Nestled high in Banff National Park’s Skoki Valley, experts have worked by trial and error to restore the ideal environment for the native and endangered West Slope cutthroat trout. This summer, thousands of small fish strong enough to survive in the wild are swimming freely in the lake again. “I can’t even believe we’re finally bringing the trout back, it’s like the pinnacle of our work,” said biologist Megan Goody. “A day I thought we might never see, but here we are.” Fertilized eggs are transported from the hatchery to remote incubators that protect them from becoming prey. The buckets house the developing trout and simulate a nesting environment as water flows through pipes and a valve is placed just so in a moving stream. Karly Upshall carries tubes that are streamside incubators that help trout thrive in Hidden Lake. (Helen Pike/CBC) To hikers it looks like nothing more than an assortment of pipes you might find at Home Depot. But for those working on the project, it means years of work finally paying off. If all goes well, in five years this population of tiny fishers will be mature enough to reproduce. “They were self-sustaining in this lake in the ’50s,” said aquatic expert Shelley Humphries. “So we fully expect it to be fine in this lake going forward.” Fertilized eggs are transported from the hatchery to remote incubators by the stream that protect them from becoming prey. (Helen Pike/CBC) The problem began in the 1900s, when officials introduced non-native species into many of the National Park’s lakes to stock them for anglers looking for an exciting fishery. The park stopped the practice decades ago, but the damage was done. Brook and rainbow trout flourished and drowned out native species. Then, rising water temperatures made it more difficult for fish to survive. Parkwide, they now occupy less than 10 percent of their historic range. Nestled in a remote corner of the Skoki Valley in Banff National Park, Hidden Lake is an ideal spot for reintroducing trout because it’s cool and secluded. (Helen Pike/CBC) “These feed ospreys and bears,” Humphries said. “The brook trout are not to the same extent because of the timing of when they spawn and when the bears and birds are here. We’re correcting a mistake we made about 50 years ago at this location.” To correct this mistake, Parks had to complete several uphill battles:
Fish need cool lakes to thrive. Because of years of breeding with imported populations, they had to find genetically pure trout. The introduced species, namely the non-native trout, had to be removed from Hidden Lake.
When the province first listed trout as endangered, Humphries said they launched a spawning survey to find where these fish nest. Then a chance discovery helped establish Hidden Lake as an ideal habitat for this conservation project. They found a waterfall in the stream. A waterfall in Banff’s Skoki Valley offers protection for endangered fish. (Helen Pike/CBC) “It’s not on our maps and you can’t see it from aerial photos,” Humphries said. “We’re so happy to have this waterfall down in the valley. It’s going to keep the trout from coming back here and undoing this conservation work we’ve done.” With nearby glaciers to keep it cool and sheltered from this waterfall downstream, Hidden Lake became the refuge the team was looking for. Then they got to work, first trying to remove the non-native species by hand with nets, fishing and electrofishing. But this proved frustrating and ultimately unsuccessful. Water treated with rotenone turns pink, but the color disappears as the water flows down. (Provided by Parks Canada) “After about four years, we realized that actually, it wasn’t working,” Humphries said. “We were still getting a lot of spawning of the imported trout, so we had to change methods.” That’s when they decided to take a new route and introduce rotenone, a natural fish toxin derived from plant roots. Humphreys explained that the pink powder is added to the water and enters the fish’s system through the gills, inhibiting its respiration at a molecular level. It is toxic only to fish and is not dangerous to humans, mammals or birds at the levels used. “It breaks down on its own quickly in the sun, and with the turbulent water as it flows through here, it collapses.” It was much more efficient, he said. After two years, that treatment gave Parks a blank slate—a lake free of any fish and ready to bring back the West Slope trout. This, Humphries added, started a whole new process: finding the hardiest fish with the best chance of survival. “They’re endangered. There aren’t that many of them, and we can’t go buy them somewhere. We had to find them in the landscape,” Humphries said. After training from a hatchery and raising the eggs in a mobile incubator, the eggs are hardy enough to live in the current. And those are the alevins — the newly hatched trout that still carry the yolks — that swim in the bucket preparations and are checked by Parks keepers until they’re ready for release.
