Gough,

There is a much higher probability that the GSF came by some way other than the RES stocking. Surely you would have made the connection and noticed the more bass-like appearance of them. It would have stood out. To be sure, they must have comprised a small proportion of the stocking to have gone unnoticed if the stocking was contaminated. Even so, as few as a single pair could contaminate the pond. Generally, however, growers use ponds that have no watershed and source water is well or filtered so that is why I suggest the contamination comes from somewhere else.

Anyways, GSF love to travel in high water events and could very well be sourced to water above or below your pond. Some yaywho may have stocked it by bucket. This sucks and I feel your pain. I noticed you have HSB and RES, so were these intended to be the sole species mix? What is your focus? The predator or the prey? IOW do you want a pan fish pond or one with large predators?

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers