The present invention comprises the identification, characterization and sequencing of a gene within the V. anguillarum genome, the mugA gene, a live, attenuated strain of V. anguillarum which comprises a mutated mugA gene, methods of making the strain, vaccines comprising the strain and methods of making such vaccines and administering the vaccines to animals. The invention further comprises vaccines comprised of proteins encoded by the mugA gene, to methods of making such vaccines and administering the vaccines to animals, to vectors comprised of the attenuated strain of V.anguillarum and additional immunizing materials, methods of making the vectors and methods of administering the vectors to animals. Also disclosed are probes, passive vaccines and monoclonal antibodies for the detection and prevention of vibriosis.