Dave like Bill reminds us "it all depends". If you have/want a LMB pond and have an established BG or BG/RES population then it should not matter if some (small %) GSF are there. If however you want a BG pond you would get a different answer. I bet Bruce would not want GSF in his trophy BG ponds. Ask him if he would mind if you put a couple dozen adult female GSF in his all male BG pond. :p Also if you were just starting your BG forage base I don't think you would be to happy if the hatchery gave you 25% GSF. Then you would end up with a substantial portion of your forage base being HBG which don't reproduce enough to sustain your predators. It would be like having a new engine with a couple fouled spark plugs. No matter if running at high speed or low it is not what you paid for and is not efficient.

I do think that it is not unusual for a few GSF to slip in via the sources noted above especially from the less careful hatcheries. I think unfortunately some growers/sellers will add HBG to an order to make up a load when they may be short on BG. Very hard for the average pond owner to tell them apart when small even if they take the time to look. As ML notes they will deny that there is any problem. I have seen a couple of new ponds at 3 yrs old where there is no up or down stream source of contamination who ordered BG/RES and ended up with a fair % of HBG. That did not come from a couple GSF slipping in .