![]() Non-native fish have already been removed from Helen and Katherine lakes however, there is no plan to put native fish in those water bodies because they were historically fishless lakes. With reintroduction of westslope cutthroat unlikely happening until 2025 in Margaret Lake in order to make sure all the invasive fish are gone, Parks Canada will turn its attention back to Helen Creek again next year. They are also in trouble in Alberta because of hybridization with rainbow and Yellowstone cutthroat trout, habitat loss and damage, and increased water temperature related to climate change. ![]() Now listed as threatened provincially and federally, westslope cutthroat trout were once widespread within the Old Man and Bow River watershed, but over the last century have disappeared from all but 10 per cent of its historic range in Alberta.Īfter being stocked in the mountain national parks beginning in the 1940s, non-native fish like brook trout have flourished and squeezed out westslope cutthroat. Margaret Lake, the biggest and most remote of the five lakes, was the last. Over the last decade, Parks Canada has been working hard to restore critical habitat for westslope cutthroat trout in Banff National Park at five alpine lakes – Helen Lake, Katherine Lake, Hidden Lake and Little Herbert Lake. “The fish just can’t jump up it anymore, whereas before a motivated big fish could have gotten up it.” “If we want Margaret Lake to work, and to be able to successfully reintroduce westslope cutthroat, we had to make it a full barrier to fish passage,” said Humphries. To do that, a section of the creek was blown up using controlled detonations to create a 2.5- to three- metre high waterfall, which will stop non-native species or hybrid cutthroat trout in Hector Lake from returning to Margaret Lake. “Then, we’ll move to putting westslope cutthroat trout back into Margaret Lake.”īecause Margaret Lake’s outflow stream had a stepped cascade that fish can swim up in high water from the creek and nearby Hector Lake, Parks Canada had to create a fish migration barrier on the creek to prevent non-native fish from swimming back into the lake. “If we pass that test, then we’ll be starting to look at the food web and make sure all the zoo plankton in the lake and the invertebrates have recovered,” said Humphries. ![]() Using environmental-DNA, the team will be able to tell what species remain in the lake by scooping up a few litres of water for testing. “We just need to first not get ahead of ourselves and make sure that we were successful with getting all of the brook trout out,” she said. Now that the non-native fish have been removed from Margaret Lake, located about 23 kilometres north of Lake Louise, Humphries said she expects the threatened westslope cutthroat trout will be returned to their home there in 2025. “When we do the rotenone treatment, about 20 per cent of the fish in the lake come up to the surface and then the rest sink.” “We caught thousands and thousands of brook trout,” said Shelley Humphries, Parks Canada’s aquatic specialist for Lake Louise, Yoho and Kootenay field unit. Invasive brook trout, which choke out native fish like westslope cutthroat trout, were removed from Margaret Lake using rotenone – a natural fish toxicant derived from plant roots that enters the bloodstream of fish and quickly kills them.Īfter the second application of rotenone was put into the water earlier this month following the previous summer’s first round, Parks Canada staff stayed on site to apply a neutralizing agent to work alongside rushing water and sunlight to help safely break down the natural poison. BANFF – Parks Canada killed off thousands of non-native fish in a remote Banff National Park lake to make way for a threatened trout species.
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