Banff lake may be drained to stop spread of deadly whirling disease in fish

An entire lake in Banff National Park may have to be drained of all its trout — or all of its water — to stop a deadly fish parasite from spreading to more waterways.

Parks Canada officials are considering these extreme measures for Johnson Lake, where the first Canadian case of whirling disease was detected in August.

Since then, whirling disease — which targets trout and salmon and causes them to swim in a circular pattern — has been detected in 14 more locations.

“Just because of the proximity, there’s possibility of birds moving the parasite through … fish or fecal matter, and also recreational use connecting between the water bodies,” said Bill Hunt, the manager of resource conservation with Banff National Park.

Hunt said officials are particularly concerned that the disease could eventually infiltrate two more Banff lakes — Minnewanka and Two Jack.

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‘We do know that removing fish from a water body puts a break in the life cycle of the parasite,’ says Bill Hunt with Banff National Park. (File Photo/John Hart/The Associated Press)

Draining the lake

Hunt said removing the water from Lake Johnson would expose the parasite to colder temperatures.

Evidence suggests that freezing is another way to reduce the prevalence of the parasite,” he said.

“Whether that is a full dewatering of the lake or a partial dewatering just to remove spores within the shoreline area, these are questions we’re looking at right now.”

Hunt said “oddly enough,” it’s not that tough to drain a lake. Many construction companies in Alberta that are already doing this for various industrial projects, he said.

“It’s expensive, and we’d want to make sure there’s a reasonable likelihood of a successful outcome.”

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This rainbow trout displays the characteristic black tail and skeletal deformities indicative of whirling disease. (Stephen Atkinson/Oregon State University)

Toss the trout

The other option would see all the rainbow, brown and brook trout scooped from the 15-hectare lake.

“We do know that removing fish from a water body puts a break in the lifecycle of the parasite,” Hunt said.

He said the CFIA would destroy the trout, which are all non-native species that were introduced to Johnson Lake years ago.

Hunt said at this point, Parks Canada is just brainstorming ideas and will not take any action until after completing public consultations and an environmental assessment.