Natural fresh feed for successful production of G1 hybrid of mud crabs Scylla tranquebarica (Fabricius, 1798) and Scylla olivacea (Herbst, 1796)

Abstract

Natural fresh feed influences the growth and reproduction of female mud crabs. We conduct a set of feeding experiments using natural fresh feed. Twenty subadult female Scylla tranquebarica were individually reared in a plastic bucket with a recirculation system. The first group, consisting of 10 crabs, was fed with low-value fish Leiognathus equula (A), and the second group, with a similar number of crabs, was fed with a combination of L. equula and oyster Crassostrea irredalei (B). The feeding rate was administered twice daily at 5–10% of the total biomass. The moulting of females was observed daily. Upon moulting, growth was recorded, and the individual can mate with adult males of Scylla olivacea. The new mate females were reared until they matured their gonads, spawned, and produced hybrid G1 larvae. Larvae were reared until they reached the crablet stage. The crablet G1 hybrid growth in the brackish water pond was controlled with crablet non-hybrid from the hatchery. We found that the sub-adult female crab S. tranquebarica receiving treatment B had faster growth, indicated by earlier moulting, mating, and spawning periods, followed by larval production, compared to those treated with diet A (p < 0.05). Thus, treatment B allowed faster production of the G1 hybrid than treatment A. Those G1 hybrid larvae from the broodstock fed with treatment B grow faster than those of larvae obtained from the hatchery (control), as reflected in the higher larva development index (LDI) value.