Effects of Artificial Substrates on Growth, Spatial Distribution and Non-Specific Immunity Factors of Litopenaeus vannamei in the Intensive Culture Condition

In order to investigate the effects of artificial substrates on shrimp growth, spatial distribution and non-specific immunity factors, such as phenoloxidase (PO), superoxide dismutase (SOD), peroxidase (POD), antibacterial activity (Ua), lysozyme (UI) and hemolysin activity, 30-day old Litopenaeus vannamei post-larvae (PL30) were reared intensively for 60 days at a density of 500 shrimp m(-2) of water surface area in each of 8 PVC aquaria (1.0x1.0x1.5m, water surface area 1 m(-2), water volume 1000 L). Two aquaria containing no artificial substrate were a control group, and 1, 2 and 3 artificial substrates were present in other 6 aquaria. Shrimp growth (gain in weight), survival and yield increased significantly (P < 0.05) when more artificial substrates were added. The percentage of shrimp on artificial substrates increased with increasing number of artificial substrates and rearing time. As for non-specific immunity factors, the activities of PO, Ua, UI, POD, SOD and hemolysin of groups with artificial substrates were lower than those of control group significantly (P < 0.05). With an increasing number of artificial substrates, the activities of PO, Ua, UI, POD and hemolysin reduced, but SOD activity increased. It was suggested that artificial substrates could alleviate the negative effect of the high stocking density by providing well living environment for shrimp.