I use to fish a lake like that in Wisconsin. Find deep structure and you should find the Crappie during the winter. Especially off main lake points. They will chase the bait fish as already said. The warm water discharge would also be a good place to start and work away from it until you find the temps that they are holding in. I did find out that with the water temps being warmer, that it does mess with the crappie spawning patterns though. It usually made it much earlier than most other lakes. That was kind of nice though because it gave me a lot bigger window for phenomenal prespawn fishing. I use to use a very slow presentation. Without ever fishing the lake it is pretty tough to give advice! I'll get a hold of a buddy that still lives up there and fishes the lake and see what he says!