Yes to a certain extent. The thing to keep in mind is that the fisheries scientists who surveyed the pond are the ones who actually saw the fish and the water and the whole system interaction. We only have your posts wrt what they said and what you have seen. They are in a better position to tell what is needed. We can tell you what we think and offer things to consider. There are 3 basic ways to approach the situation :

1. Do nothing and the results will get worse.
2. Kill the pond off and start over.
3. Add predators and reduce the GShad population through some combination of actions.