Saprolegniasis in Salmonids

Abstract

The papers on a taxonomical study of Saprolegnia fungus was very few in Japan. Therefore the studies on classification of it isolated from the lesions of salmonid fish with fungus disease have been done by author. As literature which deals with the taxonomy of Saprolegnia species isolated from fishes including salmonids is scanty in Japan, it was decided to investigate this problem. During the course of the investigation for the past six years three species of fish pathogenic fungi, S. australis, S. shikotsuensis and S. diclina, were identified. S. australis was isolated from the base of the dorsal fin of rainbow trout fingerlings of about 1.2 g in body weight with saprolegniasis at the Koide branch of the Niigata Prefectural Freshwater Fisheries Experimental Station in 1976. S. shikotsuensis sp. nov. was isolated from the caudal fin of wild kokanee salmon, Oncorhynchus nerka var. adonis, with fungus disease in Lake Shikotsu of Hokkaido Island in 1974 and 1975. S. diclina was isolated from the abdominal cavity of hatchery-reared fry of amago salmon, Oncorhynchus rhodurus with visceral mycosis at farms in Gifu Prefecture in 1975.Recently, NEISH (1976) mentioned that S. parasitica might be regarded as a synonym of S. diclina. His new conception of S. diclina was reviewed and some other problems on the taxonomical study of the genus Saprolegnia (fungus) were discussed in this paper.