The true cost of non-native trout

This spring, native westslope cutthroat and bull trout will stage for their epic journeys from Flathead Lake to spawning streams in the Middle and North Forks Flathead River. Once quite common, their numbers are significantly diminished from the recent past because many cannot navigate the gauntlet of predacious non-native lake trout (and illegally introduced northern pike) that occupy the lake and river.

Our neighbors, the Confederated Salish and Kootenai Tribes, want to bolster the populations of native fish to once again provide a diverse sport fishery as well as revive an important part of tribal culture. With the support of anglers, the assistance of objective science and a review panel of biologists from state and federal agencies, as well as the university system, the tribes are working hard to strike a reasonable balance in the fishery at Flathead Lake. They deserve your support.

Flathead Lake once hosted one of Montana’s most popular and robust sport fisheries, featuring millions of kokanee salmon, cutthroats, yellow perch, bull trout and lake trout. Today, the salmon are gone and cutthroat and bull trout numbers have been reduced dramatically. Also gone are many fishermen. Perch and lake whitefish remain, but their availability fluctuates year to year, depending on water levels and predation.

Well-meaning state managers who introduced mysis shrimp into the Flathead system in the 1980s triggered the decline in the lake’s fishery and fishing opportunities. The shrimp provide an ample food source for young lake trout, improving their survival rates. Once these lake trout get larger, they feed on other fish.

In the ‘90s, the exploding lake trout population consumed about 10 million kokanee in Flathead Lake, collapsing perhaps the most popular lake fishery in the state. Angling numbers then dropped by about 50 percent. When the kokanee disappeared, so did hundreds of bald eagles that gathered each fall to gorge on spawning salmon at McDonald Creek in Glacier National Park. Thousands of tourists then stopped coming to view the eagles. Tourism dollars dropped.

The large lake trout population — as well as illegally introduced northern pike — also preys on bull trout. The result has been an alarming loss of the native fish in the lake and the connected North and Middle Forks. Today, adult bull trout in Flathead Lake are estimated to be only about 3,000 fish. Localized spawning populations continue to disappear. It is now illegal to fish for them.

Scientists estimate lake trout numbers, however, are around 1.8 million. They are tough to catch without a large boat and specialized gear. Lake trout migrating from Flathead Lake have also nearly eliminated bull trout from 10 of 13 lakes on the west side of Glacier Park.

Further, they have severely reduced cutthroat numbers in the upper Flathead system, reducing their population to less than half of what they were before mysis arrived.

Because many of the easier-to-catch cutthroats in the upper Flathead River system migrate from the lake, angling opportunities — and the tourism dollars they generate — in the Middle and North Forks are threatened by lake trout.

The near monoculture of lake trout in Flathead Lake threatens the future of sport fishing in the upper Flathead basin. The tribes, however, are addressing this challenge head-on. They are evaluating tools, including maintaining fishing tourneys coupled with limited and scientifically based netting, that can reduce the lake trout population to a reasonable number.

This could reduce predation and benefit native bull and cutthroat trout, as well as other sport fish such as perch and lake whitefish. It would also still maintain a lake trout fishery for the minority of anglers who can afford powerboats and the specialized gear it takes to pursue them. Despite the fears of the small cadre of commercial charter operators who fish for lake trout, it would be impossible to eliminate their favored fish from Flathead Lake.

Without new approaches at Flathead Lake, bull trout and cutthroat trout will eventually be reduced to a tiny fraction of their historical numbers, or even extirpated.

Without new approaches, angling opportunities and the economic benefits they generate will continue to dwindle. Without trying, and instead turning the lake and river over to lake trout, we will be judged harshly by future Montanans who will never feel the tug of a large cutthroat on their line at Flathead Lake.

Chris Schustrom is the president of Flathead Valley Trout Unlimited, and Bruce Farling is the executive director of Montana Trout Unlimited.