DNR blames large fish kill near Twin Cities on illegal release of ornamental goldfish

The introduction of nonnative ornamental goldfish is the suspected cause of large numbers of dead carp washing up on a lakeshore just south of the Twin Cities, according to state conservation officials.

A virus from the koi goldfish also has been found in at least eight other southern Minnesota lakes in the past year, the state Department of Natural Resources (DNR) said Friday.

Reports of dead fish showing up on Lake Byllesby near Cannon Falls sent staff from the DNR’s Lake City fisheries office to the scene, where they collected samples and brought them to the agency’s pathology lab and to the Minnesota Aquatic Invasive Research Center at the University of Minnesota.

Both laboratories confirmed that the fish died from infection with the koi herpes virus, which only afflicts common carp and koi, an ornamental member of the carp family raised in East Asia for centuries and kept by some people in aquariums and outdoor ponds.

The virus kills carp by damaging their gills and skin. It cannot be transferred to humans or to other animals.

Other southern Minnesota lakes where the virus has been detected include Jonathan, Washington, Elysian, Tetonka, Gorman, Dora, Sabre and Cottonwood, the DNR said. The agency once caught a koi near Albert Lea that was 9 to 11 inches long.

The virus “likely found its way into Minnesota waters by the release or escape of ornamental koi,” a statement from the DNR read. “Releasing ornamental fish into the wild is illegal and can upset the balance of natural systems.”

The preferred solution for getting rid of unwanted living aquarium fish and plants is to donate them. Minnesota Sea Grant and the Minnesota Aquarium Society have for the past two years in the Twin Cities hosted the Habitatattitude Aquarium Fish and Plant Surrender. Click here to see when the next donation opportunity will be scheduled.

On the silver lining side of things, the U researchers are trying to determine whether the virus might be an option for controlling the carp population, which can cause serious damage to aquatic ecosystems.

Most fish kills this time of year are due to natural processes, not by outside forces, the DNR said.

Fish kills can be reported to the state at 651-649-5451 or 1-800-422-0798. Property owners with dead fish on their shoreline can bury them or leave them for other wildlife to consume. The DNR said it does not collect and remove dead fish.

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