Upstream Migration of Adult Pacific Lamprey in the Columbia and Snake Rivers

Migration of adult Pacific Lamprey through the lower Columbia and Snake rivers contrasts with adult salmonids because dam passage rates by lamprey are ~50% per dam versus >90% for salmonids.  We have conducted an integrated, multi-scale set of studies to quantify behavior, inform passage improvement design, monitor the effectiveness of improvements, and estimate passage rates to spawning tributaries.  Telemetry studies have quantified passage at twelve dams, identified passage bottlenecks, evaluated movement through reservoirs, and monitored movement into spawning tributaries.  At finer scales, we have used optical and DIDSON imaging to quantify behavior in key fishway locations with respect to structural and hydraulic features and to sturgeon predators.  Concurrent studies in an experimental flume evaluated swimming behavior and passage in relation to velocity, turbulence and structural features.  Key findings include poor passage through entrances, transition areas and vertical-slot weirs of fishways, high rates of passage through mainstem reservoirs, evidence of tributary entry in spring after mainstem overwintering, and potential for long migrations after passage of the impounded system.  Collectively, the results suggest that relatively low observed passage rates by Pacific Lamprey at dams are caused by a combination of fishway conditions and factors affecting motivation including fish size and genetics.