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Whirling disease detected in Yoho's Emerald Lake

“This is terrible news. We’ve been working super hard to have a prevention and education and monitoring program in place and we were hoping to prevent this.”
Emerald Lake in Yoho National Park has been closed to recreational use, such as paddling, fishing and swimming. Designated trails remain open. PHOTO PARKS CANADA

YOHO NATIONAL PARK – A deadly disease known to kill off trout, salmon and whitefish in large numbers has been discovered in Emerald Lake – the first case in Yoho National Park but also in all of the province of British Columbia.

Up until now, whirling disease had been contained to neighbouring Banff National Park and Alberta provincial lands since it was first discovered in Canada in 2016, but a PCR test on Sept. 19 confirmed the disease in non-native brook trout in Emerald Lake, about 11 kilometres northwest of Field.

Parks Canada was quick to shut down Emerald Lake to fishing, swimming, paddling, and boating on the weekend to prevent further spread of the disease, although designated trails around the lake remain open.

Shelley Humphries, Parks Canada’s aquatics specialist for Lake Louise, Yoho and Kootenay, said the federal agency has been on high alert since the diseased was first detected at Johnson Lake in Banff National Park in 2016.

“This is terrible news,” she said, noting although it still considered a suspected case until more sampling is sent to the Canadian Food and Inspection Agency, Parks is confident is confident with its testing lab.

“We’ve been working super hard to have a prevention and education and monitoring program in place and we were hoping to prevent this.”

Named for the circular swimming patterns of infected fish, whirling disease can affect several fish species, including at-risk bull trout and westslope cutthroat trout as well as rainbow trout, mountain whitefish, brown and brook trout.

Whirling disease is not spread directly between fish, but a parasite is spread through contact between fish and a freshwater worm.

Once the parasites have invaded the cartilage of the fish, it can result in deformities in the jaws, head, gill cover, and body, and can also cause the tails of infected fish to turn black. It can also impair the nervous tissue, resulting in the characteristic whirling swimming behaviour.

After the deadly disease was discovered in Banff’s Johnson Lake, the small lake near the Banff townsite was drained and all the fish were killed. The main concern was it would cause harm to at-risk species like bull trout and westslope cutthroat trout.

Humphries said sampling for whirling disease in Emerald Lake in 2016 and again in 2019 turned up negative; however, a staff member fishing in August caught a few fish that had some clinical signs that raised suspicions.

“We quickly resampled the lake and last week, we found out that a few of the fish came back positive for whirling disease using the PCR testing,” she said.

There are currently no known treatments for whirling disease, but next steps for Parks Canada involve assessing fish in Emerald River, which flows out of the lake and in turn flows into the Kicking Horse River and eventually into the Columbia River.

“Before we rush out and make any bold plans, we need to understand if it is it just in the lake itself at the back where the positives were found, or if it is already in the river system, and has it spread further into the Kicking Horse,” said Humphries.

Humphries said she will likely talk to her Parks Canada colleagues who dealt with whirling disease at Johnson Lake.

“Johnson was a fairly tiny lake and it had a control structure and they were able to draw the lake down and try to remove all the fish – and we believe we've gotten all of the susceptible species at at Johnson,” she said.

“I’m unsure if that is an option for Emerald Lake.”

In addition, Humphries said Parks will need to get a better understanding on what is happening in watersheds in the United States, where whirling disease has been detected on a much larger scale in some areas.

“They're really trying to live with it and in some locations, after a long period of time, some natural resistance has sprung up to the whirling disease in the fish, and they’ve also also been working with their hatcheries to try to breed some resistant fish,” she said.

“I think that there are a few options and I think we'll need to talk to the folks in Colorado and some of the other Western states that have a lot more experience with this than we do, and get a sense from them about what they think the best strategy is.”

While the disease is not harmful to humans, it can have a significant impact on some fish populations.

Thought to have been introduced from Europe, whirling disease was first detected in the United States in 1958. It became major concern in the 1990s when losses of up to 90 per cent of the wild rainbow trout in several streams in Colorado and Montana were attributed to whirling disease.

“It can be super devastating to the populations of trout, and it can totally reshuffle the cards about which species are present in the future, because not all species have the same susceptibility,” said Humphries.

“The outcomes are super variable. In the U.S., they've had like 90 per cent loss of some species in highly infected areas, so that would just be really devastating for Yoho National Park to have that happen,” she added.

A statement from B.C.’s Ministry of Water, Land and Resource Stewardship said the immediate priority is confirmation of the suspected detection through additional sampling and testing in Emerald Lake and downstream locations within Yoho National Park.

Since the detection of whirling disease in Banff in 2016, the statement said the B.C. ministry has been working with CFIA and Freshwater Fisheries Society of BC to conduct surveillance testing.

“The majority of samples have been collected in southeastern B.C. because of its proximity to whirling disease prevalence in Alberta,” according to the statement.

“To date, no suspected positive cases of whirling disease have been detected in other B.C. waterbodies.”

Although Parks Canada has had a mandatory self-certification system for people using equipment such as paddle boards, canoes, kayaks, boats or fishing gear, Humphries said that is the most likely cause of the introduction of whirling disease into Emerald Lake.

She said Parks Canada does not have the compliance rates just yet, although they have been working on a risk assessment for Emerald Lake and other areas in the parks.

“We know that there are people that go right past the self-inspection stations and they don't even bother to fill out their permits,” said Humphries.

“We know that some people that are self certifying that they're boats are cleaned, but we do know that we do get some boats failing inspections.”

Under the clean, drain, dry rule, all equipment must be cleaned of all mud, sand, plant and animal materials, and drained of all water.

“We need people to be fastidious about cleaning their equipment in the ways that we've asked them to,” said Humphries.

A spokesperson for the province of B.C. did not get back to the Outlook by press time.

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