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Fisheries Applied Research and Technical Assistance


Helena Field Office

Decision support tools to support native fish management:  tradeoffs between threats of nonnative invasions and isolation

Habitat fragmentation and invasion of nonnative fishes are primary contributors to the decline of native salmonids in the western US, but attempts to ameliorate their different effects may elicit different and often conflicting management approaches.  Removal of migration barriers to connect native populations to larger stream networks could allow upstream invasions of nonnative fishes, while installing migration barriers to preclude these invasions may exacerbate effects of habitat fragmentation and population isolation.  Both actions could threaten native species and integrity of aquatic systems, but fish biologists may employ both barrier installation and barrier removal strategies across the western US without evaluation of the opposing threats.  The potential conflicts highlight a challenge in native fish conservation.

Our goal was to formalize an evaluation of tradeoffs between intentional isolation, invasion and conservation of native salmonids.  We focused on persistence of native westslope cutthroat trout (Oncorhynchus clarkii lewisi), potential invasion and subsequent effects of nonnative brook trout (Salvelinus fontinalis), and the primary environmental and anthropogenic factors influencing both species and their interactions.  Our objectives were to develop and explore the application of a Bayesian Belief Network (BBN) as a decision support tool and highlight results that provide general guidance for biologists and managers.  We focused this work on cutthroat trout and brook trout because they represent a widespread and well defined problem in central and northern Rocky Mountain streams (Fausch et al. 2006), but we believe our approach can be readily adapted to other species.




Figure 1 from Peterson et al. 2008.  Conceptual model depicting environmental conditions and processes influencing persistence of westslope cutthroat trout (WCT) and the tradeoffs between intentional isolation and invasion by brook trout (BKT).  Shaded ovals indicate input variables or nodes (prior conditions) believed to affect WCT and brook trout populations, dashed ovals indicate influences that originate outside the local stream network, the rectangle for invasion barrier indicates the primary management decision, and arrows indicate conditional relationships among variables (nodes).  The conceptual model was formalized using a Bayesian Belief Network (BBN) implemented using the software program NETICA.


CollaboratorsDoug Peterson (USFWS); Bruce Rieman and Mike Young, US Forest Service – Rocky Mountain Research Station; Kurt Fausch, Colorado State University; Jason Dunham, US Geological Survey – FRESC


Funding:  Region 1, US Forest Service


Research products:


      InVAD 1.1 -  BBN decision support model.  To run the model:

     1.  Download PDF of user’s guide

     2.  Download free version of proprietary NETICA software to run the model.  Note: The use of trade or firm names is for reader information only and does not imply endorsement of the US Department of Interior of any product or service.

     3.  Download the  BBN decision support model file (.zip that will extract to .dne).  Note: the .dne file will only open after downloading NETICA

     Additional model details are presented in Peterson et al. 2008


Related publications

Fausch, K.D., Rieman, B.E., Young, M., Dunham, J.B., 2006, Strategies for conserving native salmonid populations at risk from nonnative fish invasions - tradeoffs in using barriers to upstream movement.  USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-174. (pdf)

Peterson, D.P., B.E. Rieman, J.B. Dunham, K.D. Fausch, and M.K. Young.  2008.  Analysis of trade-offs between threats of invasion by nonnative brook trout (Salvelinus fontinalis) and intentional isolation for native westslope cutthroat trout (Oncorhynchus clarkii lewisi).  Canadian Journal of Fisheries and Aquatic Sciences 65:557-573. (pdf)

Fausch, K.D., B.E. Rieman, J.B. Dunham, M.K. Young, and D.P. Peterson.  2009.  The invasion versus isolation dilemma: tradeoffs in managing native salmonids with barriers to upstream movement.  Conservation Biology 23(4): 859–870. (pdf)

Peterson, D.P., B.E. Rieman, J.B. Dunham, K.D. Fausch, and M.K. Young.  2007.  Analyzing Tradeoffs Between the Threat of Invasion by Brook Trout and Effects of Intentional Isolation for Native Westslope Cutthroat Trout Pages 51-57 in R. F. Carline and C. LoSapio, editors. Wild Trout IX: Sustaining wild trout in a changing world. Wild Trout Symposium, Bozeman, Montana. (pdf)

Other Links:

Rocky Mountain Research Station flier

Rise to the Future Award for Research Achievement (2008)


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Updated 3/26/10