For the first time, Glacier National Park is attempting to eradicate non-native trout species and restore native westslope cutthroat trout. The project on the west side of the park specifically aims to preserve genetically pure westslope populations.
Fishery managers delivered lethal doses of rotenone last week in the Camas Creek drainage in the middle of the Park. Park Service Biologist Chris Downs says the goal is to eliminate Yellowstone cutthroat trout, which were stocked in the historically fishless stream and connected lakes.
"Those fish are now perched at the top of a native westslope cutthroat drainage, posing a genetic risk of hybridization."
Downs says hybridization has been documented between Yellowstone and westslope cutthroats in nearby Arrow Lake. He says hybridization can break down genetic adaptations in westslope populations, which vary from stream to stream.
Downs says genetically-pure and disease-free westslopes from the North Fork of the Flathead River will be used to restock the Camas drainage as it detoxifies in the coming weeks, "And create sort of a refuge for North Fork strain westslope cutthroat trout."
The park will work with Montana Fish, Wildlife and Parks (FWP) to collect roughly 200 live fish from the North Fork annually and release thousands of their fry into the Camas drainage over the next three to five years.
It’s hoped that the new, genetically pure population in Camas creek will persevere the genetics of westslopes from the North Fork, which are also at risk of hybridization.
The park’s efforts are working in tandem with FWP, which just wrapped up a decade-long restocking effort on the South Fork of the Flathead River.
"If your goal is to conserve westslope cutthroat trout and its genetic variation, you’re going to need to conserve as many genetic variations as possible," says FWP’s Matt Boyer.
The South Fork now accounts for half of all westslope cutthroat trout statewide, representing a success.
Managers like Downs say these projects will give westslopes the time they need to adapt to long-term pressures like climate change by removing genetic influences from non-native species.