I think it is either the black bullhead (Ameiurus melas) or the Brown bullhead (A. nebulosus), I can never tell them apart. They both sometimes get large, 26 1/2" for the black, and 22" for the brown, but 12" is much more common. In crowded waters they stay small. Here is a picture of the black by Delgado Saez and one of the brown by Phil Degginger.