The effects of acute capture stress duration on survival, gill histomorphology, osmoregulation, antioxidant capacity and non-specific immunity of juvenile red swamp crayfish, Procambarus clarkii

Fingerling harvesting is a crucial stage in red swamp crayfish Procambarus clarkii farming, but the process often subjects the fingerlings to stress. The study was conducted to evaluate the effects of acute capture stress on survival, gill histomorphology, physiological state of juvenile P. clarkii. For this purpose, a total of 1200 juvenile crayfish were divided into 15 cage nets evenly to exposure to acute capture stress for 0 h; 6 h; 12 h; 18 h; 24 h. Following that, 120 live crayfish were randomly chosen from each treatment group and distributed equally into three enclosures for a week. The results are as follows. The stump rate and mortality rate gradually increase with longer capture stress periods, reaching, respectively, 2.81 % and 10 %, when the stress is 24 h long. Meanwhile, as indicated by increased respiratory epithelial cells shed and damage to the gill structure over time under acute capture stress, juvenile crayfish have altered gill histomorphology. And acute capture stress mostly affected osmoregulation in the gill, where Na+ /K+-ATPase (NKA) activity increased with increasing stress duration. We discovered that mortality rate was substantially linked with the activity of NKA in both tissues and gill LYS activity. Additionally, the juvenile crayfish under capture stress displayed a general trend of increasing and subsequently decreasing antioxidant parameters and non-specific immunity enzyme activities in gill and hepatopancreas. The post-release survival rate (PRS) of juvenile crayfish decreased as the duration of stress increases. In conclusion, acute capture stress will degrade the physical condition, the physiological status of juvenile crayfish and reduces their likelihood of surviving after release.