Northern Brook Lamprey Identification Guide
Identify a Northern Brook Lamprey by its small size, single continuous dorsal fin, and weak oral disc teeth.
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Key identification features
- Small, slender, eel-like body, generally 10-18 cm at maturity
- A single, continuous dorsal fin running along the back with no clear division into two fins
- Uniform dark gray to brown coloring without strong blotching
- Oral sucker disc present but with small, blunt, degenerate teeth unsuited for feeding
- Single nostril on top of the head, as in all lampreys
- Non-feeding, short-lived adult stage that exists only briefly to spawn before dying
- No paired fins, consistent with all lampreys
Common look-alikes
- Silver lamprey and chestnut lamprey share the same single continuous dorsal fin but grow much larger and retain sharp, functional feeding teeth.
- American brook lamprey is similarly small and non-feeding but has two separate dorsal fins with a distinct notch, rather than one continuous fin.
- Sea lamprey larvae burrow in sediment much like this species, but adult sea lampreys grow far larger and develop a heavily toothed feeding disc.
Where you'll see one
Northern brook lamprey occurs in small, clean, gravel- and sand-bottomed streams of the north-central United States and adjacent Canada, where larvae burrow into silty banks for several years before a brief non-feeding adult phase entirely within freshwater.
Frequently asked questions
How do I tell Northern Brook Lamprey from American Brook Lamprey?
Check the dorsal fin: northern brook lamprey has one continuous dorsal fin, while American brook lamprey has two separate dorsal fins with a visible notch between them.
How do I know a small lamprey isn't a young Silver or Chestnut Lamprey?
Look at the teeth on the oral disc: northern brook lamprey teeth are weak and blunt, while silver and chestnut lampreys of any size retain sharp, functional teeth.