A Montana river that fisheries biologists have been working to protect as habitat for native Yellowstone cutthroat trout has been invaded by an illegal introduction of smallmouth bass.
“The Shields River is one of the best remaining strongholds of Yellowstone cutthroat trout,” said Travis Horton, fisheries manager for FWP’s Region 3 in Bozeman.
The presence of smallmouth bass in Cottonwood Reservoir was confirmed by a Montana Department of Fish, Wildlife and Parks biologist this spring. The reservoir is about three miles north of Wilsall along Highway 89. The irrigation reservoir’s outlet drains into Potter Creek, a tributary to the upper Shields River.
“Expansion of a smallmouth bass population in the Shields could threaten the cutthroat population via predation and competition for habitat,” FWP wrote in a proposed update to its fishing regulations.