Welcome to the board.
I have caught a bunch of black crappie in the Mississippi River fishing the back of rock dikes. Minnows or jigs tipped with minnows will do the trick. Plus this time of year, you may find a bonus sauger using the same technique. Be careful though, you are liable to catch anything out on the river. Good luck and let us know how you do.
Btw, I've caught some slabs out of those bar pits!!!