Entosphenus tridentata

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General Information
Common Name: 
Goose Lake lamprey

Conservation Status in California: Class 2, Vulnerable (Moyle et al. 2011).
Goose Lake lamprey apparently do not face any immediate extinction risks but their populations are probably small and isolated, so climate change and other factors could change their status quickly.

Life History: 

Life History: The life history of this taxon is largely unknown, but presumably the adults live for a year or two in Goose Lake, preying on Goose Lake tui chubs, suckers, and redband trout. In 1989, adult lampreys were observed attached to gill-netted tui chubs and lamprey wounds were common in larger chubs (P. Moyle and R. White, unpublished observations). They migrate up suitable tributary streams in spring for spawning, with a peak in May (Kostow 2002). They have to move up far enough to find gravel for spawning and to have enough suitable soft-bottomed habitat downstream of the spawning area for survival of the ammocoetes. Thus, spawning areas may be as much as 20-30 km upstream from the lake. Ammocetes probably spend 4-6 years in the streams before metamorphosing into adults (at about 8-13 cm TL) in the fall and moving into the lake in spring (Kostow 2002). During periods of drought, when access to the lake is not available, adult lampreys will feed on stream fishes although survival appears to be low (Kostow 2002).

Habitat Requirements: 

Habitat Requirements: Adults live in shallow, alkaline Goose Lake where they prey on larger fishes. Goose Lake is described in the Goose Lake tui chub account. Like other lampreys, Goose Lake lampreys require gravel riffles in streams for spawning, and the ammocoetes require muddy backwater habitats downstream of the spawning areas. Kostow (2002) characterizes the habitat of ammocoetes as “fine silt lenses along low gradient stream meanders, most often through meadows…(p. 18).” However, the habitat requirements of this lamprey have never been specifically studied.


Distribution: The Goose Lake lamprey is endemic to Goose Lake and its tributaries in Oregon and California. However, the streams most important for spawning and as habitat for the ammocoetes have not been identified with certainty. In California, they have been collected only from Lassen and Willow creeks, Modoc County (G. Sato, BLM, pers. comm.), above and below potential migration barriers (Hendricks 1994), but a thorough search of the tributary streams for lampreys has not been done. Ammocetes were also found to be common in Cold Creek. No ammocetes were found in Davis, Pine or Willow creeks. It is likely that dams now restrict the distribution of ammocoetes by blocking the migration of adults and by drying up suitable habitats downstream. In Lake County, Oregon, they are common in Thomas Creek and a population apparently exists in Cottonwood Reservoir on Cottonwood Creek (Oregon Dept. of Fish and Wildlife, unpubl. data, 1995).

Abundance Trends: 

Trends in Abundance: Goose Lake lampreys were fairly common in the Goose Lake until the lake dried up in the summer of 1992. They were readily collected from large tui chubs caught in gillnets (R. White, USFWS, pers. comm., 1995). The Goose Lake lamprey has a high probability of becoming extinct during a period of prolonged drought, if the lake and lower tributaries are dry for several years in a row. However, adults may survive by preying on stream fish and the ammocoetes may persist for 3-4 years if there is adequate water flowing over the habitats they occupy. The Cottonwood Reservoir population is of unknown size but the reservoir may serve as a refuge, provided a minimum pool is maintained throughout extended drought periods. In Lassen and Willow creeks, lamprey were common at densities of 11-50 individuals per 150 ft of stream (Hendricks 1994).


Species Description: This predatory lamprey is similar to the widespread Pacific lamprey, E. tridentatus, except that it is much smaller (adult TL 19-25 cm vs. 30-40 cm for Pacific lamprey). Both forms can be recognized by the sharp, horny plates in the sucking disc, the most distinctive being the crescent-shaped supraoral plate, which has three distinct cusps. The middle cusp is smaller than the two lateral cusps. Adult Goose Lake lamprey are shiny bronze color. Ammocetes can be distinguished from those of the sympatric E. lethophaga (or other undescribed non-predatory lamprey) by the larger number of myomere segments (64-70 between the last gill opening and anus).