Carapace width and weight relationships, condition factor, relative condition factor and gonado-somatic index (GSI) of mud crabs ( Scylla spp. ) from Chilika Lagoon, India.

Abstract

Carapace width (CW)-weight relationship, condition factor (K), relative condition factor (Kn) and gonado-somatic index (GSI) for meaty and post-moulted crabs of both sexes of the two mud crab species, Scylla serrata (Forskal) and S. tranquebarica (Fabricius) co-existing in Chilika lagoon, Orissa, India, were studied during August, 2005 to July, 2007. CWweight equations and correlation co-efficient (r) obtained for both sexes of meaty and water crabs of the two species were significant (P< 0.05-0.01). Regression slopes (b) were higher for males and fattened crabs in both the species. The K and Kn values recorded in each month for different size groups of both sexes of the two species were higher in male and values were relatively higher in S. tranquebarica than S. serrata. Increase in Kn values beyond 1.0 from 81-91 mm CW in S. serrata and 111-120 mm CW in S. tranquebarica indicated the size at first maturity. Higher monthly values indicated that breeding period was extended from August-November and March-July in S. serrata and S. tranquebarica respectively. Speciesspecific study aimed at establishing difference in biological characters between two species of Scylla[a] from same brackishwater habitat. CW-weight relationship may be useful in setting feeding rates for a particular species in aquaculture.