I think it's considered illegal in public rivers and/or lakes. Don't quote me on that. Personally, I don't care. There are plenty of bluegill. I've caught some big fish in saltwater by keeping croaker and throwing them back out there. My dad was on a charter in Mexico and caught a small blackfin tuna. He hooked it and threw it back out. 10 ft 350+ lb blue marlin that hangs on the wall. That's probably totally illegal in the US