The Arctic lamprey is an eel like fish, characterized by a jawless mouth with 2 large teeth on the tongue. Average length is 13-16cm. The dorsal fins arise far back on body, the anterior dorsal lower than the posterior, the fins higher in males. The lower lobe of caudal fin is somewhat larger than upper, the fin joined to both dorsal and anal fins. The anal fin is small, in males represented only by a low ridge. Colour ranges from brown to olive to grayish above, paler below.
Its life cycle consists of a lengthy larval stage followed by metamorphosis in which the lamprey develops eyes and teeth. It then migrates to sea to feed by attaching parasitically to various species of fish. The Arctic lamprey prefers sites with stony or sandy bottoms, shaded by riparian vegetation. It feeds on small aquatic invertebrates, algae and organic matter contained in detritus.