I attended a seminar on pond management some years back. The biologist commented upon crappie in ponds. The basic issue seems to be that crappie spawn earlier than the other panfishes, early enough that the crappie fry are big enough to prey upon the bass, blue gill fry which, over the course of time results in an out of balance population.

One solution was to stock some hybrid stripers. Seems that there is a pelagic stage during the life cycle of crappie that allows them to be easy pickings for the hybrids.