Salmon louse

The salmon louse (Lepeophtheirus salmonis) is a species of copepod in the genus Lepeophtheirus. It is a sea louse, a parasite living mostly on salmon, particularly on Pacific and Atlantic salmon and sea trout, but is also sometimes found on the three-spined stickleback. It feeds on the mucus, skin and blood of the fish. Once detached, they can be blown by wind across the surface of the sea, like plankton. When they encounter a suitable marine fish host, they adhere themselves to the skin, fins, or gills of the fish, and feed on the mucus or skin. Sea lice only affect fish and are not harmful to humans.

Salmon lice are ectoparasites of salmon. In the 1980s, high levels of salmon lice were observed on pink salmon smolts. Salmon lice are found in the Pacific and Atlantic Oceans; they infect pink salmon, Atlantic salmon, and chum salmon.