American Eels: Freshwater Species of the Week

Photo: Juvenile American eels
Juvenile American eels. They may look like snakes, but they are 100% fish. Photo: Uwe Kils, Wikimedia Commons


We recently wrote about European eels for freshwater species of the week, but now we take a look back across the pond at our homegrown version. American eels (Anguilla rostrata) are equally intriguing.

As Water Currents’ Brian Richter told us via email, “I’ve always been fascinated by the life cycle of the American eel  — they spawn at great depths in the Sargasso Sea, and then the gulfstream carries their young north into the Gulf of Mexico and the Atlantic shore of the eastern U.S., where they manage to make their way up the rivers.  Pretty phenomenal migration!”

freshwater species of the week
Click on the image to see more freshwater species, from sharks and scorpions to weird cave-dwelling fish.

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.

Sandra Postel, National Geographic’s Freshwater Fellow and host of Water Currents, said, “This is great news for the American eel — and another indication that removing a dam that obstructs fish passage can fairly quickly allow some fish populations to rebound.  We’re seeing huge numbers of fish returning to the Kennebec River in Maine, since the removal of the Edwards Dam in 1999, and now the American eel and other species rebounding in the Rappahannock since the removal of the Embrey Dam. With more dams coming down in Maine, the Pacific Northwest and elsewhere, it’s crucial that we monitor for these ecological and biological effects. ”

“This study demonstrates that multiple benefits can be realized by removing obsolete dams such as Embrey,” Alan Weaver, fish passage coordinator for the Virginia Department of Game and Inland Fisheries, said in a statement. “Shad, herring, and striped bass are also using reopened habitat on the Rappahannock River, so it’s exciting to see a growing number of species benefitting from dam removal in Virginia.”

American eels were an important food source for Native Americans and many species of wildlife. The slender fish are said to be good eating, although modern anglers are often put off by their slimy skin and snake-like appearance (they are still used as bait, however, which has also decreased their numbers). American eels feed on a range of crustaceans and other invertebrates, which they usually hunt for at night.

Because it’s so cool, let’s take another look at the awesome Condit Dam removal in Washington State:


Brian Clark Howard is an Environment Writer and Editor at National Geographic News. He previously served as an editor for and E/The Environmental Magazine, and has written for,,, Yahoo!, MSN, Miller-McCune and elsewhere. He is the co-author of six books, including Geothermal HVACGreen Lighting and Build Your Own Small Wind Power System.