The North Dakota Game and Fish Department has confirmed the presence of invasive zebra mussels in Twin Lakes, LaMoure County, after a local cabin owner reported adult mussels attached to a floating log.

Aquatic nuisance species coordinator Ben Holen said follow-up sampling found more zebra mussels attached to woody debris. In addition, Game and Fish Department ANS staff processed plankton tow net samples collected from Twin Lakes June 22, and zebra mussel veligers were detected in those samples indicating a breeding population of mussels within the lake.

The 1,735-acre lake is a popular fishing destination located a few miles north of LaMoure. Twin Lakes is located approximately six miles from Lake LaMoure, which had a confirmed finding of zebra mussels in 2020.

“This situation is yet another example of the importance for all water enthusiasts including boaters, anglers and skiers, to be aware of aquatic nuisance species and to take all precautions to prevent their spread,” Holen said.

Prevention is the best way to avoid spreading ANS. They often travel by “hitchhiking” with unsuspecting lake-goers.

“Always clean, drain and dry boats and other equipment before using another lake,” Holen said. “Also, don’t transfer lake water or live fish to another body of water. This can help stop the spread of not only zebra mussels, but most aquatic nuisance species that may be present.”

Twin Lakes is now considered a Class I ANS Infested water, joining Lake LaMoure, Lake Ashtabula, the lower portion of the Sheyenne River, and the Red River in this designation. Emergency rules will go into effect immediately to prohibit the movement of water away from the lake, including water for transferring bait. Notices will be posted at lake access sites and ANS watercraft inspections will be increased at Twin Lakes.

Zebra mussels are dime-sized mollusks with striped, sharp-edged, two-part shells. A large female zebra mussel can produce one million eggs, and then fertilized eggs develop into microscopic veligers that are invisible to the naked eye. Veligers drift in the water for at least two weeks before they settle out as young mussels which quickly grow to adult size and reproduce within a few months.

Zebra mussels are native to the Black and Caspian seas of western Asia and eastern Europe and were spread around the world in the ballast water of cargo ships. They were first discovered in North Dakota in 2015 in the Red River.