Effect of Stocking Density on Intermediate Cultivation of Litopenaeus vannamei Postlarvae

Abstract:

Intermediate cultivation of shrimp postlarvae (ICSP) is an important part of industrial shrimp farming. Full-scale ICSP experiment in an aquafarm (21 d) was conducted to investigate the effect of stocking density (15000~22500 pieces/m3) on the shrimp growth performance, aquaculture water quality, and bacterial community. The results indicated that the shrimp growth performance (Expressed as yield rate, special growth rate, survival rate, and feed conversion rate) was enhanced with the increasing stocking density when the stocking densities were 15000~22500 pieces/m3. For all aquaculture ponds, the pH values and the concentrations of ammonia, nitrite and COD gradually decreased and increased，respectively over the ICSP period, while Vibrio concentrations fluctuated in the range of (0.3~7.5)× 104 CFU/ml. Furthermore, higher stocking density resulted in lower pH and higher concentrations of ammonia and COD in the water. However, little effect of stocking density on Vibrio concentration was observed in this study. At the end of ICSP, the aquaculture pond with higher stocking density had higher bacterial biodiversity. Proteobacteria (56.52%~71.22%) and Bacteroidetes (20.65%~38.23%) constituted the main taxonomic groups (Phyla) of the bacterial community in all aquaculture ponds, and Vibrio (2.3%~9.4%) was the dominant genus. During the ICSP period, daily-increasing amounts of water exchange could control the decrease in pH and the increase in COD concentration to some extent, but failed to stem the rise of ammonia and nitrite concentrations.