The Use Of Barriers to Protect Westslope Cutthroat Trout Populations from Genetic Introgression and Competition by Nonnative Salmonids David Moser Montana Fish, Wildlife & Parks

Tarbela Dam – Pakistan Third Largest Dam in World 143 Meters Nerek Dam – Turkmenistan Tallest Dam in World 300 Meters

Status Assessment 2002 and 2009 Multistate, massive effort, many bio’s Historical & Current Distribution Population Health –(#s mature, habitat quality, non native presence, habitat network Barriers Disease Risks Hybridization

Historical Range 58,030 Miles Current Range 33,500 12,741 Miles in Montana

5,934 Miles Genetically Unaltered and Suspected Unaltered 1,410 Miles No Risk Hybridization

WCT Classification MT Types of Conservation Populations ReasonDescription CoreGenetically unaltered; donor ConservationCore and known or probable unique life-history present (fluvial, adfluvial) <10% introgressed SportfishManaged for Recreational Fisheries

Montana Conservation Agreement Signed agreement and MOU; 2000 and 2007 Supported by many different groups 6 NGO’s 5 Fed 1 Tribe Montana Farm Bureau and Montana Stockgrowers Association

Goals of Conservation Agreement Yellowstone & WCT 2007  Maintain number and miles of conservation populations (pure as well) at 1999 levels  Work on 40 conservation projects a year for WCT  Reduce genetic and demographic risks through conservation projects

Barriers vs. Connectivity or Continuum? Fausch et al. 2009, Peterson et al Cottonwood Creek (Beartooth WMA) Cottonwood Creek (Highwood Mountains)

Consequences of Barriers Large and Small Populations  May protect genetic purity, but if too small puts that local population at higher risk of extinction  To hedge against local extinctions need to replicate as many isolated, local populations as possible; human dispersal agents  Barriers protecting larger metapopulations are rare and inherently more prone to failure (e.g. human movement or high flows)

Missouri River Drainage: Reality  The majority of unprotected conservation populations threatened by hybridization and competition  Genetically pure WCT are nearly always protected by some form of barrier and have persisted for > 80 years  In many cases initial genetic samples are pure - further sampling reveals introgression if no barrier present

Constraints on Barriers  Usually can’t build unless channel is incised and high gradient  Higher public access more chance of (un)intentional sabotage  Cost/benefit  Every situation is very different….

Human Dispersal and Maintenance Minimum for Long Term Survival, Sensu Hilderbrand and Kershner 2000 Risks of introgression and re-invasion of non-natives increases with drainage size

Some Public Access Good to Excellent Barrier Site (Tyrell Creek) Drainage Size Miles Multiple Landowners Road Networks High Public Access Marginal Barrier Site Recreational Opportunities (Tenderfoot Creek) Private Landowner Controlled Access Excellent Barrier Site (Cherry Creek) Probability Sabotage Over Time Private Landowner Little Public Access Excellent Barrier Site (Smith Creek) Opportunities Increase Barrier Failure Over Time High Public Access Good Barrier Site (North Fork Highwood Creek)

1.Isolation  Reduced risk due to introgression, disease, competition/predation  Increased risk due to demographic and stochastic processes; human dispersal and maintenance  Many opportunities for these projects, Not really recreational, except for dentists! Strategies Summarized

2.Full Connectivity  Reduced risk due to demographic and stochastic processes  Can conserve life-history variation  Increased risk for introgression, disease, competition/predation – increases with drainage size/access  Opportunities for recreational WCT fisheries and harvest Strategies Summarized, Cont.

3.Continuum?  Many different lengths of projects  Large enough but with a barrier to benefit from both strategies…5 to 15 miles?  Irrigation reservoirs on private lands? Recreational Opportunities? Strategies Summarized, Cont.

Costs Missouri Drainage  Barriers typically cost $100,000 +  Even small projects tend to be costly if designed for the long term  Culvert barriers cost $30,000 to $80,000 +  ≈ 46 Potential projects-just pure WCT  $2,000,000 to $5,000,000

Average Stream Length6 Median Stream Length3 Range Stream Miles0.5 to 65 Number of Projects41 Total Miles228 Restoration Projects Missouri River Drainage Barriers and/or Transfers Smith Creek (Highwood Mountains)Whites Creek (Big Belt Mountains)