Translocation of imperiled fishes: Conservation introduction of threatened bull trout in Glacier National Park

Science Center Objects

There is an urgent need to consider more aggressive and direct interventions for conservation of freshwater fishes threatened by invasive species, habitat loss, and climate change. Conservation introduction - moving species to areas outside their previous range, where conditions are predicted to be more suitable - is one type of translocation strategy that fisheries managers can use to establish new conservation populations and potential refugia (safe havens). To date, however, there are few examples of successful conservation-based introductions, and many attempts fail to establish new populations likely due in part to inadequate assessment of environmental factors influencing success prior to implementation.

Capturing juvenile bull trout by electroshocking Logging Creek and then transporting them to another lake upstream.
Capturing juvenile bull trout by electroshocking Logging Creek and then transporting them in a backpack up the trail to Grace Lake.Public domain

Glacier National Park (GNP) supports about one-third of the remaining natural lakes supporting threatened bull trout in the United States. However, the vast majority of lake-dwelling bull trout populations in western GNP have dramatically declined in the last 25-30 years, owing to the invasion and establishment of nonnative lake trout. Lake trout have invaded nine of the 12 connected lakes west of the Continental Divide where bull trout are native in GNP, and in lakes where data exist, bull trout populations have declined to the point of functional extirpation (local extinction) in less than 30 years.

In response, the USGS, NPS, and Montana State University completed a recent study to assess the feasibility of “rescuing” imperiled bull trout populations through translocation of drainage-specific populations into novel stream and lake habitats in GNP. This decision-making framework provides a flexible platform to help managers make informed decisions for moving threatened fishes into potential refugia for conservation and recovery programs. The suitability of potential translocation sites was evaluated based on four major components: the recipient habitat, recipient community, donor population, and future threats. A series of key questions was developed within each component, and the final assessment was based on a scoring system that evaluated each potential site, using criteria based on characteristics representative of highly suitable habitats. This framework was then applied to evaluate the proposed within-drainage translocation of three bull trout populations in GNP, including the Logging Lake system (insert link).

Fisheries biologists concluded that a conservation introduction of bull trout within the Logging Lake system was the best management option considering its overall suitability score, the imperiled state of the bull trout population, the potential impacts to other endemic or threatened aquatic species, and long-term threats. Therefore, in 2014, 111 juvenile bull trout were captured in Logging Creek downstream of the Logging translocation site and transported upstream within the same drainage into formerly unoccupied Grace Lake. Translocation involved capturing juvenile bull trout by electroshocking Logging Creek from its mouth upstream to a barrier falls, measuring and individually marking each captured fish, and then transporting them in a backpack up the trail to Grace Lake where they were released. Future work will focus on assessing the growth, survival, abundance, and genetic diversity of translocated bull trout through time.

 

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

 

Collaborators: National Park Service (Chris Downs), Montana State University (Dr. Chris Guy), USFWS (Wade Fredenberg), and Montana Fish, Wildlife and Parks (Matthew Boyer)

 

References:

Galloway, B.T. Feasibility assessment for translocation of imperiled bull trout populations in Glacier National Park, Montana. Master’s Thesis. Montana State University, Bozeman. (Graduate Advisor:Clint C. Muhlfeld)

Galloway, B.T., Clint C. Muhlfeld, ChristopherS. Guy, ChristopherC. Downs, and WadeA. Fredenberg. In-press. A framework for assessing the feasibility of native fish translocations: applications to threatened bull trout. North American Journal of Fisheries Management.