Environmental Protection Department spokesman Larry Ragonese told the Asbury Park Press the likely scenario is a huge group of fish ended up in a small estuary and a slightly low oxygen levels resulted in their deaths.
The weather may have had a hand in the die-off, too. Warm weather prompts algae growth, and with heavy rains, Rangonese told nj.com, the algae, nutrients and pollutants at the bottom of the river comes to the surface.
The fish are mainly bunker or menhaden, a small bait fish.
The DEP has taken samples to make sure a disease is not to blame.