Debates on flows put fish in focus

Resolving the dispute over how much water must be released from Thurmond Dam will depend, at least in part, on the breeding habits of one of the planet's oldest fish: the sturgeon.

 

"What we are doing, in conjunction with The Nature Conservancy, is trying to determine what impact this lower flow is having on the shortnose sturgeon," said Army Corps of Engineers spokesman Billy Birdwell.

Fewer than 2,000 of the federally endangered fish are believed to still inhabit the river and its coastal estuaries, and populations have continued to decline. Studies are under way to determine whether lower river flows will prevent upstream spawning runs.

The Savannah River's annual average flow is about 9,000 cubic feet per second, but the drought last year brought those releases down to 3,600 cubic feet per second under a federally approved drought plan.

In November, the corps made an exception to its plan and further reduced flows -- to a 20-year low of 3,100 cubic feet per second -- in efforts to slow the decline of upstate lakes.

Upstate groups concerned about the low water's effect on real estate sales and the recreation industry have asked that those lower flows be extended indefinitely.

The corps has proposed keeping the lower flows only through the end of February, but even that will depend on the sturgeon studies, Mr. Birdwell said.

"We have authority to take it through the end of January and take it back up to 3,600 at the start of February," he said. "But if we see the impacts on sturgeon are minimal or nonexistent, we will pass that information back to the National Marine Fisheries Service to see if they will allow us to go all the way through February, which was the original request from the states of Georgia and South Carolina."

So far, it remains unclear whether the low flows are affecting sturgeon, said Amanda Meadows, the Savannah River program director for The Nature Conservancy.

She and other scientists are using ultrasonic transmitters placed on coastal sturgeon to determine when they swim upstream to spawn, and in what numbers.

"Historically, we think they like to have as much water as possible for spawning," Dr. Meadows said. "Most of their historic spawning grounds are on the other (upstream) side of the New Savannah Bluff Lock and Dam, but we think they may be using lesser quality gravel bars below the lock and dam."

Though previous studies show many sturgeon spawn in March and April, they also detected spawning activity as early as February, she said.

"We've moved a bunch of receivers upstream, and we're waiting to see where the fish go," she said.

The data gathered in the current studies will be shared -- without formal recommendations -- with resource agencies.

The lakes have risen several feet from heavy rains in December and January, but long-range forecasts still call for waters to recede throughout the summer and fall.

Reach Rob Pavey at 868-1222, ext. 119, or rob.pavey@augustachronicle.com.

STURGEON FACTS

- Two sturgeon species inhabit the Savannah River: the federally endangered shortnose, which can weigh 30 pounds or more, and the federally protected Atlantic sturgeon, which can reach 8 feet in length and weigh 300 pounds or more.

- Both species are categorized as "living fossils" and have survived almost unchanged for more than 220 million years. They are also important "indicator species" that help document the quality of a given habitat.

- Sturgeon swim upriver to spawn and require fast-flowing water and rocky shoals. Their sticky roe, known as caviar, clings to the rocks in spawning grounds until the eggs hatch. Juvenile sturgeon remain in the shoals until they are large enough to swim downstream to coastal estuaries.

- Damming of rivers and the creation of reservoirs have prevented upstream migration and eliminated spawning grounds, contributing to their decline.

- In the Savannah River, sturgeon are blocked by New Savannah Bluff Lock and Dam below Augusta but are believed to use gravel beds downstream for limited spawning. Above the city, just 4 percent of the shoals where they once spawned remains intact.

Source: National Marine Fisheries Service, The Nature Conservancy