The removal of the Embrey Dam on the Rappahannock River in Virginia has led to a recovery of the American eel (Anguilla rostrata), according to a paper published in the journal Transactions of the American Fisheries Society. The American eel has been on the decline due to factors such as overfishing, the introduction of the parasitic Asian worm and habitat degradation.
The eel population on the river was affected by the construction of the dam, which prevented it from spawning. The dam, 22 feet high, and built in 1910 was removed in 2004. Scientists began a study of the effects of dam removal on eel populations between 1996 to 2010, which included the time the dam was removed. What they found were the eel populations increased in streams after the dam was removed. The eel populations went from 1.6 eels per 100 meters of water to 3.9 eels per 100 meters after the dam was removed. The increase was noted starting in 2006 and has been increasing in numbers nearly every year since the dam’s removal.
“Our study shows that the benefits of dam removal can extend far upstream,” said Dr. 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.”
The American eel is a catadromous fish that lives in freshwater and in estuaries but migrates out to sea to spawn. The larvae then move back into freshwater streams where they grow to adulthood. It is currently being considered as a threatened species by the U.S. Fish and Wildlife Service under the Endangered Species Act.