Pacific Lamprey Passage during the Wanapum Dam Emergency

On February 24, 2014, a fracture discovered in Wanapum Dam resulted in reservoir drawdown, compromising fish ladder function.  Pacific lamprey (Entosphenus tridentatus) passage was facilitated through installation of false weirs at ladder exits and other measures to prevent extended attachment. Over 2,400 lamprey were estimated to have passed volitionally using the exit systems. An additional 2,269 lamprey were trapped and transported. Grant PUD employed a trap and transport program to reduce the potential migration delay and increase passage success until the Wanapum Reservoir returned to normal. Thirty-six tube style traps were distributed between Wanapum and Priest Rapids Dams, and four mechanical weir traps were operated at Priest Rapids Dam. The highest percentage of lamprey was trapped in the Priest Rapids Dam right-bank fish ladder (39%) while the lowest was from the Wanapum Dam right-bank fish ladder (4%).  The mechanical weir style traps caught the majority of the total lamprey trapped at Priest Rapids Dam (72%), while at Wanapum Dam a majority of the lamprey were caught in the tube traps in the middle of the ladders, concentrated near the fish count station crowders and video count station (52%). This presentation details this successful emergency response.