AN ABSTRACT OF THE THESIS OF Andrew G. Talabere for the degree of Master of Science in Fisheries Science presented on November 21. 2002. Title: Influence of Water Temperature and Beaver Ponds on Lahontan Cutthroat Trout in a High-Desert Stream, Southeastern Oregon Abstract approved Redacted for Privacy Redacted for Privacy The distribution of Lahontan cutthroat trout Oncorhynchus clarki henshawi was assessed in a high-desert stream in southeastern Oregon where beaver Castor canadensis are abundant. Longitudinal patterns of beaver ponds, habitat, temperature, and Lahontan cutthroat trout age group distribution were identified throughout Willow Creek. Three distinct stream segments were classified based on geomorphological characteristics. Four beaver-pond and four free-flowing sample sections were randomly located in each of the three stream segments. Beavers substantially altered the physical habitat of Willow Creek increasing the depth and width of available habitat. In contrast, there was no measurable effect on water temperature. The total number of Lahontan cutthroat trout per meter was significantly higher in beaver ponds than free-flowing sections. Although density (fish! m2) showed no statistically significant (P < 0.05) increase, values in beaver pondswere two-fold those of free-flowing sections. Age- 1 and young-of-the-year trout were absent or in very low numbers in lower Willow Creek because of elevated temperatures, but high numbers of age-2 and 3 (adults) Lahontan cutthroat trout were found in beaver ponds where water temperatures reached lethal levels (>24°C). Apparently survival is greater in beaver ponds than free-flowing sections as temperatures approach lethal limits. Influence of Water Temperature and Beaver Ponds on Lahontan Cutthroat Trout in a High- Desert Stream, Southeastern Oregon by Andrew G. Talabere A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented November 21, 2002 Commencement June 2003 Master of Science thesis of Andrew G. Talabere presented on November 21, 2002. APPROVED: Redacted for Privacy Co-Major Professorepresenting Fisheries Science RedactedRedacted forfor Privacy Privacy Co-Major 1frssor, representing Fisheries Science Redacted for Privacy Head of the Department of Fisheries and Wildlife Redacted for Privacy Dean of thGraduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Redacted for Privacy Andrew G. Talabere, Author ACKNOWLEDGEMENTS This thesis is truly a collaborative effort. The many organizations and people that contributed are greatly appreciated. A sincere thanks to my co-major advisors Dr. Bob Gresswell and Dr. Bill Liss. Your guidance and understanding helped make this project a success. I am grateful to my committee members Dr. Bob Beschta and Dr. Boone Kauffman. I am indebted to the following organizations who contributed monetary, material, and/or moral support: Oregon Department of Fish and Wildlife, Oregon Wildlife Heritage Foundation, Trout Unlimited, Bureau of Land Management, U.S. Fish and Wildlife Service, Oregon Flyfishers, Whitehorse Ranch, and the town of Fields, Oregon. Thank you to my field assistants Jared Jebousek and Justin Gerding who endured early mornings, long afternoon siestas, thunderstorms, dustdevils, rattlesnakes, and me. I extend sincere thanks to my cohorts in Fisheries and Wildlife who provided discussion, inspiration, and humor. A special thanks to Colden Baxter, Joe Ebersole, Bill Gerth, Steve Hendricks, Jeff Manning, Sue Mauger, Mark Meleason, Christian Torgerson, Lowell Whitney, and Kris Wright. To the best group of friends ever, I extend a very special thank you for keeping me sane and providing unending support. Thank you "Compost Pile:" Scott & Jodi Andrews, Finlay & Amy Turnbull Anderson, Steve & Tern Bovingdon, Shawn & Kaela Ultican, Loren & Kira Willson, and Marc & Jean Olson. Thank you to my family, especially my mom and dad, Herb and Laurel Talabere for caring and ecouraging me to achieve my goals. Kim Jones provided generous work flexibility that enabled me to complete the analysis and writing phase of this project. Wayne and Patty Bowers deserve special thanks for being good friends and providing home base and logistical support. Finally, there are not enough ways to thank or show the depth of my appreciation to Stephanie Gunckel. Your love, support, and faith in me kept me going and provided that extra kick to get finished. TABLE OF CONTENTS CHAPTER 1: INTRODUCTION....................................................................................... StudyArea and background............................................................................................ 5 Methods........................................................................................................................... 8 SampleSection Selection............................................................................................ 8 PhysicalHabitat........................................................................................................... 9 Temperature ............................................................................................................... 10 Lahontan cutthroat trout............................................................................................ 11 Data Summary and Statistical Analysis..................................................................... 11 CHAPTER3: RESULTS.................................................................................................. 13 PhysicalHabitat............................................................................................................. 13 Temperature ................................................................................................................... 17 Lahontan cutthroat trout................................................................................................ 21 Ageand Length Analysis........................................................................................... 21 Lahontan Cutthroat Trout Size Distribution Patterns................................................ 22 Measures of Lahontan Cutthroat Trout Abundance.................................................. 25 Habitat Relations of Lahontan Cutthroat Trout......................................................... 27 CHAPTER4: DISCUSSION............................................................................................ 33 BIBLIOGRAPHY............................................................................................................. 39 LIST OF FIGURES Figure I. Conceptual diagram of decreasing trout abundance (---) with increasing stream temperature () and the hypothesized response of water temperature and trout density to beaver pond complexes (A)................................................................ 4 2. Willow Creek in Coyote Lake basin southeastern Oregon.............................................. 6 3. Means and standard error bars for wetted width and depth of beaver-pond (LI) and free-flowing () sections of Willow Creek, Harney County, Oregon. Asterisks (*) indicate statistical difference (P < 0.05)................................................ 15 4. Longitudinal stream profile of elevation, 7-day maximum temperature, width:depth, and abundance of trout........................................................................... 16 5. Discharge, mean shade, and mean maximum temperature from July............................ 18 6. Mean hours/day that the water temperature exceeded 20, 22, 24, and 26°C in beaver-pond (B;LI) and free-flowing (F;U) sections of the Canyon, Transition, and Valley segments of Willow Creek, Harney County, Oregon.............19 7. Diel temperature pattern of Willow Creek, Harney County, Oregon, for July 14, 1999; the day with the highest recorded water temperature (26.7°C) where data were available for all segments........................................................................... 20 8. Length frequency histograms of Lahontan cutthroat trout from Willow Creek, Harney County, Oregon in July and September, 1999................................................ 23 9. Length of Lahontan cutthroat trout captured in beaver-pond (LI) and free- flowing(a)sections from three segments of Willow Creek, Harney County, Oregon, July and September, 1999............................................................................. 24 10. Mean Lahontan cutthroat trout linear-density (trout/m) and areal-density (trout/m2)in July and September, 1999 in Willow Creek, Harney County, Oregon. Bars represent standard errors...................................................................... 26 11. Mean linear-density (trout/rn) and areal-density (trout/m2) for age-I, age-2, and age-3+ Lahontan cutthroat trout in July and September, 1999 in Willow Creek, Harney County, Oregon................................................................................... 29 12. Scatter plots of age-I, age-2, and age-3+ Lahontan cutthroat trout-per-meter and temperature for the July sampling period........................................................... 32 LIST OF TABLES Table I. Mean habitat values for beaver-pond and free-flowing sections in three segments of Willow Creek: Canyon, Transition, and Valley.................................... 14 2. Fork length means and SE and medians and