Arctic Lamprey Identification Guide
Identify an Arctic Lamprey by its dark body, closely set dorsal fins, and circumpolar northern range.
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Key identification features
- Slender, eel-like, scaleless body, typically around 25-33 cm in the parasitic adult phase
- Two dorsal fins set close together, narrowly separated or nearly touching
- Dark brown to blackish back fading to a lighter, silvery-gray belly
- Oral sucker disc with well-developed, functional teeth in the feeding (parasitic) life stage
- Single nostril on top of the head, positioned between the eyes
- Seven small round gill openings along each side of the head, as in all lampreys
- Both anadromous, ocean-feeding forms and smaller, dwarf freshwater-resident forms occur within the species
Common look-alikes
- Pacific lamprey grows larger and has a distinctive three-cusped supraoral tooth plate that the Arctic lamprey lacks.
- American brook lamprey is a non-parasitic dwarf relative with weak, degenerate teeth rather than the Arctic lamprey's functional feeding dentition.
- River lamprey shows dorsal fins that are more clearly separated by a wider gap than the Arctic lamprey's closely spaced pair.
Where you'll see one
Arctic lamprey has a circumpolar distribution across far-northern river systems and coastal waters of Siberia, Alaska, and northwestern Canada, spawning in cold gravel-bottomed streams while feeding forms spend part of their life in coastal seas or large connected lakes.
Frequently asked questions
How do I tell an Arctic Lamprey from a Pacific Lamprey?
Look at the tooth plate: Pacific lamprey has a distinctive three-cusped supraoral plate and grows larger, while Arctic lamprey lacks that three-pointed plate and stays comparatively smaller.
What is the easiest clue that a small dark lamprey found far north is an Arctic Lamprey?
Its closely spaced, nearly touching dorsal fins combined with a uniformly dark body and a far-northern, circumpolar location are strong indicators.