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As river temperatures rise each spring along the Atlantic seaboard, nature signals shortnose sturgeons to migrate from saltwater to their natal spawning grounds in these rivers — sometimes hundreds of miles upstream. © Andrew Davis Tucker

"We can use this information to influence sustainable river management worldwide."

Amanda Meadows, Savannah River project director for The Nature Conservancy in Georgia

By Christine Griffiths

As river temperatures rise each spring along the Atlantic seaboard, nature signals shortnose sturgeons to migrate from saltwater to their natal spawning grounds in these rivers — sometimes hundreds of miles upstream.

For thousands of years, this intrepid fish has made the same journey, repeating a prehistoric ritual that has sustained its species. Yet, today a combination of factors — dams, pollution, over-harvesting — has brought this species to the brink of extinction.

Controlled Floods and Ultrasonic Transmitters

But The Nature Conservancy is employing innovative conservation techniques to restore the shortnose sturgeon in these rivers:

• We're working with the U.S. Army Corps of Engineers to release controlled floods to help the sturgeon swim around old dams in the Savannah River.
• And Conservancy scientists are tracking some of the migrating fish by tagging then with ultrasonic transmitters to determine the floods' effectiveness.

"This research has implications far beyond the Savannah River," says Amanda Meadows, Savannah River project director for The Nature Conservancy in Georgia.

"If we can determine how best to manage the water flows for the benefit of the sturgeon and other native species," she adds, "then we can use this information to influence sustainable river management worldwide."

A Helping Hand around the Dams

In the Savannah River, which forms the border of Georgia and South Carolina, sturgeon populations have suffered a drastic decline due to a series of dams that have removed 96 percent of their spawning habitat and now obstruct passage to what’s left of their spawning grounds upstream. The dams also have altered the natural water flow needed for the sturgeon to thrive.

"The sturgeon fish are just one casualty of the dams," said Meadows. "The dams have caused an ecological chain reaction that has impaired the health of the floodplain forests, the shoals and the estuaries, putting many species of plants, birds, fish, and mammals at risk."

So under the national Sustainable Rivers Project, a national collaborative to restore America’s rivers, the Conservancy and the U.S. Army Corps of Engineers have conducted a series of controlled floods on the Savannah River, beginning in 2004.

The releases mimic the natural seasonal flows that occurred prior to the dams. Scientists are hoping that the sturgeon can use the increased flow of water during the releases to swim past an old lock and dam to reach its upstream spawning grounds.

Catch, Release and Track

Before scheduled water releases last March, Meadows and biologists from the South Carolina Department of Natural Resources captured four sturgeon and surgically implanted ultrasonic transmitters into the fish to track their migration during the release.

"We'd hoped to tag at least 10," Meadows said. "The fact that we only found four may relate to the plight of the sturgeon. Their numbers are few."

None of the tagged sturgeon made it past the dam, but one sturgeon traveled downstream more than 300 miles in a week to the Santee-Cooper river system near Charleston, South Carolina.

This finding has been hailed as a significant discovery by project scientists, possibly indicating that the Savannah sturgeon may be a source of genetic diversity for other river systems.

This spring, Meadows and her partners at South Carolina DNR will continue their efforts to revive this endangered species as they once again set out to net and tag sturgeon to track their spawning migration this year.

"While continued water releases are vital to the overall health of the river system, they may not be enough to help pass the sturgeon through the dam," said Meadows.

"But the information we've gathered from monitoring the tagged fish is proving essential to helping the Conservancy and our partners consider alternative solutions to ensure this ancient fish can thrive in the Savannah."

About the Author

Christine Griffiths is a marketing specialist for the Conservancy. She is based in Georgia.