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NATURAL HISTORY

PACIFIC LAMPREY } Lampetra tridentate
FAMILY: Petromyzontidae

DESCRIPTION: Pacific lamprey are slender, eel-like fish that are dark blue or brown in color and grow to about 30 inches long. They have lateral eyes, lack paired fins, and have no scales. Adult lampreys have a jawless, sucker-like ventral mouth consisting of a circular disc set with horny teeth.

HABITAT: Typical spawning habitat is similar to that for salmon or steelhead trout, in medium- and large-sized, low-gradient rivers and streams.

RANGE: The species lives around the Pacific Rim from Japan through Alaska, British Columbia, Washington, Oregon, and California, down to Baja California, Mexico.

MIGRATION: Pacific lampreys migrate from freshwater streams to the Pacific Ocean, then return upstream to spawn.

BREEDING: Lampreys construct a nest (called a redd) in small gravel substrate. Females can lay up to 100,000 eggs, which are fertilized externally by the male. Adult lampreys die within four days of spawning.

LIFE CYCLE: Pacific lampreys spend most of their life in freshwater streams before entering the ocean as adults to feed. Young lamprey burrow into the muddy bottoms of backwater pools and eddies, where they filter the mud and water. After a two-month metamorphosis they emerge as adults less than five inches long, then migrate downstream to saltwater. In the ocean they grow to 16 to 27 inches before returning after one or two years to fresh water to spawn and die. The juveniles, called ammocoetes, live in fresh water for up to five or six years.

FEEDING: Juvenile lampreys are filter feeders. Adults are parasitic on other fish, scavenge, or are predators while in the ocean. Pacific lampreys do not feed while traveling to spawn.

THREATS: Pacific lampreys are vulnerable to habitat losses due to reduced river flows, water diversions, dredging, streambed scouring, channelization, inadequate protection of streamside vegetation, chemical pollution and spills, and impeded upstream passage due to dams and poorly designed road culverts.

POPULATION TREND: Pacific lampreys have declined throughout their range in California, Oregon, Washington, and Idaho, with the most precipitous documented declines in the upper Columbia, Snake, and North Umpqua river basins. For example, Pacific lamprey counts at Winchester Dam on the Umpqua River in Oregon decreased from a maximum of more than 46,000 fish in 1966 to 34 lamprey in 2001. Counts at Ice Harbor Dam in the Snake River decreased from a maximum of more than 49,000 fish in 1963 to 203 lamprey in 2001. The formerly large lamprey runs described as great "wriggling masses of lampreys" once characterizing streams such as northern California's Eel River have largely disappeared.

Photo by John Brunzell, USFWS