Pacific Lamprey

Handle with care

Entosphenus tridentatus

Also known as: Three-toothed Lamprey, Pacific Lamprey Eel

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Description

The Pacific Lamprey (Entosphenus tridentatus) is an anadromous, jawless fish belonging to the family Petromyzontidae. It is characterized by its eel-like body, a distinctive oral disc lined with numerous teeth, and a unique life cycle that includes a prolonged larval (ammocoete) stage in freshwater, followed by a parasitic marine phase, and a return to freshwater for spawning. This species plays a crucial ecological role in Pacific Rim ecosystems.

Physical Characteristics

Body shape: eel-like
Coloration: Adults are typically dark blue to black dorsally, fading to silvery-white or grey ventrally. Spawning adults may become darker and develop a reddish hue. Ammocoetes are uniformly tan or brownish.
Scale type: none
Mouth position: inferior
Distinctive features: Jawless, circular, suctorial mouth (oral disc) armed with concentric rows of sharp, horny teeth., Three prominent cusps on the supraoral lamina (a plate above the mouth opening), giving it the 'tridentatus' name., Seven distinct gill openings (pore-like) on each side of the head., Absence of paired fins (pectoral and pelvic fins)., A single nostril on top of the head., Lack of scales.
Dorsal fin: Two distinct dorsal fins, separated by a small gap. The first dorsal fin is lower and shorter than the second. The second dorsal fin is continuous with the caudal fin.
Tail fin: Slightly emarginate (not deeply forked) and continuous with the second dorsal and anal fins.
Pectoral fin: Absent
Distinctive fins: Anal fin is present and continuous with the caudal fin.

Identification Tips

Oral Disc and Teeth

Examine the oral disc. Pacific Lamprey have a large, circular oral disc with numerous sharp, horny teeth arranged in concentric rows. Crucially, look for the supraoral lamina (a plate above the mouth opening) which has three distinct cusps (points). This 'three-toothed' feature is key to its scientific name and identification.

Gill Openings

Count the gill openings. Like all lampreys, they have seven small, pore-like gill openings on each side of the head, posterior to the eye.

Dorsal Fins

Observe the dorsal fins. Pacific Lamprey possess two distinct dorsal fins, separated by a noticeable gap. The second dorsal fin is larger and continuous with the caudal fin.

Absence of Paired Fins and Scales

Note the lack of pectoral and pelvic fins, and the smooth, scaleless skin. This distinguishes them from true fish.

Body Size

Adult Pacific Lamprey are among the largest lamprey species, typically reaching lengths of 50-80 cm, which can help differentiate them from smaller lamprey species in their range.

Habitat

Water type: freshwater
Depth: Ammocoetes inhabit shallow, soft-bottomed areas of rivers and streams (typically <1 meter). Adults are found in coastal marine waters, often at depths of 0-200 meters, and return to freshwater for spawning.
Environment: Anadromous; freshwater rivers and streams for larval and spawning stages, and coastal marine environments for parasitic adult feeding. Requires clean, cool, well-oxygenated water with suitable substrate (sand, silt) for ammocoete burrowing.
Geographic range: North Pacific Ocean and its tributary freshwaters. Extends from Baja California, Mexico, north to Alaska, and across to the Asian coast from Kamchatka, Russia, south to Japan and Korea.

Aquarium Information

Care level: expert
Temperament: aggressive
Diet: carnivore
Minimum tank size: Not suitable for typical home aquaria due to specialized needs and parasitic nature.
Temperature: Varies significantly with life stage (freshwater ammocoetes: 10-20°C; marine adults: variable; spawning adults: 8-15°C)
pH level: Freshwater: 6.5-8.0; Marine: 8.0-8.3
Hardness: Freshwater: Soft to moderately hard
Compatibility: Not compatible with other fish due to parasitic feeding habits in the adult stage. Ammocoetes are filter feeders and can coexist with other benthic invertebrates.
Special requirements: Requires highly specialized facilities mimicking natural riverine and marine environments, including specific substrate for ammocoetes, strong currents, and access to host fish for adult feeding. Not recommended for private aquarists.

Wild Information

Conservation status: vulnerable
Seasonality: Spawning runs typically occur from late winter to early summer, depending on geographic location and water temperature. Ammocoetes reside in freshwater for several years. Adults spend 1-3 years in the marine environment.
Market price: N/A (not typically sold commercially for food or aquarium trade)
Commercial importance: low
Taste: Described as rich, oily, and distinct, often compared to eel or salmon.
Texture: Firm, fatty, and somewhat gelatinous.
Cooking methods: smoked, roasted, fried, stewed
Nutritional value: High in omega-3 fatty acids, protein, and vitamins A and D. Historically a significant food source for Indigenous peoples.

Key Facts

Ancient Lineageevolution

Lampreys are among the oldest living vertebrates, with a fossil record extending back over 360 million years, predating jawed fish.

Ecological Engineersbehavior

Ammocoetes (larval lampreys) are filter feeders that burrow in stream sediments, improving water quality and providing food for other species. Spawning adults transport marine-derived nutrients into freshwater ecosystems.

Unique Life Cycleamazing

Pacific Lamprey undergo a dramatic metamorphosis from blind, filter-feeding ammocoetes to parasitic, migratory adults, and then to non-feeding, spawning adults.

Cultural Significanceinteresting

Pacific Lamprey have been a culturally significant and traditional food source for Indigenous peoples of the Pacific Northwest for millennia, often harvested using traditional methods.

Conservation Concerninteresting

Populations of Pacific Lamprey have declined significantly throughout much of their range due to habitat degradation, passage barriers (dams), pollution, and climate change, leading to their 'Vulnerable' status.

Safety Information

Handle with care

Safety level: caution
Venomous: No
Edibility: edible
Handling notes: Pacific Lamprey are not venomous, but their powerful suctorial mouth and sharp teeth can inflict a painful bite if handled carelessly. They are also very slippery. Handle with thick gloves if necessary, and avoid direct contact with the oral disc. They are a protected species in many areas, and handling may require permits.

Similar Species

Western Brook Lamprey

Lampetra richardsoni

Smaller size (typically <20 cm), non-parasitic (adults do not feed), and the supraoral lamina has only two cusps (bicuspid) or is sometimes absent. Teeth are blunter and less developed.

River Lamprey

Lampetra ayresii

Generally smaller than Pacific Lamprey (up to 30 cm), parasitic but typically on smaller fish, and the supraoral lamina is bicuspid (two cusps), not tricuspid. Teeth are also less robust.

Arctic Lamprey

Lethenteron camtschaticum

Found further north, generally smaller, and the supraoral lamina is bicuspid. The teeth arrangement and morphology differ upon close inspection.

Scientific Classification

Kingdom: Animalia
Phylum: Chordata
Class: Petromyzontida
Order: Petromyzontiformes
Family: Petromyzontidae
Genus: Entosphenus
Species: tridentatus

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