EVALUATION OF ADULT PACIFIC LAMPREY MIGRATION AND BEHAVIOR AT McNARY AND ICE HARBOR DAMS, 2008

During the 2007 Pacific lamprey migration, we used radio-telemetry and half-duplex PIT (HDX) monitoring to calculate passage efficiency and identify areas of difficult passage at McNary Dam. Dam passage efficiency was 89% with 12 of 14 lamprey that approached the dam successfully passing the dam. Median time from release to first approach a McNary Dam fishway was 7.6 d. Median time from first fishway approach to first fishway entrance was 0.01 d (24 min) with only one lamprey taking more than a day to enter a fishway. After entering fishways, lamprey passed quickly through the non-weired portions of fishways and through transition pools. Median time to pass this fishway segment was 0.38 d (n = 8) as was the median time from first transition pool record to last transition pool record (n = 6). Median time to pass from the last transition pool record to exit a fishway was 1.0 d. In all, median time from fishway entry to exit was 2.8 d (n = 7). HDX antennas located within auxiliary juvenile passage channels in the pier walls of the Oregonshore fishway indicated lamprey entered these passages and one fish apparently used a juvenile passage channel to enter the forebay. Of the twelve lamprey believed to have passed McNary Dam, five fish were recorded at upstream dams through December 2007. Two lamprey were detected at Ice Harbor Dam on both telemetry and HDX systems and three lamprey were detected by telemetry receivers at Priest Rapids Dam. Both lamprey detected at Ice Harbor entered a fishway quickly (< 3 h); passage times from fishway entrance to exit were 6.9 and 16.7 h. The three lamprey detected at Priest Rapids passed the McNary reservoir and Hanford Reach in 8.7, 16.6 and 39.7 d (4.3 – 19.4 km/d).