A cluster of dead bunker in the Red Bank borough marina at Marine Park earlier this month. (Photo by John T. Ward. Click to enlarge.)

By JOHN T. WARD

A massive die-off of bunker fish in the Navesink and Shrewsbury rivers this spring poses no health threat to recreational users of those waters, environmental scientists said Thursday night.

Meantime, experts are still trying to determine what environmental “stressors” might have turned a bacteria that’s common to the species into a mass killer that has littered shores with tons of dead, putrid carcasses.

The occasion was a widely anticipated forum at which environmental scientists from the New Jersey Department of Environmental Protection fielded questions during the latest Rally for the Navesink meeting, a confab of organizations led by Sandy Hook-based Clean Ocean Action.

Whereas past rally sessions have largely focused on limiting human pollution into the rivers, this one tried to puzzle out what turned a common annual die-off of Atlantic menhaden, or bunker, into a “severe” episode that’s lasted about two months.

“The scope and magnitude is really what we’re concerned about,” said COA founder and executive director Cindy Zipf. The die-offs have been increasing in recent years, but “it was a real shocker this year,” she said.

As to the cause, experts have identified a species of the Vibrio bacterium, commonly found in in the environment and in healthy bunker as well, said Bob Schuster, bureau chief in the Marine Water Monitoring unit. It appears to enter their brains, which may explain the frenetic spinning movement they exhibit as they’re dying, he said.

But while a handful of the bacteria species do affect humans, “this is not one of them,” he said.

“From a human health perspective, the dead fish in the water were not affecting bacteria levels for things that we would be concerned with, such as recreational bathing,” he said, referring to sampling. “I would not see an issue with paddleboarding and other activities.”

Likewise, there’s no danger to birds, crustaceans and other fish that feed on the carcasses, said Ray Bukowski, assistant commissioner of Natural and Historic Resources.

The outbreak was not unlike a human pandemic, with menhaden transmitting the illness from one to another as they migrate, said Bukowski.

“It does have to do with the nature of these fish and how they travel and the density of their schools,” he said. “They don’t socially distance really well. They’re horrible at it.”

A secondary bacteria has been isolated, said Jan Lovy, a fish pathologist, but “it’s difficult to pinpoint stressors that could be triggering this actual bacterial outbreak,” he said. “It’s likely that we won’t find a single smoking gun.”

Participants also focused how to get rid of the rotting, smelly mess. Gloves, rakes and double-bagging carcasses for residential trash pickup, or burying them in gardens as fertilizer, were recommended for small-scale cleanups.

Eleventh-district State Senator Vin Gopal said he’s trying to obtain state and federal funding to help finance cleanups conducted by contractors in three towns.

But a broader approach needs to be developed to deal with future catastrophes, said Oceanport Mayor Jay Coffey, “rather than each town having to worry about their specific shoreline. Because this is state water.”

Here’s a DEP FAQ about the die-off.

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