I'm with Theo on his "basics of pond genetics" recommendations.
Culling fish on an individual basis to manipulate gene quality is a daunting task. Probably impractical in almost every respect. I do think that it is easier to damage the genetics than it is to help them. Catching and keeping all large reproductive male bluegill off their nests is a good example on down-pressure on genetic quality. Why risk it? It's too easy to release these fish and pressure (harvest) the smaller individuals.
This is a whole new thread but I'm watching two thousand age-1 bluegill grow in two different small ponds of mine. These fish were all progeny of BIG, healthy parent fish that happened to like artificial feed. I'll protect and breed the best growers next fall. I'll keep everybody informed as to the progress of this craziness.
