The culprit: the fish themselves.
The wash-up of small menhaden, most about 4 inches long, was discovered Wednesday morning. It occurred on about eight miles of shoreline from Kimbles Beach in Middle Township south to the Villas in Lower Township, just north of Cape May.
In a Friday morning news conference, the DEP said as many as one million fish gathered near the shore of the Delaware Bay.
The massive school used up all of the available oxygen in the water and the fish suffocated.
Furthermore, officials previously said water sampling conducted Thursday suggested that oxygen levels in the bay were probably very low as a result of very warm air and water temperatures.
While many of the dead fish were washed out by the tide, clean-up crews still had to be called in to remove the rest.
While the DEP estimates that about one million fish died, they say that represents less than one percent of the local population.
Tests revealed nothing toxic in the water.