Preliminary Study on the Mud Crab Fishery in Mannar District

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Date
2013
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Uva Wellassa University of Sri Lanka
Abstract
Mannar district situated along the west coast of Sri Lanka lies between north latitude 8.8667 and east longitude 80.0667 . The district is the unique assemblage of marine, brackish and freshwater and adjacent ecosystem with numbers of economically significant wild harvest. Scylla serrata (Forskal), popularly known as mud crab and widely distributed throughout the Indo-West pacific region is also found here. It belongs to the family portunidae and to the group of swimming crabs. Scylla serrata is locally known as Kali nandu (in Tamil) and Kalapu kakuluwa (in Sinhala). They are predominantly estuarine but move towards the offshore and mangrove habitats for spawning and early larval life. In recent years, mud crab appears to be the most important export commodity in Sri Lanka and it triggered the continuous and irresponsible exploitation of the species. Hence, the present study was undertaken to study the status of mud crab fishery in Mannar. Methodology The present study was carried out during May 2013 to August 2013. Four landing sites, Southbar, Pallemunai, Achankulam and Illuppakadavai were selected after the careful analysis of available literature considering the mangrove density and the mud crab availability. Live mud crab specimens, which were collected from the morning till evening was observed daily in roster basis at each landing center in the evening during the study period. After the cautious observation of the crabs the suitable individuals were selected for the study. The width of carapace (CW) between the ninth teeth of left and right antero-lateral boarder was measured with a caliper and the body weight was recorded in grams using a digital weighing scale. Identification of mud crab species in the field was performed following Keenan (1994). Additional information regarding the capture method, capture time and number of fishers engaged in this activity were recorded by interviewing the fishermen. The meteorological data were obtained from the meteorological department of Mannar while the monthly harvest data were obtained from the daily records of fishers. The carapace length frequency pattern of Scylla serrata was drawn separately for both male and female of each sampling site to observe the length frequency distribution of the harvest. Results and Discussion Two species of mud crabs; Scylla serrata and Scylla olivacea were recorded from Mannar Lagoon. Scylla serrata was found in almost all the sites throughout the district but Scylla olivacea existed in sites where mangrove forests occur (Table 1). Baited traps, gill nets and hand picking from crab holes using a stick are practiced for catching crabs, but the baited traps was the most dominating gear type used by fishers in all the sites. The size of the trap and the mesh size of the nets vary from lagoon to lagoon.
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Keywords
Animal Sciences, Aquaculture and Fisheries, Fisheries, Aquatic Resources, fish Industry
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