Live zebra mussels have been found in Riding Mountain National Park in Manitoba/Jennifer Bain

Parks Canada has found live zebra mussels — an aquatic invasive species — at Boat Cove on Clear Lake in Riding Mountain National Park.

The boat launch area of the Manitoba park is closed until 2024. Parks Canada is working with partner organizations to analyze these results and promises to share more details and hold public meetings.

Zebra mussels don’t harm humans but can significantly affect aquatic biodiversity. These small, clam-like aquatic animals native to Eastern Europe and Western Asia. They are 0.4 to 1.2 inches long, have triangular or “D” shaped shells, and most have light and dark brown bands on their shells.

Last January, Parks Canada was notified that one water sample taken in August 2022 tested positive for mussel eDNA. In November, preliminary test results from water samples collected from Clear Lake throughout the summer indicated the presence of environmental DNA (eDNA) for zebra mussels throughout the season. Staff then conducted further monitoring and sampling and confirmed the presence of live zebra mussels.

It’s the first time that zebra mussels have been found in Riding Mountain.

Zebra mussels were discovered in Lake Erie in the mid-1980s. They were accidentally transferred from their native range by cargo ships. Within a decade, the mussels had spread throughout the Great Lakes and many inland water bodies in the Mississippi watershed to the Gulf of Mexico. They have now spread to hundreds of other water bodies, mainly in eastern North America.

Parks Canada says zebra mussels aggressively invade new areas and reproduce quickly since females produce upwards of one million eggs per year. They colonize almost any hard underwater surface, including watercraft hulls, and can interfere with engine cooling systems. They threaten native fish and wildlife by reducing algae and food resources at the base of the food chain.

Zebra mussels are a costly nuisance to boaters, commercial fishers, anglers and beach-goers. They can reduce recreational potential by littering beaches with sharp shells and producing foul odors from decaying, dead zebra mussels.

Adult zebra mussels can survive out of water up to 30 days depending on temperature and humidity. Zebra mussel veligers (larvae) aren't visible to the naked eye and can survive in very little water.