Spawning Distribution and Habitat Use of Adult Pacific and Western Brook Lampreys in Smith River, Oregon

—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. * Corresponding author: stephanie.gunckel@oregonstate. edu Introduction Coastal Oregon populations of Pacific lamprey Entosphenus tridentatus (formerly Lampetra tridentata) and western brook lamprey L. richardsoni are considered depressed due to habitat loss and passage problems (Close et al. 2002; Nawa 2003; ODFW 2006). The Pacific lamprey was listed as an Oregon State sensitive species in 1993 and in 1996 was protected through restriction of harvest (ODFW 2006). The western brook lamprey is not protected and has no special state status. Abundance of Pacific lampreys throughout the coast and Columbia River has declined dramatically since the1960s. Dam counts at Winchester (Umpqua River), Bonneville (Columbia River), and Leaburg (McKenzie River) dams show a dramatic decrease from historical levels (Kostow 2002; Nawa 2003; ODFW 2006). In 2003, 11 environmental groups petitioned the U.S. Fish and Wildlife Service to list Pacific, western brook, and two other lamprey species as endangered in the Pacific Northwest and California (Nawa 2003). Even though the petition cited habitat losses due to reduced instream flows, water diversions, dredging, scour and channnelization issues, pollution, and degradation of riparian communities, the U.S. Fish and Wildlife Service determined that the petition did not contain adequate information to warrant a listing (USFWS 2004). The Oregon Department of Fish and Wildlife recently reviewed the status of western brook and Pacific lampreys and found populations to be “at risk” of extinction (ODFW 2006) due to habitat loss, passage barriers and pollution. However, data necessary to conduct a more thorough and detailed assessment are lacking. Many of the lacking data are critical to the effective management and conservation of Oregon’s coastal lamprey species. The Columbia River Basin Lamprey Technical Workgroup