Outbreaks of water-borne fungal infections of fish, amphibians, and reptiles are a common problem, especially in fish farms and hatcheries. Of particular concern is saprolegniasis, which is an infectious fungal disease that is widespread in all stages of the life cycle of fish. The disease causes serious losses in fish farms and hatcheries, especially among salmonid species. The initial clinical sign was characterized by the growth of cotton-like mycelia on the body surface, especially the head, adipose fin, and caudal fin, but the mycelia were not visible to the naked eye in the internal...