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 – PakistanThird Largest Dam in World

143 MetersNerek Dam – Turkmenistan

Tallest Dam in World300 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 Range58,030 MilesCurrent Range33,500

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

Reason Description

Core Genetically unaltered; donor

Conservation Core and known or probable unique life-history present (fluvial, adfluvial) <10% introgressed

Sportfish Managed 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. 2008

Cottonwood Creek (Beartooth WMA)Cottonwood Creek

(Highwood Mountains)

Consequences of BarriersLarge 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,

SensuHilderbrand and Kershner 2000

Risks of introgression and re-invasion of non-natives increases with drainage size

Some Public AccessGood to Excellent

Barrier Site(Tyrell Creek)

Drainage Size Miles

Multiple LandownersRoad Networks

High Public AccessMarginal Barrier Site

Recreational Opportunities

(Tenderfoot Creek)

Private LandownerControlled Access

Excellent Barrier Site(Cherry Creek)

Pro

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Private LandownerLittle Public Access

Excellent Barrier Site(Smith Creek)

Opportunities IncreaseB

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High Public AccessGood 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 Length 6Median Stream Length 3Range Stream Miles 0.5 to 65Number of Projects 41Total Miles 228

Restoration Projects Missouri River DrainageBarriers and/or Transfers

Smith Creek (Highwood Mountains) Whites Creek (Big Belt Mountains)