A favorite catfish bait around here is sand toads (about golfball size). When I first moved here a couple of years ago, my father in law asked me if I wanted to go "Toad Pickin'". I thought sure he was joking. But sure enough, the first summer rain found us on an old country road, picking up a bucketful of sand toads for our bank poles. Funny how a little toad dipped in the river on a full moon can turn into a 30 flathead overnight!
As for shooting the "Killer Catfish," a .22 might have a hard time getting through to his brain, which is small anyway. If the fish is under any more than six inches or so of water, a whole lot of energy will be lost by the bullet. Also, hollowpoint bullets may even shatter on water impact.