Zebra mussels have been found in Clear Lake, in Riding Mountain National Park.
While conducting a visual survey on July 17, Parks Canada snorkellers found a partial shell and one living, adult-sized zebra mussel attached to a rock.
As well, they say water samples taken from Boat Cove between June 19-27, also tested positive for environmental DNA from zebra mussels.
Parks Canada staff continue to focus on taking steps to prevent the spread of the aquatic invasive species.