NO-MUCUS SKIN-DISEASE OF RAINBOW-TROUT, ONCORHYNCHUS-MYKISS (WALBAUM)- A CASE-REPORT

A skin disease of intensively reared salmonids in Ontario hatcheries, known to the farmers as 'no-mucus skin disease', is reported for the f irst time. It was characterized by erosive and ulcerative lesions foun d mainly on the flanks of fingerlings, which resulted in exposure of t he tips of the scales. Associated with these lesions were colonies of bacteria seen in the SEM to be clustered round the mucous cell pores a nd under-running the margins of epithelial cells. The cause of this co ndition is unknown, although the response of fish to formalin treatmen t, and the presence of bacilli seen in skin scrapings and in the SEM, suggest that bacteria are responsible.