Spawning Distribution and Habitat Use of Adult Pacific and Western Brook Lampreys in Smith River, Oregon
Stephanie L. Gunckel, Kim K. Jones, and Steven E. Jacobs
Abstract.—Pacific lampreys Entosphenus tridentatus (formerly Lampetra tridentata) and western brook lampreys L. richardsoni are observed in many coastal Oregon basins; however, few data are available to adequately describe their distribution and spawning habitat associations. To document landscape-scale distribution and habitat use of spawning adult lampreys, we conducted biweekly redd surveys at 62 randomly selected sites in Smith River (Umpqua basin, Oregon). Characteristics of lamprey habitat were measured at the redd, habitat unit, and reach scales to quantify available and occupied habitat. Pacific lampreys were found primarily in wider, low-elevation streams, whereas western brook lampreys were more widespread but concentrated in headwater and low-order streams. At the unit scale, unit type and dominant substrate were weakly correlated to presence of spawning lampreys. Both species spawned in gravel rich habitats, predominantly pool tail-outs and low gradient riffles. This study infers habitat associations and broad-scale distribution within a coastal basin to assist in the design of monitoring strategies and population assessments at a regional scale.