Excellent protection against vibriosis was provided to ayu, Plecoglossus altivelis, vaccinated by the immersion method with either formalinkilled bacterin, sonicated bacterin, or lyophilized formalinkilled bacterin of Vibrio anguillarum. Lipopolysaccharides of V. anguillarum also induced protective immunity against vibriosis in fish vaccinated by the immersion method. No agglutinating antibodies were detectable in the serum of fish vaccinated by immersion with vibrio bacterin; however,

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... s were detected in the serum of fish vaccinated by intraperitoneal injection of formalinkilled bacterin mixed with Freund's com plete adjuvant. There were no differences in the profiles of protein components of the serum of immersion vaccinated fish and nonvaccinated fish. No differences were recognized in the protective immunity against vibriosis between fish which received the serum from immersion vaccinated fish and those which received the serum from nonvaccinated fish.