Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 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 Objective Estimate smolt mortality due to tern and cormorant predation Methodology Demand-based bioenergetics estimates of fish consumption Complimentary Methodologies PIT-Tag Based Predation Rates: • ESU or stock specific • Rearing or migration history, etc. can be examined • Number of fish available based on detections at upstream dam (Bonneville) Bioenergetics Based Predation Rates: • Species specific – not ESU or stock • Number of fish available more difficult to estimate, but possible • Not subject to tagging sampling bias • Not subject to possible deleterious effects of tags Caspian Tern Management Chronology 1999-2000 Relocation 2001-2007 East Sand Island 1987-1998 Rice Island Many Marine Fish Nearby Few Marine Fish Nearby 2008-2012? Dispersal of ~60% of estuary population Rice Is. East Sand Is. Salmonid Mortality Rates due to Tern Predation 1997-2006 1997-1999 2000-2006 All Salmonids 4.8 - 10.3 3.2 - 5.5 Coho 13.7 - 19.6 6.1 - 12.4 Sub-yearling Chinook 2.6 - 10.9 0.6 - 1.8 Yearling Chinook 2.8 - 6.9 Steelhead 7.4 - 12.2 Salmonid Mortality Rates (%) due to Tern Predation: Anticipated Improvements due to Tern Dispersal 1997-1999 2000-2006 Anticipated All Salmonids 4.8 - 10.3 3.2 - 5.5 2.0 Coho 13.7 - 19.6 6.1 - 12.4 3.6 Sub-yearling Chinook 2.6 - 10.9 0.6 - 1.8 0.4 Yearling Chinook 2.8 - 6.9 1.9 Steelhead 7.4 - 12.2 3.7 Cormorant and Tern Comparison Tern Cormorant Numbers (2006) 18,400 27,500 Population Trend Stable Increasing 650 2500 % Salmon in Diet 17 – 47 2 – 25 Chicks Raised per Pair 0.4 – 1.4 1.2 – 2.1 April – mid August April - September Size (g) Present in Estuary Conclusions •Tern 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 chinook •Preliminary 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 analysis