Adult Pacific Lamprey Migration in the Lower Columbia River: 2007 Radiotelemetry and Half-duplex Pit Tag Studies.

摘要

Monitoring Pacific lamprey (Lampetra tridentata) run size and migration behaviors in the Columbia River basin is difficult given their cryptic and photo-negative behaviors. In this study we tagged lamprey with half duplex (HDX) passive integrated transponder (PIT) tags and radio transmitters and monitored their passage at Bonneville, The Dalles, John Day, McNary, and Ice Harbor dams. Our objectives were to calculate lamprey passage times, to estimate escapement past the monitored sites, and to evaluate potential correlates with lamprey passage success. In 2007, we radio-tagged 398 lamprey and HDX-PIT tagged 757 lamprey. Conversion estimates from release below Bonneville Dam to top-of-ladder antennas were 21% for radio-tagged fish and 52% for HDX-PIT tagged fish. Conversions from the top of Bonneville Dam to top-of-ladder antennas at The Dalles Dam were 25% for radio-tagged fish and 63% for HDX-PIT tagged fish. Conversions from the top of The Dalles Dam to top-of-ladder antennas at John Day Dam were 43% for radiotagged fish and 52% for HDX-PIT tagged fish. Large lamprey in both the telemetry and HDX-PIT studies were significantly more likely than small lamprey to pass through most of the monitored damto- dam reaches. Lamprey migration times were highly variable, but tended to be slow at dams and relatively rapid through reservoirs. Median passage times for radio-tagged fish were 7.6 days from release past Bonneville Dam, 3.8 days between top-of-ladder antennas at Bonneville and The Dalles dams, and 2.4 days between antennas at The Dalles and John Day dams. Median times for HDX-PIT tagged lamprey over these same reaches were 6.5 days, 4.0 days, and 4.3 days, respectively. Lamprey with both tag types migrated more rapidly later in the season, coincident with increasing river temperatures and decreasing river discharge.