nynj baykeeper dissolved oxygen testsPHOTO: NY/NJ Baykeeper staff testing for dissolved oxygen (credit: NY/NJ Baykeeper)

Over the last several days, thousands of dead juvenile bunker (also known as “peanut bunker”) have been spotted in Thornes and Waackaack Creeks and along the Raritan Bayshore in Keansburg.  The suspected cause of death is low dissolved oxygen in the water, which causes the fish to suffocate and die.  Just like humans, fish need oxygen, but they take the oxygen from the water in which they live.

Low dissolved oxygen can occur due to warm water temperatures and nutrients or organic material in the water.  Bacteria in water can consume oxygen as organic matter decays.

“The NY/NJ Baykeeper office started getting alerts from local residents last week, concerned over dead fish in local waterways, including Natco Lake, Thornes Creek, Waackaack Creek and along the Raritan Bayshore in Keansburg,” said Debbie Mans, Executive Director, NY/NJ Baykeeper.  “We called the state hotline and contacted Monmouth County to report the sightings.”

“We conducted water quality tested in the impacted areas on Tuesday, August 23, and discovered the dissolved oxygen temperatures to be between 1.90 and 2.46 milligrams per Liter (mg/L),” said Meredith DeMarco, NY/NJ Baykeeper.  “Once the dissolved oxygen gets below 2.0 mg/L fish will begin to suffocate and die.  Ideally, dissolved oxygen should be above 5.0 mg/L.”

“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,” said Greg Remaud, Deputy Director, NY/NJ Baykeeper.

“Our understanding is that local government entities will now coordinate removal of the fish in certain areas,” said Mans.