Maturity and breeding of the mud crab,Scylla serrata (Forskal) (Decapoda: Brachyura: Portunidae)

Females of Scylla serrata attained sexual maturity after reaching 80 mm carapace width and above. 50% of females at size range 91-100 mm carapace width were sexually mature. The growth rate of abdomen width or length with respect to either carapace width or length was generally much higher in mature females than in the immature specimens. A sharp transition at 80 mm carapace width indicated the morphological changes accompanied with the sexual maturity. The relationship between abdomen allometry and carapace measurements was highly significant. S. serrata , although breeding all through the year, exhibited two peaks, one between Dec-Mar and another in Sep-Nov. The sex-ratio in two biotopes varied considerably with the breeding season and size of the female population. The females were found to be in berried state in inshore and offshore waters of Karwar (India) at 90 mm carapace width and above. Spawning of S. serrata was found to occur only inshore and offshore but not in backwaters.