Stock

This study was conducted to find a suitable program and procedure for blue swimming crab (BSC) stock enhancement which is guided by the fishery community and to identify the level of agreement and cooperation of the fishermen in assessing BSC management options. This study also explored the primary information on socioeconomic status of BSC fishers and BSC fishing characteristics in the study areas. The sample respondents of this study included three groups: 265 BSC fishers, 27 BSC dealers, and 8 local authorities. The first group was selected by accidental sampling technique whereas the second and the third groups were selected by purposive sampling techniques. Survey results revealed that most of the fishers agreed (WAI=4.11±0.85) to set up the stock enhancement project in their communities by using the following procedures; 1) select a suitable site; 2) explain the rationale and objectives of the project; 3) establish fisher groups; 4) arrange workshop and training about berried female BSC hatching; 5) set up a meeting for working procedure and assign working groups; 6) practice on hatching the BSC; 7) release of the larvae; and 8) management of female BSC after hatching. In practice, the process should be thoroughly investigated and experimented in pilot communities to confirm the methodology and acceptance from the fishers before starting the project. There also should be specialists consulting and assessing the working group regularly. Proper guidelines should be established for the communities in order for them to continue the stock enhancement of BSC, using their own funds as a long term activity.

This study was the qualitative research based on the participatory action research (PAR), which has been conducted by cooperation of small fishing-boat fishery communities
earning for living by crab gill net fishery at the Phe Bay of Rayong Province, and other officials and technical specialists from related agencies in the area. The result showed some local fishery wisdom such as observation of Blue Swimming Crab habitat, tideway, wind, fishing operation, removal of crabs from crab gill net, crab catch seasons, season and environmental changes, etc. It was found that there have been some changes in Blue Swimming Crabs regarding the reduction of crab amount and size. Causes of changes in Blue Swimming Crabs at the Phe Bay included: 1) changing natural environment, e.g. delayed monsoon season; 2) impact resulted by leak of crude oil at Phrao Bay, Samed Island of Rayong at the end of July 2003; 3) use of smaller mesh-size net, catch of small-sized crabs, and selling of berried females; 4) destruction of marine and coastal resources resulted by the government policy in the coastal area development at Rayong; and 5) commercial fishing vessel operators’ employment of alien labors and use of high-tech tools to catch Blue Swimming Crabs regardless of crab types and sizes. The guidelines for management of Blue Swimming Crabs at the Phe Bay of Rayong Province to be implemented includes setting of core area as the fishery free zone, and establishment of Blue Swimming Crab bank to feed berried females.

Supmee V, Sawusdee A, Sangthong P, Suppapan J. 2020. Population genetic structure of Blue Swimming Crab (Portunus pelagicus) in the Gulf of Thailand. Biodiversitas 21: 4260-4268. The Blue Swimming Crab (Portunus pelagicus) is an important commercial fishery product in the Gulf of Thailand. To provide a strategy for management, information on genetic features is needed. In our study, the population genetic structure and demographic history of the P. pelagicus living in the Gulf of Thailand were analyzed based on the variation of the nucleotide sequence of the mitochondrial DNA in the control region (mtDNA CR). Ninety-seven samples were collected from 5 sampling sites: Rayong, Chonburi, Chumphon, Surat Thani, and Nakhon Si Thammarat provinces in the Gulf of Thailand. Forty-nine haplotypes were identified and 39 private haplotypes were found. An AMOVA showed no genetic structure among populations. The pairwise F ST also indicated no statistically significant difference between all possible regional combinations. The topology of a minimum spanning network revealed a star-like topology that was not separated by geographic structure. The historical demographic analysis revealed a stable population size for a long period and followed by a very recent expansion. An absence of a population structure of the P. pelagicus was possibly caused by a high level of gene flow. The results of this study differ from previous studies that used genetic markers in nuclear DNA. Thus, to clear the genetic structure information of P. pelagicus in the Gulf of Thailand, we suggested that more sensitive markers to detect genetic structure should be used in further analysis.

การศึกษานี้มีวัตถุประสงค์หลักเพื่อวิเคราะห์การแบ่งออกเป็นประชากรย่อย และความแตกต่างทางพันธุกรรมของประชากรสัตว์ทะเลภายในอ่าวไทย จากการรวบรวมรายงานการศึกษาโครงสร้างพันธุศาสตร์ประชากรของสัตว์ทะเลในอ่าวไทยตั้งแต่ปี พ.ศ.2546 จนถึงปัจจุบัน พบโครงสร้างพันธุศาสตร์ประชากรและความแตกต่างทางพันธุกรรมระหว่างประชากรอ่าวไทยตอนบนและตอนล่างในสัตว์ไม่มีกระดูกสันหลังในทะเลหลายชนิด เช่น หอยลาย หอยเสียบ กุ้งกุลาดำ กุ้งแชบ๊วย และปูม้า ยกเว้นในสัตว์กลุ่มหอยบางชนิด เช่น หอยแมลงภู่ หอยตะโกรม และหอยเชลล์ สำหรับสัตว์มีกระดูกสันหลังในทะเลกลุ่มปลา พบว่าประชากรปลากะพงขาว ปลาช่อนทะเล และม้าน้ำดำในอ่าวไทยมีความคล้ายคลึงกันทางพันธุกรรม ยกเว้นในประชากรปลาทู ปัจจัยที่ทำให้เกิดความแตกต่างทางพันธุกรรมในประชากรสัตว์ทะเลบางชนิด ภายในอ่าวไทย ได้แก่ การไหลเวียนของกระแสน้ำ ระยะห่างระหว่างประชากร และความแตกต่างของปัจจัยทางกายภาพและปัจจัยทางชีวภาพ