Effects of different stocking densities on tiger grouper juvenile (Epinephelus fuscoguttatus) growth and a comparative study of the flow-through and recirculating aquaculture systems

Abstract

Two experiments at different water-flow conditions and stock densities in the critical 6-week nursery phase determined growth, survival and feed conversion of brown-marble grouper juveniles at 35 Day After Hatching (DAH) with initial mean body weight of 0.045±0.02 g and total mean length of 15.08±0.4 mm. In the first experiment, juveniles of 35 DAH were kept in an 80 L fiberglass tank with the flow-through system for 42 days of the nursery phase at three densities: 1, 3 and 5 ind/L. The highest specific growth rate (P 0.05) were found in the survival rate of fish groups held in any stocking density. In the second experiment, juveniles of 35 DAH were reared with a re-circulating aquaculture system (RAS) at three densities, 1, 3 and 5 ind/L, to evaluate the effects density has on grouper growth and survival rate in the RAS system, and results were compared with the open flow-through system. No statistically significant differences (P>0.05) were found in total length and body weight between treatments (1, 3, 5 fish/L) in the RAS system, while the weight and total length of the fish reared in open water flow-through conditions were significantly larger (P<0.05) than fish reared in the RAS. This study suggests that optimum stocking density in a flow-through system is 3 fish per liter and flow-through water is preferred to the RAS system.