Minnesota conservation officials are blaming the illegal introduction of nonnative ornamental goldfish for large numbers of dead carp washing up on a lakeshore south of the Minneapolis area.
The Minnesota Department of Natural Resources says a virus from the koi goldfish also has been found in at least eight other southern Minnesota lakes in the past year.
The investigation began after dead fish began showing up on Lake Byllesby near Cannon Falls. Both the DNR and Minnesota Aquatic Invasive Research Center labs showed the fish died from infection with the koi herpes virus, which only afflicts common 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 to other animals.