Nursery Rearing of Orange Mud Crab, Scylla olivacea (Herbst, 1896): Optimizing Pond Habitat and Stocking Density

Abstract

Orange mud crab, a species of the genus Scylla is a seafood product having a high demand for local and international trade. Traders supply live crab regularly from the wild to the domestic and foreign markets however, its commercial seed production has not been started yet. Knowledge production from different nursery rearing strategies is essential for successful commercial seed production of orange mud crab. This study aimed to optimize the stocking densities and pond habitats for better survival, intactness and growth during the nursery management of orange mud crab juveniles. Here, the first experiment (E1) was designed with three treatments depending on nursery habitats i.e., T1 (nursery in pond bottom without shelter), T2 (nursery in hapa), and T3 (nursery in pond bottom with shelters). In contrast, the second experiment (E2) was designed with stocking densities such as T1 (30 crablet.m-2), T2 (50 crablet.m-2), and T3 (70 crablet.m-2). Water quality was monitored regularly and we found all water quality parameters (e.g., salinity, temperature, pH, dissolved oxygen, alkalinity, and total ammonia) within the desirable range for farming of S. olivacea. The observed crab growth was higher in T3 of E1 and in T1 of E2. Similarly, the crab survival (64.0±5.0 %) and intactness (82.0±5.0 %) were significantly (p<0.05) higher in T3 of E1 than T1 and T2. Besides, the survival (68±4.0 %) and intactness (85±6.0 %) in T1 of E2 were significantly (p<0.05) higher than T2 and T3. In summary, keeping crabs on pond bottom with sufficient shelters in low stocking density showed better survival and intactness for S. olivacea. The findings of this study will be a cornerstone in rearing of juvenile orange mud crab at coastal crab hatcheries and nurseries for supplying inputs to grow out crab farms in Bangladesh.