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2011
Ecology of marine crabs possess the life-cycle, competition, predation, feeding, migration and species-environment relationships. Population ecology dealt with the population dynamics of the species which interact with their surrounding environment. The main concept of population ecology is to predict species distribution within the study area. The dynamics of population shows population size, density and abundance where population size change over time. The resources limitation factor affected the population size where environment sustain maximum population size called carrying capacity.
2008
Crabs are amongst the most conspicuous and ecologically important organisms inhabiting nearshore environments. Their complex life cycle and bioindicator capacity makes them good models for the study of distribution and abundance patterns of marine fish and benthic invertebrate populations. Such knowledge is essential for explaining species occurrence and demographic patterns, predicting the success of biological indicators and controls, as well as for conservation and management purposes of exploited populations and ecosystems. In this study, the impacts of specific environmental constraints at different life phases of estuarine and coastal crabs on population structure and physiological condition were evaluated and related to habitat quality. During settlement and recruitment events, the patchiness of artificial substrates significantly influenced settlement estimation, and strong water currents might have resulted in a decoupling pattern between supply and settlement. Estuarine sandy habitats presented higher quality for early recruits than seagrass ones. In fact, vegetated habitats were not of higher quality for crab populations than non-vegetated and rocky-shore ones. Adult-juvenile cannibalism showed potential to structure intertidal crab assemblages, especially under shortage of food and refuge. Interestingly, mangrove crabs were more affected by climatic season than by pollution, and coped well with several combinations of vegetation and sewage load. Specific constraints of different life stages, individually and in combination, must be considered for full understanding distribution and abundance patterns of crab populations. Furthermore, the relative importance of a specific constraint is likely to change throughout ontogenesis, and the mechanisms by which it interacts with other environmental variables and processes, sometimes synergistically, have also to be considered. This study constitutes an extension to the knowledge on population structure and physiological condition of coastal and estuarine crabs and other marine invertebrate and fish species, and on their use as indicators of ecological status of habitats and ecosystems.
We studied the size structure and population dynamics of blue swimming crab (Portunus pelagicus Linnaeus 1758) in Lasongko Bay, Central Buton - Indonesia from April 2013 to March 2014. We assessed the size structure, growth parameters, recruitment, mortality, and rate of exploitation due to local fisheries. We collected crabs monthly by gillnets with mesh sizes of 1.5, 2.5 and 3.5 inches. The size structure of male and female crabs consisted of one to two groups, most of which were adults. The growth parameters of male and females crabs were CW∞ = 152.04 mm and K = 0.93 year -1, and CW∞= 173.04 mm and K = 0.68 year-1, respectively. Total, natural, and fishing mortality of males were 2.80, 1.09 and 1.71, and 2.95, 0.86, and 2:09 for females, respectively. The exploitation rate of males and females were 0.61 and 0.71, respectively, which suggests overfishing.
Digha coast is the most popular sea side in the West Bengal renowned for its extended beaches which support varieties of animal life. The present study emphasizes on the composition, distribution and abundance of different crabs in the entire Digha coast including Talsari of Jaleswar district, Odisha. The actual study period was in middle of January to the end of June, 2014. The total species were found to be 34 belonging to 9 families, out of which 28 species were collected in summer and the rest was collected in winter. The populations of commercially important marshy crabs are gradually declining day by day due to indiscriminate fishing of berried females and different anthropogenic activities of the coast. The most dominated family was Ocypodidae and Portunidae and the leading species of crabs includes Scylla serrata, S. tranquebarica, Portunus pelagicus and P. sanguinolentus. In last few years, the local peoples have tried to convert marshy areas to aquaculture ponds for achieving higher production of tiger shrimp. Consequently, habitat as well as breeding places of these crabs reduces day by day. Simultaneously, the discharged effluents from the shrimp farms are also causes serious threat to the crab population. From our observations it has been revealed that maximum crabs were found in summer and less abundance during winter.
2009
The population dynamics and stock assessment of blue swimming crab (Portunus pelagicus Linnaeus, 1758) in the coastal area of Trang province, Southern Thailand was done through stratified sampling of 7,499 crabs that were caught by crab gill nets and crab traps. The sampling was done from September 2006 to August 2007. The carapace width and weight relationship was measured, including parameters such as asymptotic outer carapace width (OCW α), curvature (K), asymptotic inner carapace width (ICW α), total mortality coefficient (Z), natural mortality coefficient (M), fishing mortality coefficient (F), exploitation rate (E), and total stock at first catch (L c). The maximum sustainable yield (MSY), maximum economic yield (MEY) and total biomass (B) were estimated. Results showed that the asymptotic outer carapace width was 17.30. The asymptotic inner carapace width was 16.70 cm and its curvature was 1.5 per year. The total mortality coefficient was 8.96 per year, natural mortality coef...
Aceh Journal of Animal Science
Blue swimming crabs Portunus pelagicus occupied Tiworo Strait waters has been experiencing heavy pressure due to high exploitation and damaging its habitat caused by conversion to be a port or jetty particularly in the intertidal and subtidal zones closed to mangrove areas and river mouth. Those zones constitute main habitats of BSCs. The study aimed to analyze temporal sex ratio (SR), growth patterns and condition factor (CF) of BSCs in Tiworo Strait waters which was conducted in June–December 2018. The BSC samples were taken monthly using collapsible pot. Each sample taken was identified its sex, measured its CW and weighed its BW. Monthly SR of male and female was counted, while BW–CW relationship was analyzed using a simple linear regression. Growth patterns and CF were derived and analyzed from BW–CW regression. The results of study showed that monthly BSC SR of male and female showed females preponderated over males, except in November. The growth pattern of male and female wa...
Tomini Journal of Aquatic Science
Management and conservation of the blue swimming crabs by the marine protected area method require the abundance and environmental parameter information of the blue swimming crab. The aim of this study is to analyze the changes in the relative abundance of the blue swimming crab and its environmental parameters. The study was conducted from March to July 2015, in the waters of Salemo Island, Spermonde Archipelago. The specimens were collected at the three fishing locations around the mangrove, seagrass, and coral reef ecosystems. The variable of relative abundance of the blue swimming crab is determined catch per effort. Samples of environmental parameters such as temperature and current speed are measured in situ. However, for the salinity, dissolved oxygen, ammonia, nitrate, plankton, and chlorophyll-a were analyzed in the laboratory. A comparison of the blue swimming crab abundance in each ecosystem was conducted by One Way ANOVA. Moreover, the relationship between blue swimming ...
LAP Lambert Academic Publishing, 2016
ABSTRACT Filemon G. Romero Adviser: University of the Philippines – 2009 The blue swimmer crab, Portunus pelagicus (L) supports the major marine crab fishery of the Philippines. It is the main target species for the crab meat processing industry and the 7th most important fishery export product contributing to the national economy. However, there were indications of decline in catch between 1995-96 and the year of sampling, 2002-03. The density of fishermen was estimated to be about 11 fishermen per kilometer of coastline which is an indication of high fishing pressure. For this study, the mean CPUE for crab pots was highest in October at 0.012 kg/pot-hr and lowest (0.006 kg/pot-hr) in June. The CPUE for gill nets was highest at 0.15 kg/segment-hr in July and August and lowest in April 0.06 kg/segment-hr. There was no significant difference in CPUE across sites but there were significant interactions between CPUE and season (ANOVA, α < 0.05). The size range of crabs was 6.0 to 18.5 cm CW. The mean size of crabs caught by crab pots ranged from 10.61 to 14.3 cm CW while for gill nets the range was 11.41 to 13.3 cm CW. The size frequency distribution showed that majority of the crabs caught were above the size at sexual maturity. Overall, the ratio between males and females was close to 1:1. However, for crab pots, females outnumbered the males. The population growth rate of P. pelagicus was estimated using the von Bertalanffy Growth equation and this showed that males grew faster than females. The estimates of L∞, was determined through the routines in ELEFAN1 and this ranged from 18.9 to 19.95 while the growth constant K ranged from 0.58 to 1.4 for the landed catch from different sampling sites. Estimated total mortality (Z) ranged from 2.147 yr-1 to 5.285 yr-1. When all the carapace width frequency data from all samples for the four sites were pooled, treating the entire Visayan Sea as one fishing ground, Z was estimated to be 3.095 yr-1, natural mortality (M) was 1.578 yr-1 while fishing mortality(F), was 1.52 yr-1. Exploitation ratio (F/Z) was 0.49 which indicates that the fishery is exploiting almost 50% of the biomass of the blue crab stock or that the fishing mortality is almost equal to the stock’s natural mortality. The value of Y/Rmax was at 142.8 g/recruit (approximately 13 cm CW). A significant portion of the landed catch, about an average of 44.5% ±7.3 of the males and 38.3% ±6.6 of the females in gill nets and 61.2% ±5.3 of the males and 59.2% ±5.8 of the females in crab pots, was below this 13 cm CW indicating that there is growth overfishing. The Beverton and Holt yield per recruit analysis gave the value of E/E10 = 0.96 implying that the fishery is at the brink of overexploitation. Recruitment patterns into the fishery showed two major pulses, one higher than the other. Given that the peak in the incidence of egg-bearing females was in February and March and that larvae will recruit into the fishery after 8 to 9 months based on the larval duration and estimated age at size (CW), the major recruitment pulse in the fishery would be in October to November. These months coincided with the months with the highest CPUE which suggests that the spawning resulted to local recruitment. The other peak of incidence of egg-bearing females for the three sites was in October and November and recruitment into the fishery for this batch of larvae would be sometime in August. However for all these sites, this corresponded with months of low CPUE. This suggests that larvae spawned in October or November may not recruit locally. The fecundity of P. pelagicus in the Visayan Sea was comparable to other sites in the Philippines and it conformed with published works that fecundity increases with carapace width. The Index of Reproductive Potential (IRP) was highest in Baud and Igbon (760), followed by Nabulwang (573) and Pasyagon (456). Overall, female crabs 12.5 to 14.5 cm CW have the highest potential reproductive output relative to other sizes. The estimated contribution to the population’s reproductive output of this size class range was 48.6% in Igbon, 42.4% in Baud, 58.4% in Nabulwang and 54.7 % in Pasyagon. Genetic analysis showed that the populations of the crabs in the Visayan Sea had genetic affinities with that of Bohol but not with Tawi-Tawi. There was no significant genetic structuring among the sites in the Visayan Sea and the P. pelagicus species in the Visayan Sea belongs to one stock. This concurs with results of the larval dispersal modeling which indicate larval exchange within the Visayan Sea during different monsoon periods. While Igbon and Baud have higher IRP, the larval dispersal model showed that a higher percentage of the particles (simulating larvae) from these sites were advected out of the Visayan Sea in April and November with some retention in May and August. In contrast, while the IRP of crab population in Nabulwang was lower, majority of particles released from this site were entrained within the Visayan Sea particularly in Asid Gulf during different monsoon periods. Furthermore, results show that the fishery in the Visayan Sea is replenished by local populations and these populations are likewise important sources of blue crab larvae for areas outside the Visayan Sea. An Ecosystems-Based Approach for Fisheries Management for the Visayan Sea, treated as one fishery management unit, is recommended. A suite of management options to respond to each of the problems of the fishery have been recommended. A Multi-Criteria Analysis tool was formulated using biological/ecological, social and economic indicators to score each option according to the relative degree of impact, either positive or negative. From the initial scoring, the shift from gill nets to crab pots appears to be a better management option.
Graven in Het Groen Jg 2 Nr 1, 2012
Asia Pacific Journal of Public Health, 2024
2017
International Journal of Advanced Computer Science and Applications(IJACSA), 2019
Indonesian journal of business and management, 2023
Transplantation Journal, 2013
Frontiers in medicine, 2024
The Sport Psychologist, 2006
Analytical and Bioanalytical Chemistry, 2016
Journal of Clinical Immunology, 2013