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How Does a Four-Inch Eel Hurdle a 40-Foot Greenwich Dam?

Baby eels are making their annual migration from Long Island Sound to rivers across Connecticut, but along the way, they're encountering one persistent obstacle: river dams. Now, one man in Greenwich is working to make the eels' journey a little easier.

"Adults go out to sea to spawn. What we get coming back upstream are juvenile eels, little baby guys."
Joe Cassone

When you think about fish migrating, your mind probably pictures one image: salmon jumping upstream, pushing against the current to lay their eggs. "But eels do the opposite," explained Joe Cassone with Greenwich's Conservation Commission. "They spend their adult lives in fresh water. The adults go out to sea to spawn. What we get coming back upstream are juvenile eels, little baby guys."

Historically, those "little baby guys" would travel from Long Island Sound upstream into Greenwich's watershed. They'd grow up, bear eggs, and swim back into the ocean to spawn. Then dams started getting in the way.

Credit Town of Greenwich
Baby eels captured in a bucket. Last year, Cassone collected around 500 eels. This year, he hopes to boost that number into the thousands.

Credit Town of Greenwich
A map highlighting the dozens of dams on Greenwich's Byram River. Dams can hinder a juvenile eel's ability to safely travel upstream.

On Greenwich's Byram River alone, there are 43 of those dams. This reporter met Cassone at the first of them, a vertical monolith about 40 feet tall. That's a big hurdle for a baby eel between one and four inches long. "Trying to climb over a dam like this, the flow is obviously so strong it'll knock them down," Cassone said. "So they end up piling up down below. There's almost a logjam of eels below the first dam."

But eels are adept climbers. Amazingly, Cassone said some lucky eels would be able to make it up that 40-foot-tall dam if they stuck to the edges, where the current is less strong. "They have so much surface area and they have a mucus coating that they can actually, if this is damp, climb right up this wall," Cassone said. "There's enough roughness on there that they can serpentine their way up. So that's kind of how our project works. It takes advantage of that, There's something in my way, I'll climb over it behavior the eels have. We use it to collect them and help them on their migration."

At the base of the dam is Cassone's eel trap. It's one of two in the city's watershed. (The other is at the Mianus River.) It's homemade: a gigantic collection tank with a PVC tube extending into the river.

"My volunteers and I affectionately call it 'Eelbot,'" Cassone said. "At one point, we had solar panels down here, and it was quite an operation. We use a pump to supply flowing water. That water we use two different ways... First, we use the majority of the flow to fire into the standing water, to attract the eels. After all, they're looking to go upstream. That's called our attraction flow."

The pitter-patter of the water tells eels, "Hey, here's something interesting! Don't go towards the big scary dam, come check this out."

"Then we use a small portion to keep water circulating through the tank to keep it fresh for the eels," Cassone said. "As we circulate that water, it comes out smelling like eels. So it's more attraction."

Credit Patrick Skahill / WNPR
Cassone's Byram River trap includes a collection bin, pictured above, that's outfitted with an electric-powered water pump that circulates and disturbs ambient water to attract eels.

Extending out of the PVC pipe is a piece of trawling. Think of it as a kind of "eel ladder" leading from river to collection tank. "Picture a little eel working its way through here." Cassone said. "It's like a kid in a cargo net. It comes right up."

Once the eels are caught in the collection bin, Cassone said his network of volunteers carry the eels up and over the dam, and distribute them upstream at a number of points. "Greenwich Audubon Society has been a great partner for us," Cassone said, "and let us have access to all of their properties in the watershed. It really helps redistribute the eels more evenly throughout their historic range."

During his first year, Cassone said he collected about 500 eels. This year, he hopes to boost that number into the thousands.

Once those eels grow up, they'll head back out to sea. People have never witnessed eels spawning, and no one is quite sure where they do it, but the current theory is that the Greenwich eels may eventually swim as far as the Bermuda Triangle to lay their eggs. 

Patrick Skahill is a reporter and digital editor at Connecticut Public. Prior to becoming a reporter, he was the founding producer of Connecticut Public Radio's The Colin McEnroe Show, which began in 2009. Patrick's reporting has appeared on NPR's Morning Edition, Here & Now, and All Things Considered. He has also reported for the Marketplace Morning Report. He can be reached at pskahill@ctpublic.org.

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