Smelt, a slender, silvery food fish. Smelt are rarely more than 14 inches (36 cm) in length. They swim in large groups and feed on smaller fish, shrimp, and worms. Smelt inhabit the cold and temperate waters of the Northern Hemisphere. Most smelt are saltwater species that enter freshwater to spawn. Some species live entirely in freshwater.

The rainbow, or American, smelt has a greenish back with silvery sides and is about seven to nine inches (18 to 23 cm) in length. It is native to the Atlantic coast of North America from Labrador to New Jersey. Although it is basically a saltwater species, populations of this fish have been found landlocked and surviving in freshwater lakes in Canada and parts of New England. In 1912, the American smelt was successfully introduced into the Great Lakes.

The rainbow smelt is Osmerus mordax of the smelt family, Osmeridae.