“American eels were once found in great abundance on the East Coast, often quite far inland, but dams have sealed off much of their routes and their population has plummeted. However, the good news is that some of those old dams are no longer needed and are being torn down.

In 2004 the 22-foot-high Embrey Dam on the Rappahannock River in Virginia was dismantled. Since then, American eel numbers have shot up in headwater streams nearly 100 miles away, according to research just published by the U.S. Geological Survey, U.S. Fish and Wildlife Service, and National Park Service.

Researchers measured eels in Shenandoah National Park streams and found significant increases in numbers two years after the dam came down, with those gains accelerating since.

“Our study shows that the benefits of dam removal can extend far upstream,” Nathaniel Hitt, a USGS biologist and lead author of the study, said in a statement.  “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.”

The study authors noted that the American eel is being considered by the U.S. Fish and Wildlife Service for listing as a threatened species under the Endangered Species Act.”

Via National Geographic