PRELIMINARY BIOLOGICAL INFORMATION OF SCYLLA SERRATA (FORSKAL, 1775) (BRACHYURA, PORTUNIDAE) IN THE PERSIAN GULF AND GULF OF OMAN: A CONSERVATION PRIORITY

The status of the populations of the mud crab Scylla serrata (Forskal 1775) is poorly known in the western Indian Ocean. Biological aspects of the species have been studied using 96 specimens collected between autumn 2009 and summer 2010 from the northwestern Gulf of Oman and 22 specimens collected in spring 2009 from the northeastern Persian Gulf. The population was found to be sparse in the northwestern Gulf of Oman (about 1 crab per hectare) and only one small population was recorded in the Persian Gulf. In total, 81.3% of the crabs in the Gulf of Oman were males, which may be a result of the breeding migration of females into offshore waters. The carapace width of the Gulf of Oman specimens ranged from 89.7 to 196.5 mm (males) and 91.7 to 170.1 mm (females). The smallest mature female measured was 12.4 cm in carapace width. The carapace width (CW)/weight (W) relationships in the crabs of the Gulf of Oman were calculated to be W = 2 x 10(-5) cw(3.48) and W = 1.8 x 10(-3) CW2.52 for males and females, respectively. The gill chamber in many of the Gulf of Oman's crabs was covered with the lepadomorph barnacles, Octolasmis cor (Aurivillius, 1892) and O. angulata (Aurivillius, 1894). Although, the reason of the low abundance of the crab in the Persian Gulf and the Gulf of Oman is still unknown, conservation programmes seem to be necessary.