Utilizing Fish Barriers to Protect Westslope Cutthroat Trout Populations: Balancing Opportunity, Long Term Success, and Recreation

An updated status assessment in 2009 was used to qualitatively evaluate populations and catalog threats to the persistence of Westslope Cutthroat Trout (WCT) throughout Montana.  These data summarize the miles of stream with protected populations and those at risk for hybridization and competition.  Analysis of the database revealed that in 2009, 4% of historical habitat supported WCT populations that were completely protected from hybridizing and competing species.  Since 2008, in northcentral Montana, 14 new populations of WCT increased the 4% mark to 6%.   The primary tool for protecting WCT from hybridization and competition is the construction of fish barriers.  Where feasible, the installation of fish barriers generally requires balancing extinction risks due to isolation (demographic, genetic, environmental catastrophe) vs those due to connectivity (disease, hybridization, and competition).  To achieve this balance, fisheries professionals will likely have to accept low levels of genetic introgression in larger connected stream systems.  Recent research and anecdotal evidence indicates, at least for Westslope Cutthroat Trout, the amount of habitat necessary to support populations over longer time periods (50 to 100 yrs.) is less than predicted by previous research.