IMO it's a matter of bigger mouths. Any of the predatory species, SMB, LMB, HSB, WE will all feed on crappies. Crappies most likely aren't their preferred species to feed on, but when you have a boom spawn year and they will no doubt target them. However, what ends up happening is you have too many crappies grow too fast and get to the 4"-5" mark. In many ponds, this is larger than the predatory mouths can eat. This is especially true in newly stocked ponds where there are no bass over 14". Now those crappies that reach that size are no longer able to be preyed on. They now stock pile at that size...
Whereas in a pond with a good percentage of larger size predators, those crappies even if they get to 4", 5" even 6" still can be effectively preyed on.
Keeping aquatic vegetation under control and limiting structure where smaller crappie can take refuge will also help these larger predators effectively prey on the crappies.
