The beneficial effects of multispecies Bacillus as probiotics in enhancing culture performance for mud crab Scylla paramamosain larval culture

Mud crabs (Scylla) are promising aquaculture crustaceans due to their fast growth and good market demand. High rates of larval mortalities associated with bacterial diseases in hatcheries are one of the major obstacles to the growth of Scylla aquaculture. Currently, antibiotics are used extensively in Scylla larval culture to improve survival rate, but its use poses numerous risks. The aim of this study was to determine the culture performance of Scylla paramamosain larvae with the use of a probiotic, namely a multispecies Bacillus, at various concentrations. In this study, the effects of Bacillus spp. were tested in three trials. There were higher average larval survivals in treatments with a multispecies Bacillus probiotics added compared with the control, especially at concentrations of 1.00 x 10(4) (12.33-18.33 +/- 1.76-3.76 % compared to 1.67-3.67 +/- 1.67-1.76 %; P < 0.05) and 2.00 x 10(4) cfu/ml. This was significantly lower than the control (1.33 +/- 1.33 cfu/ml compared to 32.67 +/- 11.05 cfu/ml) during the later days post-hatching. Green colonies Vibrios are known to be pathogenic to Scylla larvae, and thus lower numbers are desirable in culture. The recommended concentration of the multispecies Bacillus to be added into S. paramamosain larvae was therefore 1.00 x 10(4) and 2.00 x 10(4) cfu/ml (0.50 and 1.00 g/50 l, respectively). The use of Bacillus as a probiotic is an ideal alternative to antibiotics in Scylla hatcheries to provide a consistent, commercially feasible production of seedlings.