Lake Oahe Fish Kil

A fish kill in Lake Oahe that is mostly affecting young-of-the-year white bass has slowly moved into North Dakota.

Paul Bailey, south central district fisheries supervisor for the North Dakota Game and Fish Department, said 99 percent of the fish kill is of white bass, but yellow perch, black crappie and freshwater drum were also observed. “Apparently there was an extraordinarily large year-class of white bass, and a heavy external parasite load and bacterial infection is causing the mortality,” Bailey said.

In mid-August, South Dakota Game, Fish and Parks personnel found large numbers of dead young-of-the-year white bass near the Cheyenne Arm of Lake Oahe, approximately 35 miles upstream of Oahe Dam. Samples were sent to a SDGFP’s fish health specialist who identified Aeromonas and Columnaris bacteria as the likely culprits.

The bacterial outbreak has since spread upstream, reaching Beaver Bay Aug. 27. “The greatest concentrations of dead fish observed were near Four-Mile Bay,” Bailey said. “Beaver Bay was the farthest upstream we saw any dead fish.”

Aeromonas and Columnaris bacteria are naturally present in virtually all bodies of water. These bacteria typically do not pose a problem unless fish become stressed and/or crowded. Bailey said warm water during the last several weeks likely was the stressor needed to make these fish susceptible to a bacterial outbreak and extensive fish kill.

“Lake Oahe had phenomenal white bass reproduction this year and young-of-the-year white bass are extremely abundant,” Bailey said. “These fish are also a schooling species which allows bacteria to quickly move from one fish to another.”

Anglers catching adult white bass shouldn’t worry about consuming their catch because the bacteria doesn’t affect the muscle of the fish. “I’d expect this fish kill to continue moving upstream until water temperatures cool,” Bailey said.