The Peconic River teeming with bunker fish last month. Photo: Brian Nigro

Almost a year after the major fish kills in the Peconic Estuary last summer, bunker fish are being seen in large numbers in the river almost a month earlier than usual this spring.

The Peconic River has been teeming with bunker fish since the second to last week of March, according to reports from local fishermen and a Stony Brook University scientist.

Bunker fish do not usually start appearing in such large numbers in the Peconic River until the middle of April.

“This is earlier than usual,” said Dr. Christopher Gobler, a Stony Brook University research professor who studies and monitors the Peconic Estuary. “It’s been an unusually warm winter.”

Bunker swarming in the Peconic River in downtown Riverhead. Photo: Brian Nigro
Bunker swarming in the Peconic River in downtown Riverhead. Photo: Brian Nigro

During last summer’s fish kill, bunker fish were washing up dead by the hundreds of thousands on the shores of the Peconic and Flanders bays during the months of May and June. It was the worst fish die-off in decades, spurring a multi-agency investigation into its cause.

That investigation found nitrogen-fueled algal blooms were to blame. A spike in algal blooms, which are fed by increased levels of nitrogen in the water, deprived the river of oxygen and caused “mass asphyxiation” in the river’s bunker, the investigation found.

Oxygen levels dropped all the way down to zero on the night of the largest kill, according to Gobler and his research team.

Gobler’s research has found that residential septic systems and cesspools are responsible for most of the nitrogen loading in the Peconic River, which in turn fueled the algal blooms and triggered the fish die-off.

“We now know that more than two-thirds of the nitrogen that’s responsible for this increase is from on-site wastewater – individual homes with septic tanks and cesspools,” Gobler said in his annual State of the Bays lecture in Southampton Friday.

With the early arrival of the bunker this spring, Gobler’s lab has initiated its monitoring program of the Peconic Estuary for 2016. Oxygen levels have been good so far, but they will begin decreasing as the temperatures warm up.

“They vary inversely with temperature, so let’s see what happens through the spring,” Gobler said.

With such large bunker populations already appearing in the Peconic River, however, oxygen levels could begin depleting more quickly than usual.

Alfred Allen, a longtime Riverhead resident and fisherman, said he began hearing reports of bunker the week before Easter. On Easter Sunday, he decided to go and see for himself.

“I was fishing in the shadows of the [Route 105] bridge,” he said. “And the river was so thick with bunker – there were so many bunker in there – I was almost unable to make a normal cast and retrieve without having them bang into my line multiple times.”

Allen, who keeps a fishing log, said he didn’t observe bunker in such numbers until April 28 last year. “We had a rough winter last year, and everything was a little late, but this is unusually early,” he said.

He pointed out that the Peconic Bay at Indian Island was “teeming” with juveniles last fall. “Before those bunker died off last spring, they were still able to spawn,” he said.

Gobler said the bunker fish remained in the waters of the Peconic “well into November” last year due to warm temperatures.

“Some have hypothesized they never left, although I have not seen any data to confirm that,” Gobler said.

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