Occurrence, Detection and Habitat Use of Larval Maprey in Mainstem Environments: the Lower Willamette River. 2009 Annual Report

摘要

Pacific lamprey Entosphenus tridentatus in the Columbia River Basin (CRB) have declined to a remnant of their pre-1940s populations concerning tribal and regional agencies (Close et al. 2002). Lamprey are culturally important to Native American tribes, are ecologically important within the food web, and are an indicator species whose decline provides further insight into the impact of human actions on ecological function (Close et al. 2002). Pacific lamprey populations are declining and have been given protected status within Oregon due to declines along the coast and in the Columbia River Basin (Close et al. 2002; Kostow 2002). Increased knowledge of the biology, population dynamics, ecology, and identification of Pacific lamprey and sympatric species such as the western brook lamprey Lampetra richardsoni will help managers understand and conserve these important species. Pacific lampreys have a complex life history that includes a three to seven year larval (i.e., ammocoete), migratory juvenile (i.e., macrophthalmia) and adult phases (Scott and Crossman 1073). Ammocoetes and macrophthalmia are strongly associated with stream and river sediments. Ammocoetes live burrowed in stream and river sediments for periods up to seven years after hatching, where they filter feed detritus and organic material (Scott and Crossman 1973; Sutton and Bowen 1994). Ammocoetes metamorphose into macrophthalmia from July to December (McGree et al. 2008) and migrate downstream to the Pacific Ocean. The timing, duration, and habitat use at the ammocoete and macrophthalmia life stage are poorly understood.