It depends on where and how bad. On Trout it is not a good thing. They are not as tough as some other fish. They did a radio tag study on Musky and hooked one really badly. They had to cut a part of the gill plate, cut hooks and it was a serious bleeder. They tagged it anyway and decided they could just use it to see how long it took to croak from an injury that bad. It didn't croak. It was recaptured two years later and was bigger. The gill plate was healed but scarred. If it has a chance of making it I let them go. Once you kill them they are a goner. If it's a big fish I give them the chance to make it. If it's not a big one I keep bad bleeders. I made it to the top of the food chain and I can eat a fish once in a while.