the use of barriers to protect westslope cutthroat trout populations from genetic introgression and...
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The Use Of Barriers to Protect Westslope Cutthroat Trout Populations from Genetic
Introgression and Competition by Nonnative Salmonids
David Moser
Montana Fish, Wildlife & Parks
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Tarbela Dam – PakistanThird Largest Dam in World
143 MetersNerek Dam – Turkmenistan
Tallest Dam in World300 Meters
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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
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Historical Range58,030 MilesCurrent Range33,500
12,741 Miles in Montana
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5,934 Miles Genetically Unaltered and Suspected Unaltered
1,410 Miles No Risk Hybridization
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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
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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
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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
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Barriers vs. Connectivity or Continuum?
Fausch et al. 2009, Peterson et al. 2008
Cottonwood Creek (Beartooth WMA)Cottonwood Creek
(Highwood Mountains)
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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)
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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
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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….
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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
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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
bab
ility
Sab
ota
ge
Ove
r T
ime
Private LandownerLittle Public Access
Excellent Barrier Site(Smith Creek)
Opportunities IncreaseB
arri
er F
ailu
re O
ver
Tim
e
High Public AccessGood Barrier Site
(North Fork Highwood Creek)
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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
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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.
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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.
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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
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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)