Far Eastern Brook Lamprey Identification Guide

Key identification features

• Slender, eel-like body with no scales and no paired fins (no pectoral or pelvic fins at all)
• Round, jawless sucking mouth disc, small in adults, ringed with tiny rasping teeth rather than true jaws
• Seven small round gill openings in a row behind each eye
• Continuous low dorsal fin that runs into the tail fin, rather than two clearly separated dorsal fins
• Small adult size, usually under 16 cm (6 in), with a dark olive-brown to gray-brown back fading to pale on the belly

Common look-alikes

• Arctic lamprey — grows noticeably larger as an adult and carries a more heavily toothed oral disc; this species stays smaller with weak or blunt disc teeth
• American eel (where ranges are confused) — eels have true hinged jaws, small paired pectoral fins, and tiny embedded scales, all absent here
• Other freshwater lampreys of the region — best separated by dorsal fin notch pattern and disc tooth counts on a captured specimen

Where you'll see one

Look for it in small, clear, gravel- or sand-bottomed streams across Japan, the Korean Peninsula, and adjacent parts of the Russian Far East and northeastern China, where larvae burrow in silty margins for years before a brief, non-feeding adult stage.