Journal of Sustainability Science and Management Volume 7 Number 1, June 2012: 1-8 ISSN: 1823-8556 © Universiti Malaysia Terengganu Publisher Introduction The blue swimming crab, Portunus pelagicus, is distributed throughout the Indo-Paciic region and is closely associated with sheltered near- shore marine water and estuaries (Ikhwanuddin, M., Shabdin, M.L. & Abol-Munai, 2009a, b; de Lestang, 2003). Large numbers of P. pelagicus frequently enter estuaries as juveniles (Potter & de Lestang, 2002) and the female P. pelagicus sometimes become ovigerous in estuaries (Potter & de Lestang, 2002). Studies also showed that the portunid crabs that often occupied the marine embayment would not leave this environment to spawn which always occur in high-salinity regions (Potter & de Lestang, 2002). Literature reviews shows that the movement of P. pelagicus in and out of estuaries into open ocean occurs for spawning and as a reaction to lower salinity MOVEMENT PATTERNS OF BLUE SWIMMING CRAB, Portunus pelagicus IN THE SARAWAK COASTAL WATER, SOUTH CHINA SEA M. IKHWANUDDIN* 1 , NURFASEHA, A. H. 1 , ABOL-MUNAFI, A. B. 1 AND SHABDIN, M. L. 2 1 Institute of Tropical Aquaculture, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu and 2 Faculty of Science Resource Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak. *Corresponding author: ikhwanuddin@umt.edu.my (Potter & de Lestang, 2002). Study shows that P. pelagicus has strong swimming ability and are capable of moving through substantial distances of 20 km per day as in Queensland, Australia (Sumpton & Smith, 1991). However, a tagging study by Potter et al. (1991) in Queensland, Australia showed fairly small-scale movement of crab populations, where, of the recaptures, 79% were caught less than 2 km from their release point and only 4% were recaptured more than 10 km from the release point. Literature reviews shows that there is no study on the movement patterns of P. pelagicus in any of the water bodies of Malaysia. Thus, the main objective of the present study was to determine the movement patterns of P. pelagicus within the near-shore marine embayment of the Sarawak coastal water, South China Sea. The movement patterns of crabs were assessed through the tagging study within the study area. Received: 06 November 2011 / Accepted: 22 January 2012 Abstract: A study was carried out to determine the movement patterns of P. pelagicus within the near-shore marine embayment of the Sarawak coastal water, South China Sea. These mark-recapture tagging studies were conducted for about ive months from 26 th March till 30 th August 2005 comprising 48 sampling trips. Out of 976 crabs tagged and released, 212 (21.72%) were recaptured. The mean distances moved by male and female crabs were 7.36 km ± 1.78 and 9.15 km ± 1.87 respectively. The study shows that the female crabs moved signiicantly (p=0.01; p<0.05) further than males. The percentage of tagged crabs recaptured within the original release site were 50.0% for male and 45.83% for female crabs. The result shows that the male crabs only signiicantly (p=0.01; p<0.05) moved towards the deeper off-shore areas as compared to the near-shore areas. On the other hand, the female crabs moved signiicantly more towards both deeper off-shore and shallow near -shore areas. Most of the tagged crabs were recaptured within the sampling site of 2 km radius after a minimum of 30 days at liberty. The movement activities from the study were not necessarily limited because only 21.72% of the tagged-and-released crabs were recaptured. Thus, the main movement activities were attributed to the migration movements associated with reproduction and this can be seen from the tagged crabs which were recaptured at the off-shore deeper water. KEYWORDS: Movement patterns, mark-recapture, tagging, Portunus pelagicus, Sarawak coastal water