I'm really going out on a limb here....
IF I remember my biology, if you cross a Hybrid and Hybrid and get five offspring, you generally get 2 native BG, 2 Green Sunfish, and a Hybrid because of the genetic blender. Now if each seperate species has its own breeding zones, they are not likely to re-hybrid, plus the fact that most of them are male. So undesireable fish (green sunfish and hybrids)outnumber the native bluegill, outcompete them for food, and also compete for food with the bass. So if a hybrid coupling produces 10,000 young (I have no real idea, just ballparking) only 4,000 are native bluegill (what we really want) only 400 are going to be reproducing females. Looks like pretty stiff odds to me.
I really don't know if this is the way it is, I'm just bored at work and needed to write something!
