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Study of blue swimming crab.

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Assessment of stock and movement pattern in blue swimming crab Portunus pelagicus Linnaeus, 1758 at Kung Krabaen Bay was conducted from October 2008 to September 2009. This study was divided into 4 parts; 1) assessment whether the blue swimming crab population in crisis 2) populations both inside and outside the bay are the same group 3) assessment of the present blue swimming crab management in Kung Krabaen Bay and finally 4) the sustainable management of blue swimming crab was proposed based on scientific findings. ...

งานวิจัยชิ้นนี้เป็นการศึกษาการแพร่กระจายของความอุดมสมบูรณ์สัมพัทธ์ (Relative abandance) ซึ่งชี้วัดได้โดย ค่าผลจับต่อหน่วยการลงแรงประมง (Catch per Unit of Effort, CPUE) ของประชากรปูม้า (Portunus pelagicus Lin) ...

In Prachuap Khiri Khan province, Thailand, fishers observed that the blue swimming crab resources had rapidly declined due to overfishing, especially in the areas of Ao Noi Bay, Prachuap Khiri Khan Bay, Klongwan Beach and Baan Krut Beach. The crab bank is a sustainable crab conservation project set-up in a fishing village for a pilot scheme on marine resources conservation. The objectives of this study were to clarify the changes in the blue swimming crab yield after the crab bank implementation, determine the participation level of fishers in the crab bank activity, and appraise the economic considerations for guidelines on the long-term implementation of the crab bank and for the improvement of subsequent projects to be undertaken in these areas. The study revealed that the juvenile crab yield in the study areas increased after the crab bank had been in operation for 4-8 months. The participation of fishers in the crab bank at the Baan Krut fishing village was at a high level, but the crab bank at the Ao Noi, Ta Monglai and Klongwan fishing villages were at a low level. After 8 months of crab bank operation, the crab banks at the Ta Monglai and Baan Krut fishing villages were still active but the crab banks at the Ao Noi and Klongwan fishing villages were closed temporarily because participation of fishers was at a very low level and there was a lack of subsidy for the operating expenses and maintenance of the crab bank. The study concluded that the success of a crab bank project is primarily dependent on the local communities and thus it is recommended that the local government should use all means available to encourage higher program participation by the fishers (e.g. promotional activities) and to support maintenance of the crab bank.

The stock assessment of the blue swimmer crab, Portunus pelagicus was made based on monthly length frequency data collected from four landing sites along the Oman coasts on both Arabian and Oman Seas from January, 2011 to May, 2012. Age and growth have been estimated from the length-frequency distribution of up to 1000 specimens. Age composition was determined using Bhattacharya's method and the results showed that the maximum life span of P. pelagicus was about 15 months. Bertalanffy (1938) growth parameters didn’t differ significantly between sexes and the obtained values of K were K = 1.85, 1.68 and 1.68 y-1 and CL50 values were 102.83, 109.57 and 108.46 mm for male, female and sexes combined, respectively. The values of total mortality coefficient (Z), natural mortality coefficient (M) and fishing mortality coefficient (F) were 7.85, 3.15 and 4.7 y-1. The yield per recruit and SSB analysis showed that the crab stock is being exploited beyond its maximum biological limit, but the increasing of fishing mortality to the level which gives the maximum Y/R (83% of its current value) will accompanied with a negligible increase in Y/R (2.7%) and a considerable decrease in both biomass per recruit (21.1%) and spawning stock biomass (37.6%).