Thirty years ago Montana’s Flathead Lake and the connected Flathead River system supported a popular native fishery for large migratory cutthroat and bull trout. Bull trout sometimes exceeded 20 pounds. Twenty-inch cutthroats were not uncommon. Native bull trout ranged throughout the river and its tributary system. Generations of Montanans would fish the river and lake zeroing in on these fish. Today this fishery is a shadow of its formal self. Bull trout are now a federally listed threatened species. You cannot deliberately fish for them, let alone harvest them. The cutthroat population is catch-and-release and much diminished.
The downward trend in both species can be blamed on habitat loss and overharvest, as well as predation, competition and hybridization resulting from the presence of non-native species. Today the primary culprit preventing the rebound of bull trout and cutthroat populations in Flathead Lake and the Middle and North Forks of the Flathead River is the robust, busting-at-the-seams population of lake trout that occupy Flathead Lake, as well as lakes on the west side of Glacier National Park. Though lake trout were first introduced to Flathead Lake in the early 20th Century, for decades their numbers were limited, providing an opportunity for anglers to catch a trophy fish. But when state biologists introduced non-native Mysis shrimp to the Flathead system in the 1970s things went awry. This abundant food source dramatically increased survival of juvenile lake trout. Soon after, the once populous and popular kokanee salmon fishery collapsed, mainly because of predation from lake trout, but also because Mysis competed with the salmon for the same food sources.
The lake trout population has since exploded, and the fish target the Flathead’s remaining fish species, including cutthroat and bull trout. Because kokanee, cutthroats and bull trout are either gone or survive in low density, sportfishing opportunities have diminished. Angling pressure on Flathead Lake, on average, is less than half of what it was before lake trout exploded.
The Confederated Salish and Kootenai Tribes – who own the southern half of Flathead Lake — in consultation with some of the nation’s top fisheries scientists, as well as federal and state biologists and TU are increasing annual harvest of lake trout on Flathead Lake to reduce their impact on native cutthroats and bull trout. If successful, the result could be more native sportfish available for anglers in the lake and in the connected river system.
As the Flathead region’s famous bull trout and cutthroats continue to decline, this might be the last chance to ensure future generations can enjoy these majestic fish.
TU & MTU Comments on Flathead National Forest Plan Revision (May 14, 2015)
The Flathead system – before and after coming of lake trout (Daily Inter Lake, August 2)
A sad tale of three trout (Missoulian, July 24)
Battle over two species reveals gaping split in Flathead Lake fish management (Missoulian, July 15)
Draft plan for lake trout netting unveiled (Interlake, June 24)
Feds, CSKT release draft EIS on reducing lake trout in Flathead Lake (Missoulian, June 23)