Survival Estimates for the Passage of Spring-Migrating Juvenile Salmonids through Snake and Columbia River Dams and Reservoirs, 2004-2005 Annual Report.

Abstract

In 2004, the National Marine Fisheries Service and the University of Washington completed the twelfth 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 tags (PIT tags). We PIT tagged and released a total of 19,621 hatchery steelhead, 8,128 wild steelhead, and 9,227 wild yearling Chinook salmon at Lower Granite Dam. In addition, we utilized fish PIT tagged by other agencies at traps and hatcheries upstream from the hydropower system and sites within the hydropower system. PIT-tagged smolts were detected at interrogation facilities at Lower Granite, Little Goose, Lower Monumental, 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 2004 were to (1) estimate reach survival and travel time in the Snake and Columbia Rivers throughout the migration period of yearling Chinook salmon O. tshawytscha and steelhead O. mykiss; (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 2004 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. Results are reported primarily in the form of tables and figures; details on methodology and statistical models used are provided in previous reports cited here. Survival and detection probabilities were estimated precisely for most of the 2004 yearling Chinook salmon and steelhead migrations. Hatchery and wild fish were combined in some of the analyses. Overall, the percentages for combined release groups used in survival analyses were 68% hatchery-reared yearling Chinook salmon and 32% wild. For steelhead, the overall percentages were 73% hatchery-reared and 27% wild. Estimated survival from the tailrace of Lower Granite Dam to the tailrace of Little Goose Dam averaged 0.923 for yearling Chinook salmon and 0.860 for steelhead. Respective average survival estimates for yearling Chinook salmon and steelhead were 0.875 and 0.820 from Little Goose Dam tailrace to Lower Monumental Dam tailrace; 0.818 and 0.519 from Lower Monumental Dam tailrace to McNary Dam tailrace (including passage through Ice Harbor Dam); and 0.809 and 0.465 from McNary Dam tailrace to John Day Dam tailrace. Survival for yearling Chinook salmon from John Day Dam tailrace to Bonneville Dam tailrace (including passage through The Dalles Dam) was 0.735. We were unable to estimate survival through this reach for steelhead during 2004 because too few fish were detected at Bonneville Dam due to operation of the new corner collector at the second powerhouse. Combining average estimates from the Snake River smolt trap to Lower Granite Dam, from Lower Granite Dam to McNary Dam, and from McNary Dam to Bonneville Dam, estimated annual average survival through the entire hydropower system from the head of Lower Granite reservoir to the tailrace of Bonneville Dam (eight projects) was 0.353 (s.e. 0.045) for Snake River yearling Chinook salmon. We could not empirically estimate survival through the entire system for steelhead in 2004 because of low detection rates for this species at Bonneville Dam. For yearling spring Chinook salmon released in the Upper Columbia River, estimated survival from point of release to McNary Dam tailrace was 0.484 (s.e. 0.005) for fish released from Leavenworth Hatchery, 0.748 (s.e. 0.015) for fish released from Entiat Hatchery, 0.738 (s.e. 0.036) for fish released from Winthrop Hatchery, and 0.702 (s.e. 0.048) and 0.747 (s.e.0.047) for those from Methow Hatchery, Chewuch Pond and Twisp Pond, respectively. Using pooled data, estimated survival for these groups was 0.741 (s.e. 0.038) from McNary Dam tailrace to John Day tailrace and 0.840 (s.e. 0.111) from John Day Dam tailrace to Bonneville Dam tailrace. For 13 groups of steelhead released in the Upper Columbia River, estimated survival from point of release to McNary Dam tailrace ranged from 0.510 (s.e. 0.025) for fish released from Wells Hatchery in the Similkameen River (507 km from McNary Dam) to 0.293 (s.e. 0.022) for fish released from East Bank Hatchery into Nason Creek (373 km from McNary Dam). Using pooled data, estimated survival for these groups was 0.786 (s.e. 0.059) from McNary Dam tailrace to John Day tailrace and 0.620 (s.e. 0.264) from John Day Dam tailrace to Bonneville Dam tailrace.