Entosphenus tridentatus (Richardson, 1836)
Pacific lamprey
photo by The Native Fish Conservancy

Family:  Petromyzontidae (Northern lampreys), subfamily: Lampetrinae
Max. size:  76 cm TL (male/unsexed); max.weight: 500.0 g; max. reported age: 9 years
Environment:  demersal; freshwater; brackish; marine; depth range 0 - 1508 m, anadromous
Distribution:  North Pacific: Bering Sea coasts of Asia and Alaska southward to the Yuhutu River, Hokkaido, northern Japan and Punta Canoas, central Baja California, Mexico. The populations were, at one time, split into two groups (Ref. 10015) as Entosphenus tridentatus tridentatus which ranged from the Columbia River to Alaska, and Entosphenus tridentatus ciliatus which ranged from Klamath River southwards (Ref. 1998). This division no longer holds (Ref. 1998). Freshwater resident populations exist in Culrus Lake and the Columbia River, British Columbia, the Sprague River in Oregon, the Goose Lake in Oregon/California, and the Klamath and Shasta rivers and Copco Lake in California (Ref. 12269).
Diagnosis:  Characterized by the presence of 3 (rarely 2) large sharp teeth on the supraoral bar and three sharp points on each of the central lateral tooth plates. Dorsal fins arise far back on the body, the anterior fin lower and shorter, higher in males; lower lobe of caudal fin larger than upper, the lobes joined to dorsal and anal fins; anal fin rudimentary, virtually absent in males. Adults from the sea blue-black to greenish above, silvery to white below; spawning adults become reddish brown (Ref. 27547). Other diagnostic characters: oral disc as wide or wider than head; usually 64-71 trunk myomeres; dark blue or brown above, light or silver below (Ref. 86798). Adults: 9.6-80.0 cm TL. Specimens 38-62 cm TL weigh 120-510 g wet weight. Body proportions, as percentage of TL (based on 274 specimens measuring 9.6-71.6 cm TL): prebranchial length, 9.8-18.0; branchial length, 7.8-12.6; trunk length, 40.3-54.0; tail length, 23.6-34.9; eye length, 1.3-4.5; disc length, 4.6-9.1. The urogenital papilla length, as a percentage of branchial length, in two spawning males measuring 21.1-21.7 cm TL, 12.0-12.5. Trunk myomeres, 60-71 (may be as low as 57 and as high as 78). Dentition: marginals, 48-62; supraoral lamina, 3 unicuspid teeth, the median one being smaller; infraoral lamina, 5-6 unicuspid teeth, predominantly 5; 4 endolaterals on each side; endolateral formula, typically 2-3-3-2, the first endolateral rarely unicuspid and the second and third endolaterals rarely bicuspid; 2 rows of anterials; first row of anterials, either 1 or 5 unicuspid teeth; exolaterals absent; 1 row of posterials, 12-21 teeth, of which 0-5 may be bicuspid and the remainder unicuspid; transverse lingual lamina, 14-23 unicuspid teeth, the median one slightly enlarged; longitudinal lingual laminae parentheses-shaped, each with 20-27 unicuspid teeth [50-63 according to McPhail and Lindsey (1970)]. Velar tentacles, 10-18, with tubercles; the dorsal wings may each consist of up to 5-6 long tentacles that reach the median tentacle. Median tentacle about the same length as the lateral ones immediately next to it. Four of five specimens from the Sprague River did not possess wings and had 7-10 tentacles. Body coloration (preserved), dorsal, lateral, and ventral aspects bluish gray in older individuals and ventral aspect either dark gray or almost white in recently metamorphosed individuals. Lateral line neuromasts unpigmented or darkly pigmented. Caudal fin pigmentation, +++. Caudal fin shape, rounded or spade-like. Oral fimbriae, 94-105. Oral papillae, 12-18 (Ref. 89241).
Biology:  Anadromous, but also a number of permanent freshwater resident populations (Cultus Lake, British Columbia; Sprague River, Klamath River Basin, Oregon). In marine waters, adults mostly inhabit the mesopelagic zone down to 800 m depth and have been documented as far as 117 km off the coast of Oregon. In fresh waters, ammocoetes and adults inhabit lakes, rivers, and creeks. Ammocoetes occur in soft sediments in shallow areas along stream banks (Ref. 89241); in silt, mud, and sand of shallow eddies and backwaters of streams (Ref. 5723). Spawning adults are found in gravel riffles and runs of clear coastal streams; feeding adults usually in the ocean, but landlocked populations occur (Ref. 1998). Stops feeding once upstream spawning migration is underway (Ref. 1998). Parasitic adults attach themselves to the side or undersurface of its prey, from which it draws blood and body fluids as food. Preys on fishes and sperm whales (Ref. 6885). Adults are found in the Strait of Georgia from December to mid-June. The duration of the feeding phase at sea has been estimated at 20-42 months. In British Columbia, return to fresh water begins as early as April and is completed by September. In the Columbia River, prior to the completion of the Grand Coulee Dam in 1941, spawning migrations of 800 km up to Kettle Falls, Washington occurred. In order to cross barriers such as falls, they use their suctorial disc to attach to the vertical surfaces and slowly make their way up. In British Columbia spawning is in June to the end of July, while in Oregon, it begins in May at water temperatures of 10-15 °C and continues through July. Fecundity, 98,300-238,400 eggs/female in Oregon populations from Clear, Trout, and Cow creeks, respectively, in the John Day, Molalla, and Umpqua river basins. Death of spawners follows 3-36 days after spawning. Eggs are eaten by two species of fish in the Umatilla River, Oregon (Ref.89241). Rarely consumed as food; prepared fresh or smoked (Ref. 6885). Sometimes processed into meal (Ref. 27436). The Native American tribes of the mid-Columbia River Plateau have an ongoing tradition dating back hundreds of years of harvesting Pacific Lamprey. The adults are caught either by hand or dipnet in areas where they congregate prior to spawning. They are prepared for human consumption either by drying or roasting. Caloric values for Pacific Lamprey range from 5.9 to 6.3 kcal/g wet weight. Their oil is also extracted and used for medicinal purposes. Ammocoetes are used as bait for introduced Micropterus dolomieu in the John Day River, Oregon. In 1812, Americans of European descent obtained Pacific Lamprey from the Umatilla tribe of Oregon for the purposes of consumption. In the early 1900s, fur trappers utilized Pacific Lamprey as bait for coyotes. A fishery for adult lamprey has existed at Willamette Falls on the Willamette River, Oregon at least since 1913. That year, 24.5 metric tons were harvested and ground into fishmeal for young hatchery salmon. Between 1943 and 1949, 740 metric tons in total were harvested and used for vitamin oil, food for livestock, poultry, and fishmeal. In 1994, about 1.8 metric tons were exported to Europe for human consumption. The North Carolina Biological Supply House regularly collects adults from this locality for use as teaching material (Ref.89241). The effects of Pacific lamprey attacks on commercial species needs further studies (Ref. 6885).
IUCN Red List Status: Least Concern (LC); Date assessed: 20 May 2020 Ref. (126983)
Threat to humans:  harmless

Source and more info: www.fishbase.org. For personal, classroom, and other internal use only. Not for publication.