The effects of dissolved oxygen concentration and stocking density on growth and non-specific immunity factors in Chinese shrimp, Fenneropenaeus chinensis

The effects of dissolved oxygen (DO) concentration and stocking density on growth performance, such as growth, survival, ecdysis, oxygen consumption, ingestion and food conversion efficiency (FCE), and non-specific immunity factors, such as phenoloxidase (PO), superoxide dismutase (SOD), peroxidase (POD), antibacterial activity (Ua), lysozyme (Ul) were investigated in the Chinese shrimp Fenneropenaeus chinensis. Shrimp growth (gain in length and weight), survival rate, ecdysis, ingestion and FCE were not significantly different among DO concentration treatments. The activities of SOD, POD, Ua, Ul and hemolysin were significantly affected by DO concentration. Mean oxygen consumption was significantly higher under high DO concentration (HDO) compared with medium (MDO) and low DO concentrations (LDO). Shrimp growth (gain in length and weight), survival rate, FCE and the activity of PO enzyme decreased, whereas ingestion and the activity of POD enzyme increased with increasing stocking density. The activity of hemolysin was significantly higher in high stocking density (HSD) compared with medium (MSD) and low stocking density (LSD). There was an interactive effect of DO concentration and stocking density on shrimp weight gain, ecdysis, O2 consumption, ingestion, the activities of Ua and hemolysin. The results revealed that DO concentration was one of the key factors which affecting shrimp through influencing activities of non-specific immunity factors (SOD, POD, Ua, Ul and hemolysin), while stocking density affected the growth performance of shrimp mainly by influencing ingestion or activities of enzymes (PO, POD and hemolysin), and the interactive effects of DO concentration and stocking density (P < 0.05) played a crucial role in the production of shrimp farming.