I agree...White Crappie.
I've actually heard the opposite about Bluegill & Crappie hybrids....Although Bluegills, Redears, Pumpkinseeds, Green Sunfish, etc, hybridize amongst themselves fairly readily, Crappies never interbreed with these other sunfish. I haven't even heard of it being done in a lab.
Black Crappies and White Crappies can and do interbreed.