Visitors to Jordan Lake are finding the beaches littered with dead fish after the largest die-off of striped bass in the history of the reservoir.
More than 5,000 striped bass have died in Jordan Lake since Aug. 1; state wildlife officials counted 1,800 on Aug. 9 alone.
The affected area includes the Haw River near Robeson Creek to the main basin of the lake near the U.S. 64 bridge.
The fish kill is due to what biologists call a "dissolved oxygen/ temperature squeeze," according to Brian McRae, Piedmont Region fishery supervisor with the N.C. Wildlife Resources Commission. In the deeper portions of the lake, the water is cooler, but there is less oxygen; meanwhile in the upper part of the water, the oxygen supply is more plentiful, but the water is hot.
"They get squeezed from both sides," McRae says. "The record summer temperatures finally put them over the edge."
The water temperature in Jordan Lake has hovered around 84 degrees since early July, chronically stressing the striped bass, which, more so than other fish in the reservoir, are susceptible to temperature extremes. They prefer water in the 80–81-degree range.
"The hot water increases their metabolism, which means they need to eat more, but they don't want to eat," McRae explains.
State wildlife officials have excluded other causes for the fish kill, such as excessive algae blooms, which can also deplete the water of oxygen, because so far only striped bass have been affected. Larger bass, those 18–30 inches, and a favorite of anglers, are dying in greater numbers than smaller fish, whose metabolisms are lower.
Although wildlife officials restock the lake every spring with about 70,000 striped bass, anglers could catch fewer of them this winter until the next crop of fish moves in.
Jordan Lake is a "pretty severe environment" for striped bass, McRae says, adding, "We never thought striped bass would do well in the system." However, under normal conditions, the bass have thrived, likely because the food supply is adequate and the fish have enough reserves to endure the stress.
However, this year's heat wave has stressed them beyond what they could withstand. More than 6,000 striped bass in the lake could die before temperatures return to normal.
And this summer has broken all semblance of normal.
"The only thing that will turn it around is colder weather," McRae says.