and a growing number of crab dealers.

Top-down and bottom-up controls on southern New England salt marsh crab populations.

Southern New England salt marsh vegetation and habitats are changing rapidly in response to sea-level rise. At the same time, fiddler crab (Uca spp.) distributions have expanded and purple marsh crab (Sesarma reticulatum) grazing on creekbank vegetation has increased. Sea-level rise and reduced predation pressure drive these changing crab populations but most studies focus on one species; there is a need for community-level assessments of impacts from multiple crab species. There is also a need to identify additional factors that can affect crab populations. We sampled crabs and environmental parameters in four Rhode Island salt marshes in 2014 and compiled existing data to quantify trends in crab abundance and multiple factors that potentially affect crabs. Crab communities were dominated by fiddler and green crabs (Carcinus maenas); S. reticulatum was much less abundant. Burrow sizes suggest that Uca is responsible for most burrows. On the marsh platform, burrows and Carcinus abundance were negatively correlated with elevation, soil moisture, and soil percent organic matter and positively correlated with soil bulk density. Uca abundance was negatively correlated with Spartina patens cover and height and positively correlated with Spartina alterniflora cover and soil shear strength. Creekbank burrow density increased dramatically between 1998 and 2016. During the same time, fishing effort and the abundance of birds that prey on crabs decreased, and water levels increased. Unlike in other southern New England marshes where recreational overfishing is hypothesized to drive increasing marsh crab abundance, we propose that changes in crab abundance were likely unrelated to recreational finfish over-harvest; instead, they better track sea-level rise and changing abundances of alternate predators, such as birds. We predict that marsh crab abundance will continue to expand with ongoing sea-level rise, at least until inundation thresholds for crab survival are exceeded.

Evaluation of fishery-induced sperm limitation in Chesapeake Bay blue crab using an individual-based model

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 596:127-142 (2018) - DOI: https://doi.org/10.3354/meps12595 Evaluation of fishery-induced sperm limitation in Chesapeake Bay blue crab using an individual-based model Sarah A. M. Rains*, Michael J. Wilberg, Thomas J. Miller University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, PO Box 38, Solomons, MD 20688, USA *Corresponding author: sarah.rains@accsp.org ABSTRACT: Sperm limitation, where the reproductive output of a population is restricted by its sperm production, is a concern for several crustacean species around the world. We used a simulation study to evaluate the effects of different fishing pressures and regulations on the male to female sex ratio and the average number of sperm received per female for the blue crab Callinectes sapidus population in Chesapeake Bay. We created an individual-based model that tracked a cohort of immature females on a daily step over a 2 yr period as the cohort grew, matured, and mated with mature males. The model included sex-specific growth, maturity, and mating of a closed population. We ran the model under multiple scenarios of mate choice behavior to quantify the patterns in sperm counts and sex ratios across a broad range of simulated fishing pressures and regulations. Average sperm counts in mated females and male to female sex ratios of the modeled population varied among scenarios, but were not related to each other. Fishing pressure had a significant negative effect on average sperm per female only in scenarios with unfished females and the exploitation rate for males at 5 times that currently estimated in Chesapeake Bay. Our results suggested that sperm per female is not linearly related to mature male to female sex ratios and that sperm limitation does not appear to be a concern for the blue crab population of Chesapeake Bay under current regulations. KEY WORDS: Callinectes sapidus · Sperm limitation · Crustacea · Fisheries management · Demographic model · Blue crab Full text in pdf format PreviousNextCite this article as: Rains SAM, Wilberg MJ, Miller TJ (2018) Evaluation of fishery-induced sperm limitation in Chesapeake Bay blue crab using an individual-based model. Mar Ecol Prog Ser 596:127-142. https://doi.org/10.3354/meps12595 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 596. Online publication date: May 28, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Using of microsatellite DNA profiling to identify hatchery-reared seed and assess potential genetic risks associated with large-scale release of swimming crab Portunus trituberculatus in Panjin, China

Many economically important species in demand in the market and with depleted populations have been artificial bred and their seed intensively released into the wild. As one of the most important fishery species in China, the swimming crab Portunus trituberculatus has been stocked in Panjin at a large scale since 2012. Nevertheless, no genetic profile considering genetic effects of these practices has been constructed. The present study traced the crab population enhancement in Panjin. In 2015, a total of 1671 crabs were captured in Panjin and among them 120 individuals were identified as being hatchery-raised, indicating that hatchery-raised seed contributed to the local resource. To address possible genetic effects from the hatchery stock, we compared the genetic characteristic among female broodstock, recaptured hatchery-raised, recaptured non-hatchery-raised and a wild control population based on six microsatellite markers. Results showed obvious reductions in gene diversity and effective population size (Ne) and increased relatedness in recaptured hatchery-raised crabs. Moreover, recaptured non-hatchery-raised – the local population in Panjin – also exhibited similar patterns of dramatic loss of Ne and increased degree of relatedness. The genetic homogeneity involving low Wright's fixation index (Fst), large percentage genetic variance among individuals and strong gene flow appeared in all sample locations distributed in the Bohai Sea and the Yellow Sea. Our data suggest that large-scale stock enhancement of P. trituberculatus presents strong potential genetic risks to the Panjin local population and even the whole waters surrounding the Liaodong Peninsula. Several approaches were proposed to gain better insight into P. trituberculatus enhancement practices in the future.

Development of snow crab Chionoecetes opilio (Crustacea: Decapoda: Oregonidae) invasion in the Kara Sea

With current climate trends, longer ice-free periods and increased human activity are observed in the previously hard to access Arctic Siberian seas. This provides for a rare opportunity to observe the progress of species invasion in pristine areas. The snow crab, Chionoecetes opilio, is a unique example of an alien Brachyura crab in the Arctic. Its distribution, population size structure, as well as biotic and abiotic conditions affecting its survival in the Kara Sea are discussed. Crabs were collected using trawl sampling in 2014. It has been estimated that the invasion took place in the late 2000s through the northern and eastern borders with the Barents Sea. Presently, snow crabs are found throughout the western part of the sea, from Kara Gates to St. Anna Trough; the entire area between Yamal Peninsula and Novaya Zemlya; and the northeastern shelf of the sea. Benthic abiotic conditions of the Kara Sea are unlikely to limit survival and further progress of snow crab population. However, the length of the ice-free period could limit its reproduction potential. The collected data do not allow us to presume the existence of a reproducing population, yet the presence of a settler-size group in the central part of the western Kara shelf could indicate local recruitment. Food availability in the Kara Sea is unlikely to limit growth of early benthic stages of snow crabs such as those collected in 2014. However, the question remains open whether benthic productivity is sufficient to allow these crabs to reach commercial sizes.