Western Lake Trout – Just Say Whoa!

Abstract

In Montana lake trout (Salvelinus namaycush) are a self-sustaining introduced species in approximately 20 lakes west of the Continental Divide. Less than half those lakes were intentionally stocked and lake trout naturally invaded the others through connected waterways. Lake trout populations are a detriment to native fish recovery in the majority of waters where they occur, including large lakes in Glacier National Park as well as Flathead, Swan, Whitefish, and others. In lakes with threatened native bull trout (S. confluentus), lake trout management runs headlong into the Endangered Species Act. In addition, ongoing lake trout expansion ranks high amongst future threats to bull trout in the Clearwater lakes (Salmon, Seeley, Alva, Inez, etc.), Lindbergh Lake, Holland Lake, Lake Koocanusa, and others. In oligotrophic lakes of the Columbia Basin, introduced lake trout are well adapted and reproduce liberally, preying upon and competing with other native and sport fishes. Lake trout preference for deepwater habitat and in-lake spawning limits their exposure to land-based and avian predators. Lake trout are long-lived, hardy and resistant to starvation. In systems where Mysis relicta are added to the mix, a tipping point has often been exceeded for maintaining a diverse native ecosystem. Historically, lake trout management strategies were often designed to produce both maximum yield and trophy specimens. A recent review of seven western states revealed agencies are increasingly implementing strategies to reduce lake trout populations in attempts to minimize their impacts. However, management action to deter proliferation of lake trout has often been too little, with too few viable options, too costly, and sometimes too late. In addition, marginal support for lake trout suppression from an unhappy and divided angling public is also an issue.