The fish disease VHS has been confirmed as the cause of a large fish kill of mostly sheepshead in Lake Winnebago in April.
“We’ve received final lab test results from the La Crosse Fish Health Center confirming that VHS caused the fish kill,” says Kendall Kamke, DNR fisheries supervisor in the Oshkosh area. “Results for all fish species tested were positive for VHS and negative for all other common fish pathogens.”
A DNR fisheries biologist first responded to reports of dead fish in the Fond du Lac area on April 24 and found hundreds of dead fish, mostly sheepshead, as well as common carp, black crappie, yellow perch, largemouth bass and bluegill.
Time of year, lake conditions and the behavior of the affected fish suggested VHS, short for viral hemorrhagic septicemia, as a possible cause. Additional samples were collected as reports of dead and dying fish started coming in from just north of Oshkosh and on the north end of Lake Winnebago.
A total of 60 drum, seven black crappie, and one each of yellow perch, bluegill and largemouth bass collected from the lake at Fond du Lac, Oshkosh and High Cliff were sent to La Crosse for pathogen testing.
VHS is a deadly virus of fish which does not affect people who handle infected fish or want to eat their catch. VHS does, however, pose a threat to more than 25 Wisconsin fish species including musky, walleye, yellow perch and northern pike.
The virus has been detected in lakes Michigan and Winnebago for more than a decade. Most recently, the fish disease was associated with 2018 fish kills of gizzard shad in Port Washington Harbor on Lake Michigan and in the Menomonee River in Milwaukee County.
Kamke does not expect the die-off to have a significant effect on the Winnebago fishery. But the confirmation that VHS caused the fish kill is an important reminder to all anglers about the critical importance of disinfecting boats and gear when moving between bodies of water, he says.
“This time the fish kill was confined to mostly sheepshead on the big lake – next time we might not be so lucky. VHS could affect our walleye when they are concentrated on the marshes during spawning. We can’t get lax about following the safeguards.”
Rules for preventing the spread of invasive species and pathogens require that boaters do not transfer water, fish or vegetation from one body of water to another. Drying or disinfection of boat and gear is recommended before moving between waterbodies. More information is available by searching the DNR website, dnr.wi.gov, for “boat transportation and bait laws.”