Difficulties in estimating survival for adult chinook salmon in the Columbia and Snake rivers
adult, behavior, chinook, Chinook salmon, COUNTS, current, DAM, factors, harvest, hydroelectric, Lower Snake River, methods, migrate, migration, migration timing, monitoring, NUMBER, Oncorhynchus, Oncorhynchus tshawytscha, passage, project, RATES, river, Rivers, run, salmon, size, Snake River, spawning, straying, summer, survival, survival estimates, technique, timing, UNCERTAINTY, upstream, variability
Journal or Book Title
We reviewed current methods used to estimate survival of adult chinook salmon (Oncorhynchus tshawytscha) as they migrate upstream past hydroelectric projects in the Columbia and Snake rivers, evaluated known and unaccounted-for loss factors, and assessed how adult survival estimates could be improved. Dam counts and associated passage conversion rates do not always provide accurate estimates of adult survival between hydroelectric projects. Expansion techniques for reconstructing run size and harvest rates also contribute to variability in estimates of run size and potential loss between hydroelectric projects. Use of passage conversion rates to estimate in-river survival of adult spring chinook salmon had less uncertainty than for estimates of other runs. Fixed-run cui off dates for migration timing result in a high uncertainty for monitoring relative numbers of summer chinook salmon. We also found it difficult to reconstruct run size to spawning areas or to estimate interdam survival for fall chinook in lower Snake River darns because of straying and high incidence (e.g., up to 40% at some projects) of fallback behavior. In-river survival estimates of adult chinook salmon would be improved by factoring adult fallback percentages into passage estimates, combining spring and summer runs for accounting purposes, methods.