Effect of water recirculation rate and initial stocking densities on competent larvae and survival of the Pacific oyster Crassostrea gigas in a recirculation aquaculture system

The present study evaluated the effect of initial stocking density and water recirculation rate on larval yield (percent of initially stocked larvae alive at the end of the experiment) and production of competent larvae (percent of initially stocked larvae alive at the end of the experiment retained on a sieve with mesh size 239 mu m) of Crassostrea gigas in a recirculation aquaculture system (RAS). Different initial larval stocking densities (80, 160 and 320 larvae mL(-1)) and water flow rates (100, 200 and 300 mL min(-1), totalling renewal rates of 60, 120 and 180 times day(-1) of water volume in culture tanks, respectively) were evaluated in 2.4-L tanks using a completely randomized design in a factorial scheme. The physicochemical parameters of the water (temperature, salinity, pH, dissolved oxygen and conductivity) were stable in all treatments during the experimental period. Our results demonstrated that the production of C. gigas larvae was feasible at the proposed densities. However, the water renewal rate affected both yield and competent larvae in the recirculation aquaculture system. Oyster cultures with densities of 160 larvae mL(-1) and flow of water of 300 mL min(-1) showed the best yield (89.34 +/- 18.43%) and rate of competent larvae (84.09 +/- 16.38%) and are therefore recommended with the aim of optimizing larvae cultivation.