Degree of Threat: B?
Comments: Lampreys are vulnerable to habitat losses due to reduced river flows, water diversions, dredging, streambed scouring, channelization, inadequate protection of stream side vegetation, chemical pollution, and impeded upstream passage due to dams and poorly designed road culverts (Center for Biodiversity).
Hydropower development, habitat alterations, and land management practices (e.g., irrigation) are thought to be responsible for the declines in the Columbia and Snake rivers (Claire and Cochnauer). Many declines are probably the result of obstructions (i.e., dams) that prevent spawning migration of adults and cause habitat degradation of spawning and larval rearing areas (Weeks 1991). Pacific lampreys were formerly common in the Snake, Clearwater, and Salmon river drainages in Idaho, but dams have had an adverse impact on their migration up the Snake River (Wydoski and Whitney 2003). The population in Elsie Lake in British Columbia was apparently extirpated approximately seven years after dams were constructed on the lake's outlet (Beamish and Northcote 1989). The Goose Lake, California, population may be negatively affected by dams and other obstructions that prevent adults from reaching spawning areas and by stream channelization, grazing, and diversions of water for irrigation, which may cause ammocoete habitat to dry up or become unsuitable (Moyle et al. 1989 and 1995).
Severe declines in salmon abundance may also be influential in the lamprey decline because salmon are one of the primary food resources (Wydoski and Whitney 2003).
Pacific lampreys were historically used extensively for food, trade, ceremonial, and medicinal purposes by Indian tribes in Oregon and British Columbia (Scott and Crossman 1973, Weeks 1991). In the 1940s, they were commercially harvested at Willamette Falls on the Willamette River, Oregon. Harvests averaged 300,000 pounds annually and were used to produce a chemical to aid in blood coagulation. Currently, commercial harvest at Willamette Falls ranges from 3,000 to 11,000 pounds annually and is sold as bait or to biological supply houses. Commercial harvest is now prohibited in some areas in Oregon. However, Indian tribes still harvest lamprey for personal use. At Willamette Falls, native harvests are probably comparable to the present level of commercial harvest. In Oregon, native harvests now occur primarily at Bonneville Dam and to a lesser extent at Sherar Falls on the Deschutes River and Willamette Falls, on the Willamette River.
A 1990 spill of hydrochloric acid in John Day River, Oregon, resulted in the death of an estimated 10,000 ammocoetes (Weeks 1991).