The Revival of the American Eel
The American eel has a slender snakelike body that is covered with a mucous layer, which makes the eel appear to be naked and slimy. The American eel is found along the Atlantic coast including Chesapeake Bay and the Hudson River and as far north as the St. Lawrence River region. Is also present in the river systems of the eastern Gulf of Mexico and in some areas further south. American eels are declining across their range but are showing indications of a population revival following the removal of a large dam in Virginia. The removal of Embrey Dam on the Rappahannock River increased American eel numbers in headwater streams nearly 100 miles away, according to research just published by U.S. Geological Survey, U.S. Fish and Wildlife Service, and National Park Service researchers.
American eels undergo long-distance migrations from their ocean spawning grounds in the Sargasso Sea to freshwater streams along the Atlantic coast from northern South America to Greenland. Dams may slow or even stop upstream eel migrations. However, prior to this research, little was known about American eel responses to dam removal.
The new study evaluated eel abundances in Shenandoah National Park streams before and after the removal of the large dam in 2004. The researchers found significant increases in eel numbers beginning 2 years after dam removal and continued increases nearly every year since. The rebounding eel populations in Shenandoah National Park present a stark contrast to decreasing numbers elsewhere throughout their range.
Dr. Nathaniel Hitt, a USGS biologist and lead author of the study, said: "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 American eel is currently 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 a contributing cause to range-wide decreases over the last 50 years. The authors hypothesize that dam removal could have long-term benefits for eel conservation by increasing the reproductive success of females, which are typically found in headwater streams.
"Eel populations in the Park continue to show recovery," said Jeb Wofford, a biologist at Shenandoah National Park and co-author of the study. "This research highlights the fact that ecosystems in the Park extend far outside Park boundaries and that downstream conservation can have important upstream benefits."
Embrey Dam was built in 1910 on the Rappahannock River near the city of Fredericksburg, Virginia. Until the 1960s, the dam provided hydroelectric power for Fredericksburg.
he 22-foot-tall, 770-foot-long, 1910 hydroelectric Embrey Dam was blown up with 600 tons of explosives by the U.S. Army Corps of Engineers on February 23, 2004. The aim of removal was to re-open miles of spawning grounds to aid populations of American Shad, herring, American eel, and other species.
For further information see Dam Removal.
Eel image via Wikipedia.