This document is the 1998 annual progress report for studies of Pacific lampreys (Lampetra tridentata) conducted by the Confederated Tribes of the Umatilla Indian Reservation (CTUIR), Columbia River Inter-Tribal Fish Commission, and University of Minnesota (U of M). Bonneville Power Administration (BPA) funded activities through Project 94-026. The Pacific Lamprey Research and Restoration Project began after completion of a status report of Pacific lamprey in the Columbia River in 1995. The project started as a cooperative effort between the Confederated Tribes of the Umatilla Indian Reservation (CTUIR), Columbia River Inter-Tribal Fish Commission (CRITFC), and Oregon State University (OSU). Lamprey are a valuable subsistence food and cultural resource for Native Americans of the Pacific Northwest. The once abundant Pacific lampreys above Bonneville Dam are currently depressed (Close et al. 1995). Declines in Pacific lampreys have impacted treaty secured fishing opportunities by limiting tribal members catch and access to Pacific lampreys in the interior Columbia basin. Tribal members now harvest lampreys in lower Columbia River locations such as Willamette Falls near Oregon City, Oregon. Pacific lampreys are also an important part of the food web of North Pacific ecosystems, both as predator (Beamish 1980; Pike 1951; Roos and Gillohousin 1973), and prey (Semekula and Larkin 1968; Galbreath 1979; Roffe and Mate 1984; Merrell 1959; Wolf and Jones 1989) and as a vehicle for recruitment of marine nutrients. The decline of Pacific lampreys in the interior Columbia River basin has become a major concern. Effective recovery measures for Pacific lampreys can only be developed after we increase our knowledge of the biology and factors that are limiting the various life history stages. Prior to developing a restoration plan, we have carried out studies to review status, distribution, abundance, homing ability, and stock structure. These studies will culminate in the development and implementation of a restoration plan for the Umatilla River. Multiple pass electrofishing surveys to assess densities and distribution of lamprey larvae in the Umatilla River were conducted in 1998. Electrofishing surveys in the Umatilla River are useful for baseline comparison. Forty-two index sites were sampled from the mouth to river kilometer (RK) 124. Lamprey larvae were found in 4 of the 42 index plots. All sites with larvae were found at and below RK 9.3. Nine larvae were captured during the surveys. However, no larvae were caught on the second pass in each plot. Pacific lamprey larvae and adult lampreys were studied to determine their ability to produce and detect pheromones. Larval gall bladders were removed and gall bladder fluid was extracted and analyzed by high performance liquid chromatography (HPLC). Adult lampreys ability to detect pheromones were tested using electro-olfactogram (EOG) methods. Fifteen compounds including Petromyzonol sulfate (PS), a migratory pheromone found in sea lamprey larvae (Petromyzon marinus) (Li et al. 1995) were tested. Larval lampreys produced large amounts of (PS). Adult Pacific lamprey can detect PS and have an olfactory sensitivity to pheromones that is similar to sea lampreys. iv Pacific lamprey abundance, as indexed by fish ladder counts in 1998, was; Bonneville 37,478; The Dalles 7,665; John Day 12,579; McNary 3,393; Ice Harbor 763; Lower Monumental 69; Little Goose 90; Lower Granite 110; Rock Island 1,410; and Rock Reach 819 dams, respectively. Enumerating Pacific lamprey at counting stations remained extremely problematic, since excessive up- and downstream movement at the counting windows reduces the confidence in fish ladder passage estimates. This may be an indication of passage problems encountered by Pacific lampreys. In-season homing of Pacific lamprey was studied using radio telemetry. Pacific lampery were captured at Willamette Falls and Bonneville Dam, outfitted with radio transmitters and released approximately 26 km downstream of the Willamette River confluence. A total of 50 fish were instrumented. Results will be presented in next year’s report. Natal homing was also investigated using mtDNA analysis of fish captured at Bonneville Dam and from Willamette Falls. These results will also be presented next year. We collected lamprey tissues, from fish captured in several locations throughout the Columbia River Basin, to develop a genetic database for use in determining population structure. Additional samples for populations outside the Columbia River Basin were used to scale the results. Results from this investigation will be presented in next year’s annual report. Since the initiation of the CTUIR lamprey research and restoration project, additional lamprey studies have been proposed that have created uncertainties regarding the prioritization of projects and needs of lampreys. At the request of the Northwest Power Planning Council, a multi-agency Pacific lamprey technical workgroup (TWG) was established in 1996. Annual meetings are held to coordinate projects and prioritize research needs. The TWG identified critical uncertainties and needs to help in determining priorities of ongoing and proposed projects (Appendix A). Finally, an annotated bibliography of relevant lamprey literature was compiled (Appendix B).