In Reply to: Re: Re: Also on Lingcod, Cabezon, and Wolf Eels posted by Ross-O on December 07, 2005 at 10:33:02:

No, they are not true lice. However, parasitic copepods of the caligoid and lernaeopodoid oreders are sometime referred to as fish lice.

Copepods are probably the most common parasitic crustaceans, although isopods are also found as parasites on fish.

The two "tentacles" on the rear are probably the gills which would be very sensitive and therefore withdrawn quickly.

I have never seen them embedded within the skin, only free-moving on the head. There were a few that did appear embedded in the eyeball, but I think it was an illusion and that they were on the outer surface.

I've asked several other biologists with more expertise than I have in this area, so hopefully I can post a definitive response later.