YOHO, KOOTENAY NATIONAL PARKS – Parks Canada continues to investigate how extensive whirling disease is in Yoho and Kootenay national parks, prompting an extension of the closure of all waterbodies in the two parks until spring 2026.
Jeanette Goulet, aquatic invasive species regional coordinator for Parks Canada, said the agency is in the information gathering stage to determine the actual extent of the parasite in the two British Columbia national parks.
“We haven’t got our results from the lab back from our 2024 sampling, so we just don’t have that full picture yet,” she said.
“We want to have that information in hand before we make any further management decisions. That will give us time to get us results and do more monitoring as well.”
In September 2023, whirling disease was discovered in non-native brook trout in Emerald Lake – the first known case in Yoho National Park but also in all of the province of British Columbia.
It was later discovered in Kicking Horse River, Wapta Lake, Finn Creek, Monarch Creek and the confluence of Emerald River and Kicking Horse River. The province of British Columbia has since discovered it in Kootenay Lake.
Whirling disease is not spread directly between fish, but a parasite is spread through contact between fish and a freshwater worm.
Last year, several locations along the Kootenay River were monitored for the disease using several types of methods. Sites were also monitored in Yoho National Park, including Sherbrooke Lake and Lake O’Hara.
Goulet said one monitoring method was through environmental DNA, whereby a water sample is taken through a filter and the filter is sent to the lab.
“They will test any DNA of the parasite that was captured … that was a cool new technique,” she said.
Parks Canada teams were also out electro-fishing, a technique that captures or kills fish by running a low electrical current through the water.
“We send those fish off to the lab and the lab will do their testing to see if the fish are positive for whirling disease,” Goulet said.
Another way to monitor for the disease is to place fish from a hatchery into a cage that sits in the river for a month or two.
“At the end of the season we sample those fish and see if they picked up the parasite while present in the river,” Goulet said.
Goulet said there are ongoing discussions with Parks Canada’s provincial counterparts in B.C.
“It is looking like the disease is most present in Yoho and if there are new results in Kootenay, or if it’s more widespread in the province, we might take a different path,” she said.
Named for the circular swimming patterns of infected fish, whirling disease can affect several fish species, including bull trout and westslope cutthroat trout as well as rainbow trout, mountain whitefish, brown and brook trout.
Goulet said whirling disease is a result of a microscopic parasite originally from Europe that infects trout, salmon and whitefish, noting some of the mountain parks’ native fish are highly susceptible to the disease.
“In other jurisdictions in the United States where they have had the parasite for a while, it has known to cause up to a 90 per cent decline of species,” she said.
“The mortality rate potentially could be really high so if we do have an opportunity to prevent the spread, then we really want to take that action as soon as we can.”
Parks staff did compliance checks last year when all waterbodies were shut down in Yoho and Kootenay to watercraft and fishing. At Emerald Lake in Yoho National Park, 18 tickets were issued and two were issued in Kootenay National Park.
“We want to thank all visitors who were compliant with the closures, but we did have enforcement officers issue a few tickets because some people did enter into closure areas, unfortunately,” Goulet said.
Part of the plan for this year is to have more staff at popular spots, such as Emerald Lake and the Kootenay River day-use area, which is a popular put-in spot for paddlers.
“We’ll have staff talking to visitors about whirling disease and providing that information so that people know what to do and what to expect,” Goulet said.
Waterbodies were initially closed to swimming, however, the ban no longer applies because swimming is considered low-risk to the spread of whirling disease.
“We have been doing a literature review on equipment risk and trying to rank different equipment based on what the risk of transporting aquatic invasive species would be,” Goulet said.
“Swimming and using bathing suits ranked as a very low-risk activity. We’re not expecting people to go from one water body in a wet bathing suit to another water body in a wet bathing suit.”
The first case of whirling disease in Canada was at Johnson Lake in Banff National Park in 2016. The lake was drained and all fish were killed.
Goulet said one of the unfortunate things about whirling disease is there isn’t a “great silver bullet to kill it.”
She said management options usually include breaking the life cycle, which would involve removing the fish or removing the worm, which is the other host.
“There have been other locations to remove fish, but in situations where it is a river system, there’s no good way to isolate it,” she said.
“We would be looking at more long-term management scenario for whirling disease, so going through evidence-based decisions and working with provinces and other mountain parks and basically trying to determine next steps once we get more results.”
Goulet reminded everyone of the importance of checking the regulations and requirements for water-based recreational activities and respecting all closures.
“Preventing AIS (aquatic invasive species), including whirling disease, is something everyone can help do because by taking a few simple steps can make a big difference,” she said.
François Massé, superintendent of Lake Louise, Kootenay and Yoho field unit, said aquatic invasive species are a growing threat, noting a northern crayfish was discovered in Bow Lake in 2022 – the first time the non-native species had been found in the Bow River system upstream of Calgary.
“Thankfully, we haven’t detected any others since then, but it is a constant risk that these species get introduced in waterbodies in the park, and that they drive away the native species,” he said during the 25th annual Banff planning forum on March 18.
Mussels are also a huge threat to the parks.
“They’ve been detected in water bodies within a day’s drive of the park, and thankfully as of now, there’s been no detection of invasive mussels in Banff National Park,” Massé said.
“Most aquatic invasive species once established are almost impossible to remove, so it’s extremely important to deliver prevention programs.”
In Banff National Park, it is mandatory to clean, drain and dry all watercraft, fishing equipment and water-related gear.
“And yes, that includes your rubber ducky and inflatable unicorns,” Massé said.
Self-certification permits are also required for all rivers and lakes in Banff National Park, with a 48-hour dry time rule required.
Motorized boats at Lake Minnewanka must be inspected prior to each launch at an inspection station.
“The Minnewanka inspection station is also available to non-motorized watercraft and water equipment that do not meet the self-certification requirement,” Massé said.
Massé said the “picture is changing” as the threat of aquatic invasive species is “coming closer to the park.”
“We’re also taking a hard look at this prevention model and considering whether it needs to be adjusted,” he said.
“There’s mountain park-wide regional work underway and we may see changes for summer of 2026.”
