1/4 Acre isn't very big, but 17' is nice depth to hold a few fish. Guessing it's just overpopulated for the carrying capacity, so when oxygen levels got low during freeze up it killed some off, hopefully not all of them.

The big cats make it worse when they are all gathered up in the deepest hole and stir up the silt. I'd get the cats out of there and go with hybrid bluegills.