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    Benefits of dam removal reach further than expected

    Dam breach

    Photo By Patrick Bloodgood | A controlled explosion breaches a section of Embrey Dam on Feb. 23, 2004, as part of...... read more read more



    Story by Patrick Bloodgood 

    U.S. Army Corps of Engineers

    FREDERICKSBURG, Va. – Nearly eight years after the removal of Embrey Dam here, scientists are seeing a return in aquatic life further away than expected.

    In an area roughly 73 to 93 miles upstream from where the dam once stood on the Rappahannock River, researchers with the U.S. Geological Survey noticed resurgence in the American eel population in their once-natural habitat, now that they are longer impeded by the 22-foot-high structure.

    “We’ve known that dams can have significant consequences for movement of shad and striped bass in large rivers, but what we learned in this study is that the effects can reach up into the smallest mountain streams,” said Dr. Nathaniel Hitt, a research biologist with the USGS.

    The findings are significant: scientist and engineers knew removing the dam, and dams like it -- would have a beneficial environmental impact on the river and nearby estuaries with the return of native aquatic life. According to scientists like Craig Seltzer, who worked on the removal project and is now retired from the Norfolk District, the resulting impact that far upstream wasn’t planned.

    “While we understood that it was possible to return catadromous species -- fish that spend much of their lives in freshwater, but breed in ocean waters -- such as the American eel, to their freshwater stream habitats, we had no conclusive evidence that this could happen,” Seltzer said. “It's exciting that now, eight years later, we have firm evidence, and we are reaping the benefits that were largely unaccounted for.”

    Scientist hope the American eels’ return to the Appalachian Mountains could help the overall numbers of the fish, which start their life cycle in the Atlantic Ocean’s Sargasso Sea and migrate to freshwater estuaries, like those found in the upper reaches of the Rappahannock River, where they live for around 15 years before returning back to the ocean to spawn.

    Currently, the U.S. Fish and Wildlife Service is evaluating whether or not to list the species as “threatened” under the Endangered Species Act.

    “Connectivity to the freshwater environment could really improve population viability by recruiting more large females into the breeding population,” Hitt said.

    Ultimately, the return of the species to their native grounds means a return of balance to the natural ecosystem in the mountain streams of Virginia.

    “By restoring the American eel to headwater streams we are restoring a piece of Virginia‘s natural heritage; these are native fish, they’re a part of the natural ecosystem there,” Hitt said.

    Scientists are continuing to monitor the eel abundances in Shenandoah National Park and to investigate how their return will affect stream fish communities in the future.

    Some estimates conclude there are thousands of unmaintained dams that have outlived their useful purpose in the United States. According to researchers like Hitt, findings like the American eel’s resurgence only bolsters the call to remove the obstructions allowing natural aquatic life to return to their historic habitats.



    Date Taken: 08.09.2012
    Date Posted: 08.09.2012 09:38
    Story ID: 92908

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