BANFF – With westslope cutthroat populations declining across their historical range, Parks Canada is leading the way in Alberta to improve habitat and reintroduce the threatened species in Banff National Park.
Although westslope cutthroat trout can still be found in Banff in isolated bodies of water and streams flowing into the Bow River, historic stocking practices that began in the 1940s to promote sport fishing led to cross-breeding with non-native trout and created hybrid fish populations.
Luckily, Parks Canada aquatics experts say a few genetically pure populations of westslope cutthroat trout still exist in Banff that will allow for the reintroduction of the threatened species into some lakes and streams where they once thrived.
“Parks Canada has a history of stocking non-native fish and we did it to increase recreation. We have been doing it since the early 19th Century and we did it right through until the late 80s,” said Brad Stitt, project manager for the Saving Threatened Trout project in Lake Louise, Yoho, Kootenay field unit.
“As we all know climate change has started to rear its head and aquatic invasive species have started to rear their heads and now we also realize that these non-native fish competitively exclude and hybridize with native fish like westslope cutthroat trout.”
Westslope cutthroat trout are listed as threatened under the federal Species At Risk Act (SARA).
Although historically a widespread species once found in the montane and foothill streams of southern Alberta within the Old Man and Bow River watersheds, westslope cutthroat trout over the last century have disappeared from all but 10 per cent of their historic range in Alberta.
The decline is due to overfishing, hybridization with other trout and habitat deterioration.
Detection in Alberta in 2016 of whirling disease – a deadly fished disease named for the circular and erratic swimming patterns of infected fish – presents an additional threat to this species, which are viewed as an indicator species of general ecosystem health because of their strict habitat requirements.
Stitt said the historic distribution of westslope cutthroat trout is “completely diminished and very segmented”.
“In fact, within Banff National Park, there are very few actual genetically pure populations of westslope cutthroat trout remaining,” he said during a recent virtual presentation hosted by Bow Valley Naturalists. “So we have a responsibility to take action to help conserve and restore these populations.”
With a federal five-year funding injection for the project, Parks Canada got to work on a plan to remove non-native brook trout, rainbow trout and Yellowstone cutthroat trout from several headwater systems in Banff National Park.
Thousands of non-native fish have been removed from Helen Lake, Katherine Lake, Hidden Lake and Little Herbert Lake. Margaret Lake, the biggest and most remote of the five lakes, is planned for later this year.
Aquatics teams poisoned fish with rotenone, a naturally occurring compound derived from the roots of a tropical plant in the bean family. It enters the bloodstream of fish and quickly kills them, essentially through suffocation.
It has been used by Indigenous peoples to catch and eat fish, and has been also widely used for native trout restoration in the western United States, including in national parks and designated wilderness areas, as well as Quebec’s La Mauricie National Park.
Stitt said rotenone is relatively harmless to other life forms, noting it breaks down readily through sunlight and hydrolysis.
“For example, I would have to drink an Olympic swimming pool-size amount of water treated with the concentration that we use to have any effect from rotenone,” he said.
More than 3,500 non-native brook trout were killed with the poison at Hidden Lake, a small 10.3-hectare subalpine lake near Lake Louise, and another 252 fish were killed from the stream in 2018-19.
“In 2020, physical monitoring methods found no presence of fish and eDNA (environmental DNA) analysis revealed no brook trout DNA signatures within the treatment area,” said Stitt.
With that in mind, Parks Canada turned to thoughts of reintroducing westslope cutthroat.
“The most exciting thing for me is the reintroduction,” said Stitt. “There’s a lot that goes into it.”
But first, Parks Canada worked with geneticists from Montana in the United States, who specialize in westslope cutthroat trout.
Staff collected and tested westlsope cutthroat in Banff to find genetically pure populations to send to the geneticists for processing.
“This has provided us with concrete evidence of the genetically pure westslope cutthroat populations in proximity to our restoration sites,” said Stitt.
“It’s pretty cool and this is definitely a requirement before reintroduction, knowing that we’re reintroducing, restoring genetically pure westslope cutthroat trout.”
Next up, pathogen testing was needed on the donor fish populations. They were tested for three bacteria, three viruses and the parasite that causes whirling disease.
“The spread of an invasive species into an area intended to be westslope cutthroat refuge will not be tolerated,” said Stitt.
“This is something we absolutely have to do to ensure that we’re not moving anything on the landscape that we’re not supposed to be moving.”
Parks Canada also had to consider restoration stocking options – adult translocation, remote site stream-side incubation in the wild, creation of a restoration brood or a single-use hatchery.
Stitt said adult translocation is an option, but the main one Parks Canada is pursuing for now is stream-side incubation – basically a set up of PVC pipes and five-gallon buckets.
He said adult translocation can be more harmful to the donor population.
“Removing those large adults out – and ideally you want to get about 50 or more individuals from a population – that can impact a population and then there’s disease testing that has to be done on them,” said Stitt.
“That is an option for us, but our main option is the remote stream-side incubation. Basically what we do is we go in and collect gametes, fertilize the gametes, incubate them until the ‘eyed stage’ and then put them back on the landscape.”
In fact, Parks Canada ran a pilot of this technique.
With the help of Alberta Environment and Parks (AEP), Parks Canada collected gametes from trout in two locations in Banff National Park – Outlet Creek and Cataract Brook.
AEP incubated eggs to the ‘eyed stage’ at the Allison brood stock hatchery. The ‘eyed’ eggs were returned to Banff National Park where incubation was completed within the so-called remote incubation units.
“This was just for us to see if we can do it, how we can do it, and whether we’re successful – and it was very successful, with higher than natural reproductive rates in the two populations,” said Stitt.
“We collected about 3,200 eggs and we released just about 1,900 live fish, so that’s a 60 per cent egg-to-fish success rate, which is outstanding considering the wild survival rate is about 10 to 12 per cent.”
With the pilot project declared a success, a decision was made to move forward with reintroducing westslope cutthroat trout into Hidden Creek now that it and the lake are completely void of invasive brook trout.
Again with the help of AEP hatchery teams, staff from Banff, Yoho, Kootenay and Waterton national parks collected gametes from cutthroat trout from Big Fish Lake in June 2021.
More than 4,000 eggs were collected, but Stitt said it turned out that conditions were not optimal for collecting and fertilizing.
“We went out during the heat dome to do this, so it was not optimal and water temperatures were very high,” he said, noting the water temperature at the outlet to Big Fish Lakes was 20 C and 16 C even two metres below the surface of the lake.
“Ice had come off a week, a week-and-a-half earlier; it was mind boggling for us,” said Stitt.
“Air temperatures and sun exposure made it difficult just working around trying to get the eggs fertilized… we flew in coolers of ice just to try to be able to do this work.”
AEP incubated the eggs to the “eyed stage’ at the Allison brook stock hatchery. The initial egg pick dropped from 4,080 to 2,568.
“Following the incubation to the ‘eyed stage’ we had 471 eggs remaining, which was not what we expected after having 4,000,” said Stitt.
Park aquatics crews did put the 471 remaining eggs in the remote stream-side incubators.
“We were able to release 311 fry (recently hatched fish) into Hidden Creek, which was amazing,” said Stitt.
Ideally, Stitt said more fish would have gone out from the initial 4,000 eggs.
“We will work on improving our skills and our timing to get better at this each year,” he said.
The next big step for Parks Canada’s aquatics team is the removal of invasive brook trout from Margaret Lake, the largest and most complex lake they’ve tackled to date. The non-native species has competitively extirpated the population of westslope cutthroat historically found there.
The plan is to use rotenone treatments in 2022 and 2023 to kill the brook trout.
Before westslope cutthroat trout can be reintroduced into Margaret Lake, though, Parks Canada plans to make an existing natural waterfall barrier impenetrable to prevent any brookies from migrating up into the lake.
To do this, the federal agency is working with Tetra Tech – a consulting and engineering firm – on a series of small controlled detonations to create a 2.5-metre to three-metre sheer face waterfall to make the natural barrier better.
Stitt said that plan, which is hoped can happen this coming fall, is undergoing an environmental impact analysis and review by the federal department of Fisheries and Oceans Canada.
“The barrier is a seasonal barrier to fish migration, it is not a permanent barrier to fish migration,” said Stitt.
“We are going to work with engineering and geotechnical services to do a controlled detonation to make a sheer two-and-a-half to three metres waterfall face, which is a barrier to fish migration that will allow us to reintroduce westslope cutthroat trout back into this system.”
