American eel numbers rise after dam removal

American eel numbers are up in the headwater streams of Shenandoah National Park, following the 2004 removal of a large downstream dam.

Significant increases in upstream American eel populations began two years after the Rappahannock River's Embrey Dam was removed and have continued nearly every year since, according to a report released last week by the U.S. Geological Survey (USGS), U.S. Fish and Wildlife Service (USFWS) and National Park Service (NPS) researchers.

Image courtesy EricksonSmith/Flickr.

Dams can act as travel barriers to American eels, which undertake long-distance migrations from their ocean spawning grounds to freshwater streams along the Atlantic coast. While American eels can surpass substantial natural barriers--like the rapids of the Potomac River's Great Falls, for instance--dams pose a more difficult obstacle and have contributed to the widespread decline in American eel populations. Dam removal, therefore, could have long-term benefits for eel conservation.

"Our study shows that the benefits of dam removal can extend far upstream," said USGS biologist Nathanial Hitt. "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."

Embrey Dam, which once provided hydroelectric power to Fredericksburg, Va., was breached in 2004 following years of work by nonprofit organizations and city, state and federal government agencies. Its removal was intended to benefit more than the American eel, however, as dams can impact a number of fish that must migrate up rivers to spawn.

"Shad, herring and striped bass are also using reopened habitat on the Rappahannock River," said Alan Weaver, fish passage coordinator for the Virginia Department of Game and Inland Fisheries. "It's exciting to see a growing number of species benefiting from dam removal in Virginia."

Learn more about American eel abundance in Shenandoah National Park.