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Study: Dam removal helped eels in Shenandoah park

Tuesday - 7/31/2012, 12:41pm  ET

WAYNESBORO, Va. - The removal of a large dam in Virginia has meant good news for the American eel population, according to a new study by the U.S. Geological Survey, U.S. Fish and Wildlife Service and National Park Service.

The research, published this month in Transactions of the American Fisheries Society, shows that the removal of Embrey Dam on the Rappahannock River increased American eel numbers in headwater streams nearly 100 miles away.

American eels migrate from their spawning grounds in the Atlantic Ocean to freshwater streams along the coast. Dams were thought to slow or even stop the migration.

Researchers studied eel populations in in Shenandoah National Park streams before and after the removal of the large dam in 2004. The study shows significant eel numbers beginning two years after the dam removal and nearly every year since.

"Our study shows that the benefits of dam removal can extend far upstream," said Nathaniel Hitt, a USGS biologist and lead author of the study. "American eels have been in decline for decades and so we're delighted to see them begin to return in abundance to their native streams."

American eel populations elsewhere are declining, and the species is being considered by the U.S. Fish and Wildlife Service for listing as a threatened species under the Endangered Species Act. Migration barriers such as dams have been recognized as contributing to population decreases over the past 50 years.

Embrey Dam, built in 1910 on the Rappahannock River near Fredericksburg, measured 22 feet high and nearly 800 feet wide. The dam provided hydroelectric power for the city until the 1960s. It was removed due to concerns about the hazards it posed and the potential for fish restoration.

"This study demonstrates that multiple benefits can be realized by removing obsolete dams such as Embrey," said Alan Weaver, fish passage coordinator for the Virginia Department of Game and Inland Fisheries.

Weaver said shad, herring and striped bass also have benefited from the dam removal, as their populations have grown.

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