Migratory fish including striped bass and American shad benefited from experimental surges of water sent down the Savannah River in March, but one of the region's rarest fish might not have been helped at all.
"There's a lot more we need to know about the sturgeon and how far it can go upstream," said Amanda Wrona, of Savannah, Ga., a marine scientist with The Nature Conservancy.
The Savannah River is home to both the Atlantic sturgeon, which can live 80 years and reach lengths of 7 feet, and the slightly smaller and rarer shortnose sturgeon, an endangered species.
The Nature Conservancy, the Army Corps of Engineers and resource agencies in Georgia and South Carolina conducted experiments in March involving artificial pulses of excess water sent downstream from Thurmond Dam.
The experiment, which bumped river flows from 4,500 cubic feet per second to more than 18,000 cubic feet per second, had several objectives, Dr. Wrona said.
Scientists wanted to see whether more water would make it easier for fish to swim upstream past New Savannah Bluff Lock and Dam, which blocks the river channel and separates sturgeon and other species from spawning grounds in the rocky shoals above Augusta.
Sturgeon, she said, produce sticky roe and spawn where boulders are found. Because of dams such as New Savannah Bluff and three Corps projects farther upstream, less than 4 percent of the Savannah River's original 110 miles of rocky shoals remain.
"The Savannah River has one of the best populations of sturgeon, but we also know the population is in decline," she said. "Because they are such a long-lived species, we still may not know the full impact of having these dams on the river."
This summer, scientists plan to implant captured sturgeon with radio tracking devices and conduct further studies.
"We'll be trying to find out if they can pass through the gates at New Savannah Bluff, and - if not - can they pass through the locks," she said.
The lock gates are opened repeatedly during fish-spawning season to aid upstream migration.
The Savannah's sturgeon population is somewhat of a mystery because it is not known how well the fish reproduce or where reproduction occurs if they cannot reach traditional spawning grounds in the shoals.
"They've found juvenile sturgeon, but not really any great numbers of very small ones," she said. "So we don't know all we need to know about their spawning."
The increased flows were maintained for three-day increments in late March and have been found useful in rejuvenating swampy floodplain habitats along the lower Savannah.
The experiments were part of the conservancy's Sustainable Rivers Project, which involves 14 dams and 10 rivers in 11 states.
Dr. Wrona was in Augusta on Wednesday with a group of scientists and Nature Conservancy members from China who are learning more about the Sustainable Rivers Project.
Reach Rob Pavey at 868-1222, ext. 119, or firstname.lastname@example.org.
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