YOHO – A ban on swimming, paddling, boating and fishing on all waterbodies in Yoho and Kootenay national parks has been extended another year until March 31, 2026.
“This measure helps prevent the spread of whirling disease as we as we chart a safe path forward,” states a social media post on Monday afternoon (March 17).
“Future reopening decisions will be guided by scientific evidence and a consistent standardized, data-driven approach across the mountain national parks.”
After discovering whirling disease in Yoho’s Emerald Lake last month, Parks Canada officials say further sampling and preliminary test results found suspected cases of the disease in the Kicking Horse River, Wapta Lake, Finn Creek, Monarch Creek and confluence of Emerald River and Kicking Horse River.
On Sept. 20, 2023, whirling disease was discovered in non-native brook trout in Emerald Lake – the first 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 confluence of Emerald River and Kicking Horse River.
In an unprecedented move, Parks Canada shut down all waterbodies and shorelines in both parks until March this year.
Until then, whirling disease had been contained to neighbouring Banff National Park and Alberta provincial lands after its initial discovery in Canada in 2016 – in Banff’s Johnson Lake.
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.
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 in 2016, the small lake near the Banff townsite was drained and all fish were killed. The main concern was it would cause harm to at-risk species like bull trout and westslope cutthroat trout.
Thought to have been introduced from Europe, whirling disease was first detected in the United States in 1958. It became a 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.
The Outlook contacted Parks Canada last week about information on this story, but was told an interview is not available until Thursday, March 20.
