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Crab species are increasingly important socioeconomic resources that are threatened by human exploitation, climate change, and invasive species, such as European green crabs (Carcinus maenas). However, the continued health of their populations is often uncertain given the limited long‐term population data, necessitating alternate approaches to ensure their continued viability. Furthermore, C. maenas are one of the most highly invasive and destructive marine species globally, posing a threat to local ecosystems and species, including socioeconomically important crabs and their mollusc prey. Improved understanding of C. maenas invasions and their impacts on local crab and mollusc resources is therefore vitally important. Here, we present a new method for identifying species‐level presence and relative abundances of important crab species, including invasive C. maenas, from the scars they leave on their prey. We conducted controlled manipulative feeding experiments in which individuals of Dungeness crabs (Metacarcinus magister), red rock crabs (Cancer productus), and C. maenas, were allowed to attack snails (Tegula funebralis) and produce sublethal shell damage. Resulting shell damage was photographed and landmarked for geometric morphometric analyses to determine any differences in the shape of shell damage between crab species. There were statistically significant differences between the shape of shell damage created by all three crab species (p <.0001). Shell damage formed a gradient from narrow/deep (C. productus) to shallow/wide (C. maenas) with M. magister as an intermediate form. Our method provides a novel, cost‐effective tool for long‐term species‐specific reconstructions of crab populations and assessing the broader ecological impacts of C. maenas invasions that can inform management and mitigation for these three important crab species. [ABSTRACT FROM AUTHOR]

The article presents a comparative analysis of the fecundity of the Barents Sea red king crab, its size composition, and size at 50% maturity during the period of its expansion and acclimatization and at present during intense fishing. In addition, based on the published literature data, differences are estimated between the above parameters of Barents Sea individuals and individuals from the crab's natural habitat. In 2019–2022, the Barents Sea red king crab showed a trend of decreasing its fecundity compared to the period of active acclimatization (1995–2003) before commercial exploitation started. In recent years, changes in the reproductive parameters of the Barents Sea red king crab population have increased the similarity of these characteristics to those for native populations from the Pacific region that began to be actively exploited in the early 20th century. [ABSTRACT FROM AUTHOR]

Introduction: Intertidal habitat preferences and spatiotemporal variation in the abundance of juvenile Chinese mitten crab Eriocheir sinensis in Yangtze Estuary are reported. Methods: The size and abundance of this crab are reported for mud flat, gravel, root belt, and marsh habitats in this estuary's lower, middle, and upper reaches from June 2021 (spring) to February 2022 (winter) using quadrat method. Results: Juvenile E. sinensis of carapace length (CL) 5.5 ± 2.1 mm (mean ± standard deviation) were collected; no juveniles were found in February 2022. Crab abundance in root belt and gravel habitats usually exceeded that of marsh habitat; no juveniles were found in mud flat habitat. The greatest abundances and smallest individuals were found when megalopa recruited in early spring (June); juvenile abundance decreased sharply afterwards, and crabs were absent from the intertidal during winter. Size and relative growth rate of juvenile crabs were greater in root belt and gravel habitat than in marsh habitat from June to August. Recruitment primarily drove changes in crab abundance and size during June and July, and temperature best correlated with changes in the winter. Many stage I juveniles (CL < 3.1 mm) occurred in the lower estuarine reaches, while stage III and IV juveniles (CL 3.9-6.5 mm) primarily occurred in the middle and upper estuarine reaches. Discussion: Although intertidal wetland habitat in Yangtze Estuary is severely degraded and reduced in area, it remains important for recruitment and maintenance of mitten crab populations. An understanding of the habitat requirements of this species will benefit management of this crab resource and the prioritized restoration of intertidal habitat. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Anatolian Environmental & Animal Science is the property of Bulent Verep and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The timing of American horseshoe crab (Limulus polyphemus) spawning behavior along the coast of Florida (United States) is generally associated with the highest tides during the spring and fall lunar cycles. All Florida estuaries support horseshoe crab populations, but tidal characteristics vary markedly among locations, which may influence the timing of horseshoe crab spawning behavior. The Indian River Lagoon is a large microtidal estuary on Florida's east coast. Given the microtidal nature of the lagoon, it is unclear which environmental factors affect horseshoe spawning. In 2019, volunteers of Florida Horseshoe Crab Watch conducted daily surveys at two sites in the northern Indian River Lagoon during peak spawning months (February–April). During each survey, volunteers counted all spawning horseshoe crabs and recorded environmental variables, including water temperature, air temperature, wind speed, wind direction, salinity, and tide height. We developed a suite of negative-binomial regression models to quantify relationships between the number of spawning horseshoe crabs and environmental factors. Modeling results indicated a positive relationship between onshore wind speed and number of spawning horseshoe crabs. Our study suggests that in the absence of tidal cues, onshore wind speed may be an important driver of horseshoe crab spawning activity in microtidal estuarine systems. [ABSTRACT FROM AUTHOR]

Introduction: Seabirds and other insular birds are an important part of marine ecosystems and are increasingly threatened worldwide. Phenology, abundance, distribution, and breeding success are important baseline parameters needed to evaluate population trends and dynamics, identify biodiversity hotspots and potential breeding sites, and assess habitat selection. In the Red Sea basin, reliable and complete data on birds are lacking for islands in most of the Important Bird Areas (IBA). Such data are now especially important since development projects have started at several of these locations. Here, we assess the distribution, abundance, phenology, and population trends of 13 bird species that breed in the Duba Islands, Al Wajh Bank, and Al Lith Islands. Breeding success and habitat selection for six species were also assessed. Methods: Between December 2020 and August 2023, more than 90 islands were visited multiple times with different frequencies. All nests were counted, and the area occupied by the different colonies was georeferenced. Breeding success was assessed by visiting selected colonies multiple times until the chicks were ready to fledge. Habitat selection was determined by analyzing the habitat found in the georeferenced colonies. Results: More than 25,000 nests were counted each year, mainly in the summer, on more than 75 islands. Of the 13 species studied, the most abundant and widespread species was the White-cheeked tern, and the second most widespread was the Osprey. Discussion: We estimate that the Al Wajh Bank hosts the following percentages of global breeding populations: Crab plover: 5%, Sooty gull: 17%-35%, White-eyed gull: 15%, Bridled tern: 1%, White-cheeked tern: 4%, and Lesser crested tern: 2%, making the area a regional and global hotspot for these species. Some of the islands occupied by breeding birds are slated for development for tourismactivities as part of the Kingdom's tourism expansion plans. At the same time, there are several ambitious conservation programs underway in these areas. To be effective, such programs require reliable and comprehensive data of the kind presented here. [ABSTRACT FROM AUTHOR]

During cruise 89 of the R/V Akademik Mstislav Keldysh in September–October 2022, search for the snow crab Chionoecetes opilio were conducted in benthic communities of the Kara Sea using a Sigsby bottom trawl and the TUV Videomodule; as well, plankton samples were collected with a Bongo net in order to record crab larvae in the water column. Single large individuals of snow crab were found for the first time in the eastern Kara Sea, on a transect from the Voronin Trough towards the coast of Taimyr, starting at a depth of 490 m. At the same time, not a single crab larva was caught, which indicates penetration of mature crabs into these areas across the bottom. Conversely, in the western part of the sea and in Blagopoluchiya Bay, large numbers of all size groups of C. opilio on the bottom, as well as crab larvae in the water column, were observed. The differences in the speed and nature of the snow crab invasion are explained by the contrast in the ice conditions in the western and eastern Kara Sea. The snow crab population is likely to spread further in the eastern Kara Sea due to trends towards an increase in the ice-free period in the Arctic. [ABSTRACT FROM AUTHOR]

We present a case study using trapping data and species accumulation theory to assess the sampling effort needed to detect species that are rare in habitats sampled as part of the management of invasive European green crab Carcinus maenas on the coast of Washington State and Salish Sea shorelines, such as is desired for early detection of invasive species. In response to detections of green crab on the west coast of North America monitoring efforts, including early detection monitoring, have increased. The goal of invasive species early detection monitoring programs is to detect new infestations soon after introduction so that eradication and quarantine measures can be used to control their spread. However, detection of newly introduced invasive species often occurs after populations are large and well established. The ability to detect newly introduced invasive species is affected by sampling procedures, including how much effort is expended. To assess the level of trapping effort needed to detect green crab and other taxa when they are rare, we calculate sample-based rarefaction curves, total species richness, and estimates of sample completeness. We then use these estimates to describe the relationship between sampling effort and detection at two different spatial scales. Our results suggest that high probability early detection of green crabs or other rare taxa in many coastal waterbodies will require significantly more trapping effort than was expended in 2020. Our analyses further suggest that the effort required to provide for early detection was less at the site-specific spatial scale than at the waterbody scale. However, sample completeness at the site-specific spatial scale was negatively correlated with species richness. Current efforts to look for new green crab populations and to manage existing populations provide an opportunity to look for other invasive organisms that may establish in similar habitats. [ABSTRACT FROM AUTHOR]

Tourism pressure on the Red Sea ecosystem have posed significant threats to numerous endemic species, including the Ghost Crab Ocypode saratan, which is exclusively found along a small stretch of beach in the Eilat/Aqaba Red Sea Gulf. Due to the limited understanding of their ecology, we investigated how tourism impacts the behavior of this species. Employing a natural setup, we compared burrow dimensions, pyramid structures, and density across three distinct beach sections subjected to varying levels of human interference. Access to a secluded beach, referred to as "No Man's Land," provided a crucial control for our study. This facilitated a comparative analysis of ghost crab activity among beaches experiencing differing levels of human disturbances: (1) a tourist beach characterized by continual high disturbance, (2) a naval beach subject to moderate and sporadic disturbances, and (3) the isolated "no man's land" beach devoid of human presence. Our observations revealed notable differences in ghost crab density among the three beaches. Furthermore, we observed that on the secluded beach, larger individuals tended to establish burrows farther from the waterline and construct taller sand pyramids. Given the significance of sexual selection processes, their conservation becomes imperative for the survival and potential expansion of the ghost crab population across the Gulf of Eilat/Aqaba. We propose a straight-forward and cost-effective strategy: the designation of short, secluded beach enclaves along this gulf. We believe that this approach will mitigate adverse impacts of tourisms while simultaneously benefiting various sandy beach species. [ABSTRACT FROM AUTHOR]

Predation by invasive species can threaten local ecosystems and economies. The European green crab (Carcinus maenas), one of the most widespread marine invasive species, is an effective predator associated with clam and crab population declines outside of its native range. In the U.S. Pacific Northwest, green crab has recently increased in abundance and expanded its distribution, generating concern for estuarine ecosystems and associated aquaculture production. However, regionally-specific information on the trophic impacts of invasive green crab is very limited. We compared the stomach contents of green crabs collected on clam aquaculture beds versus intertidal sloughs in Willapa Bay, Washington, to provide the first in-depth description of European green crab diet at a particularly crucial time for regional management. We first identified putative prey items using DNA metabarcoding of stomach content samples. We compared diet composition across sites using prey presence/absence and an index of species-specific relative abundance. For eight prey species, we also calibrated metabarcoding data to quantitatively compare DNA abundance between prey taxa, and to describe an 'average' green crab diet at an intertidal slough versus a clam aquaculture bed. From the stomach contents of 61 green crabs, we identified 54 unique taxa belonging to nine phyla. The stomach contents of crabs collected from clam aquaculture beds were significantly different from the stomach contents of crabs collected at intertidal sloughs. Across all sites, arthropods were the most frequently detected prey, with the native hairy shore crab (Hemigrapsus oregonensis) the single most common prey item. Of the eight species calibrated with a quantitative model, two ecologically-important native species–the sand shrimp (Crangon franciscorum) and the Pacific staghorn sculpin (Leptocottus armatus)–had the highest average DNA abundance when detected in a stomach content sample. In addition to providing timely information on green crab diet, our research demonstrates the novel application of a recently developed model for more quantitative DNA metabarcoding. This represents another step in the ongoing evolution of DNA-based diet analysis towards producing the quantitative data necessary for modeling invasive species impacts. [ABSTRACT FROM AUTHOR]

The early life of most decapod crustaceans takes place in the water column as larvae before they settle in benthic habitats. The spatial and temporal variability in the settling of larval stages offers valuable insights into the potential recruitment of natural populations. To explore this, we studied megalopa assemblages at various segments of coastline on El Hierro and Lanzarote islands, both within and outside the Marine Protected Areas (MPAs) of each island. The study spanned four consecutive oceanographic periods in the Canary Islands (NW Africa), employing light traps for sample collection. The low number of recorded species suggested that light traps exhibit selectivity, particularly for megalopae belonging to Portunidae and Grapsidae. El Hierro, which experienced warmer sea surface temperatures, displayed higher megalopa abundance values than Lanzarote and distinct larval assemblages was observed between these two islands. Similarly, we identified significant variations in abundance and species composition between stratified and mixing seasons. These seasonal differences were influenced by the dominance of Achelous hastatus, Percnon gibessi, and Cronius ruber during the stratified season. In Lanzarote, C. ruber was not recorded during the mixing season, suggesting that the colder conditions there may constrain its reproduction. Interestingly, we observed that species traditionally harvested from the intertidal zone for human consumption (Plagusia depressa) or used as bait for recreational fishing (Pachygrapsus spp. and P. gibessi) exhibited highermegalopa abundances within theMPAs. Incontrast,wenoted lowermegalopadensities of the non-indigenous species C. ruber within the protected areas. These results indicate a positive effect ofMPAs controlling indigenous and nonindigenous crab populations. Moreover, the study provides novel data, showing that light traps are suitable formonitoringthe temporaloccurrence, abundance, andspatial distribution of non-indigenous and commercially exploited species. This is key for adopting an ecosystem-based approach to manage marine resources. [ABSTRACT FROM AUTHOR]

We report here for the first time the occurrence of the diogenid hermit crab species Diogenes curvimanus from the Canary Islands, which has been recorded previously from Atlantic European waters and the Mediterranean Sea. The species had been placed under the synonymy of D. pugilator until recently, and is the sole representative of Diogenes known from the islands. The specimens studied were observed between 2019 and 2023, suggesting that these could have recently settled into local habitats and developed a population capable of reproducing. [ABSTRACT FROM AUTHOR]

Marine Protected Areas limit fishing to protect a broad range of species and enhance biodiversity. Consequently, closures may not benefit species equally and species‐specific assessments are required to determine the impact of closures.Relative abundance and size of Giant Mud Crab (Scylla serrata) was compared across no‐take and fished zones in Port Stephens‐Great Lakes Marine Park, on the temperate east coast of Australia (32.45°S). In addition, passive acoustic telemetry was used to estimate daily space‐use areas.Similar abundances were observed between no‐take and fished zones; however certain no‐take sites had higher abundances than others. In addition, crabs were 9.9 mm larger in no‐take zones on average. Daily crab space‐use varied widely (~4 to 1000 m2), and generally increased with water temperature and conductivity.These patterns indicate that recruitment processes interact with marine park protection to shape crab abundances across estuaries. However no‐take zoning appears to primarily limit fishing mortality on legal size crabs (i.e., carapace length >85 mm) resulting in larger crabs within no‐take zones. This may mean no‐take zones enhance reproductive output of crab populations since larger individuals are likely to be more fecund. [ABSTRACT FROM AUTHOR]

Land use changes are heralded as a major driver of biodiversity loss. However, recent findings show that cities, perhaps the most radical habitat transformation, sustain increasing numbers of threatened species. This emerging trend has been mostly chronicled for vertebrates from landlocked cities, although loss of biodiversity and rates or urbanization are higher in coastal marine systems. To advance our understanding on how threatened species may conquer human‐dominated systems, we studied the threatened edible crab Cardisoma guanhumi and assessed how it is proliferating in croplands and urban systems at different spatial scales and whether populations show consequences of long‐term exploitation. We gathered the data on crab populations covering the whole distribution range, including three countries reporting this as a threatened species. The abundance, distribution, and size structure of crab populations among different land uses at local scales were compared and published data for populations thriving in different habitats throughout their distribution range were compiled. We found that at local scale this species is able to thrive in natural and human‐disturbed habitats, where food sources are heavily altered. At larger scales, the species showed no differences in abundance and size structure among natural and anthropogenic habitats. In areas near the southern distribution edge, crab populations were more abundant and composed of larger animals in urban areas and croplands than those in natural habitats, suggesting that human‐disturbed systems are stepping stones to extend the geographic range. However, we found a long‐term reduction in maximum body size, exacerbated by land use changes, that likely reflects exploitation regimes consistently targeting larger crabs. Despite its status as a threatened species, the long history of human exploitation combined with livestock farming practices may explain the proliferation of this crab in human‐dominated systems, which emphasize the need to consider conservation in human‐dominated systems. [ABSTRACT FROM AUTHOR]

Polyculture of black tiger shrimp Penaeus monodon, mud crab Scylla paramamosain, and red seaweed Gracilaria tenuistipitata, were applied in improved extensive ponds in the Vietnamese Mekong delta to evaluate production and financial efficiency. The trial consisted of two treatments: (1) non-feed supplement, in which shrimp consumed only natural food in the culture pond; and (2) feed supplement, in which shrimp received commercial feed (50% feeding rate). Treatments were in triplicate; ponds featured natural occurrence of red seaweed. Postlarvae of shrimp and crab were stocked at densities of 4 ind./m2 and 0.15 ind./m2, respectively, and culture for six months. Results showed that shrimp receiving feed supplement demonstrated much better (P < 0.05) growth and survival than those without feed supplementation. Shrimp yield was significantly higher (P > 0.05) in the feed supplement pond (348.9 kg/ha) than in the non-feed supplement pond (169.2 kg/ha). Crab production was similar between the two treatments (P > 0.05), varying from 88.1 to 92.4 kg/ha. Production cost (456.2 US$/ha) in the non-feed supplement pond was significantly lower than that in the feed supplement pond (944.8 US$/ha), but the former produced less profit (2,230.9 US$/ha) than the latter (4,169.2 US$/ha). Notably, the average benefit–cost ratio in the non-feed supplement group (4.84 times) was relatively higher compared to the feed supplement group (4.35 times). These findings suggest that polyculture of shrimp, crab, and seaweed in the improved extensive pond could be applied either non-feed supplement or feed supplement for shrimp, depending on the financial conditions of the farmers. [ABSTRACT FROM AUTHOR]

Widely dispersed fragmented populations are a challenge to monitor because subpopulation sizes may be very small, difficult to access and time consuming to sample regularly. We use the coconut crab (Birgus latro) on Pemba, United Republic of Zanzibar as a case study for estimating highly fragmented populations and metapopulation sizes. The species is a very large terrestrial decapod threatened by exploitation and habitat alteration and now classified as vulnerable. We developed an integrated model to analyse capture‐mark‐recapture (CMR) data from five sites jointly with count data from 24 sites to estimate site‐level densities and population sizes, predicted total population size across the Pemba archipelago, and investigated the effect of six predictors of human influence on density. We fitted separate models to test the effect of the same predictors on raw counts and individual body mass. We estimate the total population of coconut crabs on the Pemba archipelago to be c. 6700 terrestrial individuals. We show that government protection generally affects crabs positively, whereas presence of agriculture negatively affects their densities. This study highlights that time‐consuming CMR data can be leveraged to estimate densities on less visited sites, and that fully protected islands are critical for maintaining relatively high population densities. Our overall population estimate suggests that Pemba still hosts a viable coconut crab population in a part of its range where the species is otherwise in steep decline. [ABSTRACT FROM AUTHOR]

Objective: Recent estimates of the North Carolina blue crab Callinectes sapidus stock found that the stock is overfished and overfishing is occurring. Threats outlined in the 2018 stock assessment include climate change and estrogenic endocrine‐disrupting chemicals (EEDCs). The objective of this study was to use an individual‐based modeling approach to simulate the long‐term effects of climate change and EEDCs on the North Carolina blue crab stock. Methods: To do this, we built an individual‐based model that simulated the life history of individual blue crabs, including but not limited to growth, reproduction, and mortality. We then tested our population of blue crabs against 30 different combinations of temperature and EEDC scenarios over 50 years to determine the long‐term effects on the population. Result: Our simulations suggested that the North Carolina blue crab population may be relatively resilient to climate change‐related temperature shifts but that there may be significant impacts at the population level as summer temperatures become more extreme. Endocrine‐disrupting chemical effects resulted in an alternative stable state of lower catch or the total extinction of the population. Conclusion: These results suggest that management strategy changes may be necessary as temperatures become more extreme in the region. In addition, more research is necessary to fully understand the effects of EEDCs on blue crabs and other crustaceans at the individual and population level. Impact statementThis study used a novel approach to connect fine‐scale blue crab ecology to broadscale population ecology. This model can be a useful predictive tool that allows for assessment of the effects of future threats or regulation changes and can be modified to simulate other important crustacean species. [ABSTRACT FROM AUTHOR]

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Bioinvasions constitute both a direct and an indirect threat to ecosystems. Direct threats include pressures on local trophic chains, while indirect threats might take the form of an invasion of a microorganism alongside its host. The marine dinoflagellate Hematodinium perezi, parasitizing blue crabs (Callinectes sapidus), has a worldwide distribution alongside its host. In Greece, fluctuations in the blue crab population are attributed to overexploitation and the effects of climate change. The hypothesis of the present study was that blue crab population reductions cannot only be due to these factors, and that particular pathogens may also be responsible for the fluctuations. To investigate this hypothesis, both lethargic and healthy blue crab specimens were collected from three different fishing sites in order to assess the health status of this important species. Together with the lethargic responses, the hemolymph of the infested crabs presented a milky hue, indicating the first signs of parasitic infestation with H. perezi. The histopathological results and molecular identification demonstrated the effect of the presence of H. perezi in the internal organs and their important role in the mortality of blue crabs. Specifically, H. perezi, in three different tissues examined (heart, gills, hepatopancreas), affected the hemocytes of the species, resulting in alterations in tissue structure. Apart from this dinoflagellate parasite, the epibiotic peritrich ciliate Epistylis sp. was also identified, infecting the gills. This study represents the first detection of H. perezi in the eastern Mediterranean, demonstrating that this is the main causative agent of blue crab mortality on Greek coastlines. [ABSTRACT FROM AUTHOR]

The once plentiful population of the tufted ghost crab, Ocypode cursor, a legally protected species, suffered a steep decline along the densely populated Mediterranean coast of Israel.Here we assessed the effects of recreational disturbance on crab populations in three sandy shore nature reserves and adjacent bathing beaches with differing accessibility during the summers of 2020–2021, employing burrow counts and burrow opening diameter as proxies for population abundance and population size structure.A total 6270 burrows were identified, counted and their opening diameter measured during the study period. The number of burrows was greatest close by the waterline and diminished landwards; this landwards decline was notable in the smallest burrows (<20 mm), representing the youngest population fraction. Comparison of population abundance between the surveyed nature reserves and adjacent bathing beaches revealed greater numbers in the former. However, a pronounced postweekend reduction in the number of burrows was apparent in nature reserves during both survey years, across sites and months and clearly indicates elevated recreational activity. The number of burrows in the nature reserve nearest to main population centres and abutting a popular bathing beach was smaller compared with the peripheral nature reserves.We observed no postsunrise activity of adult crabs, though in strictly access‐restricted beaches, crabs were active diurnally. We thus suggest that the crabs shifted their diel activity patterns as avoidance response to chronic anthropogenic disturbance, enduring a forced curfew and a temporal habitat loss.If the sandy nature reserves are to function as true refugia for the tufted ghost crab, restorative management is to include significant conservation and mitigation intervention measurements/actions. [ABSTRACT FROM AUTHOR]

Objective: The Atlantic blue crab Callinectes sapidus (hereafter, "blue crab") is an ecologically and economically important species that supports one of the highest valued commercial fisheries in coastal South Carolina, USA. Researchers at the South Carolina Department of Natural Resources conduct multiple surveys to monitor the status of the blue crab by using a variety of gear configurations. Demographic characterizations can often be influenced by sampling gear‐related biases. Methods: We compared blue crab sex ratios between passive, pot‐based sampling and active, trawl‐based sampling in the fall across three estuaries and for year‐round sampling in a single estuary (Ashley River, South Carolina). Result: During the fall, there was a difference of 20.1% between the percentage of males collected in pot‐based sampling (73.5%) and the percentage of males in trawl‐based sampling (53.4%). Furthermore, an overall male bias of 23.0% was observed for year‐round sampling in the Ashley River; however, this bias was only significant in certain months. Conclusion: Our findings suggest that although particular sampling gears may have specific advantages, such as greater suitability to effectively sample certain habitats, the resulting characterizations of blue crab population demographics can differ among gear types. Recognizing gear‐related biases is important for ensuring that field surveys are representative of population demographics, particularly when sex‐specific modeling approaches are used as part of stock assessments to determine population status. Impact statementIn this study, we found that fisheries‐independent, pot‐based sampling produced blue crab catches that in many cases were significantly biased toward males when compared to catches from trawl‐based sampling. This finding has implications for sex‐specific stock assessments of blue crabs using fisheries‐independent data. [ABSTRACT FROM AUTHOR]

Global temperatures are rising across marine ecosystems in response to climate change. Marine and estuarine-dependent species including the blue crab, Callinectes sapidus, may adapt to warming temperatures phenologically, by shifting the seasonal timing of biological events, such as reproduction. In Chesapeake Bay, average water temperatures have risen by an average 0.02°C per year since the 1980s. Extension of the blue crab spawning season, through earlier onset and later conclusion, may augment annual brood production and alter the efficacy of management strategies. The duration of the potential spawning season from 1985 to 2019 was assessed using degree days, and the observed spawning season from 1995 to 2019 was assessed using the occurrence of ovigerous crabs from the Virginia Institute of Marine Science Trawl Survey in the James River and in the mainstem of lower Chesapeake Bay. Spawning degree days (SDD) and reproductive degree days (RDD) were defined using minimum temperatures of 19°C and 12°C, respectively. The mean duration of the potential spawning season increased by 25% in SDD and 10% in RDD between 1985 and 2019 in the James River and lower Chesapeake Bay, respectively. This progressive expansion of the potential spawning season was not, however, reflected in the observed spawning season. Rather, the onset, conclusion, and duration of the observed spawning season were variable over the time series. The observed month of onset was driven by RDD in spring, whereby spawning began earlier during warmer springs. The spawning conclusion date was driven by the onset of spawning, rather than Fall temperature, such that the duration of the observed spawning season and, therefore, annual brood production did not change over time. In Chesapeake Bay, the spawning stock is protected by a sanctuary that is closed to fishing from mid-May to mid-September during the putative spawning season. An earlier start to the spawning season during warmer springs, as seen in recent years, is expected to reduce the efficacy of the spawning sanctuary and intensify exploitation of the spawning stock, without enhancing brood production, thereby reducing reproductive output of the blue crab population in Chesapeake Bay. [ABSTRACT FROM AUTHOR]

In Thailand, the populations of a commercially important crab Portunus pelagicus (Linnaeus, 1758) have been decreasing due to overfishing, raising concerns about the conservation efforts of this crab species. The Crab Bank Project has recently been established to restore crab populations by releasing crab larvae from each crab bank station. However, the fate of crab larvae after the release is poorly understood. Here, we assessed the dispersal and settlement patterns of the larvae P. pelagicus released from crab banks along the coast of Trang Province, Southern Thailand. The Lagrangian particle tracking model was employed to simulate the larval dispersal and settlement patterns after release from the crab banks during the inter-monsoon, southwest monsoon, and northeast monsoon. Our simulation revealed that virtual larvae were predominantly retained within inshore areas after the release for 14 days, regulated by tidal-driven currents, wind-induced currents, and local coastal topography. Monsoon periods affected the larval dispersal, with some larvae being transported into estuaries due to the SW monsoonal effects. After the 14-day release period, our modelled simulations suggested that the crab larvae arrived at numerous seagrass meadows along the coast, indicating potential settlement and growth. This result highlights the connectivity of sources and sinks for crab larvae after release from crab banks. Moreover, significant implications for conservation efforts and the fishery management of P. pelagicus were also discussed based on our modelled simulations. [ABSTRACT FROM AUTHOR]

Reductions in the size of mature blue crabs, Callinectes sapidus , which are commercially harvested, are of concern to the aquaculture industry. Through their role in the production of viable offspring, aquaculturists focus their attention in particular on female crabs, although the phenomenon will, of course, also affect the males. Meanwhile, decreases in size at maturity throughout the crab population may be the result of temperature alterations, at present also due to global climate change. Temperature-based shifts in growth can lead to changes in reproductive efficiency, as well as in size and age at maturity. In this study, the effects of temperature on the moulting frequency of blue crabs were investigated and survival rates have been calculated. The purpose of this study was to investigate the temperature dependence of survival and of the moulting processes for blue crab larvae, and to determine the effect of increasing temperature on moulting. The stages from zoea-1 to zoea-5 were examined at 16, 22, 26 and 30°C. The results show that there is a significant difference in growth and moulting, depending on the rearing temperature. As the temperature increases, the interval between moulting days can be seen to be shortened, and increasingly so with the progress in the growth of the crabs. Moulting-interval days became less with the growth of the crabs. The effect of a rise in temperature on growth per moult is also significant, and along the temperature range tested the optimum temperature was found to be 26°C. A reduction in the length of the intermoult period was observed from the lowest to the optimum temperature, while a sudden, sharp increase in the intermoult period above 26°C was observed as well. [ABSTRACT FROM AUTHOR]

Copyright of Revista Catalana de Dret Ambiental is the property of Universitat Rovira I Virgili and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Current knowledge of age at legal size in Newfoundland & Labrador (NL) and other snow-crab stocks is incomplete due to historic estimations not accounting for skip-molting growth delays. Previous work has shown skip-molting incidence to occasionally be very high in males, both in NL and some other major snow-crab stocks. This warrants research to better understand impacts of skip-molting on snow-crab age and growth dynamics, which are central to population assessment and resource management. We simulated the impact of skip-molting on growth dynamics of snow crabs from three regions around NL by coupling a nineteen year time series of molt-type probabilities derived from field trawl surveys to historical data on age-at-instar based on cohort analysis of wild populations that do not consider skip-molting in making age estimations. Trawl surveys and simulations showed that skip-molting is a prominent feature in NL snow crabs, with up to four skip-molts being a reasonable maximum possible estimate for males in portions of the NL snow-crab stock. A complementary analysis examining the ability to age snow crabs using gastric mill band counts showed overall strong agreement with published growth trajectories that were modified to include skip-molting as well as reasonable average age approximations for most crabs, but unexpectedly high variability in age estimates for individuals of a same instar stage and unexpectedly low age estimates for younger crabs. Our study leads to a refinement of age at legal size for NL snow crab from the current nine-year estimate to a range of 9–13 years. Although this range is deemed to capture virtually every crab reaching legal size in NL snow-crab populations, ages higher than 11 years to fishery recruitment (2 skip-molts) are relatively infrequent. [ABSTRACT FROM AUTHOR]

Copyright of Jurnal Ilmu dan Teknologi Kelautan Tropis is the property of IPB University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Simple Summary: On one hand, the females of some crabs can store the sperm from copulations for several years. On the other hand, it is reported that DNA repair mechanisms in sperm cells are less effective than in other cells. Taking into account these two considerations, we conducted a study into the viability and possible genetic damage of DNA in spermatozoa stored in female spider crabs for up to 14 months. The results show that during the first 3–4 months, both the viability and the DNA integrity fall considerably. Natural populations of the spider crab Maja brachydactyla constitute a fishery resource of great economic importance in many countries. As in the rest of eubrachyurans, the females of this species have ventral-type seminal receptacles where they store sperm from copulations. Sperm can be stored in these structures for months and even years before egg fertilisation, with the consequent degradation of the sperm cells during the time. In this work, we analyse the viability and the possible genetic damage in sperm accumulated in the seminal receptacles of M. brachydactyla females as a function of the storage time (from 0 to 14 months) using the comet assay technique. On one hand, we developed an algorithm for comet image analysis that improves the comet segmentation compared with the free software Open comet v1.3.1 (97% vs. 76% of detection). In addition, our software allows the manual modification of the contours wrongly delimited via the automatic tool. On the other hand, our data show a sharp decline in sperm viability and DNA integrity in the first four months of storage, which could lead to a decrease in the fecundity rate and/or viability of the embryos or larvae from the second and third clutches of the annual cycle if the repair capacity in these gametic cells is low. [ABSTRACT FROM AUTHOR]

Anthropogenic alterations to river flow could have repercussions for flow-dependent species downstream but few studies account for these dynamic relationships or quantify impacts of altered river flow. Scylla serrata— a widely distributed portunid crab—was used as an example of a flow-dependent species to model impacts of altered flow on species abundance and catch. Crab population dynamics were modelled across a large semi-enclosed tropical sea in northern Australia. Environmental drivers, primarily river flow, but also temperature and the Southern Oscillation Index were linked to crab dynamics to explain variability in historical catches. Catch and abundance could then be predicted under altered flow scenarios. River flow significantly improved the ability to explain historical catches for some regions but not all, and the strength of this relationship varied across catchments. Altered flows had negligible effects for perennial rivers but for ephemeral and temporally variable rivers, predicted decreases in abundance and catch ranged from 36 to 46% on average. Our modelling approach showcases a way to dynamically and rigorously quantify impacts of altered river flow on a key species with potential to help inform natural resource management, including policy decisions on the timing, quantity, and method of water removed from rivers. [ABSTRACT FROM AUTHOR]

While oxidative stress pathways are associated with a wide variety of tissue pathologies, its applications for evaluating and discerning ecological risks are limited. This study seeks to associate trends of lipid peroxidation and oxidative stress to risks of muscle pathologies in blue crabs inhabiting regions of the Lagos Lagoon. Crab samples (n = 520) were selected from pollution-impacted sites of the lagoon at Iddo, Ajah, Okobaba, Makoko, and the mid-lagoon area (control site). Antioxidant enzyme capacity, i.e., superoxide dismutase, catalase, glutathione peroxidase (GPx), and glutathione-S-transferase, and lipid peroxidation were evaluated in the muscle tissue of the blue crabs. The study findings showed distinct patterns of metal uptake in muscle, with redox-active metals (Cu and Zn) and redox-inactive metals (Pb and Cd) exhibiting site-specific differences. Additionally, there were changes in antioxidant modulation, lipid peroxidation, and the presence of associated myopathies. Blue crabs from sites (Makoko and Ajah) with greater uptake of redox-active metals (Cu and Zn) in muscle tissue showed higher trends of lipid peroxidation and the most prevalence of severe regression-type myopathies. Sites with lower uptake of redox-active metals showed the predominance of circulatory-type myopathies. This study also provides evidence of severe necrosis and myositis associated with digenean parasite cysts in crab muscle. Pathological evidence of severe skeletal muscle deterioration in the presence of greater lipid peroxidation could have implications for motor-neuron activity and reduced force-generating capacity necessary for adaptive responses in the wild. We conclude that elevated uptake of redox metals could aggravate the onset of myopathies in wild populations. [ABSTRACT FROM AUTHOR]

Objective: There is international pressure to increase the worldwide expanse of marine protected areas (MPAs). However, MPAs often lack preexisting long‐term biological baselines, which are essential for assessing MPA effects and for refining the conservation and socioeconomic benefits they confer to society. Our study addresses this issue by establishing demographic baselines for two commercially important species prior to a proposed fishing ban inside the Northeast Canyons and Seamounts Marine National Monument, a recently established MPA on the continental shelf break approximately 200 km southeast of Cape Cod, Massachusetts. Methods: Samples were obtained by the Commercial Fisheries Research Foundation's American Lobster and Jonah Crab Research Fleet, which is an industry‐based, fishery‐dependent data collection program. Specially trained participants recorded year‐round biological data from their 2013 to 2021 commercial catches of American lobster Homarus americanus and Jonah crab Cancer borealis. Samples were taken from an area inside the MPA and from two areas outside the MPA, spanning 130 km to the east and west. Result: American lobster sizes and sex ratios varied between areas, and their sizes, sex ratios, and proportion of ovigerous females differed between submarine canyons within areas. American lobster sizes, sex ratio, proportion of ovigerous females, and prevalence of shell disease were also affected by season and/or depth. Jonah crab parameters did not vary between areas, but sex ratio varied with season and depth, and the proportion of ovigerous females varied with depth. Conclusion: These demographic baselines are the only data available, at a sufficient spatial and temporal resolution, for evaluating the effects of a proposed fishing ban in the MPA, and they fill important data gaps for stock assessments. To evaluate possible future population changes, it will be necessary to continue collecting data from inside and outside the MPA using comparable methods, and to account for the preexisting sources of variation that we have identified. Impact statementMarine protected areas (MPAs) need monitoring to evaluate their benefits to society. We characterized American lobster and Jonah crab populations inside and outside a newly created MPA while commercial harvest was still operating, thereby providing essential information needed for assessing future responses to planned fishing closures. [ABSTRACT FROM AUTHOR]

Objective: Predatory invasive fishes may consume species of management interest and alter food webs. Blue Catfish Ictalurus furcatus is a large‐bodied, salinity‐tolerant species that exhibits broad diet breadth and preys on species of both conservation concern and fisheries management interest. To better understand the ecological consequences of the establishment of Blue Catfish fisheries, estimates of predatory impacts are needed. Methods: Using a Monte Carlo simulation, we integrated abundance estimates, diet information, and consumption‐to‐biomass ratios to estimate population‐level Blue Catfish predation for a large Chesapeake Bay tributary along the mid‐Atlantic coast of the United States, the James River. Result: Population‐level annual predation estimates by Blue Catfish exceeded 100 metric tons for several species or taxa of interest, including an estimated 400.7 metric tons (95% CI = 272.6–613.2) of blue crab Callinectes sapidus. Prey species abundances were unknown and thus limited opportunities to evaluate prey population responses. For instance, effects of Blue Catfish on blue crab populations remain unknown without tributary‐specific estimates of blue crab abundance, but comparisons to landings data suggests that Blue Catfish predation on blue crab in the James River may be low compared with harvest. Conclusion: Estimation of Blue Catfish predatory effects may inform development of management goals and objectives that balance diverse stakeholder interests. This work provides beneficial information to assess trade‐offs of Blue Catfish fisheries and their effects on coastal aquatic resources. Impact statementThis work provides estimates of predatory effects of a nonnative Blue Catfish population in the tidal James River, Virginia, USA. The results could inform management planning by improving our understanding of potential effects on other species of management interest. [ABSTRACT FROM AUTHOR]

Objective: This paper applies a catch multiple survey analysis (CMSA) to Atlantic horseshoe crabs Limulus polyphemus in the Delaware Bay to generate robust population estimates for harvest management. Currently, horseshoe crabs along the U.S. Atlantic coast are harvested as bait for other fisheries and collected for their blood, which is used in a biomedical industry. The Delaware Bay is home to the largest population of horseshoe crabs and is a significant stopover for shorebirds to rebuild energy by consuming horseshoe crab eggs prior to completing their northward migration. To address this interrelationship, the Adaptive Resource Management (ARM) Framework has been used since 2013 to ensure that horseshoe crab harvest within the region takes into account the forage needs of migratory birds. Since its inception, the ARM Framework has used a single trawl survey's swept area‐based population estimates of horseshoe crab relative abundance and a theoretical population model developed primarily from literature‐derived values. With more data collected in the region in recent years and other sources of mortality that can now be quantified, a catch survey model can provide horseshoe crab population estimates going forward. Methods: A CMSA was used to estimate male and female horseshoe crab population size for 2003–2021 using all quantifiable sources of mortality and three fishery‐independent indices of abundance. Result: The CMSA results indicated that adult abundance of male and female horseshoe crabs was stable from 2003 to 2013 and then began to increase through 2017, a result that is consistent with stock rebuilding following a period of harvest restrictions as recommended by the ARM Framework. Population estimates were lower in recent years but remained above the levels estimated before implementation of the ARM Framework. In 2021, the CMSA estimated that there were over 6 million mature females and nearly 16 million mature male horseshoe crabs in the region. Conclusion: The CMSA provides the best and most comprehensive population estimates of horseshoe crabs in Delaware Bay and will improve modeling efforts within the ARM Framework going forward. Impact statementBeing able to estimate the size of the Atlantic horseshoe crab population in the Delaware Bay will help managers set appropriate harvest levels that will support its fisheries while also ensuring there are enough horseshoe crab eggs to feed migrating shorebirds. [ABSTRACT FROM AUTHOR]

A population of the porcelain crab Pachycheles laevidactylus was evaluated based on sex ratio, sexual dimorphism, reproductive intensity, relative growth and sexual maturity. The porcelain crabs were identified, sexed and measured as follows: carapace (CL, length; CW, width), chelar propodus (PL, length; PH, height) and abdomen (AL, length; AW2 and AW5, the width of the 2nd and 5th abdominal somite, respectively). For the 1,109 specimens analyzed, the sex ratio was 1:1, but contrasted in some seasons. Females were significantly larger than males, and ovigerous females were recorded in all seasons, with greater intensity in autumn and winter. In males, the biometric ratios of the major chelar propodus (PHxCL and PLxCL) showed positive allometry regarding body size, with a reduction in the allometry rate after puberty. The same occurred with females for the biometric ratios of the abdomen (AW2xCL and AW5xCL). Males attain morphological sexual maturity at 3.48 mm CL, earlier than females, which occurred at 5.00 mm CL. In this study, P. laevidactylus matured with a larger size than reported for others analyzed in the temperate zone. It is the first study addressing aspects of the population biology of P. laevidactylus in a region with a subtropical climate. [ABSTRACT FROM AUTHOR]

Thaipotamon chulabhorn (Mealy Crab) is a freshwater crab, listed as 'Least Concerned' in the IUCN Red List of Threatened Species. Nonetheless, this crab is exclusively found in one small area of the Dun Lumpun Forest, Thailand, and currently faces high exposure to environmental changes. This study aims to investigate key dynamic factors that influence vulnerability to environmental changes of the Mealy Crab. The study was conducted between 15 March and 23 October 2016, covering the local summer until the end of the rainy season and being influenced by strong El Niño, thus suggesting drought episodes. This vulnerability assessment was carried out through crab population records from 1997 to 2016, field measurements/surveys, and interviews with experienced park rangers. The results revealed that drought is the major vulnerability factor that is threatening the population of the crabs and their livelihoods (7.96 out of 10), followed by an increased number of their natural enemies (7.41), variations in groundwater level (6.11), changes in groundwater quality (4.63), changes in forest soil (4.63) and human intervention (4.26). Since 1996, human intervention has been found to have a little direct impact on the crab population due to the restricted access to forest resources. The 2016 drought was accompanied by anomalously low rainfall and the early onset of the rainy season, contributing to an earlier and shorter mating period of the crabs. Nonetheless, a consistently increased number of the Mealy Crab population indicated that they are not significantly vulnerable to a larger number of their natural enemies, and even to the changes in groundwater and forest soil. In conclusion, the crab population was increasing along with changes in the habitat and climate and its growth cycle was unusual during the drought. [ABSTRACT FROM AUTHOR]

The blue crab Callinectes sapidus (Rathbun, 1896) is one of the most invasive species in the Mediterranean Sea. Understand how the populations are maintained and how the environment is driving the populations in the areas invaded is the key to an effective future management. This current study is presenting a monthly long-term monitoring of the blue crabs' population structure, body size, sexual maturity, reproduction periods and fecundity, and their relationships with environmental factors in a saltmarshes system in Italy. During winter, high densities (15 ± 8 ind m-2) of early juveniles (< 2 cm) were observed, and their numbers decreased due the population growth until summer. The size-spectra showed that across different temperature (18–26°C) and salinity (24–40 psu) gradients, the growth period for males is faster than for females. Based on abdominal analysis, sexual maturity was defined at ∼12 cm for males and females but the population was in favor of males that were more than 66% of the time mature throughout the year. Copulations periods were identified between spring and autumn when more than 50% of females were matures, and ovigerous females' migrations were observed in late summer. Our study expand our understanding of how the environment interacts to effect physiological and biological processes of alien species and improve our ability to make predictions of how environmental change the distribution of the alien species in the future. Based on our results, we also discuss which population control strategy would be most effective based on the data available in the literature. [ABSTRACT FROM AUTHOR]

The article focuses on the underrepresentation of women in advanced STEM research careers despite progress in increasing their presence in the field. Topics include the significant gender gap in doctoral-level STEM degrees, the importance of diverse participation in population and ecosystem dynamics research, and a selection of studies by women in this field showcasing diverse ecological research approaches.

The tropical rock lobster, Panulirus ornatus, is a commercially important aquaculture species exhibiting complex social interactions in laboratory culture, including cannibalism of moulting conspecifics. Cannibalism of soft-shelled post-moult stage individuals is a major limitation during the juvenile stage of culture. Not limited to P. ornatus, cannibalism is widespread across farmed decapods, limiting stocking densities in crab, freshwater crayfish, and prawn species. To understand the mechanisms driving this behaviour and reduce its prevalence, we have investigated the role of chemoreception via the aesthetasc-bearing region of the lateral antennular flagellum, in the recognition of conspecific moulting cues. Differential expression analysis of several tissues in P. ornatus shows an upregulation of 70 ionotropic receptor isoforms, including co-receptors (IR25a and IR93a) and divergent receptors (IR4, IR7, and IR21a) in the aesthetasc-bearing region of the antennules. Deafferentation of the aesthetascs via deionised water exposure prevents juveniles from responding to conspecific moulting cues in a two-current choice flume, suggesting chemoreception, possibly olfaction, plays a role in identifying moulting juveniles. This is the first step in understanding the mechanisms via which cannibalism is triggered in juvenile P. ornatus culture. Further work in this area will help discover means to limit cannibalism in laboratory and commercial culture. [ABSTRACT FROM AUTHOR]

Animal population abundance is a significant parameter for studies on invasive species that can threaten the ecosystem. Researchers have been developing population estimation methods since the 18th century, in order to evaluate species' evolution and environmental effects. However, studies on the population density of the invasive species Callinectes sapidus are very limited. The present work, using a simulation model combined with field measurements, examines an innovative methodology for estimating the current population of the invasive species Callinectes sapidus in a shallow Mediterranean coastal lagoon. The methodology presented here builds the first stage of modeling and predicting the evolution of this species' population in marine environments. The simulation model's results are validated with an estimation of the total population based on juvenile abundance, and a curvature of the species population estimation based on cage catch is implemented. The simulation experiments presented here show the possibility of a robust prediction for blue crab population estimation. [ABSTRACT FROM AUTHOR]

Microorganisms are ubiquitous in the environment and provide genetic and physiological functions to multicellular organisms. Knowledge on the associated microbiota is becoming highly relevant to understand the host's ecology and biology. Among invertebrates, many examples of endosymbiosis have been described, such as those in corals, ants, and termites. At present, however, little is known on the presence, diversity, and putative roles of the microbiota associated to brachyuran crabs in relation to their environment. In this work we investigated the associated microbiota of three populations of the terrestrial brachyuran crab Chiromantes haematocheir to find evidence of a conserved organ-specific microbiome unrelated to the population of origin and dissimilar from environmental microbial assemblages. Bacterial 16S rRNA gene and fungal ITS sequences were obtained from selected crab organs and environmental matrices to profile microbial communities. Despite the presence of truly marine larval stages and the absence of a gregarious behaviour, favouring microbiota exchanges, we found common, organ-specific microbiota, associated with the gut and the gills of crabs from the different populations (with more than 15% of the genera detected specifically enriched only in one organ). These findings suggest the presence of possible functional roles of the organ-specific microbiota. [ABSTRACT FROM AUTHOR]

Archaeological remains of brachyurans (e.g. crabs) are often overlooked as potential paleoenvironmental and paleoclimatical proxies in contrast to other marine and terrestrial invertebrates such as mollusks and landsnails. The potential for fine-scale regional paleoclimate reconstruction based upon these organisms' behavioral ecology has yet to be examined. We present novel isotopic analyses of the remains of a semiterrestrial freshwater crab (Potamon potamios) endemic to southwest Asia recovered from the archaeological site of Khirbat al-Mudayna al-'Aliya (KMA). KMA lies on a southern tributary of the Wadi al-Mujib in the Hashemite Kingdom of Jordan, approximately 40 km east of the Dead Sea. Excavations here recovered architecture, artifacts, and ecofacts dating to a single-period occupation during the early Iron Age (∼1000 cal BCE). Oxygen and carbon isotopes from these brachyuran remains were analyzed in conjunction with a two-year isotopic and morphometric study of the modern potomonautid population near the archaeological site and at nearby wadi systems to assess whether the isotopic values of modern crab populations correlated with variables such as temperature, including isotopic study of the pools in which crabs were found. In turn, these data could be used to reconstruct paleoclimate or paleoenvironment in the archaeological population. The high correlation in oxygen isotope values between crab carapaces and the water of the pools in which they were sampled suggest that variability in isotopic values of crab specimens recovered from KMA is tracking ancient human capture of these organisms across potentially different pools. Further, intra-year variability in isotopic values in modern crab carapaces as well as the similarity of isotopic values across wadi systems with different environments suggest that P. potamios remains cannot be used as reliable paleoenvironmental indicators. The implications of this research will have significance for archaeologists and other researchers in the study of paleoenvironment and paleoecology, and bears upon human mobility, resource acquisition, and human-nonhuman animal relationships. [ABSTRACT FROM AUTHOR]

The blue crab Callinectes sapidus is a portunid brachyuran native of the Atlantic coasts of America. In the last decades, the species has greatly expanded its range in invaded areas, currently including the Atlantic coasts of Morocco, the Mediterranean Sea, the Black Sea as well as the eastern Atlantic coasts of Europe from Portugal to France, Belgium, and Germany. In the present study, several specimens of C. sapidus were collected in May, June and July 2021 in the Stagnone di Marsala, a semi-enclosed basin located in the north-western coast of Sicily (southern Italy, Mediterranean Sea) characterized by low hydrodynamics and water exchange with the adjacent open sea and high salinity conditions. Juveniles at different instar stages and ovigerous females were repeatedly captured, suggesting the presence of an established population of the blue crab, despite the peculiar environmental conditions characterizing the basin. These findings are discussed in the context of the current expansion of the species along the African coasts of the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

An important aspect of the size-structured stock is the assumption that individuals progress from one size class to another after a certain time. In this study, a total of 2581 monthly samples of the swimming crab Callinectes amnicola were collected from the landings of the artisanal crab fishery in the Cross River, Nigeria over a period of 13 months, from January 2021 to January 2022. Crabs ranged in length from 6.5 cm to 15.5 cm, with most crabs caught during the dry season. The fewest crabs (n=23) were caught in August 2021, and the most (n=662) were caught in January 2021. Because moulting and other physiological obstacles make it difficult to determine crab age, length frequency data were used instead. Swimming crab assessment was based on some basic growth parameters of the von Bertalanffy growth function and the Beverton and Holt growth model. The results showed that the asymptotic length and growth rate were 16.28 cm and 0.940 per year, respectively. The best growth index was estimated to be 2.40, while longevity and mortality were 3.19 years and 3.46 per year, respectively. The calculated exploitation rate of 0.41 was below the guideline of 0.5 and the maximum yield per recruit of 0.421, confirming an underfished stock. Sustainable exploitation of the Cross River swimming crab was recommended by reducing efforts on already exploited fishery resources. [ABSTRACT FROM AUTHOR]

Predicting the impacts of predatory invasive species is important for prioritising conservation interventions. Functional response experiments, which examine consumption by predators in relation to prey density, are a useful way to assess the potential strength of novel predator-prey relationships. However, such experiments are often conducted without consideration of sex or only with males to reduce invasion risk. Here, we compared the functional responses of male and female European green crabs (Carcinus maenas), a global invader, feeding on varnish clams (Nuttallia obscurata) to test whether the two sexes have similar potential for impact. We also examined potential correlates of predation behaviour by measuring sex-specific movement and prey choice. Both sexes displayed a Type II hyperbolic functional response, which can destabilise prey populations at low prey densities. However, males and females exhibited some differences in foraging behaviour. Female green crabs had slightly lower attack rates, which were not linked to sex differences in movement, and slightly longer handling times, which were not linked to sex differences in prey choice. These small, non-significant differences nevertheless translated into significantly greater functional response ratios, which are used to predict the ecological impact of invasive species, for males than females. There was no difference in the proportion of clams consumed between males and females with similar crusher claw heights, but females have smaller crusher claws on average, hence they consumed a smaller proportion of clams. Repeated surveys of four populations of European green crabs established in British Columbia, Canada, showed that sex ratio is highly variable. Taken together, these results and population-level modelling suggest that trying to evaluate the potential impact of European green crabs on clam populations by sampling only males could result in overestimation, even in populations that have male-biased sex-ratios. Consumer sex might generally be an important feature to consider when using functional response experiments to forecast the impact of new invasive species, especially those with marked sexual dimorphism that affect foraging. [ABSTRACT FROM AUTHOR]

The Chinese mitten crab (Eriocheir sinensis) is among the most important species in China and other countries, and it contributes significantly to aquaculture and meeting protein demands for the fast-growing human population. To ensure their sustainable exploitation, management, and use in aquaculture, it is imperative to know their genetic diversity. Thus, we studied the genetic diversity of six populations of Chinese mitten crabs from six different lakes in the Yangtze River's drainage system. A total of 180 Chinese mittens crabs were collected from six lakes in China, with 30 being collected from each lake. Then, DNA was extracted using TaKaRa Dalian, genotyping was performed by the Gene Marker software for statistical analysis and the genetic parameters such as observed number of alleles (Na)were studied. A total of 87 alleles were observed in 180 individuals of six wild Eriocheir sinensis populations. The Fis results showed that six sites had negative values, and crab20 had the largest value. The results of Fit showed that the single locus had a negative value. All the Fst values among the populations were lower than 0.50, while an AMOVA analysis showed that 0.36% of the genetic variation came from among the six populations and 94.08% of the genetic variation was between individuals in a population. The six Chinese mitten crab populations showed higher genetic variability among individuals of the same population with very low genetic variability between the populations. Therefore, this illustrates that the crabs from the six lakes have similar genetic diversity and minor genetic differences among them. [ABSTRACT FROM AUTHOR]

The ecosystem of Bandon Bay, in the Gulf of Thailand (GoT), has been impacted since 2007 by the continued stocking of larval blue swimming crab Portunus pelagicus, also called a crab bank. In this study, the food web in the Bay was modelled using Ecopath software to compare the trophic status, interaction and energy flow among the components in the system in 2007 and 2016 (i.e., before and 10 years after the crab bank intervention). The models were based on data collected from trawling. Twenty fish and shellfish components were used in the 2007 model, while 22 were used in the 2016 model. A significant increase in biomass was found in blue swimming crab, but biomass declined for other demersal fishes, cephalopods, and Penaeid shrimps. The production/biomass ratios of most components were higher in 2016 but the consumption/biomass ratios were relatively unchanged. The ecotrophic efficiency indicated that shellfishes were more exploited than fishes. Changes in most of the ecological indices revealed higher maturity and stability after 10 years of crab bank operation. The mixed trophic impact indicated bottom-up regulation, and that the increase of blue swimming crab negatively impacted only Mantis shrimp. Overall, the results indicate positive impacts of the crab bank intervention. [ABSTRACT FROM AUTHOR]