CONSERVING THE PACIFIC LAMPREY (ENTOSPHENUS TRIDENTATUS)

Often shadowed by the eminence of steelhead trout, clinging to cobbles in channels throughout the watershed, lies another anadromous fish. As a California State Species of Special Concern, the pacific lamprey is threatened by diminished habitat conditions throughout Southern California watersheds. They are ranked S1 by NatureServe, signifying their population in our watershed is critically imperiled. 

Pacific lamprey, a species with a lineage tracing back to the Ordovician period 450 million years ago, is an ancient fish. The life cycle of the pacific lamprey begins in slow moving silts, where stream velocity is low. Fine substrates allow the larvae, known as ammocoetes, to burrow and embed themselves, where they will spend three to ten years filter feeding algae, microorganisms, and detritus at night. In this stage, they lack eyes and teeth. Metamorphosis occurs over a couple of months, oftentimes reaching completion between winter and spring. Once transformed to have teeth and vision, individuals make their way downstream into marine waters. 

In the ocean, pacific lamprey will spend up to seven years growing until reaching maturity. As ectoparasites, juvenile pacific lamprey will feed by attaching on their host’s skin and draw blood and fluids for nutrition. Once an adult and ready for reproduction, they will make their way up rivers during the spring and summer until they come across pheromones released by larvae, which indicates that habitat conditions for redds (nests) could be found just upstream. Migrations upstream occur at night. Conditions for breeding grounds preferred by pacific lamprey are gravelly substrates with sufficient dissolved oxygen. Artistically, they create redds by moving substrate with their mouths, creating a lined circular depression. After spawning, their life cycle comes to a close—Pacific lampreys die shortly after, leaving the next generation to emerge from the gravel. 

Conservation of this enigmatic species relies on improving in-stream conditions preferred by all life stages of pacific lamprey. In order for these habitats to properly develop, sorting of sediment must properly distribute into areas with cobbles, granules and silts, where each life stage can persist. Impairment of sediment distribution can result from excess sediment deposition from upland habitats, channelization of streambanks from invasive species, and large impediments such as dams. OVLC’s efforts in restoring riparian and upland habitat are drastically improving habitat for not only the southern steelhead, but also for the pacific lamprey. 

Martin Schenker, Restoration Field Crew Manager