I was fishing at Spy pond a few weeks back, and found a lot of dead fish, mostly sunfish but one nice sized bass to, all of them had this type of "rot" in their gills, does anyone know what it is?\
This particular fish was not dead, it almost looked like he was, as silly as it sounds, drowning.
Maybe a fungal infection. I found a bunch of small fish washing up in Jamaica Pond not long ago. There was even a turtle that was dazed and couldn't get itself back to deeper water. There are a lot of natural diseases and parasites that can cause die-offs in fresh water.