Lampetra richardsoni

Reid et al. (2011) removed Lampetra pacifica from synonymy with L. richardsoni based on morphological data (trunk myomere counts) and genetic sequence divergence, but also note that additional systematic studies are needed to resolve the diversity of western North American lampreys.

This species was derived from the genetically similar parasitic river lamprey, Lampetra ayresii (Aladykov and Follett 1965). It was referred to as L. planeri in earlier publications (Lee et al. 1980). An intermediate freshwater parasitic form, L. richardsoni var. marifuga, is found on Vancouver Island (Morrison Creek), British Columbia (Beamish 1987, Mecklenburg et al. 2002).

Widespread in streams from Alaska to California; population status and trends are not well known.

Range includes streams of the North American Pacific coast from Taku River, southern Alaska, to central California, including Vancouver Island, with major inland distributions in the Columbia and Sacramento-San Joaquin drainages (Vladykov and Follett 1965, Moyle 2002, Wydoski and Whitney 2003, Page and Burr 2011). In Washington, this species occurs in coastal and Puget Sound streams and as far inland as the upper reaches of the Yakima River; recorded in streams on the west and south sides of the Olympic Peninsula but not on the north or east sides (Wydoski and Whitney 2003). This lamprey is relatively common in forested coastal basins, such as the Alsea River, Oregon. In California, western brook lampreys have been recorded mainly from the Sacramento River drainage, including areas as remote as Kelsey Creek above Clear Lake (Lake County), but they are also present above Pillbury Reservoir in the Eel River and in Mark West Creek, a tributary of the Russian River; spawning adults were collected in the Navarro River (Mendocino County) in 1999 (Moyle 2002). Ammocoetes from an extirpated population in the Los Angeles River basin may represent this species (Moyle 2002). Western brook lamprey is easily overlooked and difficult to collect, it is likely that this species occurs in many streams in coastal California (Moyle 2002).

Populations in the Columbia River basin, Oregon are reassigned to L. pacifica (Reid et al. 2011).

This species is widely distributed and likely represented by many occurrences (more than presently recorded; species is relatively difficult to detect and identify).

No major threats are apparent at this time, but the species is likely unable to withstand severe pollution or habitat changes (Moyle 2002). Potential threats include stream pollution, habitat modification that changes stream flow rates and siltation patterns, and use of poisons in fish management practices.

The Morrison Creek population is threatened by rapid residential development along stretches of important spawning and rearing habitat; this lamprey's extremely limited distribution places it at higher risk to all threats, especially habitat modification (Fisheries and Oceans Canada 2004).