Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 9108
Title: Survival estimates for the passage of spring-migrating juvenile salmonids through Snake and Columbia River dams and reservoirs, 2016
Author/Editor: James R. Faulkner, Daniel L. Widener, Steven G. Smith, Tiffani M. Marsh, Richard W. Zabel
Publication Year: 2017
Publisher: National Marine Fisheries Service
Contracting Agency: Bonneville Power Administration. Portland, Oregon

In 2016, we completed the 24th year of studies to estimate survival and travel time of juvenile Pacific salmon Oncorhynchus spp. passing dams and reservoirs on the Snake and Columbia River.  All estimates were derived from detections of fish tagged with passive integrated transponder (PIT) tags.

We tagged and released a total of 17,974 hatchery steelhead O. mykiss, 14,775 wild steelhead, and 22,145 wild yearling Chinook salmon O. tshawytscha at Lower Granite Dam on the Snake River.  In addition to detections of these fish, we used detections of yearling Chinook and steelhead tagged for other studies.

For combined groups of wild and hatchery Snake River fish, estimated survival through the entire hydropower system was 0.473 (95% CI 0.388-0.558) for yearling Chinook and 0.443 (0.380-0.506) for steelhead.

For Upper Columbia River hatchery yearling Chinook salmon, estimated survival to McNary Dam ranged from 0.796 for Chelan Hatchery fish released to Dryden Pond on the Wenatchee River, to 0.273 for Cle Elum Hatchery fish released to Jack Creek Pond.  For Wells Hatchery steelhead, estimated survival to McNary Dam ranged 0.691-0.210.

The estimated proportion of PIT tagged fish detected as they passed monitoring sites at dams was higher in 2016 than in 2015.  However, the proportion of fish detected in 2015 was the lowest recorded during our time series at most dams.

There is an urgent need to develop PIT tag detection capability through passage routes other than the juvenile bypass systems at dams.  Specifically, development and installation of PIT monitoring systems for normal spill bays as well as for surface passage structures is needed.  Higher rates of detection are necessary if we are to maintain or enhance the precision of annual survival estimates based on data collected from PIT-tagged juvenile salmon.

Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.