Parks Canada is killing off the competition in a bid to save native fish populations in Banff National Park.
In the latest ambitious fisheries restoration project in Banff National Park, the federal agency is trying to restore the Upper Cascade River system by removing non-native rainbow trout from Rainbow Lake.
Officials say the goal is to significantly reduce the abundance of non-native trout from Cascade River headwater streams, including Rainbow Lake, Sawback Creek and Upper Cascade River.
They say they then plan to reintroduce a population of native westslope cutthroat trout into Rainbow Lake, via helicopter, from other genetically pure, or almost pure, fish populations such as from nearby Sawback Creek.
“Rainbow Lake is populated with rainbow trout that are not native to Banff National Park or the Bow River system and directly compete with cutthroats,” said Charlie Pacas, an aquatics specialist for Banff National Park.
“It’s probably one of the leading causes of cutthroat trout decimation, not only in the national parks, but in Alberta and in B.C.,” said Pacas during a Parks Canada research conservation update on May 24.
Native westslope cutthroat populations have been reduced in almost 80 per cent of their range due to over-fishing, habitat loss and competition and hybridization with introduced, non-native species.
Westslope cutthroat are one of the few trout species native to southwestern Alberta and British Columbia, including the mountain national parks of Waterton, Banff, Yoho and Kootenay.
The Alberta population has been assessed as threatened provincially and nationally and is being considered for federal listing under the Species At Risk Act (SARA).
Between 1904 and 1988, Parks Canada records indicate 35 to 40 million non-native fish were stocked in waters in Banff National Park. Rainbow Lake was stocked in 1937 and 1967.
“We want to change the system back to what it might have been like before those introductions,” said Pacas. “Our goal is to make sure all rainbow are out.”
By the fall of 2011, crews had removed 315 rainbow trout from Rainbow Lake using gill nets. The nets remained in the lake over winter and the plan is to check them again soon.
Parks Canada used electro-fishing along the entire length of Rainbow Creek and caught another 96 rainbows. A total of 370 trout were captured in 23 reaches of Sawback Creek, including 222 westslope cutthroat, 50 bull trout and 98 brook trout. The brookies were removed.
Pacas said westslope cutthroat trout were tagged with a unique identification number and had a piece of their adipose fin removed for genetic analysis.
Some of these fish, he said, were suspected to be hybrids, although genetic analysis is expected to confirm this sometime soon. “One of the biggest challenges is distinguishing,” he said.
Pacas said about 12 genetically pure populations are believed to remain in Banff National Park, mostly as severely fragmented, remnant headwater populations.
He said among those are pure, or near pure populations in Sawback Lake, Cuthead Creek and the Upper Cascade drainage.
“These pure populations are threatened by a non-native population of rainbow trout originating upstream of Rainbow Lake,” Pacas said.
