Whirling disease detected in Lake Louise, Alta.: Parks Canada

Parks Canada officials say they have detected whirling disease in Lake Louise.

Officials with Parks Canada say they have detected an aquatic invasive species (AIS) at one of Canada’s most iconic mountain parks.

Parks Canada officials announced Tuesday that a series of tests looking for AIS in waterbodies detected whirling disease in Lake Louise, the stunning crystal blue lake in Banff National Park.

At a news conference Wednesday, Parks Canada officials said biologists detected whirling disease in Lake Louise in 2025 after doing a series of tests in waterbodies in Banff, Yoho and Kootenay national parks.

François Masse, superintendent for Parks Canada’s Lake Louise, Yoho and Kootenays field unit, said the disease was likely spread to the waterbody through mud stuck to a watercraft that sailed on the lake.

“It’s unlikely whirling disease was spread to Lake Louise through natural fish movement because there’s a natural fish barrier between Lake Louise and the Bow River,” he told reporters.

Whirling disease is an infectious disease caused by a parasite that affects fish populations, with especially significant effects on trout, whitefish and salmon.

The disease has no effect on humans or other mammals but can cause a mortality rate in young fish of up to 90 per cent. It can also cause affected fish to swim in circles and cause skeletal deformities.

Officials said there was no whirling disease detected in waterbodies in Kootenay or Yoho national parks.

They added the whirling disease in Lake Louise was the first time the infection had been detected in that body of water.

The discovery came on the same day the federal agency announced new zoning rules were coming to bodies of water in national mountain parks to combat AIS.

The new rules divvy the parks’ water bodies into three different zones.

Waterbodies classified as being in recreation zones will allow regular water activities such as paddling, fishing and swimming so long as visitors clean, drain and dry their equipment before use.

Visitors at lakes and rivers in preservation zones will not be allowed to use any watercraft or wear boots or waders in the water while fishing. Visitors can still fish without waders and swim.

Bow Lake and Moraine Lake are both classified as preservation zones under the new restrictions.

The third zone — dubbed special tactics zones — covers ecologically sensitive waterbodies, which restricts non-motorized watercraft and waders, but still allows swimming and use of motorized watercraft that has been inspected by Parks Canada.

Lake Minnewanka falls under the special tactics zones.

“AIS are extremely difficult to remove. Prevention is the most effective way to project our lakes and rivers,” Masse said.

Visitors that don’t comply with the restrictions can be charged up to $25,000 under the National Parks Act.

Under the new zoning rules, Lake Louise is classified as a water recreation zone.