Pacific lamprey in the Columbia River drainage are affected by many of the same threats facing anadromous salmonids:  reduced access to spawning habitat, degradation of spawning and rearing areas, losses of emigrating juveniles to turbine entrainment, and non-indigenous predators.  In particular, recent studies have shown that hydropower dams can block or delay spawning migrations of adult Pacific lamprey in the Columbia River.  While large hydropower projects are obstacles to upstream movements of adult lamprey, there are indications that smaller structures (e.g., low-elevation dams, weirs, and irrigation diversions) may also restrict lamprey access to spawning areas.  On the Umatilla River (Oregon), Three Mile Dam has been a traditional lamprey fishing location because lamprey accumulate below the dam.  Sampling for juveniles in the Umatilla and other Columbia River tributaries has also indicated that lamprey reproduction is low in the upper reaches of these rivers (above low-elevation dams and irrigation diversions).  In addition, radiotelemetry studies of sea lamprey (Petromyzon marinus) have confirmed that very low elevation structures (< 2 m) can obstruct or delay lamprey migration.

Obstacles to pre-spawning migrants were identified as a primary threat to lamprey by the Columbia Basin Lamprey Technical Workgroup.  However, the degree to which low-elevation structures obstruct adult Pacific lamprey is unknown.  This project will leverage existing radiotelemetry arrays in the Columbia Basin and will partner with tribal biologists to address the impacts of low-elevation structures to lamprey by using radiotelemetry in the Umatilla River drainage.


OBJECTIVE

To determine the passage success of adult Pacific lamprey at Three Mile Dam and irrigation diversions on the Umatilla River, Oregon.  In addition to determining the number of lamprey that successfully pass over these structures, this study will document the rate and route of migration at each structure using radiotelemetry.