1. 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

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

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 Colorado Pikeminnow (Ptychocheilus lucius ) Extirpated Speckled Dace (Rhinichthys osculus ) Locally Common Flannelmouth Sucker (Catastomus latipinnis) AZ Species of Special Concern Bluehead Sucker (Catastomus discobulus) Locally Common Razorback Sucker (Xyrauchen texanus) Extirpated

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 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 Evaluate Efficacy of Removing Non-native Fish To what extent can we remove non-native fishes from a large reach of the Colorado River? 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 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? Will humpback chub recruitment increase as a result of non-native removal?

8. Methods 2003 to 2006 - 6 trips/year 2003 to 2006 - 6 trips/year Jan, Feb, Mar (Winter) Jan, Feb, Mar (Winter) Jul, Aug, Sep (Summer) Jul, Aug, Sep (Summer) Sampling Methods: Sampling Methods: Electrofishing Electrofishing 4-5 pass depletions 4-5 pass depletions Hoopnetting Hoopnetting Estimate relative abundance of native fish (Juveniles). 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). 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. Assumed that site-specific capture probability is drawn from a common Beta distribution. Prior on capture probability. Prior on capture probability. Assumed that site-specific abundance is drawn from a common Poisson distribution. Assumed that site-specific abundance is drawn from a common Poisson distribution. Prior on abundance. Prior on abundance. I used uninformative (Uniform) hyper-prior distributions. I used uninformative (Uniform) hyper-prior distributions. Model based aggregation of among site data Model based aggregation of among site data Allows sites with high measurement error to be informed or “shrunk” towards the common mean 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

14. 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 AND Native Fish. February 2002, GCMRC proposes a 16 year study to address questions related to providing better management of Sediment AND Native Fish. Year Mechanical Removal Fluctuating Flows Temperature Control Device 1XXXXXX 2XXXXXX 3XXX 4XXX 5XXX 6XXX 7 8 9XXXXXXXXX??? 10XXXXXXXXX??? 11XXXXXX??? 12XXXXXX??? 13XXXXXX??? 14XXXXXX??? 15XXX??? 16XXX???

23. What Really Happened Year Mechanical Removal Fluctuating Flows Temperature Control Device 1 (2003) XXXXXX “Naturally Elevated Temp” 2 (2004) XXXXXX “More Naturally Elevated Temp” 3 (2005) XXXXXX “Even More Naturally Elevated Temp” 4 (2006) XXX “Naturally Elevated Temp” 5 (2007) (Non-natives in low abundance) “Likely Elevated Temp” 6???????????????????????? 7???????????????????????? 8???????????????????????? 9???????????????????????? 10???????????????????????? 11???????????????????????? 12???????????????????????? 13???????????????????????? 14???????????????????????? 15???????????????????????? 16????????????????????????