Least Brook Lamprey Identification Guide

Key identification features

• Very small, slender, eel-like body, usually only 10-15 cm long, among the smallest lampreys in North America
• Two dorsal fins with a clear gap or notch between them
• Olive to yellowish-brown coloring, generally plain without heavy blotching
• Oral sucker disc present but bearing small, weak, degenerate teeth unable to grip prey
• Single nostril on top of the head, as in all lampreys
• Short intestine and a non-feeding adult stage that exists only briefly to spawn before dying
• No paired fins, consistent with all lampreys

Common look-alikes

• American brook lamprey grows somewhat larger on average and has a slightly different tooth arrangement on the oral disc.
• Southern brook lamprey looks nearly identical externally, with the two most reliably separated by internal trunk myomere (muscle segment) counts and geographic range rather than surface coloring.
• Sea lamprey larvae resemble this species as blind burrowers, but adult sea lampreys grow far larger with a strongly toothed, functional feeding disc.

Where you'll see one

Least brook lamprey inhabits small, clear, low-gradient streams with sand or gravel bottoms across the southeastern and south-central United States, where larvae burrow into soft substrate for several years before a brief, non-feeding adult phase confined entirely to freshwater.