A Tag Team for American Eels

With help from Aquarion Water Company, we’re creating new routes for an ancient migration.

“Eels touch the food chain from the shallowest rivers to the deepest ocean.”
- Sally Harold, the Conservancy’s director of migratory fish projects

Fall in New England brings an influx of visitors to experience colorful foliage, pumpkin patches and just-picked apples.

In Connecticut’s fresh waters, an ancient species begins a long journey in the opposite direction.

From the dark corners of rivers across the state, adult American eels swim downstream to the Sargasso Sea to breed and then die. Come spring, juvenile “elvers” replace their number as they swim against the current to reach their new freshwater homes.

Except, it doesn’t always happen as it should.

“Migrating eels often are halted by manmade structures,” says Sally Harold, the Conservancy’s director of migratory fish projects. “Going upstream, they may have to scale 50-foot dams, while the strongest current downstream can lead into the rotating turbine of a water treatment plant.”

Last year, with the help of Aquarion Water Company, the Conservancy implemented two experimental methods to route eels away from a treatment facility in the Aspetuck River watershed. A siphon flows through a nearby dam, while wind-and-solar-powered lights deter eels from the plant intake pipe.

This fall, those efforts are getting a technology upgrade. Thirty migrating eels will be implanted with radio tags at the Silvio O. Conte Anadromous Fish Research Center, then released in groups of 10 during heavy rain, which spurs migration. The Conservancy, Department of Energy and Environmental Protection, and Sacred Heart University will track the eels as they head downstream.

“Will they aim for the siphon? Investigate the lights? Hang out and make friends? We don’t know,” says Harold.

A crucial part of the experiment is Aquarion’s agreement to shut its intake pipe for three days following each release. Should most of the eels swim through the siphon or over the dam in that time frame, Harold hopes the findings will impact future operations.

“This is the first time we’ve worked with a private water company on a study like this,” she says. “If we find a solution here, we hope to replicate it at other water supply systems and hydroelectric facilities.”

For eels—which are under consideration as an endangered species—and people, the stakes are high.

“Eels touch the food chain from the shallowest rivers to the deepest ocean,” says Harold. “If we lose something that important, we lose a lot more than just a single species."


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