Saprolegnia is a genus of water moulds. Saprolegnia, like most oomycetes, is both a saprotroph and necrotroph. Typically feeding on waste from fish or other dead cells, they will also take advantage of creatures that have been injured. An infection is known as oomycosis. Saprolegniasis caused by S. parasítica affects aquaculture broodfish and incubating eggs. This disease is characterised by visible white or grey patches of filamentous mycelium on the body or fins of freshwater fish.