Sea Lice in General

The term sea lice is a common name for two seperate species of parasites that live on salmonid species. The first species, Lepeophtheirus salmonis is specific for salmonids(Salmo, Salvelinus & Oncorhynchus) whereas Caligus elongatus is not. It is found on over 70 species of fish.

Sea lice belong to the class Crustacea, the order Copepoda, the suborder Siphonostomatoida and the family Caligidae.  They have a rigid exoskeleton made of a protein called chitin which is shed every time they moult.

Sea lice hatch out of eggs, and when they do, they are visible only as small, black dots.  The early stages are free-swimming, but the later, more visible stages stay attached to or very close to the surface of the fish, where they feed on mucus, blood, and skin.

In this picture, you can see 3 female lice with egg strings, as well
as a smaller male.  You can also see that the skin of the fish is
damaged from their feeding activities.