Last November, researchers at Manitoba’s Riding Mountain National Park made a discovery they had been dreading for years.

In the shallow waters of Clear Lake, the park’s crown jewel, they found a piece of rope coated in a clump of 48 living zebra mussels — one of the most ecologically devastating aquatic invasive species in the country.

Parks Canada had been monitoring the lake for evidence of the fingernail-sized mollusks since 2011. Traces of zebra mussel DNA were first confirmed earlier that year, raising alarm among park staff, local leaders and residents. But finding living mussels triggered an emergency response. 

“The game changed a lot that day,” Dameon Wall, Riding Mountain National Park’s media relations manager, says in an interview. 

Riding Mountain National Park: an expansive forest canopy tinged in autumn yellows under a big sky with a trail winding in the foreground
Riding Mountain National Park is approximately 250 kilometres northwest of Winnipeg, and is home to the iconic Clear Lake. It’s also home to the westernmost known zebra mussels in Canada.

“There is a very small window, before those creatures become widely established throughout the waterbody, where it’s possible to have an intervention that entirely gets rid of them.”

A week before the May long weekend, Parks Canada issued a controversial edict banning recreational watercraft — including motorboats, kayaks, canoes and paddleboards — from Clear Lake for the 2024 summer season.

Riding Mountain National Park: Kayaks on a rack next to a tree under blue skies at the Clear Lake Marina along the pier in Wasagaming
In May, Parks Canada banned all recreational watercraft — including motorboats, kayaks, canoes and paddleboards — from Clear Lake for the 2024 summer season, prompting concern from businesses that rely on boating and tourism for income. Photo: Tim Smith / The Brandon Sun

The decision rocked local business owners and provincial politicians, who worry the ban will cripple the region’s tourism-dependent economy. 

But in the eyes of park staff, there’s a much greater risk on the horizon.

Zebra mussels have already invaded freshwater bodies across much of eastern Canada and the United States. Once they take hold in a waterbody, they’re nearly impossible to get rid of and have devastating impacts on tourism, infrastructure and the environment.

Clear Lake is the westernmost Canadian waterbody where live zebra mussels have been found. If a population becomes established, the ecological and economic impacts could spread across southwestern Manitoba and potentially over provincial borders. 

“The implications of a zebra mussel infestation here are not just for Clear Lake and are not just short term,” Wall says. “They are in essence permanent — or at least until the next Ice Age comes along — and they would be all the way from Clear Lake to The Forks and downtown Winnipeg.”

With millions of dollars and countless aquatic ecosystems on the line, invasive species experts believe the boat ban is a necessary tool in the fight for the health of Canada’s western waterways — even though not everyone is on board.

A devastating discovery by scientists working in Riding Mountain National Park

In the winter months after last November’s discovery, Parks Canada ecologist Tim Town, and a team of federal, provincial and First Nations scientists spent their days huddled in huts on the frozen Clear Lake.

The lake was divided into more than 200 sections, laid out in a honeycomb pattern and prioritized based on risk of zebra mussel exposure. In a methodically orchestrated relay, the inspection crews worked their way across the lake on the hunt for more evidence of zebra mussel DNA. 

First, navigation teams set up small heated shelters at predetermined co-ordinates. Then sampling teams, decked out in specialized equipment, drilled through the ice with augers, sunk stainless steel tubes (called kemmerers) to the bottom of the lake and extracted a mixture of water and sediment. 

Riding Mountain National Park: Two Parks Canada staff members in uniform collect samples from a hole in the ice inside a tent structure over a frozen lake
Last winter, federal, provincial and First Nations scientists spent their days huddled in huts on the frozen Clear Lake collecting samples to test for zebra mussel DNA. Photo: Supplied by Parks Canada

The samples were passed to the filtering teams, who worked out of a mobile lab never more than a few hundred metres from the sample site. At the lab, water samples were poured through a toonie-sized filter, similar to a coffee filter, which was then sealed, labeled and shipped to a federal laboratory in Winnipeg. 

Over a period of about 40 days, Town says the crews tested nearly three quarters of the lake, processing more than 1,000 water samples and sending nearly 600 filters to the lab. 

The winter testing program was “unprecedented,” according to Parks Canada. Typically, aquatic invasive species monitoring takes place in the summer, when water is easier to access and species are generally more active. 

But when a routine water sample taken in summer 2022 came back positive last year, parks staff decided to ramp up the testing regime. 

That one positive test, Wall says, “really caused a lot of concern for us.”

The first run of winter tests took place in the early months of 2023. All came back negative for zebra mussel DNA. 

As the ice melted, testing frequency increased. Samples were taken from 28 lakes in the Riding Mountain region. 

The 2023 summer season also came with new rules for boaters: anyone who wanted to use a boat in Clear Lake was required to get their vessel inspected by park staff, and attest the boat hadn’t been in any other lakes. Inspected boats were fitted with aluminum tags; if the boat was taken to any other water body, the tag would be removed and the boat could not come back.

“It was one lake, one boat,” Wall says.

Kayakers paddle through Clear Lake while a boat passes behind them in Riding Mountain National Park, with a densely forested shore in the distance
Last year, anyone who wanted to use a boat in Clear Lake was required to get their vessel inspected by park staff, and attest the boat hadn’t been in any other lakes. This year, boats are banned entirely from the lake, with a small handful of exceptions. Photo: Tim Smith / The Brandon Sun

In early November, the federal lab alerted Parks Canada that several samples taken from one of Clear Lake’s main boat launches, the aptly named Boat Cove to the west of the townsite’s beach, had tested positive for DNA. Park staff conducted a search. Their worst fears were realized upon discovery of the clump.

“It was no longer enough to just tag and seal your boat … we’re concerned now about transfer within the lake, we’re also concerned about the potential transfer out of the lake to other water bodies,” Wall says.

There are three exemptions to the ban: a commercial touring boat, a fishing and cultural-use vessel from Keeseekoowenin Ojibway First Nation, whose land borders the northwest corner of the lake, and Parks Canada’s research and emergency boats. The lake is still open for swimming, shoreline fishing and other recreational uses.

Riding Mountain National Park issued thousands of boat permits per year — until now

The pistol-shaped national park in Western Manitoba has long been a destination for cottagers, day-trippers and back-country enthusiasts. And for thousands of years prior, the land and the lake was considered sacred to Indigenous peoples.

For many visitors, Clear Lake and the bucolic townsite of Wasagaming, with its restaurants, ice cream shops, motels and sandy beach mixed among historic Parks Canada log buildings along the southern shore, are the main draws.

Which is why the boat ban hit so hard.

Concrete barriers block vehicle and boat access to the Wasagaming boat launch at Clear Lake in Riding Mountain National Park
Clear Lake is a main draw in Riding Mountain National Park and the boat ban has left businesses with no shortage of questions about impacts to this summer’s tourist season. Photo: Tim Smith / The Brandon Sun

Since news of the ban broke, much has been made of its potential impacts on the tourism-driven economy in Wasagaming and other towns surrounding the park. 

Manitoba Premier Wab Kinew expressed concern federal officials had made “a unilateral decision” without adequate consultation with local stakeholders.

Manitoba’s Economic Development, Investment and Trade Minister Jamie Moses wrote to the federal government pleading for a “balanced approach” that ensured both the health of the lake and economic stability of Wasagaming, and calling for financial support for industries that stood to lose out as a result of the ban.

In an interview, Moses says the province hasn’t studied the financial impact the boat ban could have this summer season. According to an impact assessment compiled by Parks Canada, the park is one of Manitoba’s most popular tourist destinations, seeing an average of 350,000 visitors and issuing between 8,000 and 9,000 watercraft permits each year.

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“A lot of folks are scared and worried about the lake, and knowing that puts into question the long term sustainability of tourism in that sector and what their future holds,” Moses says. 

Manitoba is leaving the responsibility to mitigate potential economic impacts of the boat ban in federal hands, but has increased its aquatic invasive species budget by $500,000, most of which will be spent on new cleaning and inspection stations.

Karly McRae owns several hospitality businesses in Wasagaming, chairs the region’s destination enrichment organization and has lived on the eastern edge of the park all her life. Her children are the fifth generation of her family to call the park home.

“This place is in my blood in every way you can imagine,” she says in an interview.

Riding Mountain National Park: A woman in a jacket stands looking at the camera in front of a log building with a sign reading "Lakehouse"
Karly McRae owns several hospitality businesses in Wasagaming and chairs the region’s destination enrichment organization. She has already experienced cancellations as a result of the boat ban. But, she says, “without a healthy lake, this community would be a very different place.” Photo: Tim Smith / The Brandon Sun

McRae spoke to media and politicians in the months leading up to the boat-ban decision, urging Parks Canada to hold off on banning watercraft until the impacts on the local business community were fully understood. Earlier this month, she told the Winnipeg Free Press uncertainty around the ban had already put a dent in the season’s bookings and prompted an increase in cancellations. But at the end of the day, McRae says, the health of the lake is her first priority.

“Without a healthy lake, this community would be a very different place.”

With no natural predators, as many as 700,000 zebra mussels can be found in one square metre

Despite their unassuming size, zebra mussels are capable of massive, ecosystem-wide impacts. The tiny mollusks, recognized by their striped shells, are considered among the 100 most invasive species across the globe. 

“It’s tough to understand sometimes because they’re so small — they’re about the size of your fingernail, a few millimetres long — but they can grow to such large population sizes within a lake,” says Scott Higgins, a research scientist at the International Institute for Sustainable Development’s Experimental Lakes Area in northwestern Ontario.

What sets zebra mussels apart is their ability to reproduce — fast.

A single female mussel can produce up to one million eggs per year. Their larvae, called veligers, float until they find a solid surface to cling to. With no natural predators, zebra mussel densities can reach up to 700,000 mussels per square metre. 

Millions upon millions of mussels feeding on vital phytoplankton, or microscopic algae, has a ripple effect all the way up the food chain, Higgins says. Algae is a main food source for microscopic invertebrate animals called zooplankton. In some lakes, zebra mussels outcompete the zooplankton, leading to steep population decline. Fewer zooplankton means less food available to smaller fish species that feed on the invertebrates, leading to collapse in fish populations. (As an example, the Pacific salmon population collapsed in Lake Huron, in part a result of zebra mussel infestation, causing long-lasting impacts to the local fishing industry.) 

“For a single species, they impact almost everything else in the food web,” Higgins says. 

While high populations of zebra mussels often improve water clarity by filtering out floating nutrients, the mussels are picky eaters and tend to avoid more toxic algaes, and can contribute to dangerous blue-green algal blooms. Those blooms have been associated with health risks to people and animals alike and can cause beaches to shut down entirely. 

Worse still, their tendency to cling to vital infrastructure like water intakes, irrigation pipes and power plants can create staggering maintenance costs. Manitoba Hydro spends some $2 million annually managing the impact of zebra mussels on plants in the Nelson River system. 

Ontario estimates invasive mussels costs the province $75 to $91 million each year. British Columbia, which has so far avoided the zebra-mussel plague, estimates the annual costs of an invasion could range between $64 and $129 million, including up to $12.5 million in tourism losses, $92.5 million in infrastructure costs and $30 million in lost property values.

Tiny zebra mussels hitchhike with human boaters and spread westward

“What’s really fascinating and why zebra mussels are such a poster child of an invasive species is their capacity to move between lakes that are not connected otherwise,” Higgins says.

Their main mode of transport? Hitchhiking with humans.

Because veligers — the larvae — are impossible to see with the naked eye, they can sneak onto boat hulls, trailers or anything else that spends time submerged in water. Mussels and veligers have been known to survive long periods in bilge water, or attached to plants and other organic matter tangled onto boats and trailers. Adult zebra mussels can survive for several days outside of the water, allowing them to wait out a boater’s journey from one lake to the next. 

Native to the Errol and Black seas of Europe, the first zebra mussel in North America was found at a port in Lake Erie in the 1980s. It’s assumed the mussel hitched a ride in the ballast water of a trade ship docking in ports along the St. Lawrence. Within a decade, they had spread across all five Great Lakes and into the Mississippi River. 

Map of North America showing red dots where zebra mussels have been spotted, concentrated in the east but starting to appear in the west as well

The first zebra mussels in Manitoba were detected at the south basin of Lake Winnipeg in 2013. According to Higgins, it’s not likely the mussels crossed the border from Ontario; the Canadian Shield lacks the calcium levels zebra mussels need to survive in large numbers, and serves as a bit of a buffer zone between the Great Lakes and the West. Instead, the mussels are believed to have traveled downstream on the Red River from the United States. 

By 2021, the mussels had spread to the Hudson Bay, infesting nine major provincial waterbodies, including Lake Manitoba, Lake Winnipeg and the Red and Nelson Rivers.

“Saskatchewan, Alberta and British Columbia are looking at Manitoba right now going: ‘I really hope you guys deal with this, because we don’t want this spreading into our province as well,’ ” Higgins says. 

Clear Lake offers the perfect habitat for zebra mussels. The pH is just right, the calcium levels are ideal, and there are plenty of hard surfaces to cling to.

If mussels start spreading through the water system, Wall says, the impacts could reach recreational spots along the Little Saskatchewan and Assiniboine rivers. Drinking water infrastructure, including Wasagaming’s treatment plant, would suffer. The water supply for Manitoba’s second largest city, Brandon, would be impacted if mussels hit the Assiniboine River. Flood mitigation infrastructure — notably the Portage diversion, built to protect Winnipeg from western flooding — would see maintenance costs skyrocket. 

For the seven First Nations with cultural, historical and traditional relationships to Clear Lake and Riding Mountain park, a permanent invasion would be devastating. 

“A traditional fishery on Clear Lake is a way of life, a practice to maintain our culture, ceremonies, ancestral teachings and traditions, and to exercise our responsibilities towards the lake and the beings within,” Keeseekoowenin Ojibway First Nation Chief Dwayne Blackbird wrote in a statement. “We fish to feed our people, as we have done at Clear Lake for centuries.”

Riding Mountain National Park is not alone in boat bans

Management and prevention strategies have focused on changing human behaviour. Governments across the country — including Manitoba — have adopted “clean, drain and dry” messaging urging boaters to decontaminate and dry out their watercraft to avoid spreading invasive species. 

Many provinces provide funding for boat cleaning stations at popular recreation spots. Some mandate boaters stop at provincially run inspection stations before launching in new waters. Many have begun restricting — or banning — boat access altogether.

Singush Lake, in Manitoba’s Duck Mountain Provincial Park, restricts boat access to cottage owners, who must agree to not launch their vessels anywhere else.

Riding Mountain National Park: A row of kayaks for rent at Cycle Creek Outdoor Supply in Wasagaming
Riding Mountain National Park is not alone in its decision to ban boats at Clear Lake. Similar decisions have been undertaken in other parks across the country as fears of invasive mussels grow. Photo: Tim Smith / The Brandon Sun

In 2019, Waterton Lakes National Park in Alberta’s southwest corner instituted a 90-day quarantine for all motorized boats entering the park, including its iconic chain of lakes. In April, Parks Canada announced it was expanding restrictions, prohibiting anyone from bringing non-motorized boats into the park, including inflatable kayaks, paddleboards and canoes. In its decision, Parks Canada cited the risks of zebra and quagga mussels, whirling disease and Eurasian milfoil.

National parks like Yoho and Kootenay, in British Columbia’s Rocky Mountains, have gone a step further — opting this spring to shut down lakes to boating and fishing altogether.

Other popular national parks like Banff and Jasper have not yet enacted boating bans, but require visitors to fill out a permit each time they launch a canoe, kayak, paddleboard or an inflatable toy in a lake or river. 

Fines for breaching rules can range from under $200 to more than $2,500 in Manitoba. Alberta changed its legislation in 2015 to make it mandatory that a driver transporting a boat of any kind to stop at any watercraft inspection station, along with fines up to $100,000.

Boat rules aimed at curbing the spread of invasive species also extend beyond Canada’s borders, with mandatory inspection programs existing from Yellowstone to the Adirondacks and from state parks in Wyoming to Arizona. But these restrictions aren’t enough to satisfy Canadians worried about invasive species spreading from south of the border. Last year, the Okanagan Basin Water Board in B.C.’s Okanagan region, called on the provincial government to ban U.S. boats from crossing the border to stop the spread of zebra mussels.

The idea is clear: stop boating now, or zebra mussels will ruin boating in the future.

Business owners in Riding Mountain National Park hopeful for a future that includes boats on Clear Lake

Like many business owners in Wasagaming, McRae feels Parks Canada should have done more to communicate the impact of management strategies like a boat ban. 

According to Wall, the agency held two town hall meetings last fall, an online information session in January and conversations with provincial and municipal leaders, local businesses, environmental groups, anglers, cottagers, cabin owners and First Nations leadership. 

McRae says the community found out about the watercraft restriction through the media. 

Going forward, she hopes to see Parks Canada, the provincial government and other stakeholders working together to find long term, cross-jurisdictional solutions that will protect Clear Lake, the surrounding water bodies and the park’s attractiveness as a tourism destination. 

In a letter to Parks Canada earlier this year, Christian Robin, the president of the Clear Lake Cabin Owners’ Association, said regardless of what decision was made for this summer, the organization “does not support a long-term vision of Clear Lake that does not include the ability to use watercraft.” 

Riding Mountain National Park: a man in sunglasses sits outside in the sun while working on a laptop with a coffee cup next to him
Christian Robin, the president of the Clear Lake Cabin Owners’ Association, thinks the future of Clear Lake should include the ability to use watercraft. Photo: Tim Smith / The Brandon Sun

Robin stressed the cabin association would support “the permanent implementation of stricter controls” such as one-boat, one-lake rules for all kinds of watercraft and increased education, communication and signage.

While McRae is not opposed to some restrictions on watercraft (her preference would also be a continuation of the one-boat, one-lake rule), she believes the federal government should co-ordinate with provincial staff to ensure the regulations can be successful. She also hopes to see all levels of government continue to tout Clear Lake and Riding Mountain park as one of the province’s jewels. 

“We’re fixated on this watercraft ban, but Riding Mountain National Park is over 3,000 square kilometres of basically untouched wild country,” she says.

“Without presenting how incredible this place is to Canadians, it’s very hard for them to value it and want to protect it.”

Boat bans can help contain outbreaks: Parks Canada

According to Parks Canada, all of the samples from this year’s winter testing program on Clear Lake came back negative.

While that’s hopeful news, Town, the Parks Canada ecologist, says it’s too soon to rule out the possibility of a growing mussel population. 

“We might not have hit a zebra mussel right on the head, but it allows us to determine that the lake’s not totally infested with zebra mussels,” he says. “We have reason to believe that the population is fairly isolated at this point.”

Riding Mountain National Park: Posters tacked to a bulletin board with information about "Aquatic Invasive Species: What you need to know" from Parks Canada
Parks Canada is hopeful the public will understand that this year’s boat ban should ultimately help preserve Clear Lake for future enjoyment. Photo: Tim Smith / The Brandon Sun

If that’s true, it’s a positive sign. Isolated mussel outbreaks can be contained and, if caught in time, eradicated. 

Canada approved potash as a pesticide treatment for zebra mussels in 2022. The potassium in potash is safe for humans, but kills sensitive zebra mussels. (A downside: potassium will kill native freshwater mussels too, Higgins says.) The mussels can also be eliminated with benthic mats — essentially large tarps — that starve the mussels of oxygen and nutrients over a period of several months. 

The biggest barrier to treating water bodies for zebra mussels is cost. The more the mussels spread, the more expensive treatment gets. Wall says it would cost upwards of $500 million to treat the entirety of Clear Lake, but a small infestation can be managed in a cost-effective way. 

Town says it’s too early to tell whether the population is as contained as park staff hope, or what exact eradication measures the department will take. But limiting the potential for further spread will help make eradication decisions a little easier.

That’s where the boat ban comes in.

Wall says the economic implications of banning recreational boating aren’t lost on park staff. But having boats travel through the lake increases the risk of mussels expanding from the isolated area around Boat Cove, exacerbating an already expensive eradication effort and threatening the health of downstream water bodies. 

“It’s important for everybody to remember that if zebra mussels become established in this lake there are permanent economic and ecological impacts that will have to be borne every single year,” he says. “We know people come to Clear Lake to make memories, and we’re here to help them with that. It’s just going to look a little different this year.”

Clear Lake: Visitors to Riding Mountain National Park walk along the Clear Lake pier in Wasagaming on a calm and sunny Thursday.
“We know people come to Clear Lake to make memories, and we’re here to help them with that. It’s just going to look a little different this year,” Tim Town, an ecologist with Parks Canada, says. Photo: Tim Smith / The Brandon Sun

Clear Lake is still open to the public and other lakes in the park are accessible to boaters. The park’s many biking, hiking and horseback riding trails are open too. 

The boating restrictions are temporary measures, he stresses. If new data shows it’s safe to re-open the waters, Parks Canada will reevaluate the rules.

In the meantime, Wall says park staff feel the weight of their responsibility, not only to Clear Lake, but to the many interconnected waters it touches.

“I cannot hear that this is a lost cause,” he says. “I just can’t take it. We have to try.”

Like a kid in a candy store
When those boxes of heavily redacted documents start to pile in, reporters at The Narwhal waste no time in looking for kernels of news that matter the most. Just ask our Prairies reporter Drew Anderson, who gleefully scanned through freedom of information files like a kid in a candy store, leading to pretty damning revelations in Alberta. Long story short: the government wasn’t being forthright when it claimed its pause on new renewable energy projects wasn’t political. Just like that, our small team was again leading the charge on a pretty big story

In an oil-rich province like Alberta, that kind of reporting is crucial. But look at our investigative work on TC Energy’s Coastal GasLink pipeline to the west, or our Greenbelt reporting out in Ontario. They all highlight one thing: those with power over our shared natural world don’t want you to know how — or why — they call the shots. And we try to disrupt that.

Our journalism is powered by people just like you. We never take corporate ad dollars, or put this public-interest information behind a paywall. Will you join the pod of Narwhals that make a difference by helping us uncover some of the most important stories of our time?
Like a kid in a candy store
When those boxes of heavily redacted documents start to pile in, reporters at The Narwhal waste no time in looking for kernels of news that matter the most. Just ask our Prairies reporter Drew Anderson, who gleefully scanned through freedom of information files like a kid in a candy store, leading to pretty damning revelations in Alberta. Long story short: the government wasn’t being forthright when it claimed its pause on new renewable energy projects wasn’t political. Just like that, our small team was again leading the charge on a pretty big story

In an oil-rich province like Alberta, that kind of reporting is crucial. But look at our investigative work on TC Energy’s Coastal GasLink pipeline to the west, or our Greenbelt reporting out in Ontario. They all highlight one thing: those with power over our shared natural world don’t want you to know how — or why — they call the shots. And we try to disrupt that.

Our journalism is powered by people just like you. We never take corporate ad dollars, or put this public-interest information behind a paywall. Will you join the pod of Narwhals that make a difference by helping us uncover some of the most important stories of our time?

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