Any of certain slender, silvery, carnivorous, food fishes (family Osmeridae) having a small fleshy fin.
Smelts live in cold northern seas, and most species spawn a short distance upstream. The American smelt ( Osmerus mordax ), introduced from the Atlantic to the Great Lakes, is the largest smelt, about 15 in. (38 cm) long. The European smelt ( O. eperlanus ) is similar. Among Pacific species are the rainbow herring, capelin, and eulachon, or candlefish, which is so oily at spawning time that it can be dried and burned as a candle. Silversides (see grunion ) and other unrelated fishes are sometimes called smelts.