Parks Canada finding success in reviving threatened fish species in Banff

Parks Canada finding success in reviving threatened fish species in Banff

'Overall, the numbers are in really good shape,' says aquatics specialist

Parks Canada is seeing success for a threatened fish species returning to its traditional habitat in Banff National Park.

After more than a decade of work, the federal agency said westslope cutthroat trout are beginning to spawn naturally and repopulate Hidden Lake, close to Lake Louise.

Shelley Humphries, an aquatics specialist for Parks Canada's Lake Louise, Yoho and Kootenay field unit, said they’re now self-sustaining.

“It’s so amazing … We’re not going to have to worry about them up there,” she said. “We were pretty sure it was all going to work because in the United States this work is done all the time and it's led to some delistings.”

Humphries said work began to naturally remove brook trout in 2011, but ultimately didn’t work. They used rotenone — a natural fish poison — to take out brook trout in 2018 and 2019.

They started putting eggs in Hidden Lake in 2021 for four straight years, which led to successful spawning and fully grown fish showing up this year.

She said they’ll continue to monitor, but the hope is to see them use streams and creeks to go beyond Hidden Lake.

“Overall, the numbers are in really good shape,” Humphries said. “We just want to see them now spawning in the streams because there are some places in the stream we’re also expecting them to spawn in the future, not just up in the headwater lake.”

‘Not let them go without a fight’

Westslope cutthroat trout once thrived from the northern end of Banff National Park to the southern tip of Alberta.

But when recreational fishing took off in the 1900s and non-native fish like brook trout were added, they took over the westslope cutthroat trout habitat. It left westslope cutthroat trout only in about 10 per cent of its traditional waterways.

“We’re correcting a mistake we made. It happened 50, 100 years ago and we didn’t realize it was going to be a problem. This is very correctable and the fish are imminently saveable,” Humphries said.

The federal agency has similar projects in areas such as Helen Lake, Cascade Creek, Katherine Lake and Corral Creek.

It’s also beginning plans to do similar work for threatened bull trout.

Humphries said ecologically it can help other species like birds of prey and bears more than brook trout.

Humphries said a key goal for Parks Canada is “to take care of our species at risk and not let them go without a fight.”

Parks Canada adding threatened fish species to several Banff lakes

Greg Colgan is a journalist for CBC in the Bow Valley. He was previously the editor of the Rocky Mountain Outlook in Banff and Canmore. He has also worked for media outlets in Ontario and has experience covering topics such as sports, politics, housing and development, courts and arts and entertainment. He joined CBC in 2025. He can be reached at greg.colgan@cbc.ca.