All mortalities were examined bacteriologically by culturing skin lesions or sites of erosion on plates of MSA containing 4 μg/ml neomycin sulfate (Pazos et al., 1996). Direct smears (1 cm×1 cm) were prepared for staining by Gram's method and by IFAT. Cultures were incubated at 25 °C for 2 days and the colonial morphology typical of T. maritimum recorded. Internal organs were examined grossly since fish had been vaccinated by intraperitoneal injection. Flexibac- teriosis lesion distribution and lesion size were recorded for all fish. Lesion size was measured as length of lesion along the longest axis and was recorded to the nearest half centimeter. The proportion of lesions at each site was calculated for all fish together in each group, thereby indicating differences in areas being affected. Photographs were taken of the fish to document gross pathology and samples of skin lesions or sites of erosion were taken for histological examination. Any fish surviving at the end of the challenge period were euthanased with clove oil (0.025 ml/l) and lesions or sites of erosion examined bacteriologically as described.