Effects of stocking density onimmune parameters and growth of juvenile Litopenaeus vannamei

In order to investigate the effects of different stocking density on theimmune parameters andgrowth of juvenile Litopenaeus vannamei, we cultured the shrimps body length (3.590.26) cm in 0.3 m3 fiberglass tanks (water volume 0.5 m3) at 1 800 indm-3, 1 500 indm-3 and 1 200 indm-3, respectively, for 30 d to determine the phenoloxidase (PO) activity, superoxide dismutase (SOD) activity, antibacterial activity (Ua), alkaline phosphatase (AKP) activity in hepatopancreas and muscle, as well asweight gain, survival and basic water quality factors. It is showed that the physical and chemical factors vary within suitable range with no significant difference. The PO activity, Ua and AKP activity in the muscle of shrimp reduce while SOD activity increase with the increase of stocking density.The weight gain, special weight growth rate (SGRw) and survival reduce with the increasing stocking density with significant difference in survival (P0.05). The results indicate that stocking density may obivously affect the growth and immune parameters of juvenile L.vannamei (body length4.8 cm or body weight1.2 g) when stocking density is within 1 200~1 800 indm-3.