Catastrophes and recovery goals
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Catastrophes and Recovery Goals. The Question: . What is the number and distribution of populations needed for a sustainable ESU?. Spatial Scale. Population (as per VSP) reproductive isolation independent demographics and intrinsic extinction risk ESUs may contain multiple populations.

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The Question:

  • What is the number and distribution of populations needed for a sustainable ESU?


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Spatial Scale

  • Population (as per VSP)

    • reproductive isolation

    • independent demographics and intrinsic extinction risk

  • ESUs may contain multiple populations


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The laundry list of catastrophes

  • Weather (draughts, floods)

  • Oil Spills / Shipping Risks

  • Landslides / Mass Wasting

  • Epidemics

  • Dam/Water Diversion Failure

  • Major mistakes in harvest

  • Chemical contamination

  • Volcanoes

  • Earthquakes

  • Fires


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Major Challenges

  • Predict the frequency, spatial extent and severity of potential catastrophic events

  • Establish the link between the event and salmon survival or behavior

  • Translate impacts on salmon into population and ESU level extinction risk


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Example: Southern Sea Otter

  • Ralls et al. 1996

  • Oil Spill considered most serious threat

  • Extensive modeling potential of oil spill

  • Related spill probabilities to number of contacted otters

  • Estimated mortality per contact from Exxon Valdez data


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Simulated

California

Oil Spills



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Major Oil Spills in Washington

Spills >10,000 gallons over 14 year period.

(State of Washington Dept. of Ecology)



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Increase in Sediment following 1970 Fire in Entiat River, WA (Helvey, 1980)



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SimSalmon

Nx = Number at time x

Rx = Spawners produced per Spawner at time x

R is a stochastic variable with a lognormally

distribution that can be estimated from data

Ai = Fraction that mature at age i


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More Bits on SimSalmon…

  • Extinction:

    • If Nt < Depensataion Threshold, Rt =0

    • The population is extinct if N = 0 for a number of years in a row equal to the maximum age at maturation.

  • Density Dependence

    • Simple Ceiling

    • If Nt > K, then Nt = K



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Sample Data Set

Snake River Fall Chinook

(PATH 1999)



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Question For SimSalmon

  • What is the affect of losing an entire year class on extinction risk?



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Simulation Conditions

  • Distribution of R

    • Lognormal, mean = 1, variance = 1.72

  • Depensation threshold = 10

  • Age distribution




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Major Challenges

  • Predict the frequency, spatial extent and severity of potential catastrophic events

  • Establish the link between the event and salmon survival or behavior

  • Translate impacts on salmon into population and ESU level extinction risk



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ESU Viability Guidelines

  • ESUs should contain multiple populations.

  • Populations in an ESU should be geographically widespread.

  • Populations should be geographically close to each other.

  • Populations should not all share common catastrophic risks.

  • Populations that display diverse life-histories and phenotypes should be maintained.

  • Some populations should exceed VSP guidelines.

  • Evaluations of ESU status should take into account uncertainty about ESU-level processes.


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Final Thoughts

  • Catastrophes can be the largest risk.

  • Catastrophic risk will not be eliminated and needs to be incorporated into large scale recovery plans.

  • Collaboration across many disciplines will be required.


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