Yellowtail Seriola quinqueradiata is commonly placed in a freshwater bath as a means of removing the skin flukes. However, this treatment was shown to increase susceptibility to infection and reduce nonspecific immunity. Therefore, it is necessary to determine methods to mitigate the effects of this stress on the fish. In this study, yellowtail were orally fed inulin in bait (5 g/kg diet) for a certain period, and subjected to a freshwater bathing. A stress index and nonspecific immune

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... y were monitored, and differences in susceptibility to experimental infection were examined to determine the protective effect of the inulin. The stress indicator, blood glucose concentration, was lower in the inulin group than in the control group before and 24 hours after the freshwater bathing. Nonspecific immune capability, i.e., phagocytic activity and complement levels, were higher in the inulin group prior to the freshwater bath than the control group. In the experimental infection of pseudotuberclosis, the mortality rate of the inulin group was lower than that of the control group.