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Mechanical Removal of Non-native Fishes in the Colorado River within Grand Canyon

Mechanical Removal of Non-native Fishes in the Colorado River within Grand Canyon. Lew Coggins, Michael Yard, Daniel Gwinn, and Clay Nelson 1 USGS, Grand Canyon Monitoring and Research Center 1 Arizona Game and Fish Department. The Historic Fish Community in Grand Canyon.

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Mechanical Removal of Non-native Fishes in the Colorado River within Grand Canyon

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  1. Mechanical Removal of Non-native Fishes in the Colorado River within Grand Canyon Lew Coggins, Michael Yard, Daniel Gwinn, and Clay Nelson1 USGS, Grand Canyon Monitoring and Research Center 1Arizona Game and Fish Department

  2. The Historic Fish Community in Grand Canyon Humpback Chub (Gila cypha) Bonytail Chub (Gila elegans) Roundtail Chub (Gila robusta) Speckled Dace (Rhinichthys osculus) Colorado Pikeminnow (Ptychocheilus lucius) Razorback Sucker (Xyrauchen texanus) Flannelmouth Sucker (Catastomus latipinnis) Bluehead Sucker (Catastomus discobulus)

  3. Modifications to the Aquatic Ecosystem

  4. The Present Native Fish Community Humpback Chub (Gila cypha) Federally Endangered Bonytail Chub (Gila elegans) Extirpated Roundtail Chub (Gila robusta) Extirpated Speckled Dace (Rhinichthys osculus) Locally Common Colorado Pikeminnow (Ptychocheilus lucius) Extirpated Razorback Sucker (Xyrauchen texanus) Extirpated Flannelmouth Sucker (Catastomus latipinnis) AZ Species of Special Concern Bluehead Sucker (Catastomus discobulus) Locally Common

  5. The Recent Fish Community in Grand Canyon

  6. Background and Motivation In 2002, concern for the downward trend in humpback chub Gila cypha abundance prompted experimental adaptive management actions including removal of non-native fish Melis et al. 2006

  7. Objectives • Evaluate Efficacy of Removing Non-native Fish • To what extent can we remove non-native fishes from a large reach of the Colorado River? • Evaluate Effect of Non-native Fish Removal on the Population Dynamics of Native Fishes • Will humpback chub recruitment increase as a result of non-native removal?

  8. Methods • 2003 to 2006 - 6 trips/year • Jan, Feb, Mar (Winter) • Jul, Aug, Sep (Summer) • Sampling Methods: • Electrofishing • 4-5 pass depletions • Hoopnetting • Estimate relative abundance of native fish (Juveniles).

  9. Methods

  10. Methods – Data Analysis • Constructed abundance estimates for rainbow trout using a Hierarchical Bayes Removal Model (Dorazio et al 2005). • Assumed that site-specific capture probability is drawn from a common Beta distribution. • Prior on capture probability. • Assumed that site-specific abundance is drawn from a common Poisson distribution. • Prior on abundance. • I used uninformative (Uniform) hyper-prior distributions. • Model based aggregation of among site data • Allows sites with high measurement error to be informed or “shrunk” towards the common mean

  11. Results:Efficacy of Removal Efforts

  12. Results - Electrofishing Catch

  13. Results - Electrofishing Catch

  14. Results - Rainbow Trout Abundance

  15. Results - Rainbow Trout Abundance

  16. Results - Rainbow Trout Capture Probability

  17. Results:Indicators of Native Fish Population Response

  18. Results - Humpback Chub Relative Abundance

  19. Results - Flannelmouth Sucker Relative Abundance

  20. Results - Bluehead Sucker Relative Abundance

  21. Thanks!

  22. Background and Motivation • February 2002, GCMRC proposes a 16 year study to address questions related to providing better management of Sediment ANDNative Fish.

  23. What Really Happened

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