We've talked about the chain pickerel idea before. Personally, if I was picking an Esox species to control fish in my pond, particularly a smaller one, I'd pick chain pickerel over northern pike. In smaller ponds, most times when you stock pike you end up with 5 36" pike and not much else... Chain pickerel don't get that big and won't be quite the issue. As Bill Cody said, northern pike will suck up a lot of nice sized yellow perch and walleye...