Experimental suppression of invasive lake trout: Implications for conservation of imperiled bull trout in Glacier National Park

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After 14,000 years of dominance, Glacier National Park’s (GNP) greatest native aquatic predator is at high risk of extirpation (local extinction) in several lakes on the western slopes of the Continental Divide. The decline of threatened bull trout in GNP is directly attributed to the invasion and establishment of nonnative lake trout, which consistently displace bull trout in systems where lake trout have been introduced. Lake trout have colonized almost every accessible lake to which bull trout are native on the west side of GNP and unless research-based management is implemented immediately, these ecologically unique populations face continued decline and likely extirpation.

Logging Lake, Glacier National Park.Public domain

This project involves aggressive control measures to reduce lake trout in Logging Lake. These control measures are based on methods that have proven highly successful in reducing lake trout and maintaining a healthy bull trout population in nearby Quartz Lake. Logging Lake - once considered the most productive bull trout fishery in GNP - is at imminent risk of losing bull trout as a functional part of the aquatic ecosystem. Compounding these issues is climate change, which is expected to exacerbate interactions with non-native invasive species throughout the western United States and GNP. Therefore, protected areas, such as GNP, which contains an abundance of deep, cold, glacially-carved lakes, will become increasingly important as warming trends continue because such areas will provide refugia (safe havens) from climate change and other cummulative stressors. Providing high-quality lake habitats and reducing interactions with invasive species is an urgent priority for will be critical to the future resiliency and adaptation of bull trout populations and other native aquatic species in GNP and elsewhere.

The overall goal of this project is to protect GNP's ecologically unique bull trout populations from further declines and potential extinction and rescue an imperiled bull trout population (insert link to translocation study here). Specifically, this collaborative USGS and NPS research project will assess demographics of the lake trout population and use this information to inform and implement experimental removal and control alternatives to reduce or eliminate competitive interactions in the Logging Lake system and other lakes in GNP. This information is critical to understanding the feasibility of suppressing nonnative lake trout in a small, backcountry lake that contains native bull trout. Results will be applied to management of other lakes in GNP and possibly other systems throughout the native range of bull trout. 

 

Funding: NPS Natural Resource Preservation Program, USGS Invasive Species Program 

Collaborators: National Park Service (Chris Downs)