State fish experts say a bacterial infection killed thousands of fish in Lake Delton.
Department of Natural Resources fish specialists investigated thousands of dead black crappie and white suckers that washed up ashore on lake properties late last month. The agency has determined a disease called columnaris killed the creatures.
The disease is common and typically occurs in late spring and early summer when water temperatures rise and fish are stressed from spawning and changes in water quality. It causes fatal lesions on fish's gills and skin.
The disease can't hurt humans, but DNR officials say people don't eat infected fish because other bacteria growing on the remains could be harmful.