Are you going to be feeding them? Generally, if they are fed they will prey much less on other fish and consume mostly pellets. If they won't be fed, they will prey more on fish. From the research done that I've seen where HSB have been used to control crappies, they had to be stocked in rather large numbers and the pond kept open with minimal structure and vegetation. I'd stick with between 10-25/acre annually or biannually.