I saw a picture of one a friend caught that had been shot with a high power rifle. Just back of the anus it was like you had choped it with a cleaver except for a flap of skin and meat with a 5/16" hole through the flap. The fish appeared to be in good health and the wound was all healed over.
I personallly saw a fish with a V shaped scar on its side that looked like a snaping turtle strike.
Gary