River Lamprey
River lamprey (Lampetra ayresii) are small, parasitic jawless fish that spend their adult lives in coastal marine waters before returning to freshwater to spawn.
In British Columbia, they're best known as a significant predator of juvenile Fraser River salmon and Pacific herring in the Strait of Georgia — not a sport fish, but a species that shapes the fishery every angler on the coast depends on.
Also known as River eel, Lamproie de rivière
- Eel-like body, scaleless and cartilaginous — no paired fins, no jaw; adults typically 15–30 cm, smaller than Pacific lamprey.
- Round, sucker-like mouth ringed with sharp, horn-shaped teeth surrounding a rasping tongue — the key ID feature separating it from non-parasitic brook lampreys.
- Smooth, grey-brown to olive skin; larvae (ammocoetes) are eyeless and toothless, living buried in soft river sediment for 5–7 years before metamorphosis.
- After metamorphosis, adults develop functional eyes and a fully formed oral disc — at this stage they're ready to move to saltwater and begin feeding parasitically.
What to know
Habitat Distribution
- Native to the Pacific coast of Canada; adults are present in marine waters off British Columbia, including the Strait of Georgia and the Fraser River plume.
- Larvae live buried in the soft sediments of freshwater rivers — the Fraser River downstream of Hope holds particularly dense populations, making it the dominant organism by weight in those bottom sediments.
- Adults return from the ocean to spawn in freshwater rivers and streams along the BC coast, dying shortly after reproduction — a life cycle shared with Pacific salmon.
- Adult Pacific coast river lampreys also move into deeper coastal marine waters; research documents their presence in major fishing grounds off Canada's west coast.
Key Locations
- Fraser River (BC) — larvae dominate the bottom sediments downstream of Hope; the river plume in the Strait of Georgia is a key adult feeding zone.
- Strait of Georgia (BC) — open coastal waters where adult river lampreys parasitize juvenile salmon and herring during their marine phase.
Specific Spots
- Larvae concentrate in soft, silty or sandy river-bottom sediments where they can burrow and filter-feed — look for them in low-velocity backwater areas and depositional zones of larger rivers.
- In the marine phase, river lampreys are found in open coastal waters and estuaries, attaching to juvenile salmon and herring in the Fraser River plume — a zone of intense predation pressure on out-migrating smolts.
- Spawning adults move into gravel-bottomed tributary streams, selecting clean riffles similar to salmon redds — their upstream migration follows the same corridors as returning salmon.
River Lamprey FAQ
Answers from onWater's species guide.
How do you catch River Lamprey?
River lamprey are not targeted by sport anglers in Canada. They are studied by fisheries researchers and are significant to the ecology of BC's salmon-bearing rivers, but there is no directed recreational or commercial fishery for this species in Canadian waters.
What do River Lamprey eat?
Larvae are filter-feeders, drawing in fine organic particles and microorganisms from river sediment, they have no teeth and cause no harm to other fish during this 5–7 year stage.
Where do River Lamprey live?
Native to the Pacific coast of Canada; adults are present in marine waters off British Columbia, including the Strait of Georgia and the Fraser River plume.
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