Parks Canada has identified whirling disease in Lake Louise, with the detection recorded in 2025, and officials say this is the first time the pathogen has been found in that lake. The finding has triggered new zone-based restrictions across mountain national parks that will close some backcountry waterways to paddling and large inflatables effective spring 2026.
Lake Louise Whirling Disease Detection
Parks Canada identified the presence of whirling disease in Lake Louise in 2025 and notes the lake was last tested in 2016 with no detection then. Parks Canada also stated this is the first time the disease has ever been found in Lake Louise. The pattern suggests the pathogen was introduced to the lake only recently, given the 2016 negative test and the declaration that this is a first-time finding.
Parks Canada Zone Rules
Beginning spring 2026, Parks Canada will ban paddling and the use of large inflatables, and prohibit waders or wading boots while fishing, at Lake Minnewanka, Bow Lake and Moraine Lake. Visitors may still use those devices at Lake Louise and several other area lakes and on the Bow River downstream of Hector Lake. Parks Canada is asking anyone bringing equipment to clean, drain and dry inflatables, waders or watercraft and to fill out a self-certification form before use, which points to a zoned, risk-based approach that tries to limit cross-contamination while preserving some recreation chances.
Bow Lake and Moraine Lake Measures
The new water-activity zones apply across mountain national parks in Alberta and British Columbia and include bans specifically on Bow Lake and Moraine Lake. Parks Canada framed the measures as part of an aquatic invasive species prevention strategy that will roll out more components over the next two years and be evaluated on an ongoing basis. That strategy responds to the biological risk: Parks Canada notes whirling disease can severely impact trout, whitefish and salmon, and that mortality rates among young fish can reach as high as 90 per cent in some cases. The figures point to why officials are prioritizing limits on equipment that can carry mud or water.
Human Pathways and Containment Steps
Francois Masse, superintendent of the Lake Louise, Yoho and Kootenay field unit, explained it is unlikely the organism reached Lake Louise through natural fish movement because a natural fish barrier separates the lake from the Bow River, and he said it was most likely introduced by mud or water on a watercraft or angling equipment. Marie Veillard, aquatic invasive species project co-ordinator for the Lake Louise, Yoho and Kootenay unit, said officials intend to balance protection of sensitive ecosystems with opportunities for visitors to continue water-based recreation. The explanation from Masse points directly at human-mediated transfer as the plausible trigger behind this event.
Parks Canada has also emphasized that aquatic invasive species can spread downstream beyond park boundaries through interconnected river systems and warned that, once established, aquatic invasive species may never go away. For now, the agency has set no end date for the restrictions and says implementation and specific permitting requirements may vary by park as the strategy unfolds.
Next confirmed steps: the paddling and large-inflatable bans at Lake Minnewanka, Bow Lake and Moraine Lake take effect in spring 2026, and Parks Canada will roll out further components of its aquatic invasive species prevention strategy over the next two years. If the zone rules and mandatory cleaning and self-certification reduce cross-contamination from equipment, the data suggests downstream spread could be slowed; if those measures do not limit transfers on gear, officials will need additional controls tied to the ongoing evaluation.
