LANSING — State fisheries officials are tracking a new fish virus found in Michigan waters this year that has resulted in two carp die-offs.
Officials recently confirmed a Koi herpes virus is responsible for the die-off of an estimated 2,000-4,000 adult common carp in Oceana County’s Silver Lake in August. The die-off is the second this year after a June outbreak in Kent Lake in Oakland and Washtenaw counties that killed several hundred carp.
“It is not likely it has been here very long,” said Gary Whelan, fish production manager for the state Department of Natural Resources. “We don’t know how widespread it is across the state. Our best guess is it probably came from someone releasing ornamental fish into our waters.”
Officials said the Koi herpes virus, also known as KHV, was first detected in Michigan in a private Koi pond near Grand Rapids in 2003, and officials removed those fish. In 2007 and 2008, the virus was responsible for large scale common carp die-offs in Ontario, Canada, Whelan said.
“We know it has been showing up in the Great Lakes region recently,” he said.
KHV is thought to only affect common carp, goldfish and Koi, and there are no known human health effects.
Outbreaks of the virus have been found around the world, Whelan said. It is an internationally reportable disease and is causing concerns among large scale production facilities in Japan and Germany that sell the fish for food or the aquarium trade, he said.
Michigan reported the recent outbreaks to the World Animal Health Organization.
DNR fisheries biologist Richard O’Neal said officials “didn’t see any significant die-off of any other species in (Silver Lake)” in August when thousands of carp began to wash ashore.
“The fish were dying slowly, coming up on shore, and then they were blowing from one side of the lake to the other. It was obvious that the primary species being affected was carp, and that was the first time that I’ve seen that before,” O’Neal said. “We did find many of the other species like walleye, bass, perch and suckers that did not have any visual signs of the disease.”
Those signs include bloody patches on the fish’s sides, lethargic swimming on the surface, sunken eyes and deteriorating gills. Some fish survive and become a carrier to other fish, although outbreaks are typically restricted to waters above 60 degrees Fahrenheit, according to a DNR press release.
The outbreaks have not resulted in any swimming closures or other restrictions on Kent or Silver lakes, officials said.
“It’s kind of a nuisance … but that’s mostly what it is,” O’Neal said, adding that common carp are an invasive species in Michigan.
“I think the only question we have, since this is a new virus to Michigan, is if it will affect any other minnow species, because carp is a minnow species,” O’Neal said.
Whelan said current research suggests it is unlikely to spread to other fish.
Steve Winters, president of the Bowfishing Association of Michigan, said a bowfishing tournament was in the works for Kent Lake before the virus was detected, but was canceled because of the outbreak.
He said KHV is “kind of a double-edged sword” for bowfishermen.
“In one aspect, it’s good because … that’s what we do, try to rid the lakes of these fish,” Winters said. “You don’t want the carp, but from a bowfisherman’s perspective it does take away some opportunity.”
Winters said he suspects Silver and Kent lakes may respond similarly to those frequented by bowfishermen, where other species like bluegills and perch are thriving with fewer carp.