HART, Mich. — Some of the thousands of common carp that died this summer in a western Michigan lake had a virus that until recently was not known to exist in the state’s waterways, officials said Thursday.
Between 2,000 and 4,000 adult common carp were killed in Oceana County’s Silver Lake in August, the Department of Natural Resources said. Sampling showed that some were infected with the fish virus koi herpesvirus, or KHV.
The presence of KHV was confirmed earlier this year during another fish die-off on Kent Lake in Oakland County. The virus had not been detected previously in any Michigan fish in the wild, although it turned up in 2003 at a private koi pond near Grand Rapids. Koi are ornamental carp varieties bred for use in aquariums and fish ponds.
KHV is known to affect only koi, common carp and goldfish, the DNR said. It doesn’t harm other fish species or humans.
Officials are investigating how the virus got into the Michigan Lakes. It probably happened when ornamental fish escaped or were released, the DNR said.
“While there are no treatments for this disease, the DNR is evaluating the next steps to manage this pathogen,” said Gary Whelan, DNR fish production manager.
KHV is transmitted from one fish to another and usually causes disease outbreaks only in waters 60 degrees or warmer.
Lab analysis is needed to confirm the presence of KHV because it’s easily confused with other diseases, the DNR said. Symptoms include bloody patches on the fish’s sides, lethargic swimming on the water’s surface, sunken eyes and deteriorating gills. Infected fish may survive and become carriers.
The outbreak is another illustration of the need to avoid spreading exotic species in waterways, said Jim Dexter, the DNR’s acting fisheries division chief.
“Anglers should clean their boats, disinfect their gear and not move live fish to reduce the possibility of any fish diseases being transferred to new locations,” Dexter said.
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