Juvenile American eels are known as "glass eels." As they move upstream and grow, they acquire darker pigments, giving them their brown and green coloration. Photo by Chris Bowser/Cornell University

July 3 (UPI) -- Dams are one of the main impediments to the recovery of American eels. The removal of old dams has proven a boon to the endangered species, but many dams remain and not all can be demolished.

Researchers at Cornell University have developed a solution to help migrating eels bypass dams on their journey upstream. They call their solution the "eelevator."


Eels are born a translucent gray and white in the warm waters of the Atlantic's Sargasso Sea. For this reason, they're often called "glass eels" during their juvenile stages. Shortly after birth, the eels are carried north by the currents of the Gulf Stream to estuaries along the Eastern Seaboard.

As they slowly migrate farther inland, they gain pigmentation, a combination of greens and browns. Their slow journey -- stretching across a lifespan of some 30 years -- means eels occupy a diverse array of habitats. They're a vital component -- both predator and prey -- of many aquatic ecosystems.

"Eels live in virtually every aquatic habitat, from mountain streams and farm ponds to city creeks, coastal estuaries and the vast ocean," Chris Bowser, an environmental scientist and eel expert at Cornell's New York State Water Resources Institute, said in a news release. "We talk about the connectedness of these water systems; eels are that connection."

Eel ladders have been installed along a number of dams, but the newest device is liftable and works with the assistance of human volunteers. Eels looking to move upstream can climb a ramp of netting, kept wet by hoses, into a holding tank of circulating water. Twice a week, volunteers can check to see if eels have arrived. The tank can be raised, like an elevator, and the water deposited into the river above the dam.

Bowser and his colleagues invented the device after residents of Piermont, a town along the Hudson River, approached him about helping eels move into an upstream pond blocked by a dam.

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"The 'eelevator' is a great example of grassroots citizen-science where local residents team up with environmental researchers to conserve natural resources, including eels, on their way upstream," said Brian Rahm, a researcher at the Water Resources Institute.

Bowser and his colleagues hope the eelevator concept can be translated to other sites as part of the Hudson River Eel Project, an effort by volunteers and local conservationist to track and assist the movement of eels upstream in New York.