Yes it’s a known fact that bigger species of sharks, and even smaller ones, will eat other sharks. I’ve caught good size schoolies and a Sevengiller on dogfish baits. Also the other night at the pier a guy cut up a school shark to use for bait, and not long after he hooked something big. He didn’t have much of a chance though, his drag was up real tight and while he was trying to loosen it he lost it. Also Stringray and Freshwater eels are apparently a delicacy for sharks.