Another adult zebra mussel found in Clear Lake, suggesting invasive species is established in Riding Mountain

Parks Canada found another adult zebra mussel in Manitoba's Clear Lake this week, suggesting the invasive species has further established itself in the largest body of water in Riding Mountain National Park.

Parks Canada snorkellers conducting a visual survey on Wednesday near Boat Cove on Clear Lake found one living, adult zebra mussel attached to a rock and one partial shell, the federal agency said in a news release Friday.

Water samples collected from this area of lake from June 19 to 27 also tested positive for environmental DNA from zebra mussels, Parks Canada said.

"This evidence shows zebra mussels are building a presence in Clear Lake," the statement says.

Parks Canada plans to install an impermeable curtain around Boat Cove during the week of July 22 in an effort to seal off the area from the rest of Clear Lake.

"The containment curtain is not expected to impact the operations of the tour boat the Martese, or the ability of park visitors to use the lake for swimming or fishing," Parks Canada said. "The temporary watercraft management measures for Clear Lake remain in place."

The federal agency has not yet decided whether to deploy potash in an effort to eradicate zebra mussels from the area.

"Parks Canada will review the evidence and determine the best course of action as this information becomes available. Any decision will be widely communicated before actions are taken.

"Health Canada considers open-water potash applications at concentrations needed to kill zebra mussels safe for swimming."

Winnipeg South Liberal MP Terry Duguid, a special adviser to the federal government on water, said he believes chemical treatments could still eradicate zebra mussels from Clear Lake.

"There is at least a shot at it. Parks Canada made a unpopular but prudent decision to restrict watercraft on the lake and otherwise zebra mussels could be throughout the lake and containment would be impossible," Duguid said in a telephone interview from Ottawa.

Duguid said Parks Canada will say more about treatment options next week.

Ashley Smith, who owns and operates the Turtle Village tourist accommodations near the Wasagaming campground, said in an interview she's concerned about the effects of potash treatment on Clear Lake.

Smith said her bookings are down this year since Parks Canada closed the lake to outside watercraft.

Duguid said overall visitation numbers at Clear Lake are up over last year.

Parks Canada first found live zebra mussels in Clear Lake at Boat Cove in November. The decision to ban outside watercraft was made this spring.