Pacific lamprey research and restoration : 1997 annual report

Abstract

Based on oral interviews with tribal informants, current and former state and federal fisheries personnel, review of records and literature, and presence/absence sampling, it is apparent that Pacific lamprey were once abundant in ceded area streams of the Umatilla Indian Reservation (John Day, Umatilla, Walla Walla, Tucannon, and Grande Ronde subbasins). Current population levels appear severely depressed in all subbasins except possibly the John Day, which could be classified as depressed. The most probable reasons for population declines include: dams, chemical treatment activities, declining habitat quality (e.g. high water temperatures, poor water quality, low instream flows), and angle-iron in fishways to prevent lamprey passage.