In 1941, workers built the Lake Minnewanka reservoir for power generation near Banff. It reduced the roaring Cascade River to a silent trickle and wiped out a population of westslope cutthroat trout.
This past June, Parks Canada biologists put 18,000 westslope cutthroats into special incubation trays scattered along a nine-kilometre-long, restored stretch of Cascade Creek.
More than 97 percent of the eggs hatched and now juvenile westslope are once again flashing through the waters of Cascade after an 80-year absence.
It marks an important reintroduction and conservation milestone for this endangered fish.
“They are now swimming around Cascade Creek, which is super exciting and a long time coming,” Nicole Sulewski, a Parks Canada resource management officer, told Rocky Mountain Outlook.
Westslope Cutthroat In Severe Decline
Westslope cutthroat trout have shown “severe declines,” according to the Government of Alberta.
Historically in Alberta, westslope cutthroat were found in big numbers in more than 70 watersheds.
As of 2017, the population had shrunk to just 31 watersheds, with adults assessed at “low or very low abundance.”
What’s to blame? Heavy logging, oil and gas, ranching and farming, and urbanization damage streams and watersheds.
Cross-breeding with non-native rainbow and cutthroat trout has diluted the genetic pool. These non-native fish also compete for habitat.
Overfishing, including catch and release, continues to impact westslope survival.
The thing is, westslope cutthroat are much more than pretty fish to snag on the end of a hook.
These trout are important for healthy streams.
“They are the grizzly bear of the water. They are the top of the food chain,” said Mark Taylor, an aquatic ecologist for Banff National Park. “They are consuming bugs, keeping prey populations in check, they are consuming other fish, and without that, it would be like an ocean without sharks or terrestrial landscape without bears.”
The Rebuilding of a Stream
It has indeed been a long road to recovery for the population of westslope that used to thrive in the Cascade system.
Parks Canada hired Bob Newbury, one of the world’s best stream restorationists who teaches stream restoration at the University of British Columbia, to lead the Cascade project.
Work started in 2018 and involved using an excavator to create pools, riffles, and rocky rapids to support westslope cutthroats.
Technicians also removed more than 20,000 non-native trout using a technique called electro-fishing, which stuns the fish and allows them to be easily caught.
A key piece of the project included building a waterfall near where Cascade Creek flows into the Bow River to prevent invasive fish from recolonizing the stream.
Interestingly, it was the devastating Alberta floods of 2013 that gave this project legs.
As the flood waters rose, TransAlta, which owns and operates the Cascade hydropower plant, opened the spillway at Lake Minnewanka to prevent a dam breach.
It sent a torrent of water down the natural path of Cascade Creek and cleaned out sediment and culverts that were bad for fish.
Ten years and a lot of hard work later, westslope cutthroat trout are on the mend in this little creek near Banff.
