Influence of salinity on survival and molting in early stages of three species of Scylla crabs

Early instars of three mud crab Scylla species were reared in different salinities and survival and growth were compared. Scylla olivacea were reared in salinities of 12, 16, 20, 24, and 32 g/l (control). Scylla serrata and S. tranquebarica were reared in salinities of 8, 16, 20, 24, and 32 g/l (control) After 75 days, survival of S. olivacea and S. serrata was not affected by salinity but survival in S. tranquebarica was significantly higher in 8-20 g/l than in 24 and 32 g/l. The molt interval was shorter in S. olivacea, and more animals attained the fifth molt, than in the other species. The molt interval was shorter in 12-20 g/l than in 24 and 32 g/l for S. olivacea, did not vary among test salinities for S. serrata, and was shortest in 20 and 24 g/l in S. tranquebarica where fewer animals attained a fourth molt in 32 g/l than in 8-20 g/l. The molt increment was influenced by salinity only in S. olivacea. At the end of the test, all three species exhibited lower internal carapace width and mean body weights in 32 g/l. Among the three species, S. serrata was most versatile in tolerating a wide range of salinities during nursery culture.This study was supported by the European Commission (INCO-DC) under project grant no. ICA4-CT-2001-10022 entitled ‘Culture and Management of Scylla Species’ and SEAFDEC/AQD with contribution no. 2011-04. The authors wish to thank Mr. Tonymer Castillo and Mr. Federico Ledesma for invaluable assistance in collecting samples and in the conduct of the experiments, the Crustacean Hatchery staff especially Jennette de Pedro and Quirico Ganon for helping with the larval rearing, and Dr. Jurgenne Primavera for the encouragement to work in the project