Large numbers of dead carp washing up on the shores of Lake Byllesby near Cannon Falls are the result of a virus that only affects common carp and koi, and are not a cause for public concern, according to the Minnesota Department of Natural Resources.
After receiving recent reports of dead fish showing up on the lake, staff at the DNR's Lake City fisheries office collected samples and sent them to the DNR's pathology lab and to the Minnesota Aquatic Invasive Research Center at the University of Minnesota. Both laboratories confirmed that the fish died as the result of being infected with the koi herpes virus (KHV), which only affects common carp and koi, an ornamental member of the carp family kept by some people in aquariums and outdoor ponds.
KHV kills carp by damaging their gills and skin. It cannot be transferred to humans or to other animals. The virus has been found in several other lakes in southern Minnesota over the past year, including Jonathan, Washington, Elysian, Tetonka, Gorman, Dora, Sabre and Cottonwood. The University's Aquatic Invasive Research Center is conducting studies to determine whether the virus might have utility as a control mechanism for common carp, which can cause serious damage to aquatic ecosystems.
KHV likely found its way into Minnesota waters by the release or escape of ornamental koi or pet goldfish. Releasing ornamental fish into the wild is illegal and can upset the balance of natural systems.
Fish kills can be reported to the state duty officer by calling 651-649-5451 or 800-422-0798. Most such occurrences this time of year are due to natural processes, not contaminants. Property owners with dead fish on their shoreline can bury them or leave them for other wildlife to consume. The DNR does not collect and remove dead fish.