We used to cut filets out of the sides then put 'em back in the Tappahannock River (in Virginia) and let 'em swim away. I didn't believe that they would do so when the local that took us to his fishing hole told the tale, but they did it all the time.
At other times, we'd do the same as Elvis mentions, but nail 'em into a barn rather than a 2x4.

Lots of fun outings in VA between chasing stripers, blues or flounder in the Chesapeake Bay, smallmouth bass in the Tappahannock by Fredericksburg, big ol' cats in the Mattaponi or Pamunkey, and all sorts of species in the Tappahannock River north and south of the bridge in the town of Tappahannock.