On a recent kayak fishing trip I landed a fish (Kahawai) that had a deformed looking pectoral fin, upon closer inspection I saw that it had a parasite attached to the fin which appeared to be eating the fin. Comparing the fin on the other side of the fish I would estimate that ¼ of the fin had been eaten or sucked off the fish..check out this short bit of video I took of the parasite and the fish
Parasite sucked Fin
It turns out this parasite is the tongue eating louse, which I blogged on some time ago when I discovered one in the mouth of a fish. The louse attaches itself to the tongue of the fish and sucks it dry. Once the tongue is all but gone the louse remains inside the mouth of the fish replacing the tongue. Watch the video below for more info
Why it was sucking the fin off I do not know, but a little research did tell me that the fish can live with the louse in the mouth no problems and the fish is not harmful to humans if eaten..I am pretty sure a fish with no fin might have a hard time surviving from other predators so this louse was going to be the end of this fish if left on there.