howdy pmmr, welcome to the bb and that is what we are here for, to answer your question and someday you might be able to answer someone elses or maybe one of ours.
it sounds like you have a lake full of black bullheads and yes they are good to eat. you just might want to eat the ones that are a little bit smaller thou, bexcause these are the better tasting ones. 2ft. thou sounds a little bit on the big side for these fish, i would bet if you put a tape to them they'll run closer to 15in..