The North Dakota Game and Fish Department has confirmed zebra mussels in Lake Ashtabula, north of Valley City.
Lake Ashtabula is a reservoir on the Sheyenne River.
Aquatic nuisance species coordinator Jessica Howell said an angler discovered the mussel, and turned it into Game and Fish She says it was an adult. And Howell said subsequent tests show the lake is fairly-well infested.
"On the buoys we found multiple life-stages," Howell said. "We found larger adults and some smaller 'settlers' that were likely from last fall."
Howell estimates the larger adults are about 18 months old.
"That tells us they've been there for about two years, at least," Howell said.
Howell said there's no way to know how the mussels got there, and there is no known method to completely rid a lake of zebra mussels. She said people who use the lake should be aware of this.
"If anyone is out there fishing, boating, swimming or just enjoying nature, if you find anything out of place, please report it to Game and Fish," Howell said. "I'd rather sort through 100 reports of things that turn out not to be an aquatic nuisance species, than miss that one report."
Howell said the second lesson from this is -- treat every water as if it could be contaminated.
Howell said this is also affecting the Baldhill Dam National Fish hatchery and the Valley City National Fish hatchery.
"We were getting ready to stock out walleye," Howell said. "But all of those walleye (from those hatcheries) will go back into Ashtabula now, because we don't want aquatic nuisance species to spread."
Zebra mussels have also been found in the Red River.