E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Distinguished by 2 large teeth on the supraoral bar, a large middle tooth on the tongue, 3 points (rarely 2) on each central lateral tooth plate, and the absence of posterial teeth (Ref. 27547). Anterior dorsal fin being lower than posterior, the fins separate in nonbreeding individuals but coming into contact at spawning; caudal fin lobes about equal, lower lobe joined to anal fin; anal fin virtually absent in males (Ref. 27547). Dark brown or brownish gray on sides and back; belly yellowish, silvery around head, gill openings and lower sides; caudal fin has a band of dark pigment inside its margins, symmetrical on each lobe (Ref. 27547).

The relationship between this species (river lamprey) and the western brook lamprey is unclear. They may be anadromous and non-migratory forms of the same species (not unlike the anadromous and freshwater-resident forms of threespine sticklebacks). If the river lamprey is a separate species, its spawning sites are unknown.

Eastern Pacific: Tee Harbor, Alaska to Sacramento-San Joaquin drainage in California, USA. Freshwater resident population in Morrison Creek, Vancouver Island, British Columbia (Ref. 12269).