1. Evaluation of Avian Predation on Juvenile Salmonids in the Columbia River Estuary Donald E. Lyons Ph.D. Candidate Oregon State University Department of Fisheries and Wildlife

2. Acknowledgments Oregon State University/USGS faculty and students: Dan Roby [PI], Jessica Adkins, Yasuko Suzuki, Lauren Reinalda, Nathan Hostetter RTR, Inc. colleagues: Ken Collis [Co-PI], Allen Evans, Mike Hawbecker NOAA Fisheries collaborators: Bob Emmett, Tom Good, Doug Marsh, Dick Ledgerwood, Scott Sebring, David Teel

3. Objective Estimate smolt mortality due to tern and cormorant predation Methodology Demand-based bioenergetics estimates of fish consumption

4. Complimentary Methodologies PIT-Tag Based Predation Rates: ESU or stock specificESU or stock specific Rearing or migration history, etc. can be examinedRearing or migration history, etc. can be examined Number of fish available based on detections at upstream dam (Bonneville)Number of fish available based on detections at upstream dam (Bonneville) Bioenergetics Based Predation Rates: Species specific – not ESU or stockSpecies specific – not ESU or stock Number of fish available more difficult to estimate, but possibleNumber of fish available more difficult to estimate, but possible Not subject to tagging sampling biasNot subject to tagging sampling bias Not subject to possible deleterious effects of tagsNot subject to possible deleterious effects of tags

6. Caspian Tern Management Chronology 1987-1998 Rice Island Few Marine Fish Nearby 2001-2007 East Sand Island Many Marine Fish Nearby 1999-2000 Relocation 2008-2012? Dispersal of ~60% of estuary population

7. East Sand Is. Rice Is.

8. Salmonid Mortality Rates due to Tern Predation 1997-2006 1997-19992000-2006 All Salmonids4.8 - 10.33.2 - 5.5 Coho13.7 - 19.66.1 - 12.4 Sub-yearling Chinook2.6 - 10.90.6 - 1.8 Yearling Chinook2.8 - 6.9 Steelhead7.4 - 12.2

9. Salmonid Mortality Rates (%) due to Tern Predation: Anticipated Improvements due to Tern Dispersal 1997-19992000-2006Anticipated All Salmonids4.8 - 10.33.2 - 5.52.0 Coho13.7 - 19.66.1 - 12.43.6 Sub-yearling Chinook2.6 - 10.90.6 - 1.80.4 Yearling Chinook2.8 - 6.91.9 Steelhead7.4 - 12.23.7

11. Cormorant and Tern Comparison TernCormorant Numbers (2006)18,40027,500 Population TrendStableIncreasing Size (g)6502500 % Salmon in Diet17 – 472 – 25 Chicks Raised per Pair0.4 – 1.41.2 – 2.1 Present in EstuaryApril – mid AugustApril - September

14. Conclusions Tern relocation to East Sand Island benefited sub-yearling chinook and apparently cohoTern relocation to East Sand Island benefited sub-yearling chinook and apparently coho Planned dispersal of terns away from estuary provides some benefit for steelhead and coho, less for yearling chinook, little for sub-yearling chinookPlanned dispersal of terns away from estuary provides some benefit for steelhead and coho, less for yearling chinook, little for sub-yearling chinook Preliminary cormorant results suggest similar predation rates to terns, perhaps more impacts for sub-yearling chinookPreliminary cormorant results suggest similar predation rates to terns, perhaps more impacts for sub-yearling chinook Further cormorant work required to verify preliminary results, allow NEPA analysisFurther cormorant work required to verify preliminary results, allow NEPA analysis