bowfin, primitive freshwater fish found in the Mississippi basin, the Great Lakes, and E to Vermont. The bowfin has a light covering of rounded, overlapping scales, a large mouth, and sharp teeth. Its swim bladder is capable of functioning as a lung, and the bowfin can survive out of water for a day. It prefers sluggish water and surfaces occasionally to gulp air. The female, up to 2 ft (60 cm) long, lays eggs. The smaller male builds the nest and guards the young after they hatch. Bowfins are also called freshwater dogfish; they are voracious and destructive feeders on fish and invertebrates and are sometimes cannibalistic. As game fish they are good fighters, but they are not regarded as food fish in most parts of the United States. Bowfins are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Amiiformes, family Amiidae.