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Open-File Report 2012–1067

Effects of Iron Gate Dam Discharge and Other Factors on the Survival and Migration of Juvenile Coho Salmon in the Lower Klamath River, Northern California, 2006–09

By John Beeman and Steven Juhnke, U.S. Geological Survey; and Greg Stutzer and Katrina Wright, U.S. Fish and Wildlife Service

Thumbnail of and link to report PDF (3.4 MB)Abstract

Current management of the Klamath River includes prescribed minimum discharges intended partly to increase survival of juvenile coho salmon during their seaward migration in the spring. To determine if fish survival was related to river discharge, we estimated apparent survival and migration rates of yearling coho salmon in the Klamath River downstream of Iron Gate Dam. The primary goals were to determine if discharge at Iron Gate Dam affected coho salmon survival and if results from hatchery fish could be used as a surrogate for the limited supply of wild fish. Fish from hatchery and wild origins that had been surgically implanted with radio transmitters were released into the Klamath River slightly downstream of Iron Gate Dam at river kilometer 309. Tagged fish were used to estimate apparent survival between, and passage rates at, a series of detection sites as far downstream as river kilometer 33. Conclusions were based primarily on data from hatchery fish, because wild fish were only available in 2 of the 4 years of study. Based on an information-theoretic approach, apparent survival of hatchery and wild fish was similar, despite differences in passage rates and timing, and was lowest in the 54 kilometer (km) reach between release and the Scott River. Models representing the hypothesis that a short-term tagging- or handling-related mortality occurred following release were moderately supported by data from wild fish and weakly supported by data from hatchery fish. Estimates of apparent survival of hatchery fish through the 276 km study area ranged from 0.412 (standard error [SE] 0.048) to 0.648 (SE 0.070), depending on the year, and represented an average of 0.790 per 100 km traveled. Estimates of apparent survival of wild fish through the study area were 0.645 (SE 0.058) in 2006 and 0.630 (SE 0.059) in 2009 and were nearly identical to the results from hatchery fish released on the same dates. The data and models examined supported positive effects of water temperature, river discharge, and fish weight as factors affecting apparent survival in the Klamath River upstream of the confluence with the Shasta River, but few of the variables examined were supported as factors affecting survival farther downstream. The effect of water temperature on apparent survival upstream of the Shasta River was greater than Iron Gate Dam discharge, which was greater than fish weight. The estimated effect on apparent survival between release and the Shasta River with each 1degree Celsius increase in water temperature was 1.4 times the effect of a 100 cubic feet per second increase in Iron Gate Dam discharge and 2.5 times the effect of a 1 gram increase in fish weight, and the effects of discharge and weight diminished at higher water temperatures up to the 17.91 degrees Celsius maximum present in the data examined. The rate of passage at the detection site near the confluence with the Shasta River was primarily affected by date of release, and water temperature was the only factor supported at the site near the confluence with the Scott River. Passage rates at sites downstream of the Scott River were affected by several of the variables examined, but the estimated effects were small and often imprecise. Results from this study indicate that discharge at Iron Gate Dam has a positive effect on apparent survival of yearling coho salmon in the Klamath River upstream of the Shasta River, but the effects are smaller than those of water temperature and are mediated by it. The results also support the use of hatchery fish as surrogates for wild fish in studies of apparent survival, but the available evidence suggests that study fish should be released well upstream of the area of interest, due to short-term differences in survival and migration behavior of hatchery and wild fish after release.

First posted May 3, 2012

For additional information contact:
Director, Western Fisheries Research Center
U.S. Geological Survey
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Seattle, WA 98115
http://wfrc.usgs.gov/

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Suggested citation:

Beeman, J., Juhnke, S., Stutzer, G., and Wright, K., 2012, Effects of Iron Gate Dam discharge and other factors on the survival and migration of juvenile coho salmon in the lower Klamath River, northern California, 2006–09: U.S. Geological Survey Open-File Report 2012-1067, 96 p.



Contents

Abstract

Introduction

Methods

Results

Discussion

Acknowledgments

References Cited

Appendix A. Summary of number of fish released on each date used in analyses of migration and survival of hatchery fish, lower Klamath River, northern California, 2006–09

Appendix B. Correlation matrices of variables considered for use in analyses of passage rates of hatchery fish, lower Klamath River, northern California, 2006–09

Appendix C. Model selection results from 24 models of passage rates of hatchery fish, lower Klamath River, northern California, 2006–09

Appendix D. Encounter histories of radio-tagged yearling juvenile coho salmon of hatchery origin released into the Klamath River at the hatchery based on 4 years of study, 2006–09

Appendix E. Model selection summaries from analyses of recapture probabilities and survival probabilities of hatchery fish, lower Klamath River, northern California, 2006–09

Appendix F. Model selection results from 24 models of reach-specific survival of hatchery fish, lower Klamath River, northern California, 2006–09

Appendix G. Summary of reach-specific covariate values used for migration and survival analysis based on hatchery fish released near Iron Gate Hatchery, lower Klamath River, northern California, 2006–09

Appendix H. Daily release numbers of hatchery and wild fish used in comparisons of hatchery and wild migration and survival, lower Klamath River, northern California, 2006 and 2009

Appendix I. Encounter histories of radio-tagged yearling juvenile coho salmon of hatchery and wild origin released into the Klamath River at the hatchery on dates wild fish were released, northern California, 2006

Appendix J. Model selection summaries from analyses of recapture probabilities and survival probabilities of hatchery and wild fish, lower Klamath River, northern California, 2006

Appendix K. Model selection results from analyses of selected covariates on the survival of hatchery and wild fish, lower Klamath River, northern California, 2006

Appendix L. Encounter histories of radio-tagged yearling juvenile coho salmon of hatchery and wild origin released into the Klamath River at the hatchery on dates wild fish were released, northern California, 2009

Appendix M. Model selection summaries from analyses of recapture probabilities and survival probabilities of hatchery and wild fish, lower Klamath River, northern California, 2009

Appendix N. Model selection results from analyses of selected covariates on the survival of hatchery and wild fish, lower Klamath River, northern California, 2009


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