City prepared for arrival of zebra mussels to lake that provides water supply

Zebra mussel larva detected in Shoal Lake Jon Hendricks on whether the discovery of a zebra mussel larva in Shoal Lake is cause for concern and how the city has been handling it.

The City of Winnipeg has been contacted after a single, microscopic zebra mussel larva was found in a sample of water taken from Shoal Lake, the lake straddling the Manitoba-Ontario border that Winnipeg’s water supply is drawn from.

"The quality and safety of our water is not compromised. That's an important thing to point out right now," said Winnipeg Mayor Brian Bowman Tuesday. "But is it something we need to be working with provincial counterparts, the Province of Ontario? Absolutely."

Zebra mussels are an invasive species that can clog drinking water supply pipes and threaten lake wildlife, among other harms. A single adult zebra mussel female can produce a million offspring a year.

The Provinces of Ontario and Manitoba announced the discovery Monday in a joint news release, saying the larva, called a veliger, was detected in a sample taken in August 2018 near a public boat launch at Clytie Bay.

The water sample was one of six and officials said just because a single larva has been found, doesn’t mean zebra mussels have colonized the lake.

The news release said water quality data from Shoal Lake will be reviewed to help figure out the risk of zebra mussels proliferating, and Ontario and Manitoba are working together to explore options to further prevent the spread.

The Shoal Lake 40 First Nation and the Iskatewizaagegan Independent First Nation have been contacted along with the city and other stakeholders and users of the lake.

City of Winnipeg has been planning for arrival

In some cities zebra mussels have clogged water intake pipes, and the city said it’s been planning for the mollusk species’ arrival since the 1990s.

"This is a maintenance issue," said Tim Shanks, water services manager for the City of Winnipeg. "It's a physical supply issue."

The City of Winnipeg’s intake system at Shoal Lake includes a control system which can use chlorine to eliminate the invasive species.

"We can operate that chlorination system given short notice," said Shanks. "But our long term plan would be to revisit that design and upgrade it."

Preliminary design work on a more efficient and automated system is already done. The city estimates it would cost about $1.3 million dollars for the capital upgrade. Construction could begin in 2022.

A zebra mussel expert said it still isn't 100 per cent certain the system will be called on to combat zebra mussels in Shoal Lake.

"In Manitoba we have Cedar Lake, and we have found a veliger in that lake," said Candace Parks, an aquatic invasive species specialist with the Province of Manitoba. "But we have yet to find an adult. And we found that veliger in 2015.

Help stop the spread

Parks says it will take years of monitoring to determine if zebra mussels have truly established a home in Shoal Lake, and so officials will be watching. Boaters, fishers and recreational water users have a role to play as well.

Zebra mussels spread from one body of water to the next by hitching rides on boats, boat trailers and other watercraft. People are asked to clean, drain and dry all watercraft equipment and surfaces before putting them in another body of water, as well as dispose of bait properly.

In Manitoba, people have a legal responsibility to ensure watercraft are clean, dry and free of aquatic invasive species. Set fines for aquatic invasive species offences range from $174 up to $2500.

-With files from CTV’s Jon Hendricks