That's what the book is about I posted earlier in this thread. The authors are well aware that genetics can't be changed, but they have a technique like you describe to take out the lesser quality mature bucks to give the better quality mature bucks more resources. In my scenario, I can't do what they're describing. My scenario would be like using your description of fish in the pond but in a large lake, making a section of it off limits to anyone but me and my guests. I just don't think it would work since those fish can come and go to the other parts of the lake.