We describe the migration distances and timing of the adult Pacific lamprey, Entosphenus tridentatus, in the Willamette River Basin (Oregon, U.S.A.). We conducted aerial surveys to track radio-tagged fish upstream of a major waterfall and hydropower complex en route to spawning areas. We detected 24 out of the 43 fish that passed the waterfall-hydropower complex. Of the detected fish, 17 were detected multiple times. Their maximum migration distance upstream in the mainstem Willamette approximated a normal distribution. The maximum distance migrated upstream did not significantly correlate with total body length (r = −0.186, P = 0.385) or date that the fish passed Willamette Falls (r = −0.118, P = 0.582). Fish migrated primarily during the spring to early summer period before stopping during the summer, when peak river temperatures (≥20°C). However, at least three fish continued to migrate upstream after September. Behavior ranged from relatively slow migration, followed by holding; to rapid migration, followed by slow migration further up in the basin. This study provides a basis for informing more detailed research on Pacific lamprey in the future.
|Title||Pre-spawning migration of adult Pacific lamprey, <i>Entosphenus tridentatus</i>, in the Willamette River, Oregon, U.S.A.|
|Authors||Benjamin J. Clemens, Matthew G. Mesa, Robert J. Magie, Douglas A. Young, Carl B. Schreck|
|Publication Subtype||Journal Article|
|Series Title||Environmental Biology of Fishes|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Cooperative Research Unit Seattle|