Identification and Control of Gyrodactylus, a Skin Fluke of Fish

Signs of infection In severe infections, fish will rub against hard objects, and the skin develops opaque patches that may become inflamed. Less severe infections may not show any easily noticeable symptoms. Affected fish Most species of freshwater and marine fish can be infected by Gyrodactylus and related species.

Details of the infection Skin flukes are flukes up to 0.8 mm in length. They attach themselves to the fish's skin (occasionally to the gills) by means of a sucker with two central hooks, and feed on skin cells. When viewed under a low-power microscope, the flukes can be clearly seen on the skin debris. Gyrodactylus is a monogenean, meaning that the whole unpredictable phenomenon of its life cycle, in which even a larva has an even younger larva developing inside its body, and that worm has another worm inside its body, and so on.

Recommended treatment Soaking the fish in a 3% salt solution can rid them of the parasites. An alternative is to use a new type of antiparasitic medication. Fish kept in a clean environment with good filtration may have the infection minimized; Gyrodactylus does not produce resistant eggs. As described for Dactylogyrus.