State of Utah DEPARTMENT OF NATURAL RESOURCES Division of Wildlife Resources – Native Aquatics POPULATION ESTIMATES FOR HUMPBACK CHUB (GILA CYPHA) AND ROUNDTAIL CHUB (GILA ROBUSTA) IN WESTWATER CANYON, COLORADO RIVER, UTAH, 1998–2000 Publication Number 03-51 Utah Division of Wildlife Resources 1594 W. North Temple Salt Lake City, Utah Kevin Conway, Director Population Estimates for Humpback Chub (Gila cypha) and Roundtail Chub (Gila robusta) in Westwater Canyon, Colorado River, Utah, 1998–2000 J. Michael Hudson and Julie A. Jackson Utah Division of Wildlife Resources-Moab Field Station 1165 S. Hwy 191-Suite 4 Moab, UT 84532 Final Report December 2003 Upper Colorado River Endangered Fish Recovery Program Project #22c Publication Number 03-51 Utah Division of Wildlife Resources 1594 W. North Temple Salt Lake City, Utah Kevin Conway, Director ii ACKNOWLEDGEMENTS We would like to acknowledge Tom Chart, Melissa Trammel, Steve Meismer, and Pete Cavalli, who leant their considerable biological expertise to various portions of this study. We would also like to thank Dr. Ron Ryel, Utah State University, and Dr. Kevin Bestgen, Colorado State University, for statistical guidance. Many thanks to Dr. Kevin Bestgen, Chuck McAda, and Dr. Rich Valdez for their in depth review and critique of this report. Finally, we would like to thank the numerous technicians and volunteers without whom this study would not have been possible. This study was funded by the Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin. The Recovery Program is a joint effort of the U.S. Fish and Wildlife Service, U.S. Bureau of Reclamation, Western Area Power Administration, state of Colorado, Utah, and Wyoming, Upper Basin water users, environmental organizations, the Colorado River Energy Distributors Association, and the National Park Service. Mention of trade names or commercial products does not constitute endorsement of recommendation for use by the authors, the Fish and Wildlife Service, U.S. Department of the Interior, or members of the Recovery Implementation Program. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ......................................................................................................... ii TABLE OF CONTENTS ............................................................................................................ iii LIST OF TABLES .........................................................................................................................v LIST OF FIGURES .................................................................................................................... vi LIST OF KEY WORDS ............................................................................................................. vii EXECUTIVE SUMMARY ....................................................................................................... viii INTRODUCTION..........................................................................................................................1 METHODS .....................................................................................................................................2 Study Area ...........................................................................................................................2 Sampling..............................................................................................................................2 Data Analysis.......................................................................................................................3 Population Estimate.................................................................................................3 CPUE .......................................................................................................................3 Length-Frequency....................................................................................................4 Growth .....................................................................................................................4 Movement.................................................................................................................4 Comparison with ISMP............................................................................................4 RESULTS .......................................................................................................................................4 Humpback Chub .................................................................................................................4 Population Estimates ...............................................................................................4 CPUE .......................................................................................................................5 Length-Frequency....................................................................................................5 Growth .....................................................................................................................6 Movement.................................................................................................................6 Comparison with ISMP............................................................................................6 Roundtail Chub...................................................................................................................7 Population Estimates ...............................................................................................7 CPUE .......................................................................................................................7 Length-Frequency....................................................................................................8 Growth .....................................................................................................................8 Movement.................................................................................................................8 Comparison with ISMP............................................................................................8 iv TABLE OF CONTENTS (continued) DISCUSSION.................................................................................................................................9 Population Estimates ..........................................................................................................9 Length-Frequency.............................................................................................................10 Growth ...............................................................................................................................10 Movement ..........................................................................................................................11 Comparison with ISMP ....................................................................................................12 CONCLUSIONS ..........................................................................................................................13 RECOMMENDATIONS.............................................................................................................14 LITERATURE CITED ...............................................................................................................15 APPENDICES..............................................................................................................................29 v LIST OF TABLES Table 1. Population estimate for humpback chub adults in Westwater Canyon 1998–2000..............................................................................................................17 Table 2. Total humpback chub captures in Westwater Canyon 1998–2000........................17 Table 3. Population estimate for roundtail chub adults in Westwater Canyon 1998–2000..............................................................................................................18 Table 4. Total roundtail chub captures in Westwater Canyon 1998–2000..........................18 Appendix I. Summary of population estimates generated within Program CAPTURE for adult humpback chub in Westwater Canyon, 1998–2000 .....................................29 Appendix II. Summary of population estimates generated within Program CAPTURE for adult roundtail chub in Westwater Canyon, 1998–2000........................................30 vi LIST OF FIGURES Figure 1. Westwater Canyon adult humpback chub population estimates for 1998–2000..............................................................................................................19 Figure 2. Westwater Canyon humpback chub trammel net catch per unit effort by pass for 1998–2000................................................................................................19 Figure 3. Westwater Canyon humpback chub length-frequency histograms for 1998– 2000........................................................................................................................20 Figure 4. Westwater Canyon humpback chub annual incremental growth for individuals between 1998–1999 and 1999–2000, and among all years.................21 Figure 5. Westwater Canyon humpback chub catch per unit effort for samples collected using ISMP protocol from 1988 to 2000................................................21 Figure 6. Westwater Canyon humpback chub ISMP length-frequency histograms for 1988–2000........................................................................................................22