Spring Emigration Reach-Specific Survival and Travel Time of Catherine Creek Spring Chinook Salmon Smolts through the Grande Ronde Valley

During 2011−2013, we estimated reach-specific survival for radio-tagged Catherine Creek spring Chinook salmon Oncorhynchus tshawytscha smolts emigrating through the Grande Ronde Valley, northeast Oregon. For all years, we detected no relationship between condition and travel time when successful and unsuccessful natural smolts were compared; however, during 2013, hatchery smolts that exhibited greater condition displayed significantly shorter travel times. For naturally- and hatchery-produced smolts, estimated Catherine Creek reach-specific survival ranged from 0.59 (SE = 0.10) to 0.95 (SE = 0.03), whereas survival within most Grande Ronde River reaches was 1.00. For naturally- and hatchery-produced smolts, high mortality and slow median emigration rates were documented throughout Catherine Creek, while low mortality and fast emigration rates occurred within the Grande Ronde River. During 2011–2013, naturally-produced smolts exhibited a delay in emigration that coincided with peak Grande Ronde River discharge, which has provided important insight pertaining to management objectives. Our research should increase the understanding of Catherine Creek smolt behavior and mortality within the Grande Ronde Valley during seaward migration, suggests critical issues potentially vital to the restoration of this population, and guides holistic management particularly relevant to improving survival of emigrating smolts upstream from the Snake and Columbia river hydrosystem.