Species Composition Of Crabs Research Articles

Multiple Environmental Factors Increase the Niche Complexity and Species Diversity of Brachyuran Crabs in an Intertidal Algal Reef Ecosystem in Northwestern Taiwan.

Algal reefs are one of the world's rare and poorly understood ecosystems. They are mainly distributed in the Mediterranean Sea, but one notable exception-an intertidal algal reef ecosystem in northwestern Taiwan-stretches for 27 km along the coast of Taoyuan, making it probably the largest algal reef coast found in shallow water. Despite the reef's rarity and striking characteristics, the coastal land that it is part of has undergone a series of developments and is now surrounded by industrial parks. Brachyuran crabs are one of the most abundant and visible groups of organisms in the intertidal zone. In the present study, we investigated the brachyuran crab community in this reef to provide a more detailed record of brachyuran crab species compositions in this intertidal algal reef ecosystem and illustrate the characteristics of this understudied ecosystem by comparing its species diversity and abundance with three natural variables- sampling time, tidal level, and season-in a wildlife refuge and north of the refuge. Two methods were used in the study: a qualitative method (to determine the species richness) and a quantitative method (to estimate the population density). We identified a total of 52 brachyuran species from 13 families in the habitats. The highest species richness was found in Datan G2, north of the wildlife refuge. The crab species composition in this algal reef is different from its compositions in coral and rocky reefs. Our analysis indicated that the species abundance is affected by multiple factors, and a single investigation is not enough to reflect the true population density of brachyuran crabs on this reef. In addition, we found that the sites outside the wildlife refuge were in much better condition than those in the wildlife refuge, and should therefore be included in the wildlife refuge. In particular, Datan, located north of the wildlife refuge, had the highest species richness, and the area's species composition was different from that of the nearby wildlife refuge. Thus, we strongly recommend that a) the Datan area be protected to maintain this high crab diversity and b) further research be performed to better understand brachyuran crab biology in the intertidal algal reef ecosystem.

Biodiversity of crab species composition in the regenerated forest area of Can Gio mangrove forest after storm

The regeneration of mangroves after storm in Can Gio has been interested in research with the prospect of coming up with plans to overcome similar consequences in the future. The process of restoring vegetation in the area having been damaged by previously Durian hurricane in 2006 has recorded the appearance of 3 new species such as Sarmatium germaini, Nanosesarma pontianacense, Myomenippe hardwickii following the forest regeneration. In this study, we recorded 20 species of crabs belonging to 12 genus and 7 families, among these, Sesarmidae and Ocypodidae families accounted for the highest proportion. Particularly, Perisesarma eumolpe was the dominant species in all areas indicating their ability to tolerate and adapt to many habitats. Several new species specially Uca crabs were recorded at regenerated areas. Biological indicators indicated that the crab community had higher diversity in the dry season on the contrary, in the rainy season, there was an increased number of dominant species resulting in the decrease of the crab community diversity. The densities and biomass of crabs in regenerated areas were higher than those in intact forests. Results of this study indicated that natural regeneration has created conditions for the crab population to recover and opened up opportunities for many new species to appear.

Crab communities (Decapoda: Brachyura) in mangrove and estuaries in the Eastern Part of Lombok Island

Mangroves and estuary ecosystem in East Lombok which are appointed as Local Marine Conservation Areas (Kawasan Konservasi Laut Daerah/KKLD) are Gili Lawang, Gili Sulat, Sambelia and Jerowaru districts. Inventory of aquatic fauna in mangroves and estuaries is one of the important components of the marine conservation program. The objective of this study is to determine crab species composition in mangroves and estuaries of eastern Lombok during the East Lombok KKLD program. Targeted area for this study includes Gili Lawang, Gili Sulat in southern Lombok Island, Sugian in Sambelia, Ekas Beach, Tanjung Luar and Seriwe in Jerowaru, and Kidang in western Jerowaru. The crab was collected at 0 m to 100 m of seashore by digging the burrow. The crab community recorded was analyzed for resulting the Diversity, Evenness and Similarity Index. Ten families with 35 species of crab were found from two ecosystem types, mangrove and estuary. Each location has different diversity of ecosystem and habitat. The highest diversity is recorded in Kidang and Seriwe, while the lowest diversity in Gili Sulat. Species diversity is associated with ecosystem and habitat type diversity. Kidang and Seriwe has the highest ecosystem and habitat diversity, while Gili Sulat has the lowest diversity. In addition, the population of Ocypodidae is accounted as the dominant crab family for which Austruca perplexa is the dominant species.

Deepwater Horizon Oil Spill Impacts on Salt Marsh Fiddler Crabs (Uca spp.)

The Deepwater Horizon oil spill was the largest marine oil spill in US waters to date and one of the largest worldwide. Impacts of this spill on salt marsh vegetation have been well documented, although impacts on marsh macroinvertebrates have received less attention. To examine impacts of the oil spill on an important marsh invertebrate and ecosystem engineer, we conducted a meta-analysis on fiddler crabs (Uca spp.) using published sources and newly available Natural Resources Damage Assessment (NRDA) and Gulf of Mexico Research Initiative (GoMRI) data. Fiddler crabs influence marsh ecosystem structure and function through their burrowing and feeding activities and are key prey for a number of marsh and estuarine predators. We tested the hypothesis that the spill affected fiddler crab burrow density (crab abundance), burrow diameter (crab size), and crab species composition. Averaged across multiple studies, sites, and years, our synthesis revealed a negative effect of oiling on all three metrics. Burrow densities were reduced by 39 % in oiled sites, with impacts and incomplete recovery observed over 2010–2014. Burrow diameters were reduced from 2010 to 2011, but appeared to have recovered by 2012. Fiddler crab species composition was altered through at least 2013 and only returned to reference conditions where marsh vegetation recovered, via restoration planting in one case. Given the spatial and temporal extent of data analyzed, this synthesis provides compelling evidence that the Deepwater Horizon spill suppressed populations of fiddler crabs in oiled marshes, likely affecting other ecosystem attributes, including marsh productivity, marsh soil characteristics, and associated predators.

The status of diversity and species composition of crabs in cavanthurai coastal area in Jaffna Peninsula of Sri Lanka

Crabs are economically important and a protein rich commodity in the coastal as well as offshore fisheries in Sri Lanka. Crabs are one of the potential aquaculture candidates and also form important commercial and recreational fishery. The present study was conducted with the aim of documenting the species composition and diversity of crabs inhabiting in the Navanthurai coastal area of Jaffna peninsula of Sri Lanka. The current investigation was carried out from November 2011 to October 2012 in Navanthurai coastal waters, which is a part of the Jaffna estuary situated between latitudes 9°36’– 9°50’North and longitudes 79° 40’– 80°40’ East. Specimens were collected using different types of nets; mainly driftnet, gill net, hoop net and ‘Sirahuvalai’. All crabs were brought to the laboratory and identified up to species level based on the morphological characters. Accordingly, five edible species of crabs namely; Scyllaserrata, Portunus pelagicus, Thalamita craneta, Charybdis notator and Portunus sanguinolentes , belong to four genera of the family Portunidae were recorded. . Among them P.pelagicus is the dominant species contributing 93.5% followed by T.craneta and S.serrata representing 5.5% and 1.5%, respectively. However, S.serrata is the most demanded species of crabs both for local and export markets. Only a few individuals of C.natator and P.sanginolentus were observed representing 0.37% and 0.13%, respectively of the harvest. The information and observations in this study will be of use in formulating management policies for the crab fishery off the Navanthurai coastal area. Tropical Agricultural Research Vol. 25 (4): 595 – 601 (2014)

1990-2000 年代の東シナ海・黄海におけるカニ類の種組成と，ワタリガニ科カニ類の分布密度の年変動

1990-2000 年代の東シナ海・黄海におけるカニ類の種組成と，ワタリガニ科カニ類の分布密度の年変動

Analysis of crab community characteristics in South Zhejiang coastal areas during spring

Based on three bottom trawl surveys carried out in spring(April, May, and June), 2011, crab species composition, weight density and individual density distribution, dominant species, and community characteristics were analyzed by analysis of variance, linear regression, cluster analysis, and non-metric multidimensional scaling.Thirteen crab species, belonging to 7 families of 4 orders in 1 class were sampled. Of these, four were eurythermal and eurysaline, four were hyperthermal and eurysaline, two were hyperthermal and hysaline, and three species were of uncertain ecotypes. Weight density differed significantly between April and June(P0.05), as did the number abundance density indices. The Shannon-Wiener diversity index(H′) differed significantly between May and June and between April and June. The Margalef richness index(D) and sea water depth and bottom water salinity were positively correlated(P0.05). Weight density and the H′ and pielou evenness index(J′) were negatively correlated(P0.05). During spring in the study area, the non-economic mid-minitype crab species occupied the dominant position; its community structure was simpler. D increased with increase in sea water depth and bottom water salinity, and the weight density decreased with increasing H′ and J′. In addition, Charybdis bimaculata was the most dominant species in spring, and its contribution of weight and number density in all three months was 50%, this can be used as a basis for identifying the ecotype function zone and important fisheries waters.

Preliminary data on Brachyura (Crustacea) in coastal mangrove forests from Tinh Gia (Thanh Hoa province) to Hoi An (Quang Nam province)

The surveying on Brachyura (Crustacea) in coastal mangrove forests from Tinhgia (Thanhhoa province) to Hoian (Quangnam province) was carried out in December, 2003 at 9 localities. 36 crab species, belonging to 5 families were collected and the species number was mainly in the families Ocypodidae and Grapsidae. In addition, there were several wide range species found in the northern fauna as well as in the southern fauna of Vietnam. Crabs were numerous in species in Vietnam mangrove ecosystems. The characteristics of the crab species composition in mangrove forests from Tinhgia to Hoian were following species: Parapyxidognathus deianira, Hemigrapsus penicillatus, Neoepisesarma lafondi, Scopimera curtelsoma, Ocypode sinensis and Metopograpsus thukuhar. All the crab species found in these mangrove stands were burrowers and ground-dwelling animals. The ground-dwelling crabs could be found on the lower parts of the tree trunks.

An Evaluation of Boat Basin Dredging Effects: Response of Fishes and Crabs in a New Jersey Estuary

AbstractDredging is one of the most common human modifications of estuaries and although its effects have often been studied, there has been little effort in evaluating the effects on mobile macrofauna, such as fishes and crabs. We evaluated the response of fishes and crabs to 4 d of dredging in a small boat basin within a polyhaline marsh creek of a New Jersey estuary. We used several measures, including fish and crab species composition, abundance, and size from trap collections and movements of marked mummichogs Fundulus heteroclitus before, during, and after dredging. In general, the fauna changed little during the 4 d of dredging relative to the 1.5‐month sampling period. Species composition variations that did occur may have been due to seasonal changes that are typically observed during the fall based on annual sampling at this site. The movement of tagged mummichogs was minimal, with most recaptures taking place in the boat basin. Individuals that left the boat basin moved into pools in an adjacent marsh for the winter. These results suggest that the short‐term effect of this low‐sediment‐volume dredging project was negligible for the benthic fishes and crabs studied, which we believe are representative of the high‐salinity portions of estuaries in the northeastern United States.

Spatial variations in macrobenthic fauna recolonisation in a tropical mangrove bay

Recolonisation by crab species and sediment-infauna taxa (at class level) in artificially re- generated mangrove stands of Avicennia marina, Rhizophora mucronata and Sonneratia alba (5 yr old) were studied using respective bare sites (open without mangroves or denuded) and natural sites (rela- tively undisturbed) as controls. The controls were chosen based on site history, physical proximity and tidal inundation class in reference to the particular reforested mangrove stand and samples randomly taken. A number of environmental variables were measured; interstitial water salinity and temperature (measured at low tide) were lower, whereas sediment organic matter content was higher in the areas with mangrove cover, with the natural sites having the highest content. The bare sites were generally sandier, whereas the areas with mangrove cover had higher proportions of clay and silt. Generally, there was a higher crab density in the reforested sites than in the bare sites, whereas crab species diversity (Shannon diversity index) did not vary from one site to another for any of the mangrove species. In terms of crab species composition, the reforested sites were more similar (Sorensen similarity coefficient) to the natural sites and less to the bare controls. For sediment-infauna, the reforested sites had a significantly higher density than the respective bare controls, while the natural sites had the highest density. The number of sediment-infauna taxa in both the reforested and natural sites of all the mangrove species was similar and higher than in the comparable bare sites. The results suggest that the reforested sites are supporting more faunal recolonisation, and therefore becoming more akin to the natural mangrove sites in terms of the investigated functional indicators. The findings seem to support the use of artificial mangrove regeneration (in areas where natural regeneration has been impeded by physical conditions or otherwise) as an effective management tool in the restoration and conservation of the functional integrity of degraded mangrove habitats.

Effects of Sampling Method on the Estimation of Population Parameters in Hermit Crabs

Hermit crabs were collected from intertidal and shallow nearshore habitats in the vicinity of Alligator Harbor, Florida, either by visual search of prescribed areas along transects or by collection of crabs that were attracted to baits of gastropod flesh (mimicking natural predation sites). The two sampling methods produced collections that were closely similar in crab species composition and relative abundance and in the relative abundance of the shells of the common gastropod genera that the crabs inhabited. The two collections differed in the following respects: (1) more individuals were collected at baits, (2) crabs attracted to baits probably were more secretive and less mobile, (3) significantly more crabs collected at baits occupied damaged shells (72.2%) than did those located by visual search (29.9%), (4) crabs attracted to baits occupied shells of more gastropod genera (22) than did those collected on transects (14), and (5) more individuals of small size and crabs of a wider size range were collected at baits. Our data suggest that the two methods sample different types of individuals with different efficiencies. Small secretive crabs that occupy damaged shells arc underrepresented in collections made by visual search, while larger crabs in intact shells are underrepresented at baits. Estimates of hermit crab population parameters probably should be based on a combination of sampling methods.

Competition and Mechanism of Coexistence in Three Sympatric of Intertidal Hermit Crabs

During monthly intervals over a 1—year period, 12,000 empty snail shells were added to a small, isolated, rocky intertidal reef in the San Juan Islands of Washington. The shells added were species normally used by the high intertidal hermit crab, Pagurus hirsutiusculus, and were placed in locations accessible to that species. The shell additions resulted in an increase in density of P. hirsutiusculus at the experimental reef, whereas no density change occurred at a nearby control reef, indicating the importance of shells as a limiting resource. To establish the generality of shell limitation, the hermit crab populations of four unmolested rocky intertidal sites (three of which are typical hermit crab habitats) were quantitatively samples to obtain species compositions and size distributions of hermit crabs, their shells, and unoccupied shells. Shell preference experiments determined the preferred shell sizes and species for each hermit crab species. Except for small size classes, empty shells were rate at the three typical areas. In addition, hermit crab size distributions followed shell size distributions, and all but small hermit crabs of three species occupied shells smaller than the preferred size. These results support the conclusion that empty shells are a limiting resource for these hermit crabs. Since shells constitute a common, necessary resource in short supply, these hermit crabs are in competition for available shells. The fourth area, chosen for its unusual shell—availability characteristics, exhibited a different pattern of shell utilization not suggesting shell limitation. Shell occupancy at the three representative intertidal sites was examined to determine the strength of the relationship between hermit crab species composition and resource availability. Though resource partitioning was demonstrated, the presence and numbers of each hermit crab species and its preferred shell types were poorly correlated. Differences in hermit crab species composition are explained by differences in the physical habitat, and collections from other areas show that the same shell species can support different hermit crab species in different but adjacent habitat types. Thus, the mechanism allowing coexistence apparently involves both resource and habitat partitioning.