PREDATION OF JUVENILE SALMONIDS BY RESIDENT TROUT AND OTHER FISHES IN THE LOWER CEDAR RIVER, WASHINGTON FINAL REPORT TO SEATTLE PUBLIC UTILITIES by Roger A. Tabor U.S. Fish and Wildlife Service Washington Fish and Wildlife Office, Fisheries Division 510 Desmond Drive SE, Suite 102 Lacey, Washington 98503 Hans B. Berge King County, Department of Natural Resources and Parks 201 South Jackson Street, Suite 600 Seattle, Washington 98104 Matt M. Klungle and Brad E. Thompson1 Washington Department of Fish and Wildlife 600 Capitol Way N Olympia, Washington 98501 and Daniel W. Lantz2 and Benjamin E. Price3 U.S. Fish and Wildlife Service Washington Fish and Wildlife Office, Fisheries Division 510 Desmond Drive SE, Suite 102 Lacey, Washington 98503 February 2014 1Present address: U.S. Fish and Wildlife Service, Washington Fish and Wildlife Office, 510 Desmond Drive SE, Suite 102, Lacey, Washington 98503 2Present address: King County, Department of Natural Resources and Parks, 201 South Jackson Street, Suite 600, Seattle, WA 98104 3Present address: Restorx of Washington, Auburn, WA 98001 ACKNOWLEDGEMENTS We dedicate this report to the memory of Steve Foley. He was instrumental in supporting this project and without his assistance the project would not have been successful. Funding for this project was provided in part by the Seattle Public Utilities (SPU) (through the Cedar River Anadromous Fish Committee) and the Washington Department of Fish and Wildlife. We are appreciative of Paul Faulds, Gary Spraque, and Michele Koehler, SPU for their assistance and support. Suggestions by Karl Burton, SPU and Frank Urabeck improved the final version of this report. We thank the many folks who assisted with the field work which included USFWS employees: Scott Sanders, Steve Damm, Dan Spencer, James Curtis, Terence Lee, Howard Gearns, Jeff Chan, Tim Romanski, Keith Sweeney, Eric Tallman, Nathan Hyde, and Tracy Leavy; WDFW employees: William Morris, Nathan Martens, Devin West, Shannon Vincent, Brant Boelts, Clayton Kinsel, Ann Blakely, Chad Jackson, Todd Kassler, Yong-Woo Lee, Nathanael Overman, Kelly Kiyohara, Bruce Bolding, Craig Busack, Scott Scheutzler; King County employees: Jim Lissa, Frank Leonetti, Ray Timm, Eleanor Bosman-Clark, Kollin Higgins; NOAA Fisheries employees: Sean Naman and Thomas Buehrens; and Trout Unlimited volunteers, especially Bill Robinson. We thank Lindsy Wright and James Curtis, USFWS for their long hours of processing the diet samples. Carrie Cook-Tabor assisted with editing and formatting of the draft report. USFWS student trainee employees Matt Wynn, Matt Wiley, Audry Djunaedi, Ashley Drossart, Alec Barber, and Verl Engel assisted with data entry. Genetic analysis was conducted by Todd Kassler and Cheryl Dean, WDFW. Isotope analysis was conducted by Sean Naman and Peter Kiffney, NOAA Fisheries. Trout scales were analyzed at the WDFW aging lab under the direction of Lee Blankenship. Trout otoliths were analyzed at the WDFW otolith lab under the direction of Jeff Grimm. Access to the river was greatly improved by private landowners Julie Stachawiak and Tim Allen who gave us permission to cross their property. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ......................................................................................................... ii EXECUTIVE SUMMARY .......................................................................................................... v INTRODUCTION......................................................................................................................... 1 STUDY AREA ............................................................................................................................... 3 METHODS .................................................................................................................................... 5 Study Design .............................................................................................................................. 5 Summer Field Sampling (July-August 2006 and 2007) ........................................................ 6 Winter-Spring Field Sampling (January-June 2008 and 2010) ............................................ 7 Fish Sampling ........................................................................................................................... 7 Abundance Sampling ............................................................................................................. 7 Diet Sampling ........................................................................................................................ 8 Other Fish Sampling ............................................................................................................. 9 Diet Analysis .............................................................................................................................. 9 Data Analysis ........................................................................................................................... 10 Abundance Estimation ......................................................................................................... 10 Diet Analysis ....................................................................................................................... 16 Consumption Estimation (Direct Consumption Model) ...................................................... 17 RESULTS .................................................................................................................................... 20 Abundance Estimates and Length Composition .................................................................... 20 Diet ........................................................................................................................................... 30 Trout .................................................................................................................................... 30 July-August Diet ............................................................................................................. 30 Winter-Spring Diet ......................................................................................................... 33 Coho Salmon ....................................................................................................................... 45 Mountain Whitefish ............................................................................................................. 46 Sculpin ................................................................................................................................. 47 Smallmouth Bass ................................................................................................................. 50 Consumption Estimates .......................................................................................................... 50 Trout .................................................................................................................................... 50 July-August Predation Estimates .................................................................................... 50 Winter-Spring Predation Estimates ................................................................................ 51 Coho Salmon (Winter-Spring Only) .................................................................................... 60 Other Analyses ........................................................................................................................ 61 PIT Tag Analysis ................................................................................................................. 61 Otolith Analysis ................................................................................................................... 61 DISCUSSION .............................................................................................................................. 62 Abundance Estimates and Length Composition .................................................................... 62 Predation and Diet .................................................................................................................. 64 Trout .................................................................................................................................... 64 Coho Salmon ....................................................................................................................... 70 REFERENCES ............................................................................................................................ 71 APPENDIX A .............................................................................................................................. 79 iii iv EXECUTIVE SUMMARY From 2006 to 2010, Washington Department of Fish and Wildlife, U.S. Fish and Wildlife Service, and King County undertook a cooperative project to estimate the abundance of resident trout and quantify their predation on juvenile salmonids in the Cedar River below Landsburg Diversion Dam. Summer sampling was conducted in 2006-2008, while winter-spring sampling was conducted in 2008-2010. Efforts to estimate resident trout abundance were conducted during three different summers and two winter-spring periods. Predation and diet sampling were conducted during two summer and two winter-spring periods. Summer abundance estimates of resident trout from 2006 to 2008 were remarkably similar, ranging from 16,320 to 17,435. In 2006 and 2007, trout were captured and marked for a recapture and/or resight (snorkeling)