I keep my crappie. I don't fish one lake enough to really do any damage after all the money I spend to go down there and everything to fish if like to bring home some filets. Crappie reproduce pretty well. I release all my big trophy Flathead catfish just because there far and few between and takes them so long to get to a really good size. Now I see the guys that take deep freezers down to the lakes with them and fill them up over the course of a month. Now I do believe this can do some damage because that's a serious amount of fish.