Mud crab grow out culture in West Bengal
Earlier pond trials confirmed that S. tranquebarica cultured in West Bengal was superior to the locally available S. serrata. Further trials were carried out this year with S. tranquebarica to determine if all female populations would result in higher production. In both the treatments, nursery reared juveniles were stocked @ 0.6 nos/s m2 (all female) and 0.75 pc/ m2 (mixed sex ratio 1:1) and the grow-out culture experiment was carried out for 167 and 205 days respectively. The calculated production was higher in mixed sex culture (1008 kg/ha; FCR 3.64) compared to all female (613 kg/ ha FCR 3.35). The results indicate that it is possible to achieve a production of above 1000 kg/ha of S. tranquebarica with nursery reared stocking. Proper scheduling of the crop starting from the month of April-May could result in better survival and production. Mixed sex culture of S. tranquebarica yielded better productivity than monosex culture. Although survival of the crabs in all female trials was better, the mixed sex culture resulted in higher production due to the higher average weight attained. In this low saline farming of S. tranquebarica at Sundarban, the production cost was found to be Rs.235/- per kg with a profit margin of Rs.85,000/- per ha and a rate of return of 36% over the operational cost. With proper scheduling of the crop and with better survival rate, better rate of return is achievable.