Lampetra tridentataPacific lamprey

Geographic Range

The Pacific lamprey, Lampetra tridentata, is an anadromous species. They spend the middle of their lives in the Pacific Ocean and their first and last years in freshwater habitats. Pacific lampreys are found throughout the Pacific Rim, from Hokkaido Island, Japan to Baja California, Mexico. They have been captured up to 100 miles off the West Coast of North America. Within their range, they inhabit most major river systems that flow into the Pacific Ocean. (Close, et al., 2002; Streif, 2007)


Lampetra tridentata spawns in the shallow, fast-moving headwaters of gravel-bottomed streams, at depths of 0.3-4 meters. The larvae, called ammocoetes, drift downstream after hatching and burrow into fine sediments. Ammocoetes are most successful in slow-moving reaches with an open riparian canopy. After reaching their adult stage, they migrate to the open ocean, where they have been found at depths of 90-800 meters. (Mayfield, et al., 2014; Stone and Barndt, 2005; Streif, 2007)

  • Aquatic Biomes
  • pelagic
  • rivers and streams
  • Range depth
    0.3 to 800 m
    0.98 to 2624.67 ft

Physical Description

Lampetra tridentata is distinguished from other lamprey species by its three large, sharp anterior teeth, located on the supraoral bar. Like all lampreys, they have seven breathing pores on each side of their body and a large sucking disc as a mouth. They are usually 381-635 millimeters long by the time they migrate to the ocean. Once in the ocean, they can grow up to 700 millimeters long. On average, they weigh one pound, or 453 grams. However, individuals in coastal populations tend to be smaller than those that spawn further inland. They are dark blue on top and silver or white underneath. During breeding season, Pacific lampreys turn reddish-brown, and the sexes begin to differ in appearance as a pseudo-anal fin develops on the female. Their larvae are difficult to distinguish from those of other lamprey species. (Amiotte, 2013; McPhail, 2007; Morrow, 1980; Streif, 2007)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    453 g
    15.96 oz
  • Range length
    381 to 700 mm
    15.00 to 27.56 in


Pacific lamprey ammocoetes have no eyes, teeth, or swimming ability. After 4-7 years, they enter metamorphosis, or macropthalmia. In addition to developing eyes and teeth, their fins become more defined, and their heads and naso-pineal organs enlarge. ("Oregon Lampreys: Natural History, Status, and Analysis of Management Issues", 2002; Close, et al., 2002)


Lampetra tridentata ammocoetes produce at least three different bile acid compounds. Adult Lampetra tridentata can smell these compounds and are attracted to the odor, which guides them upstream to their spawning grounds. Males and females cooperate to construct a shallow nest out of pebbles, which the female positions herself across. The male coils around her, and they release their eggs and sperm simultaneously. Pacific lampreys often construct multiple nests and spawn several times during the breeding season, and several pairs may spawn in the same nest. (Mayfield, et al., 2014; Stone, 2006; Yun, et al., 2011)

Pacific lampreys spend 3-7 years as larvae before entering macropthalmia, or metamorphosis, from July to November. During macropthalmia, Pacific lampreys grow into their free-swimming, parasitic adult form over the course of several months. Sometime between fall and spring, when macropthalmia has been completed, they begin their migration to the Pacific Ocean. Pacific lampreys spend 1-3 years in their marine life stage before returning to freshwater between February and June. They remain in freshwater habitat for approximately one year before spawning and die 3-36 days after reproduction. (Close, et al., 2002; Streif, 2007)

  • Breeding interval
    Pacific lampreys breed once during their lifetime and die soon afterwards.
  • Breeding season
    Pacific lampreys breed from March through July, with the specific time depending on their geographic region.
  • Range number of offspring
    98,000 (low)
  • Average number of offspring
  • Average gestation period
    19 days
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    5 to 11 years
  • Range age at sexual or reproductive maturity (male)
    5 to 11 years

Pacific lampreys construct their nests, called redds, by moving small stones with their mouthparts. A male and female cooperate to build a redd. The redd may be anywhere from 29-80 cm long and 30-85 cm wide, and is usually located 24-99 cm below the water’s surface. Individual Pacific lampreys will usually construct multiple redds. After spawning, adults have no involvement with their eggs or larvae. (Mayfield, et al., 2014; Streif, 2007)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • male
      • female


  • Typical lifespan
    Status: wild
    5 (low) years
  • Average lifespan
    Status: wild
    11 years


Pacific lamprey ammocoetes often cluster together at high densities. Until metamorphosis, they are unable to swim. However, they can detach from the stream bed and drift downstream, usually when the current is at high velocity. Larger ammocoetes typically drift during fall, and smaller ammocoetes typically drift during spring. In freshwater habitats, Pacific lampreys are generally nocturnal. Adults are solitary outside of spawning season. During spawning season, either the male or the female may initiate courtship by rubbing up and down a potential mate's body. ("Oregon Lampreys: Natural History, Status, and Analysis of Management Issues", 2002; Stone and Barndt, 2005)

Home Range

Lampetra tridentata does not have a fixed home range and is not territorial. (Close, et al., 2002)

Communication and Perception

Pacific lampreys rely most heavily on their olfactory and visual systems. Adults navigate to their spawning grounds by following the trail of pheromones released by ammocoetes. (Braun, 1996; Yun, et al., 2011)

Food Habits

During their larval stage, Pacific lampreys are filter feeders, consuming algae and detritus. Adults are parasitic, latching onto prey with their oral discs and consuming their blood and other bodily fluids. They feed on salmonids and a variety of other fishes, as well as several species of whale. ("Oregon Lampreys: Natural History, Status, and Analysis of Management Issues", 2002; Close, et al., 2002)

  • Animal Foods
  • mammals
  • fish
  • blood
  • body fluids
  • Plant Foods
  • algae


Ammocoetes stay hidden from predators by sheltering under substrate and only emerging at night. As they grow, they develop tougher skin that makes them less palatable. Adult cryptic coloration- dark on their dorsal side, light on their ventral side- disguises them from predators. (Close, et al., 2002; McPhail, 2007; "Oregon Lampreys: Natural History, Status, and Analysis of Management Issues", 2002)

Pacific lamprey are prey for many species of fish, birds, and mammals. Eggs that overflow the nest are eaten by fish. Ammocoetes are particularly vulnerable to predators when emerging from their burrows and when dislodged by runoff. Adult Pacific lamprey are heavily preyed upon during the migration to their spawning grounds. After spawning, their carcasses also provide food for many species. (Close, et al., 2002)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The burrowing of Pacific lamprey ammocoetes aerates the streambed and softens the substrate. Ammocoetes may digest less than half of the food they consume, excreting the rest as fine particles that can be consumed by aquatic insects and other species. Pacific lampreys are higher in fats and calories than salmon, making them a valuable food source. Steller sea lions, Eumetopias jubatus, harbor seals, Phoca vitulina, and California sea lions, Zalophus californianus, have been found to consume more Pacific lamprey than salmon when both are available. This suggests Pacific lampreys may reduce the impact of predation on salmon. They supply high-calorie meals for many additional species, and their decomposing bodies provide nutrients to the freshwater and riparian ecosystems in which they spawn. (Close, et al., 2002; Roffe and Mate, 1984; Shirakawa, et al., 2012)

Species Used as Host

Economic Importance for Humans: Positive

Pacific lampreys were historically a major food source for indigenous peoples of the Pacific Northwest. Oil harvested from Pacific lampreys was used as food, hair conditioner, and treatment for ear aches. Pacific lampreys still hold great cultural and religious significance to many native peoples, and are harvested on special occasions. During the 1800's, Pacific lampreys were used to feed livestock and farmed fish. By potentially acting as a buffer between salmon and their natural predators, Pacific lampreys may increase the available harvest for fishermen. The anticoagulants in their saliva have made them a subject of medical research. ("Oregon Lampreys: Natural History, Status, and Analysis of Management Issues", 2002; Close, et al., 2002)

Economic Importance for Humans: Negative

While Pacific lampreys may kill their hosts on rare occasions, there is no evidence that they have a significant negative impact on salmon populations. Pacific lampreys are often viewed negatively because they are mistakenly associated with sea lampreys, a pest species in the Great Lakes region. Unlike sea lampreys, which are an invasive species in the Great Lakes, Pacific lampreys are native to northwestern America and play an important role in its ecosystems. (Close, et al., 2002)

Conservation Status

Dams and other artificial barriers have restricted Pacific lampreys' access to large portions of their freshwater range, contributing to their decline in river systems such as the upper Columbia Basin. Pacific lampreys are not strong swimmers and are unable to jump. These traits make it difficult for them to use the conventional fish ladders that help other fishes traverse dams. Dams with gratings appear to be especially difficult, since they impede Pacific lampreys' climbing ability. Adding rough surfaces to fish ladders could make climbing easier and increase the number of Pacific lampreys that cross the dams successfully. Although lampreys generally have a high tolerance for pollutants, chemical spills in river systems can kill large numbers of lampreys. Lamprey ammocoetes are especially vulnerable to pollution, since the sediments they inhabit can easily accumulate chemicals. Dredging also threatens ammocoetes. Among river lampreys (a close relative of Pacific lampreys), less than a third survived a dredging event. Pacific lamprey adults rely on the pheromones released by ammocoetes to find their way to their spawning grounds. If the ammocoete population near a spawning ground decreases enough, adults will not be able to locate the habitat and will disappear entirely from that area. Scientists are attempting to create synthetic versions of these pheromones, which could be used to guide Pacific lampreys to suitable spawning habitat. ("Oregon Lampreys: Natural History, Status, and Analysis of Management Issues", 2002; Yun, et al., 2011)


Sophie("Zosia") Lynch (author), Colorado State University, Peter Leipzig (editor), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


an animal that mainly eats decomposed plants and/or animals


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


A substance that provides both nutrients and energy to a living thing.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


makes seasonal movements between breeding and wintering grounds


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).


chemicals released into air or water that are detected by and responded to by other animals of the same species


an animal that mainly eats fish


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.


reproduction that includes combining the genetic contribution of two individuals, a male and a female

soil aeration

digs and breaks up soil so air and water can get in


lives alone


uses touch to communicate


uses sight to communicate


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Amiotte, L. 2013. ""Pacific Lamprey- Lampetra Tridentata"" (On-line). Washington State Department of Natural Resources. Accessed February 22, 2018 at

Braun, C. 1996. The Sensory Biology of the Jawless Fishes: a Phylogenetic Assessment. Brain Behavior and Evolution, Volume 48, Issue 5: 262-276.

Clemens, B., L. Wyss, R. McCoun, I. Courter, L. Schwabe, C. Peery, C. Schreck, E. Spice, M. Docker. 2017. Temporal genetic population structure and interannual variation in migration behavior of Pacific Lamprey, Entosphenus tridentatus. Hydrobiologia: The International Journal of Aquatic Sciences, Vol. 794, Issue 1: 223-240.

Clemens, B., S. van de Wetering, S. Sower, C. Schreck. 2013. Maturation characteristics and life-history strategies of the Pacific lamprey, Entosphenus tridentatus. Canadian Journal of Zoology, Vol. 91, Issue 11: 775-788.

Close, D., M. Fitzpatrick, H. Li. 2002. The Ecological and Cultural Importance of a Species at Risk of Extinction, Pacific Lamprey. North American Journal of Fisheries Management, Vol. 27, Issue 7: 19-25.

Mayfield, M., L. Schultz, L. Wyss, B. Clemens, C. Schreck. 2014. Spawning Patterns of Pacific Lamprey in Tributaries to the Willamette River, Oregon. Transactions of the American Fisheries Society, Vol. 143, Issue 6: 1544-1554.

McPhail, J. 2007. The Freshwater Fishes of British Columbia. Edmonton, Alberta: University of Alberta.

Morrow, J. 1980. The Freshwater Fishes of Alaska. Anchorage, Alaska: Alaska Northwest Publishing Company.

Murasakas, J., A. Orlov, K. Siwicke. 2013. Relationships between the Abundance of Pacific Lamprey in the Columbia River and their Common Hosts in the Marine Environment. Transactions of the American Fisheries Society, Vol. 142, Issue 1: 143-155.

Roffe, T., B. Mate. 1984. Abundances and Feeding Habits of Pinnipeds in the Rogue River, Oregon. Journal of Wildlife Management, Volume 48, Issue 4: 1262-1274.

Shirakawa, H., A. Goto, S. Yanai. 2012. Lamprey larvae as ecosystem engineers: Physical and geochemical impact on the streambed by their burrowing behavior. Hydrobiologia: The International Journal of Aquatic Sciences, Vol. 701, Issue 1: 313-322.

Stone, J. 2006. Observations on Nest Characteristics, Spawning Habitat, and Spawning Behavior of Pacific and Western Brook Lamprey in a Washington Stream. Northwest Naturalist, Volume 87, Issue 3: 225-232.

Stone, J., S. Barndt. 2005. Spatial Distribution and Habitat Use of Pacific Lamprey (Lampetra tridentata) Ammocoetes in a Western Washington Stream. Journal of Freshwater Ecology, Vol. 20, Issue 1: 171-185.

Streif, B. 2007. "Pacific Lamprey- Lampetra tridentata" (On-line). U.S. Fish and Wildlife Service. Accessed February 08, 2018 at

Yun, S., A. Wildbill, A. Dittman, S. Corbett, W. Li, D. Close. 2011. Identification of putative migratory pheromones from Pacific lamprey(Lampetra tridentata). Canadian Journal of Fisheries and Aquatic Sciences, Vol. 68, Issue 12: 2194-2203.