WHERE DID ALL THE ALEWIVES GO?
Record year for fish followed by huge drop-off
There’s something mysterious going on with the alewife population in Connecticut, with numbers dropping precipitously from last year.
On the other hand, lampreys, those parasitic fish with the round mouths full of teeth, seem to be finding a home in Connecticut’s waterways.
“This year was not a stellar year for alewife migrations. The numbers were quite low statewide,” said Jon Vander Werff, fish biologist with Save the Sound.
“Last year was the record we’ve ever counted, and it was 200,” Vander Werff said. That was in Konold’s Pond in Woodbridge after the Pond Lily dam on the West River was removed a few years ago, allowing the alewives to reach the pond.
This year, however, only three alewives were caught in the pond.
Alewives, a type of herring that are a protected species in Connecticut, serve as food for ocean fish such as striped bass and bluefish and birds such as herons, cormorants and ospreys. They return from the ocean to spawn in fresh water.
Since the Pond Lily dam was removed in 2015, and it takes three to five years for alewives to reach sexual maturity, Vander Werff and others were excited to see the West River Nature Preserve returning to its natural state.
The drop-off is a mystery, however.
“Similar to what Save the Sound saw, our alewife runs are generally really down this year across the state,” said Matt Goclowski, supervising fisheries biologist with the state Department of Energy and Environmental Protection. “Generally speaking, our numbers are really down this year.”
He also supervises the diadromous fish restoration program, which includes alewives. In Bride Lake in East Lyme, which DEEP has the most data on, “over the last five years, we’ve seen 350,000 on average,” Goclowski said. This year, there were 150,000.
“They’re really the basis for the food web in a lot of systems,” he said. “When they’re young they’re an important food item for a lot of fish.”
Goclowski also said he didn’t know the cause. “Given the fact that it’s happened across the state, it’s not a localized thing that’s happening in the river. It’s more likely something
“This year was not a stellar year for alewife migrations. The numbers were quite low statewide.”
Jon Vander Werff, fish biologist with Save the Sound
that’s happening at sea.”
However, Goclowski said the drop-off could be a fluke. “This is a particularly big fluctuation, but it’s possible that next year will be looking better,” he said. “So it’s still too early to have any definitive conclusions for why our numbers are low.”
He said the falloff has been reported in other states, as well, and biologists from the region are going to “put our heads together to come to a consensus on what’s been happening to these species.”
Lampreys, on the other hand, may be on the rise. Vander Werff said “this year in the Norwalk River is the second year in a row that they’ve been documented.”
He said he has seen sea lampreys “spawning and building nests” 50 yards away from Dana Dam, which is the next dam Save the Sound plans to remove from the Norwalk River. The Flock Process Dam downriver was removed in 2018.
“They can access that habitat because the dam was blocking their migration,” Vander Werff said. He said sea lampreys’ “role in the ecosystem is similar” to alewives.
“The interesting thing about the lamprey is no one knows anything about them,” he said. “We’re giving them nursery habitat, while their adult life is a mystery.”