Caught in the Middle: Barriers to Migration Threaten Eel Population

By Michael Dinan, The Stamford Advocate, Conn.

Jun. 26–GREENWICH — Michael Aurelia raised a dripping net of a baby alewives from a pool of the Mianus River Dam’s fishway, examined them, then dumped the silver fish back into the water and pulled out a partially submerged crate.

Each month, Aurelia resets an electronic counter in the crate to track how many of the alewives swim in from Long Island Sound to spawn. But that wasn’t why he was at the dam this sunny morning. He was looking for baby American eels.

“You can see how fast they move,” Aurelia, former director of the Inland Wetlands and Watercourses Agency, said as he spotted a 2-inch baby eel wriggling in the crate. “Sometimes they get stuck in here. There’s probably thousands of them in the water.”

The Mianus River Dam, where alewives reach freshwater each April, also plays a crucial role in the lives of the Western hemisphere’s only freshwater eels. A net hanging over the dam serves as a ladder that baby, or “glass,” eels use to climb back into the freshwater. The eels remain for about 10 years in the Mianus Pond, then head out of the Sound to the Atlantic Ocean once they’re mature enough to spawn.

Threatened by overfishing, hydropower plants, dams and other obstructions, the American eel recently was considered for endangered species status by the federal Fish and Wildlife Service.

“We’re seeing fewer in Connecticut and throughout the entire (Northeast) range,” said Rick Jacobson, assistant director of the state Department of Environmental Protection’s Inland Fisheries Division. “The concern is manmade dams and other barriers to fish passage, both in terms of moving upstream and downstream. Because of their migratory pathways, they frequently go through turbines or filter systems into water supply reservoirs. That, and overall degradation of habitat.”

Nets are a primary way that conservation officials help eels circumnavigate barriers such as dams.

The Mianus River Dam net, damaged by April’s nor-easter, no longer reaches the estuary at low-tide and needs repairs.

American eels start as eggs hatching in the Sargasso Sea, a 2-million-square-mile warm-water body in the North Atlantic between the West Indies and the Azores. They may take years to reach freshwater streams, where they remain until mature. Then they return to the Sargasso Sea to spawn and die. Females can lay up to 4 million eggs per year and frequently die after egg-laying. Eels may exceed two feet in length and can reach 9 pounds.

Eels have been a part of the human diet for centuries, and glass eels have been illegally harvested in the U.S. and sold on the Asian market since at least the 1970s, conservationists say.

Federal officials undertook a study of American eels in 2004. They found that while the eel population has declined in some areas, the species’ overall population isn’t in danger of extinction for the foreseeable future.

Greenwich Conservation Director Denise Savageau said she, Aurelia and state DEP officials who serve as stewards of the dam’s fishway believe the eel pass is an essential part of the area.

“We do pay attention to eels. We think it’s important for people in Greenwich to understand that a lot of things live in these waterways,” Savageau said. “People always talk about the Long Island Sound being so important. It is, but this really is an essential estuary.”

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