The effects of starvation on some epidermal mucus immune parameters in rainbow trout, Oncorhynchus mykiss

The skin of a fish acts as the primary protective agent against biological, physical, and chemical stress. However, the effects of such stressors on fish mucosal immune responses have been hardly investigated. Fasting or feed deprivation commonly is occurred in aquaculture due to season, production policies, or disease. This research was aimed to investigate the impacts of 20-day starvation on skin mucosal immune responses of rainbow trout. The results revealed that the enzymatic activities of lysozyme (LZM) and alkaline phosphatase (ALP), as well as the total immunoglobulins (Ig) level and bactericidal activities were significantly reduced in the skin mucus of fasted fish. No significant changes were observed in the esterase and protease activities. Bactericidal activity in the mucus of starved fish was significantly lower than control group after 20 days. Therefore, it could be strongly suggested that this species should not remain under starvation stress as this kind of stress impairs mucosal immune barriers which, in turn, could make the fish more susceptible to infections or harmful agents.