This isnt a "fisheries issue," but it does concern biology- not of the fish, but of the aquatic insects trout consume. My question is: Why are the bugs that hatch on tailwaters generally smaller than the same species of bugs that hatch on mountain streams?
Are the bugs really different species, but the same fly is used to imitate both? Is is due to the abundance of bugs that are found in tailwaters (like a pond that is overpopulated with bluegill, thus stunting their growth)? Or is it just how it happens to be?

All thoughts are welcome..