Pacific Lamprey
(L. macropthalmia) recently metamorphosed form. Photo by USGS


The Center for Biological Diversity joined 10 other conservation organizations in petitioning the U. S. Fish and Wildlife Service in January 2003 for Endangered Species Act protection for four species of lamprey. Lampreys are ancient jawless fish that superficially resemble eels, but are not related. Lampreys have an anadromous life cycle (migrating to freshwater for spawning) similar to salmon and steelhead trout and play an important role as a food source in estuarine, stream, and river ecosystems. The four lamprey species petitioned for are the Pacific lamprey (Lampetra tridentata), river lamprey (Lampetra ayresi), western brook lamprey (Lampetra richardsoni), and Kern brook lamprey (Lampetra hubbsi).

Pacific, river, and brook lampreys spend most or all of their life cycles in a broad distribution of Pacific coast rivers and streams from California to Alaska, while the Kern brook lamprey is limited to a small portion of the San Joaquin River basin in California. Pacific and river lamprey are primarily concentrated in medium and large sized low-gradient Pacific streams, while western brook lampreys, which are distributed from the Sacramento River basin northward into British Columbia, prefer the small tributaries.

Large concentrations of adult and larval lamprey were once an important and dependable high-fat food source for many birds, fish, and mammals, especially seals and sea lions. Adult Pacific lampreys function as a buffer to reduce predation on migrating adult salmon by seals and sea lions and by other fish and gulls that otherwise might prey more heavily on young salmon. Similar to salmon, lampreys also play an important ecological role in transporting nutrients such as nitrogen to freshwater ecosystems.

Somewhat like salmon, adult lampreys dig depressions in gravel beds in freshwater streams to spawn. However, not all species are anadromous, nor are they all parasitic on other fish, as commonly believed. Information regarding efforts to control non-native Atlantic coast sea lamprey, which entered the Great Lakes in 1921 through the St. Lawrence Seaway, has led to unfounded prejudice toward native west coast lamprey species. The Pacific lamprey has co-adapted with its prey, which can include salmon as well as other marine fish species. Of the four lamprey species, only the Pacific and river lampreys produce parasitic adults that attach to other fish during these lampreys’ shorter marine life stages.

The scarcity of lampreys became a conservation concern in the early 1990s when populations of Pacific lamprey were noted to have declined to perilously low numbers. Human impacts to the freshwater habitats of lampreys in the Pacific Northwest have been severe, as lampreys have also been affected by the habitat destruction and alteration associated with the collapse of west coast salmon runs. Lamprey 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. Poor passage on dams contributes to Pacific lamprey declines by limiting access to historical spawning locations. For example, dams such as Bonneville, Dalles, John Day, and McNary Dams on the lower Columbia River have caused significant mortality of lampreys and blocked passage. Introduction of exotic fish predators such as small mouth bass has also been a factor in the decline of lamprey.

Formerly large spawning runs of literally millions of Pacific lamprey described as great "wriggling masses of lampreys" that once characterized streams such as the Eel River have largely disappeared. Annual counts of Pacific lampreys at the Red Bluff Diversion Dam on the upper Sacramento River have declined from 38,492 in 1972 to 107 or less since 1996. Counts of Pacific lamprey at Ice Harbor Dam on the Snake River declined from 50,000 in the early 1960s to less than 1,000 during the 1990s. Counts at Winchester Dam on the North Umpqua River in Oregon declined from 46,785 in 1966 to less than 50 annually since 1995. Counts at Gold Ray Dam on the Rogue River, Oregon have ranged from 155-2,370 since 1993, but abundance is believed to be far below historical numbers.

In addition to these four lamprey species, at least four other localized (or endemic) species in the upper Klamath River basin and upper Sacramento/Pit River system are of particular concern. Unless sufficient conservation measures are adopted, the Miller Lake lamprey, Pit-Klamath Brook lamprey, Klamath River lamprey, and non-anadromous Pacific Lamprey in the upper Klamath River basin may need to be petitioned at a future time.

The eleven petitioning conservation organizations are: Klamath-Siskiyou Wildlands Center, Siskiyou Regional Education Project, Umpqua Watersheds, Friends of the Eel, Environmental Protection Information Center, Native Fish Society, Center for Biological Diversity, Northcoast Environmental Center, Umpqua Valley Audubon Society, Washington Trout, and Oregon Natural Resources Council.

graphic Andrew Rodman ©2002
June 9, 2003
Go back