Lake Winnebago fish die-off linked to virus

Dead fish float in Lake Winnebago near Menasha April 24, 2018. (Photo submitted by Kathy Searl 1)

OSHKOSH (WLUK) -- A fish die-off last month in Lake Winnebago appears to be the result of a virus, the Wisconsin Department of Natural Resources says.

The DNR says it found hundreds of dead fish in the Fond du Lac area on April 24. Most of the dead fish were freshwater drum, or sheepshead, but there were also some carp, crappie, perch, largemouth bass and bluegill. DNR crews reported seeing dead sheepshead in other parts of the lake a few days later. On April 30, crews collected dead fish from the area of South Asylum Bay in Oshkosh and High Cliff State Park in Harrison. The DNR sent samples to the La Crosse Fish Health Center, a lab operated by the U.S. Fish & Wildlife Service.

On Wednesday, the DNR learned that the samples from Fond du Lac tested positive for viral hemorrhagic septicemia, a virus that affects fish. The DNR says the late winter and recent weather created conditions favorable for VHS, which has been found in lakes Winnebago and Michigan for more than a decade.

“This outbreak on Winnebago serves as a stark reminder to all anglers about the critical importance of disinfecting boats and gear when moving between bodies of water,” Kendall Kamke, fisheries team supervisor for the DNR at Oshkosh, said in a news release.

The DNR does not think the die-off will have an effect on the Lake Winnebago fishery. VHS is not known to be harmful to humans, the DNR says.

While the die-off is still under investigation, the DNR does not believe it is connected to the spill of titanium dioxide, a white-colored non-toxic substance, during a fire at an industrial plant in Oshkosh. Around the same time, the DNR says decaying blue-green algae, also white, was seen along Lake Winnebago's west shore. The DNR does not believe this was connected to the fish die-off, either.

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