Massive fish kill near Flanders Bay caused by lack of oxygen


A massive fish kill of bunker last week has caused an algae bloom in the Peconic River, a natural phenomenon that is giving the waterway its greenish color, according to environmentalists.

Officials with the Suffolk County Department of Health Services agree that the fish kill will improve fishing conditions this season, as the bunker will most likely attract larger fish that prey on the smaller species. In addition, they said the blue-green algae that has accumulated in the Peconic River and adjoining Peconic Bay will benefit other aquatic organisms—as long as the bloom does not last for a long time.

The fish kill was caused when predators of the bunker, namely bluefish, chased the smaller fish into the Peconic River. The resulting buildup of fish caused a lack of oxygen in the water, according to Bill Fonda, a spokesperson for the Department of Environmental Conservation. To date, between 750,000 to 1 million bunker, also known as menhaden, have died.

The bunker are also partly responsible for the ensuing algae bloom—a proliferation of the green underwater organism—in the Peconic River. The algae bloom is also lowering the oxygen levels in the water, a situation that is being closely monitored by county officials.

Mac Waters, the supervisor of the Bureau of Marine Resources in the Suffolk County Department of Health Services, explained that as the bunker decay, they provide a good nutrient source for the algae. But the growth of algae, in turn, can rob other organisms of oxygen.

“The health officials identified the algae bloom,” said Mr. Waters, who noted that the county was monitoring the area on Wednesday. “They looked at the oxygen levels at the bottom of the river and they are very low. They’re still low from the fish kill.”

Mr. Fonda explained that the standard amount of oxygen in the Peconic River is around 4.8 milligrams per liter, but, on Friday, the amount was as low as 1 milligram of oxygen per liter.

Mr. Waters explained that there is nothing that can be done to end an algae bloom and that there is no telling how long it will last. “It could last until there’s heavy rain or winds,” he said. “There is no public health effect—it’s just a nuisance, an aesthetic problem. There is no toxic algae and it will all dissipate with time.”

Mr. Fonda noted that the large number of dead bunker in the area will attract additional predators, such as bluefish and crabs. He noted that he has already received reports from local fishermen about the healthy size of bluefish that are being caught in the area.

Locals first learned about the fish kill last Sunday, according to Tammy Olson, a seven-year resident of Flanders, when bunker carcasses, numbering in the thousands, began appearing in the Peconic River and along the shores of Flanders and Reeves bays.

“People saw masses of fish,” Ms. Olson said. “The river was churning with dead fish. You could see them off of the bridge that goes over County Road 105.”

Ms. Olson’s husband, Clayton, said he has heard of men catching 28-pound bluefish, a large weight for this time of the year. “Fisherman were catching good blues,” he said. “They were what drove bunker up.”

Mr. Fonda added that because they prey on bunker, the bluefish will be of an especially large size this year. He said the area might see its highest population of bluefish in the last 20 years.

“It’ll be good for fishermen because there’s a lot of bait fish for the bluefish around,” Mr. Fonda said. “The blue fish are looking healthy because they have been feeding on bunker for some time.”

The remaining bunker in the area have now moved along with the tide into Meeting House Creek in Aquebogue and other creeks in the area, Mr. Fonda added. He added that since first reports of the fish kill on May 4, there have not been a significant number of additional deaths of bunker.

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