Preservation of Imperiled Bull Trout Threatened by Non-Native Lake Trout in Glacier National Park

Non-native lake trout threaten native salmonid populations in western North America. Glacier National Park (GNP) contains about one-third of the natural lakes supporting threatened bull trout in the United States, yet several populations are at high risk of extirpation due to the invasion and establishment of non-native lake trout from Flathead Lake. Currently, 9 or 12 accessible bull trout lakes west of the Continental Divide in GNP have been compromised by non-native lake trout, and native bull trout populations in these waters are being pushed towards functional extinction as lake trout expand.  In response, in 2009 we initiated a four-year experimental suppression project in Quartz Lake (869 surface acres) to reduce or eliminate lake trout. Suppression activities include identifying the timing and location of spawning using telemetry and experimental netting to remove adult and juvenile lake trout, respectively. Results are promising and underscore the urgency to continue suppression activities to prevent continued loss of remaining bull trout populations. This project will use population modeling to evaluate the effectiveness of various removal strategies to maximize lake trout exploitation.  Results may be used to assess the feasibility of lake trout removal in other threatened park lakes and other systems across the United States.