I caught quite a few of them in the rivers with sores like that...SCARED the sh!t out of me when i seen it for the first time...Then i asked fish and game and they said it was harmless ....GO FIGURE!!!...I don't think they were as bad as that one in the pic,the one in the pic looks like his tail is rotting away...WOW!!!
I caught one like that two years ago at CISP. Somebody from the Barn was with me though I cannot remember who. It was a 30 incher that had half a tail just like that one, looked very much like that one in color as well. Mine only had one large reddish looking sore on its side, unlike this one which looks to have many.