Survival Estimates for the Passage of Spring-Migrating Juvenile Salmonids through Snake and Columbia River Dams and Reservoirs, 2008. Page: 3 of 125
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EXECUTIVE SUMMARY
In 2008, the National Marine Fisheries Service completed the sixteenth year of a
study to estimate survival and travel time of juvenile salmonids Oncorhynchus spp.
passing through dams and reservoirs on the Snake and Columbia Rivers. All estimates
were derived from detections of fish tagged with passive integrated transponder (PIT)
tags. We PIT tagged and released a total of 18,565 hatchery steelhead O. mykiss, 15,991
wild steelhead, and 9,714 wild yearling Chinook salmon O. tshawytscha at Lower
Granite Dam in the Snake River.
In addition, we utilized fish PIT tagged by other agencies at traps and hatcheries
upstream from the hydropower system and at sites within the hydropower system in both
the Snake and Columbia Rivers. These included 122,061 yearling Chinook salmon
tagged at Lower Granite Dam for evaluation of latent mortality related to passage through
Snake River dams. PIT-tagged smolts were detected at interrogation facilities at Lower
Granite, Little Goose, Lower Monumental, Ice Harbor, McNary, John Day, and
Bonneville Dams and in the PIT-tag detector trawl operated in the Columbia River
estuary. Survival estimates were calculated using a statistical model for tag-recapture
data from single release groups (the single-release model).
Primary research objectives in 2008 were to:
1) estimate reach survival and travel time in the Snake and Columbia Rivers
throughout the migration period of yearling Chinook salmon and steelhead,
2) evaluate relationships between survival estimates and migration conditions, and
3) evaluate the survival estimation models under prevailing conditions.
This report provides reach survival and travel time estimates for 2008 for
PIT-tagged yearling Chinook salmon (hatchery and wild), hatchery sockeye salmon
O. nerka, hatchery coho salmon O. kisutch, and steelhead (hatchery and wild) in the
Snake and Columbia Rivers. Additional details on the methodology and statistical
models used are provided in previous reports cited here.
Survival and detection probabilities were estimated precisely for most of the 2008
yearling Chinook salmon and steelhead migrations. Hatchery and wild fish were
combined in some of the analyses. For yearling Chinook salmon, overall percentages for
combined release groups used in survival analyses in the Snake River were 80%
hatchery-reared and 20% wild. For steelhead, the overall percentages were 65%
hatchery-reared and 35% wild.iii
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Faulkner, James R.; Smith, Steven G. & Muir, William D. Survival Estimates for the Passage of Spring-Migrating Juvenile Salmonids through Snake and Columbia River Dams and Reservoirs, 2008., report, June 23, 2009; Portland, Oregon. (https://digital.library.unt.edu/ark:/67531/metadc926562/m1/3/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.