Biologists evaluate success of fish-saving oxygen system at Thurmond Lake

If you need help finding the proverbial needle in a haystack, try electronic surveillance.


That’s what fisheries technician Win Ott used last week while canvassing the 70,000-acre Thurmond Lake in hopes of locating 65 stripers and hybrid bass tagged with remote sensors.

The idea, he said, was to determine whether the Corps of Engineers’ new oxygen injection system is fulfilling its mission of keeping sportfish at the lake’s lower end, even during hot weather.

“We’re seeing a lot of people trolling, and some surface feeding activity too,” the South Carolina Department of Natural Resources scientist said. “We’re also finding a lot of our tagged fish.”

The transmitters, implanted last year, are being used to follow the fish as warmer weather elevates water temperatures and lowers dissolved oxygen levels.

Typically, when hot weather hits in late summer, striped bass move upstream toward the Russell Dam tailrace, where they are vulnerable to being killed during the operation of Russell Dam’s pumped storage “reversible” turbines.

The oxygen system was designed to provide oxygenated habitat at the other end of the lake. Ott’s job is to find out how well it is working.

“We’re still collecting data, and we haven’t gone through it all,” he said, noting that some tagged fish swam upstream toward Russell. “But we’re also seeing tagged fish that normally would be upstream, that are hanging around down here.”

The studies and findings will be used over a period of years to refine the manner in which the oxygen diffusors are operated.

“Depending on what we find, it might be possible to turn on the oxygen lines earlier in the year, or even later in the year, after we see when the fish are moving through the area,” Ott said.

Anglers are also tuned in to the oxygen system, and plenty of fish have been caught in that vicinity.

“Whenever I’m out during the day, they’re running the thing like crazy, and with all the bubbles it looks like a giant hot tub,” said William Sasser, a professional guide who uses the area frequently. “It’s not like a little mist of bubbles either. You absolutely can’t miss it.”

Although fish are in that area now, Sasser said the location of the diffusor lines – just offshore from the Modoc boat ramp – is also a location where baitfish typically congregate in the fall.

“Where they put the lines is also where the fish usually are this time of year,” he said. “So it’s hard to know whether it’s because of the oxygen system or not.”

LAKE LEVELS: As one of the driest years in recent memory nears the end of its third quarter, water levels are continuing to fall and likely will worsen, according to the newest corps projections.

In a summary of corps data circulated by the Friends of the Savannah River Basin, forecasts call for the lake to drop another five feet to a pool level of 318.5 feet above sea level. Full pool is 330 feet above sea level and the lake was at 323.16 on Saturday.

A hoped-for bounty of rain from Tropical Storm Irene bypassed the region, with little relief in sight. In recent months, inflows into Thurmond Lake are just 11 percent of normal, and the U.S. Drought Monitor shows most of the Savannah River Basin as being in “extreme drought.”

Extended forecasts call for a weak La Niña system this year, which could mean below-normal rainfall in the lower basin, both for the remainder of 2011 and the first few months of next year, according to the National Weather Service.



Wed, 08/23/2017 - 01:54