One of the most accurate statements I have seen on the subject of pond population balance in BG/LMB waters is that maintaining balance is like trying to balance on the edge of a knife blade. It can swing either way quickly and either way you get cut. There are numerous things that can start an imbalance from a temp drop to a poor plankton hatch or even to much or to little harvest.

Dave I think Swingle studied everything about fish - an enquiring mind !