Last time I was there visiting there were dead fish all along the river. Just wondering why?

As far as I know, current knowledge from the DEC: There was a high concentration in the river this year of a particular naturally occurring bacteria. Due to an equally high population of the local bunker fish, the infection rates were higher than usual, leading to an unfortunate mass die off. The fish population will recover, and the local wildlife that eats the fish considered this a particular generous year.

Glad I wasn't there that day!