Saprolegniosis in salmonids and their eggs in Japan

An epizootic of the fungal infection saprolegniosis that occurred in freshw ater-cultured salmons and their eggs at some hatcheries in Hokkaido (Japan) was investigated. In almost all cases, the initial clinical sign was chara cterized by the growth of cotton-like mycelia on the fishs' body surface, e specially the head, adipose fin, and caudal fin, but the mycelia were not v isible to the naked eve in the internal organs. Thirty-three strains isolat ed from lesions were classified in the genus Saprolegnia according to their morphological and biological characteristics on hemp seed cultures at vari ous temperatures. Fifteen of the strains were identified as Saprolegnia par asitica, 16 were identified as S, salmonis, and two were identified as S. a ustralis.