Scientists Explain Bunker Found Washed up on the Connecticut Shoreline

Bunker (credit: Connecticut Department of Energy and Environmental Protection)


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Masses of the ubiquitous menhaden, or bunker, have been washing up all along Connecticut’s shore – and from New Jersey to Cape Cod – over the past month, but biologists say the dead fish aren’t a cause for alarm.

The number of bunker washing up on the shore is a small percentage of the bunker still swimming in the Long Island Sound, explained Bill Lucey, of Save the Sound.

Lucey said that the first week of November, he heard reports of solid schools of bunker from Watch Hill, Rhode Island to Bridgeport. When an earthquake struck southeastern Massachusetts on Nov. 9, Lucey said a friend fishing off Old Saybrook reported seeing what looked like millions of bunker jumping out of the water, and landing “like a giant rainstorm.” 

Bunker spawn in the Chesapeake in February and March, make their way north to the Gulf of Maine in the spring, then head back down south as the water gets colder in the fall. 

This year, higher than usual numbers of the fish congregated in the Sound, and they missed their cue to start heading south because the water in the sound stayed warm into the fall. As the water temperature dropped in October and November, the supply of algae and plankton for bunker to eat diminished, leaving the fish hungry and cold and causing a small percentage to die and wash ashore.

“Some of them are dying, but there are many more alive,” David Molnar, DEEP fisheries biologist, said. “I’ve seen all the kills from Darien to New London, and we’re talking about 50 to 100, maybe 150 fish. If you look out, for example, from the New Haven Harbor up on the bluff, and you look down and see the schools, you’d just be amazed.”

Why are there so many bunker in the sound?

In November, Lucey went to the sewer outflow pipe near Black Rock Harbor in Bridgeport, where a small school of bunker can linger into January because the outflow keeps the water warmer. Bunker were massing as far as he could see across the sound, and he saw schools formed the entire stretch from Bridgeport to Norwalk.

Lucey said that part of the reason there were so many bunker in the Sound to begin with, is tightened regulations on fishing bunker, which are fished mainly by Omega Protein and processed into animal food and fish oil. They’re also a key source of food for ocean predators from striped bass to humpback whales.

The Atlantic States Marine Fisheries Commission cut the quota for commercial bunker fishing in the Chesapeake Bay – a key area for bunker to spawn – by 40 percent in 2017, and the overall quota by 10 percent in 2020. 

It takes time for such quotas to have an effect on population, but Lucey said it’s possible those effects became more apparent this fall. It’s also possible that the population of menhaden could be making a more long-term shift to the north because of warming waters.

Molnar cited the quotas, good conditions for bunker to spawn and global warming for the large population of bunker in the sound this year. Species that feed on bunker also aren’t as prevalent, so there is not an abundance of predators to balance the bunker population, he said.

“They’re the most important prey species in the Atlantic Ocean,” Molnar said. “Right now I’m seeing seals in the Thames feeding on the schools. We had three whales just south of the Statue of Liberty feeding on them just the other day.”

“I understand people are concerned when they see a dead animal on the beach, but I’ve seen this kind of abundance in Alaska with other spawning species – when you have a massive run, you just see a lot of dead ones scattered about,” he said.

Molnar said most of the bunker did migrate south, but because the stock was so large this year, there are still a lot hanging around. Some bunker always try to overwinter in the Sound because migrating comes with the risk of running into predators. Some that stay survive the cold, some don’t.

“These schools will feed and spawn based on food availability, and since we have so many nutrients in the Long Island Sound, we get extended algal blooms or plankton blooms,” Lucey said. “I think they were in here, it was warm and there was food, and then the temperature started dropping.”

New York is investigating if there is any virus that could have caused the fish to die, but Lucey said a virus likely would have spread faster considering how tightly packed the bunker are schooling.

“The population will be fine, our water quality is fine, we didn’t find any other dead fish, birds, mammals, anything else,” Molnar said. “We tested the water, the water’s fine. They’re just dealing with temperature shock, not enough food, and low salinity.”