Abstract
Recently, streptococcal infections have been frequently observed in freshwater fishes, especially in ayu, Plecoglossus altivelis, cultured in Tokushima Prefecture, Japan.
The first outbreak was observed in 1977. Since then, the epizootics have occured among ayu in the summer and autumn every year, and caused sereious economic losses.
The present paper deals with occurrence, diagnostics and clinical studies of the disease.
