Pacific Lamprey (Lampetra tridentata)

Pacific lamprey populations in the Columbia and Snake river systems have declined, and conservation initiatives have been hampered by a lack of adequate information on the historic distribution, life history, and habitat requirements of the species. Since 2003, conservation organizations have petitioned to protect Pacific lamprey under the Endangered Species Act, but inadequate data prevents an accurate analysis of the lamprey population status in their native range.  While their anadromous behavior parallels that of salmonids, Pacific lampreys spend more than half their lives as filter-feeding larvae in fine sediments of streams. They are possibly more susceptible than salmonids to physical habitat alteration and flow regulations at both broad system-wide and fine localized scales. Down- and upriver migration barriers (dams) and numerous upriver spawning/rearing habitat modifications (e.g., reduced river flows, water diversions, streambed dredging or scouring, channelization, loss of riparian vegetation, and chemical pollution) have combined to decimate lamprey populations.

FERL has several Pacific lamprey research initiatives that contribute to a growing body of knowledge about the species and its habitat:

·         A multi-year project evaluating lamprey passage behaviors and survival through the lower Columbia River using radiotelemetry and PIT tag methods.  Important results from this effort include: 1) identification of difficult lamprey passage areas; 2) development of lamprey-specific passage structures at Bonneville Dam; 3) evidence for strong size-selective dam passage success; and 4) the possibility for some stock structure in Columbia-Snake lamprey.

·         A multi-year series of controlled experiments in an artificial fishway to evaluate lamprey swimming performance in relation to flow, passage obstacles, rest boxes, attraction devices, and fishway configurations.

·         The development and evaluation of half-duplex passive integrated transponder (HDX-PIT) tag detection systems for monitoring lamprey passage at Bonneville, The Dalles, John Day, McNary, Ice Harbor, and Priest Rapids dams.

·         A project to refine adult lamprey population estimates by assessing how many lamprey pass Bonneville and The Dalles dams at night using nighttime video counts.  Although lampreys are primarily active at night, only daytime passage data have been historically collected at dams. 

·         An assessment of Pacific lamprey behavior and swimming performance at Bonneville Dam, using lowered nighttime water velocities in the fishway to improve adult Pacific lamprey passage.

·         An evaluation of the physiological and environmental factors that affect Pacific lamprey spawning success in the Snake River upstream from Lower Granite Dam, with an emphasis on final fates, distribution, and preferred spawning habitat. This project included an experiment in translocation to improve Pacific lamprey production in the Snake River.