Bill -- very interesting observation on crappie spawning behavior! Fish are more complex than we realize - time after time, we see that! Just think of the complex social behavior in bluegills.
When I was in grad school, we spawned black crappies in a series of small culture ponds. In half the ponds we added wood structures for cover (upright and overhead). In the other half of the ponds, we added no structures (bare ponds).
When structures were available, the crappies ALWAYS spawned next to them. However, the ponds without structures produced similar amounts of young crappies. When structures weren't present, they excavated nests in the Chara, and spawned just like a sunfish or bass (as you indicated above).
