Aquatic fungi often are considered secondary tissue invaders that follow traumatic injuries, infectious agents, or environmental insults such as poor water quality. Because many fungi grow on decaying organic matter, they are especially common in the aquatic environment. Fish egg masses, which usually contain tissue debris and dead ova or embryos, are especially vulnerable. Iodophors of varying iodine concentrations are used to prevent mycotic infections of nonfood-fish eggs, which can be disinfected by a 100 ppm iodine bath for 10-15 min. This solution is toxic for hatched fish, and only eggs should be treated. Formaldehyde, up to 2,000 ppm for 15 min, can be used to treat eggs of food fish (salmonid and esocid) for the control of fungi. Chronic fungal infections of eggs may suggest improper incubation temperature or poor sanitation.
- - Fusarium spp is emerging as an important disease of captive marine fish, particularly elasmobranchs. Many of these organisms have questionable status as fungi, and laboratory culture of their complete life cycle is required for accurate diagnosis.
- - Achyla, Aphanomyces, Phoma, Cladosporium, Penicillium, Ichthyochytrium spp, and others.