American Brook Lamprey Identification Guide
Recognize an American Brook Lamprey by its small size, two closely spaced dorsal fins, and weak oral disc teeth.
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Key identification features
- Small, slim, eel-like body, typically 12-20 cm as an adult
- Two dorsal fins set close together with a distinct, though shallow, notch separating them
- Olive-brown to blackish back with a paler belly and no strong mottling
- Oral sucker disc present but with weak, degenerate teeth unable to grip prey
- Single nostril on top of the head, positioned between the eyes
- Non-feeding, brief adult life stage devoted only to spawning before it dies
- No paired fins, as in all lampreys
Common look-alikes
- Northern brook lamprey is similarly small and non-feeding but has a single continuous dorsal fin instead of two separate fins.
- Sea lamprey larvae look alike as blind burrowers, but adult sea lampreys grow far larger with sharp functional teeth, unlike the American brook lamprey's degenerate dentition.
- Least brook lamprey is comparably small, and the two are best separated by internal muscle-segment counts and geographic range rather than color alone.
Where you'll see one
American brook lamprey lives in small, clear, gravel- or sand-bottomed streams across much of the eastern and central United States, where larvae spend several years burrowed in silty stream margins before transforming into short-lived, non-feeding adults that only spawn.
Frequently asked questions
How do I tell American Brook Lamprey from Northern Brook Lamprey?
Look at the dorsal fins: American brook lamprey has two fins separated by a notch, while northern brook lamprey has just one continuous dorsal fin.
Can an American Brook Lamprey attach to and feed on fish like a sea lamprey?
No, its oral disc teeth are weak and degenerate, and the short-lived adult stage does not feed at all.