However, recent data indicate that distribution of the Pacific lamprey has been reduced in many river drainages. Historically, Pacific lampreys are thought to be distributed wherever salmon and steelhead occurred. Pacific lamprey distribution patterns are similar to that of anadromous salmonids. Their distribution includes major river systems such as the Fraser, Columbia, Klamath-Trinity, Eel, and Sacramento-San Joaquin Rivers. They have been found in streams from Hokkaido Island, Japan, and around the Pacific Rim including Alaska, Canada, Washington, Oregon, Idaho, and California to Punta Canoas, Baja California, Mexico. Pacific lampreys are the most widely distributed lamprey species on the west coast of the United States. They move downstream as they emigrate to the ocean between late fall and spring where they mature into adults. Transformation from ammocoetes to macropthalmia typically begins in the summer and is complete by winter. Metamorphosis to macropthalmia (juvenile phase) occurs gradually over several months as developmental changes occur, including the appearance of eyes and teeth, and they leave the substrate to enter the water column. Anecdotal information suggests that they may occur within the hyporheic zone and may move laterally through stream substrates. We know little about movement and locations of ammocoetes within the substrates. Ammocoetes move downstream as they age and during high flow events. Several generations and age classes of ammocoetes may occur in high densities. Larvae transform to juveniles (macropthalmia) and migrate to the ocean.Īdults develop teeth on sucking disk for parasitic feeding.Īdults live in ocean 1-3 years and feed on host fish.Īdults migrate to freshwater and reside there about a year.Įmbryos hatch in approximately 19 days at 59° Fahrenheit (F) and the ammocoetes drift downstream to areas of low velocity and fine substrates where they burrow, grow and live as filter feeders for 3 to 7 years and feed primarily on diatoms and algae. Pacific Lamprey Life Cycle:Īdults spawn in gravel nest in stream riffles, and then die.Įggs hatch into larvae (ammocoetes) and drift downstream to slow velocity area.Īmmocoetes live in silt/sand substrates and filter feed for 3 - 7 years. After the eggs are deposited and fertilized, the adults typically die within 3 to 36 days after spawning. The degree of homing is unknown, but adult lampreys cue in on ammocoete areas which release pheromones that are thought to aid adult migration and spawning location.īoth sexes construct the nests, often moving stones with their mouth. Spawning occurs between March and July depending upon location within their range. Pacific lampreys spawn in similar habitats to salmon in gravel bottomed streams, at the upstream end of riffle habitat, typically above suitable ammocoete habitat. Adult size at the time of migration ranges from about 15 to 25 inches.
Most upstream migration takes place at night. They are thought to overwinter and remain in freshwater habitat for approximately one year before spawning where they may shrink in size up to 20 percent. They have been caught in depths ranging from 300 to 2,600 feet, and as far off the west coast as 62 miles in ocean haul nets.Īfter spending 1 to 3 years in the marine environment, Pacific lampreys cease feeding and migrate to freshwater between February and June. Life History:Īs adults in the marine environment, Pacific lampreys are parasitic and feed on a variety of marine and anadromous fish including Pacific salmon, flatfish, rockfish, and pollock, and are preyed upon by sharks, sea lions, and other marine animals. As larvae (ammocoetes), they are difficult to distinguish from other lampreys. Identification of lampreys depends largely on the number, structure, and position of teeth found in adult lamprey adult Pacific lampreys are characterized by the presence of 3 large anterior teeth and many smaller posterior teeth on the oral disc.
Pacific lampreys have a round sucker-like mouth, no scales, and gill openings. Lampreys belong to a primitive group of fishes that are eel-like in form but lack the jaws and paired fins of true fishes.
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