Entosphenus similis

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General Information
Common Name: 
Klamath River lamprey

Conservation Status in California: Class 3, Near-threatened (Moyle et al. 2011).
Although the Klamath River Lamprey appears to be widespread in the Klamath Basin, we know so little about this species that the conservative course of action is to consider it to be in decline until we find out differently.

Life History: 

Life History: No specific life history information is currently available, although they appear to be non-migratory and are resident in both rivers and lakes of the Klamath Basin. Adults prey on adult coho and Chinook salmon and other large fish in the basin. Wales (1951) thought that lamprey predation on migratory salmon was a major factor limiting salmon abundance in the Shasta River, because of the high frequency of salmon with lamprey wounds (41%).”

Dispersal Capability: Little is known about how Klamath River lamprey colonized new habitats.

Habitat Requirements: 

Habitat Requirements: Little is known about the habitat requirements of Klamath River lamprey. Presumably, ammocoetes have the same basic requirements as those of Pacific lamprey, living in backwaters with soft substrates. The environmental tolerances of Klamath River lamprey have not been documented but they presumably also are similar to those of Pacific lamprey.


California Distribution: The Klamath River lamprey is found throughout the Klamath River basin in main rivers, including the Trinity River in northern California and southern Oregon (Boyce 2002). Presumably its distribution in the lower Klamath and Trinity basins coincides with that of spawning Chinook and coho salmon, its presumptive main prey in the lower river, and with large suckers and cyprinids in the upper basin.
See forest-level maps and R5 distribution spreadsheet for HUC12-specific range data for this species on R5 lands.

Abundance Trends: 

California Trends in Abundance: As with other upper Klamath basin lampreys, abundance estimates for Klamath River lamprey do not exist. However, they seem common throughout their range (S. Reid, pers. comm. 2008).


Description: The Klamath River lamprey is a small (14-27 cm TL, mean 21 cm) predatory lamprey that can be identified by the strong, sharply hooked cusps on the oral plates. Three strong cusps on the supraoral plate (‘tongue’) are easily noticeable. The anterior field above the mouth has 10-15 teeth, 4 inner lateral plates on each side, resulting in the typical cusp formula of 2-3-3-2, 20- 29 cusps line the transverse lingual lamina (tongue plate), and 7-9 velar tentacles. The trunk usually has 60-63 myomeres (range of 58-65). The disc length is about 9 percent of the total body length, and is at least as wide as the head. The horizontal eye diameter is about 2 percent of the total body length. Although similar to Pacific lampreys, Klamath River lampreys tend to be more heavily pigmented. Ammocoetes have not been described.