In 2010, the National Marine Fisheries Service (NMFS) completed the 18th 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 17,602 hatchery steelhead O. mykiss, 12,860 wild steelhead, and 16,996 wild yearling Chinook salmon O. tshawytscha at Lower Granite Dam on the Snake River.
In addition, we utilized fish PIT tagged by NMFS and 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. PIT-tagged smolts were detected at interrogation facilities at Lower Granite, Little Goose, Lower Monumental, Ice Harbor, McNary, John Day, and Bonneville Dam, as well as 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 2010 were:
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
3) Evaluate the survival estimation models under prevailing conditions
This report provides reach survival and travel time estimates for 2010 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 2010 yearling Chinook salmon and steelhead migrations. Hatchery and wild fish were combined in some analyses. For Snake River fish, overall percentages by origin of the combined PIT-tagged release groups used in survival analyses were 72% hatchery-reared and 28% wild for yearling Chinook salmon and 66% hatchery-reared and 34% wild for steelhead. Based on smolt passage data at Lower Granite Dam collected by the Fish Passage Center, we estimate that 87% of the overall yearling Chinook salmon run in 2010 was of hatchery origin. We could not estimate this number for steelhead because separate collection counts for hatchery and wild fish are not available.
Estimated survival from the tailrace of Lower Granite Dam to the tailrace of Little Goose Dam averaged 0.962 for yearling Chinook salmon and 0.965 for steelhead.
Combining average estimates from the Snake River smolt trap to Lower Granite Dam, from Lower Granite to McNary Dam, and from McNary to Bonneville Dam, estimated average survival through the entire hydropower system from the head of Lower Granite reservoir to the tailrace of Bonneville Dam (eight projects) was 0.551 (se 0.038) for Snake River yearling Chinook salmon and 0.618 (se 0.032) for steelhead during 2010.
For yearling spring Chinook salmon released in the Upper Columbia River basin, estimated survival from point of release to McNary Dam tailrace ranged from 0.830 for East Bank Hatchery fish released to Dryden Pond on the Wenatchee River to 0.204 for Yakima Hatchery fish released into the Natches River.
For steelhead released in the Upper Columbia River basin, estimated survival from point of release to McNary Dam tailrace ran