The effects of hand-stripping on some epidermal mucus immune parameters in rainbow trout, Oncorhynchus mykiss

Fish epidermis functions as the first defense barrier against physical, chemical, and biological stressors. However, the effects of hand-stripping on fish mucosal immune responses have been hardly investigated. The present study investigated the effects of stripping procedures on skin mucosal immune responses of rainbow trout (Oncorhynchus mykiss) breeders. The skin mucus was sampled from six male and six female trout before and one week after the stripping handling. The results showed that stripping had significant effect on all parameters except protease activity, but gender had a significant effect only on the mucosal protease and alkaline phosphatase activity. The results did not show any effect of the interaction between stripping and gender on mucosal lysozyme activity. The data revealed that enzymatic activities of alkaline phosphatase, lysozyme, esterase, as well as the total immunoglobulin level and bactericidal activity were significantly reduced in the skin mucus of fish one week after the stripping. The reduction of immune parameters in the skin mucus could be related to immunosuppression caused by stripping stress which, in turn, might have made the fish more susceptible to microbial infections and diseases. Therefore, care should be taken during stripping to minimize the manipulation stress.