Testing to date finds no new evidence of zebra mussels in Clear Lake

Parks Canada said recent testing at Clear Lake has so far shown zero new DNA evidence of zebra mussels, after all boats and aquatic vehicles were banned from the popular lake earlier this year.

Parks Canada said that as of June 10, water samples taken from high-priority areas in Clear Lake, located in the Riding Mountain National Park, have tested negative for zebra mussel environmental DNA (eDNA).

“On June 3, a Fisheries and Oceans Canada dive team completed visual surveys of the main pier, Clear Lake Marina, and the shoreline extending from the main pier to the Boat Cove,” Parks Canada said.

“So far, no zebra mussels have been found.”

[caption id="attachment_756336" align="alignnone" width="1000"] A cluster of zebra mussels is seen in this image from the Nelson River in northern Manitoba. Parks Canada said recent tests for evidence of zebra mussels at Clear Lake showed zero new DNA evidence of the invasive species, and said they will continue to test for zebra mussels at Clear Lake throughout the summer. Manitoba Hydro [/caption]

Parks Canada added that testing for evidence of invasive zebra mussels will continue throughout the summer, after evidence of the species was first discovered in the lake during tests conducted last summer, and later confirmed by further testing.

“The likelihood of detecting zebra mussels increases as the water temperature warms,” Parks Canada said.

“Considering multiple positive tests for zebra mussel eDNA in Boat Cove throughout the summer of 2023, and the collection of live adult zebra mussels in the same area in November 2023, precautionary measures are being taken to contain and isolate the potential spread of zebra mussels in Clear Lake.”

There are also plans for containment curtains to be installed around Boat Cove and on the pier at Main Beach at Clear Lake, as Parks Canada said the curtains increase the likelihood of zebra mussel detection, by stopping lake currents and wind-generated flows.

[caption id="attachment_763999" align="alignnone" width="1000"] The Riding Mountain National Park visitor centre in the town of Clear Lake as seen in June 2024. Winnipeg Sun photo[/caption]

In early May, Parks Canada announced personal watercraft, including non-motorized items such as canoes and standup paddle boards, would not be allowed on Clear Lake this summer, as they feared they could help to spread zebra mussels, which often attach themselves to watercraft.

If zebra mussels are detected, Parks Canada said they will consider using potash molluscicide treatment to eradicate them, and said plans would be widely communicated before moving forward. They added it is considered safe for people to swim in lakes where that type of potash treatment is taking place.

Adult female zebra mussels are known to reproduce at a rapid rate, as they can typically produce 30,000 to 40,000 eggs in each reproductive cycle, and over 1 million eggs in a single year.

They can be harmful to Manitoba waterways, as they are known to deplete native fish populations, and they can be sharp and a nuisance when they wash up on shores and beaches, and they can cause damage to boats and other aquatic vehicles, as they clump and can clog engine parts and machinery.

— Dave Baxter is a Local Journalism Initiative reporter who works out of the Winnipeg Sun. The Local Journalism Initiative is funded by the Government of Canada.

Dave Baxter, Local Journalism Initiative Reporter, Winnipeg Sun