NJ Officials Issue More Info On Navesink, Shrewsbury Fish Deaths

NEW JERSEY - The state of New Jersey says it is continuing its investigation into the sweeping deaths of fish in the Navesink and Shrewsbury rivers in Monmouth County as hundreds of dead Atlantic Menhaden continue to pile up in the Raritan Bay region. Similar die-offs have been reported since last fall in Rhode Island, Connecticut and New York, officials said.

Recent tests conducted by the New Jersey Division of Fish and Wildlife have confirmed that the bacteria causing these widespread fish deaths is Vibrio anguillarum, one of numerous Vibrio species that commonly occur in saltwater environments. Previous coverage: Bacteria To Blame For Hundreds Of Dead Fish In Monmouth, NJ Says

In response to the widespread deaths, the New Jersey Division of Fish and Wildlife released a Frequently Asked Questions guide for state residents on Tuesday.

“To give some background, menhaden fish kills have been observed routinely almost every year during the spring-summer months in the Two Rivers Watershed. [New Jersey Department of Environmental Protection]'s investigations during these events indicated that hypoxia (lack of oxygen) was a factor causing these mortalities,” a representative from the Monmouth County-based Clean Ocean Action environmental group told Patch in an email.

“However, while summer fish kills due to lack of oxygen are well-known, in recent years COA and others have been questioning other causes because the menhaden were dying in the spring and some were seen spinning before death. COA has been discussing the phenomenon over the last couple years with the DEP. This year, similar fish kills are also occurring in the Hackensack and Raritan bays … Clean Ocean Action is aware of the impacts of nonpoint source runoff and climate change and we are committed to using sound science and research to support our pollution prevention efforts. That is why, we are voicing our concerns that dedicated federal/state funding should be made available immediately to investigate these fish kills.”

Subsequent testing by the DEP has indeed revealed that the Vibrio bacteria causes an infection impacting multiple organs of menhaden fish, including the brain. Neurologic signs can be seen in affected fish circling at the surface, swimming erratically or uncontrolled, and sometimes lethargic and unresponsive. However, despite the hundreds of reported dead fish spotted along the two rivers, officials maintain that the mortalities are nothing to be alarmed about.

“A recent stock assessment conducted by the Atlantic States Marine Fisheries Commission (ASMFC) reports that total biomass of the Atlantic Menhaden stock is over 4.5 million metric tons, or approximately 10 billion pounds,” reads a statement from the New Jersey Division of Wish and Wildlife. “Although the number of fish seen washing up on area beaches and waterways may appear alarming, the impact to the population as a whole has so far been negligible. The population model explicitly accounts for all sources of mortality, both natural (such as fish kills) and harvest. Menhaden mortalities have been reported as near annual events in the spring since the 1950s, though the numbers of fish impacted varies from year to year.”

There is also no evidence that other fish, birth or shellfish are being impacted by Vibrio and it is safe to eat other species that prey on menhaden, the DEP said. It is always advised to properly cook all fish or shellfish before consumption. While fish kills will eventually clear up if left alone, residents and business owners can wear protective equipment and bag and discard fish with other refuse. The New Jersey Department of Environmental Protection is working with local officials to establish larger scale cleanup operations.

According to a statement, the DEP is currently working with the Atlantic States Marine Fisheries Commission and other states in the region to better understand these mortalities as menhaden appear to be the only fish species affected by the bacteria, likely due to fluctuating water temperatures (which may suppress the fish's immune system combined with the dense schooling nature of these fish, which enhances bacteria transmission). Staff from the Office of Fish and Wildlife Health and Forensics have also been collaborating with partners from numerous fish health laboratories, such as Cornell University and the US Geological Service to identify and research the underlying cause of mortality.

The DEP also currently has three monitoring buoys deployed in the Raritan Bay/Two Rivers area to collect water quality data for numerous parameters including dissolved oxygen and temperature. One buoy is located in the Navesink River east of the Route 35 bridge, with the other two in Keansburg and Keyport. The buoys are expected to be in the water from May until October.

“Menhaden die-offs are expected to continue in the near term. The DEP will continue to provide information to local governments as appropriate and provide any public advice or advisories as necessary,” the New Jersey Division of Fish and Wildlife said. “The fish will naturally decompose and become part of the nutrient cycle in affected waterways. Local governments, at their discretion may remove fish from their riverbanks.”

While the state continues to investigate, it is recommended that bathers avoid swimming in areas of active fish kills (there are no recreational bathing beaches on the Navesink or Shrewsbury rivers, but there are recreational bathing beaches on Raritan Bay). Anyone entering the water in an affected area should wash exposed skin and clothing thoroughly with soap and water after contact with the water. Locals in the area also need not worry about affected drinking water quality in the region.

"Fish kills occur naturally and generally do not cause any long-term effects on water quality," the Division of Fish and Wildlife said.

New Jersey's beach program, in partnership with the NJ Department of Health, county and local health departments will be monitoring recreational bathing beaches as the summer approaches. Pathogen testing will occur prior to Memorial Day to ensure water quality is within recreational bathing standards.

As with any wildlife, the New Jersey Division of Fish and Wildlife recommends that people do not handle, collect, or consume any dead fish or those showing signs of disease. Fish die-offs can be reported at the New Jersey Department of Environmental Protection’s hotline at 877-WARN-DEP (877-927-6337).