Bacteria killing tens of thousands of fish in the Jersey Shore backwaters…what is the risk to humans?

Manasquan police officers wade through dead fish while performing a drill near the Navesink River.

The New Jersey Department of Environmental Protection says there’s no risk posed to humans, but for fish, the water has been fatal for the past few weeks as tens of thousands of fish, including moss bunker can be seen floating dead along the shore of the river.

The fish kill in the Manasquan River began earlier this month and it is being blamed on a bacteria called “Vibrio”.

Although the DEP says no risk is posed to humans, in 2020, the DEP also reported four cases of illness in humans consuming shellfish with the vibrio bacteria were reported.

“In these multiple source cases, it is hard to accurately determine which oyster is responsible for the illness unless directly linked to an outbreak. Two multiple source cases involved oysters harvested from the New Jersey portion of the Delaware Bay, including both dredge harvest and aquaculture harvest in 2020,” the DEP said in their 2021 Vibrio control plan.

The DEP created the plan in advance of a possible vibrio outbreak in Jersey Shore oysters in 2021. According to the CDC, Vibrio bacteria naturally live in certain coastal waters and are present in higher concentrations between May and October when water temperatures are warmer.

About a dozen Vibrio species can cause human illness, known as vibriosis. The most common species causing human illness in the United States are Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus.

Most people become infected by eating raw or undercooked shellfish, particularly oysters. Certain Vibrio species can also cause a skin infection when an open wound is exposed to salt water or brackish water. Brackish water is a mixture of fresh and salt water. It is often found where rivers meet the sea, the CDC reports.

People with compromised immune systems, especially those with chronic liver disease, are more likely to get vibriosis. Eating raw seafood, particularly oysters, and exposing open wounds to salt water or brackish water can increase a person’s chance for getting vibriosis.

The DEP is not sure which strain of vibrio has infected the waters in Central Jersey.

 “The New Jersey Department of Environmental Protection’s Division of Fish and Wildlife is actively investigating [Moss Bunker] mortalities reported in Raritan Bay and the Navesink River of Monmouth County. More laboratory work is being done to determine the specific species of bacteria. The DEP is also working with the Atlantic States Marine Fisheries Commission to better understand the mortalities.” DEP spokesperson Larry Hajna said.

“The Vibrio bacteria causing these fish kills is primarily linked to nutrient pollution from sewage, septic, and storm water runoff. It’s also linked to warmer water, which is connected to climate change. This is even more alarming because the bacteria can cause illness in humans, so anyone swimming in the water could get sick. This is a direct result of the DEP’s failure to deal with water pollution from nutrients and raw sewage,” said Sierra Club Director Jeff Tittel

Attributions in this article: Map data ©2019 Google, Photo © BigStock Photos. Hand out photos courtesy of reporting agency. Press releases are the intellectual property of the issuing agency or corporation. Please report any photo, copyright or intellectual property violations to