Mud crabs genus Scylla are distributed across the Indo-West Pacific Oceans. Among the four species, S. tranquebaricadominates the mangrove areas in Sabah, Malaysia and constitutes the primary crustacean fishery resource. Overexploitationof this economically important fisheries resource can have a significant impact on population diversity. This study wasconducted to evaluate the genetic diversity of S. tranquebarica from five important fishing grounds. The genetic diversitywas estimated based on the cytochrome c oxidase (COI) gene sequence. A total of 143 individuals were sampled across the5 fishing grounds. The findings revealed that the crabs in Sabah comprised 11 haplotypes with a mean haplotype diversity(h)of 0.5564 and a mean nucleotide diversity () of 0.0038. The molecular variance analysis (AMOVA) showed that the lowgenetic differentiation among crab individuals in the five fishing grounds. The low genetic diversity provides the basis forthe establishment of a scientific breeding program to counteract the loss of genetic diversity which is the result of over-exploitation of this ecologically and economically important fisheries resourc
