Mud crabs are a valuable crustacean resource in brackishwater aquaculture due to their high export demand. Recently, the market preference for mature female Scylla olivacea has increased. However, issues like cannibalism, dependence on wild seed and lack of formulated feed, etc. limit the scale of farming. In this context the feasibility of nursery rearing for crablet production and growout with formulated feed was studied. Hatchery produced, S. olivacea with 0.5-1 g body weight was stocked into earthen ponds at different stocking density viz; T1-5, T2-10 and T3-15/m2 and fed with minced trash fish @ 10% of the bodyweight twice daily.
After 80 days, crabs attained a carapace width and bodyweight ranging from 34.07 ± 0.78 to 45.13 ± 1.36 mm and 7.91 ± 1.29 to 17.14 ± 1.22 g respectively with significantly higher growth in T3 (15/m2). However, survival remained low (20-30 %) across different stocking density. Appendage analysis showed significantly higher intact crablets in T1 (82.22 ± 1.76%), while T3 (Intact - 61.11 ± 4 %) had more individuals with all appendages missing (12.22 ± 2.22%).
Further, selected nursery reared crablets (20-25 g) were stocked in grow-out ponds at 0.5/m² and reared for 150 days under two feeding regimes: trash fish (D1) and pelleted feed (D2, 40% CP). Crabs attained an average body weight in the range of 102.92 to 210 g combining the females and males with no significant difference between diets, confirming the ability to utilize pelleted feed. Female crabs reached 80–120 g within 80 days, after which growth slowed, while constant growth in males were observed. Female crabs attaining a marketable size of 80-120 g within a period of 80 days is beneficial which can support the supply to box based fattening system. However, survival during the nursery phase needs further refinement to enable commercial-scale crablet production (Figure 2).