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Montana Ecological Services Field Office

585 Shepard Way, Suite 1 Helena, Montana 59601 406-449-5225 (FAX) 406-449-5339



Fisheries Applied Research and Technical Assistance


Helena Field Office


Modeling suppression of nonnative brook trout to benefit native cutthroat trout

Nonnative trout species are among the most significant threats to persistence of native inland salmonids, such as cutthroat trout (Oncorhynchus clarkii spp.).  Early detection of nonnative trout invasions and subsequent eradication is the preferred management alternative to deal with this threat, but sometimes eradication is not possible for technical or socio-political reasons.  In such cases, maintenance control or suppression of nonnative species using mechanical methods (e.g., electrofishing) becomes a frequent alternative where the risk of inaction is unacceptable.

Colorado River cutthroat trout

Colorado River cutthroat trout


Brook trout

Brook trout


We conducted a population modeling project to help biologists design and implement effective electrofishing suppression programs.  To do this we built stage-based, stochastic matrix models describing sympatric populations of stream-resident brook trout (Salvelinus fontinalis) and cutthroat trout and used the models to show the demographic differences between the species and compare the efficacy of various electrofishing treatments for suppressing brook trout.  The models were used to assess the population response of cutthroat trout to brook trout suppression as a function of the frequency and temporal distribution of annual suppression visits, electrofishing intensity (number of passes) during individual suppression events, electrofishing capture efficiency, and immigration by brook trout. U.S. Fish and Wildlife Service electrofishing crew

Project investigators and Funding: Dr. Doug Peterson (US Fish and Wildlife Service),  Dr. Kurt Fausch (Colorado State University), Dr. Rick Cunjak (Canadian Rivers Institute, University of New Brunswick), and Dr. James Watmough (Department of Mathematics, University of New Brunswick)

Research products:

Peterson, D. P., K. D. Fausch, J. Watmough, and R. A. Cunjak.  2008.  When eradication is not an option: modeling strategies for electrofishing suppression of nonnative brook trout to foster persistence of sympatric native cutthroat trout in small streams.  North American Journal of Fisheries Management 28:1847-1867. (pdf)

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Updated 9/8/09