Flow field control for larviculture of the seven-band grouper Epinephelus septemfasciatus

This paper reviews recent findings on establishing flow field control for larval rearing by hydrodynamics approach from case studies of the seven-band grouper (Epinephelus septemfasciatus). We chose this species because grouper larvae are known to be highly sensitive to physical stress, although it is expected for the new target species of aquaculture and stock enhancement in Japan. We quantified and visualized the flow field by aeration in the rearing tank with hydrodynamics approach. A series of systematic experiments was conducted to evaluate the optimal flow for the survival of larvae in the 1 m3 rearing tanks. Aeration at 200 mL/min produced the highest survival and growth for grouper larvae and the flow field was identified and then a computing method for estimating the flow field was established. We expanded this approach to the mass-culture scale (100 m3) and controlled the flow field similar to the optimal flow field in the 1 m3 rearing tank. It was quite successful resulting in 3 times higher survival than the former rearing methods. The results from these studies may be very useful for estimating the stationary flow in a rearing tank and for designing suitable tanks for rearing larvae. We also discussed the possibility of larviculture without aeration.