Thousands Of Dead Fish In Monmouth County 'A Natural Phenomenon,' Activist Says [VIDEO]

KEANSBURG, NJ — The hundreds of thousands of dead fish continuing to wash ashore and float in creeks and marinas along Raritan Bay are likely the result of low levels of dissolved oxygen in the water.

That is the conclusion of the state Department of Environmental Protection and the environmental group NY/NJ Baykeeper, according to statements from the two entities.

The sheer numbers of fish — juvenile menhaden, also known as peanut bunker — have draw widespread media attention, with television crews doing flyovers along the shore in Hazlet, Keansburg and the Leonardo section of Middletown to show the fish filling up marinas and on the beaches.

Cleanup of the dead fish was underway; in Keansburg, the town was planning to use beach rakes and other equipment to gather them up and dispose of them in dumpsters, Mayor George Hoff told CBS 2 New York. Bunker are smelly even fresh out of the water; the stench of the decomposing fish is very unpleasant, residents have said in comments on social media.

“This is primarily a natural phenomenon, but it is exacerbated by polluted runoff, including fertilizers from lawns, which is why preserving stream corridors and buffers is important,” Greg Remaud, the deputy director of NY/NJ Baykeeper, told NBC 4.

Bob Considine, a spokesman for the state Department of Environmental Protection, on Tuesday said DEP conservation officers and the agency's emergency response have been monitoring the fish kill since the weekend.

"We believe at this point that the die off is due to dissolved oxygen levels in the water," Considine said. He said the peanut bunker, which average 4 to 5 inches long, were likely fleeing from larger predators, including bluefish or skates, and because the fish became so bunched up they depleted the dissolved oxygen in the water.

Watch peanut bunker beach themselves trying to escape bluefish in this video from 2008:

NY/NJ Baykeeper, a local environmental organization that works to protect the health of local waterways, including Raritan Bay, said results of water sampling it conducted on Tuesday showed the dissolved oxygen was between 1.90 and 2.46 milligrams per liter.

"When dissolved oxygen is under 2.0 mg/L, fish begin to suffocate and die. The low dissolved oxygen is likely caused from warm water temperatures and nutrients and organic material in the water (bacteria in the water consume oxygen as the organic material decays)," the group said.

NY/NJ Baykeeper monitors water quality in the bay weekly, it said in a blog post earlier this summer, recording the pH, salinity, temperature and barometric pressure of the water. Water samples also are tested for pathogens, and tests early in the summer were negative for pathogens, they said.

Peanut bunker kills are not an uncommon occurrence and frequently occur in August in the wake of a heat wave. Large die-offs have been reported going back to the 1600s.

Menhaden is an oily fish that is a filter feeder and is a key part of the ocean food chain and a favorite meal of many ocean predators, including bluefish and striped bass. They spawn in shallow tidal waters and bays and feed on algae and phytoplankton in the water. Off the coast of Virginia, menhaden are caught commercially in a process called reduction fishing and taken to a processing plant that turns the fish into fish oil, fertilizer and ingredients for a number of products used in daily life. Reduction fishing was banned in New Jersey waters in 2001; now the only commercial fishing for bunker is for bait for fishermen.

Read more about menhaden here.

Dead peanut bunker at Lentze Marina in Hazlet. Courtesy of NY/NJ Baykeeper