There arenumerous species of catfish, and bullheads are among the smaller, although not the smallest species.. There are three species of bullhead catfish...Brown bullheads, yellow bullheads and black bullheads...They seldom weigh more than a couple of pounds, with the average being much smaller, unlike larger species such as channel cats, flathead cats and blue cats which can weigh from 10 pounds to more than 100 pounds...

On the other end of the spectrum are stone catfish, which seldom grow more than 4 or 5 inches and are very popular as bait for smallmouths and walleyes ...