The Minnesota Department of Natural Resources (DNR) is blaming the illegal introduction of nonnative ornamental goldfish for large numbers of dead carp washing up on the shores of Lake Byllesby near Cannon Falls.  The virus from the koi goldfish has also been found in eight other southern Minnesota Lakes over the past year.

Both the DNR and Minnesota Aquatic Invasive Research Center labs showed the fish died from infection with the koi herpes virus, which only afflicts carp and koi.  Koi has been raised in East Asia for centuries and kept by some people in aquariums and outdoor ponds.  The virus cannot be transferred to humans or other animals.

Koi fish have beautiful colors.  The actual name is Nishigoi, the colored variety of the Amar Carp and it is believed these fish date back to the early 19th century in Japan.

Koi can grow up to 3 feet and weigh 40 pounds.  They live 25 to 35 years and are descendants of common Carp.  They were originally brown and through selective breeding by Japanese numerous colors and patterns were developed.

In the 17th century Chinese rice farmers kept carp in their rice paddies and the practice found it's way to Japan.

The DNR said that the pathogen affects the skin and gills of the fish but it cannot be transferred to humans or other animals. The agency added that releasing pet or ornamental fish into the wild is illegal.

Koi Fish in an Indoor Pond. photo
Koi Fish in an Indoor Pond. photo

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