I don't think its genetics as much as food and how the lake is maintained. Grenada has lots of gizzard shad, when the corps pulls down the lake it allows grass and the the banks to have a chance to firm up.
Water levels dropping and rising have more to do with the spawn than anything. Crappie want a firm bottom to lay their eggs.
I think this is why the Corps lakes have such large crappie.
[SIGPIC]Drake Waterfowl Prostaff, Dakota Decoys Prostaff,F&F Boats, Mercury Marine, Rig Em Right, Crappie Logic Jigs, Slab Bandits, Hayes Calls, and Kick's Choke Tubes.