The crayfish I caught years ago was a savager and he would eat whatever was laying on the bottom of the tank. I caught him using chicken liver tied to a string. As a kid I would go fishing for crabs (locally called crabben) I had minnows in the tank with him but he never went after them. I let him go after a few months.
All freshwater crayfish/ crawfish are general nocturnal scavengers and will eat anything from plants to fish, and they do catch fish at night so keep the crayfish in it's own tank.