Conversion Rate, Travel Time, and Survival of Adult Salmon and Steelhead through the Wanapum Dam Emergency Fish Passage System

Two-hundred and fifty adult spring Chinook salmon were tagged and monitored during their migration through the modified fish ladders at Wanapum Dam following the emergency drawdown of Wanapum Pool. PIT and acoustic tags were used to evaluate delay and overall passage success using travel time and conversion rates to Rock Island Dam. Historical data on conversion rates and travel times were used to establish benchmarks for determining if the ladder modification were sufficient and safe for the run-at-large. The passage criteria included: (1) 80% conversion rate to Rock Island, (2) travel time less than 356 hours for 90% of the study fish to Rock Island, and (3) less than 5% mortality at the Wanapum ladder exits. Within five weeks of the first adult arriving at Wanapum Dam all of the passage criteria were met. Conversion rate (94%) and travel time (90^th percentile = 313 hours) for spring Chinook salmon were within the predetermined criteria and commensurate with years under normal operations and zero mortalities were observed at the ladder exits. Post hoc analyses of migration patterns and escapement for the 2014 adult return above Rock Island indicate that there were no delayed effects from the ladder modifications.