Common carp dying in Rock River

Rare water virus killing off carp and koi

MADISON, Wis. — A virus that is new to Wisconsin waters and affects common carp and koi is likely to blame for two carp die-offs in Dodge County in recent days.

Laura Stremick-Thompson, a fisheries biologist serving Dodge and Jefferson counties, said DNR began investigating the first die-off on July 21 in the state and federal waters of Horicon Marsh and Lake Sinissippi.

An investigation is now underway following reports from Thursday of dead and dying carp in Silver Creek, a tributary to the Rock River in Watertown approximately 42 miles downstream from the Hustisford dam.

“The public is not at risk from the koi herpes virus and from what we have seen in other states, sport fish and forage fish such as shiners have not been harmed,” Stremick-Thompson said. “However, DNR encourages use of protective clothing such as gloves in removing the dead carp due to other bacteria the fish may be hosting.”

Given the dense carp population in the Rock River system, DNR biologists anticipate the disease will continue its advance in the days and weeks ahead. Additional carp die-offs may occur until water temperatures begin to cool with the onset of fall.

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