smelt, common name for a small, slender fish of the family Osmeridae, closely allied to the grayling of the family Salmonidae (salmon family). Most species are marine, but some ascend freshwater streams to spawn and others are landlocked in lakes. The American smelt (or icefish), Osmerus mordax, averages 10 in. (25 cm) in length and 1 lb (.45 kg) in weight. It is valued for its delicious, fragrant flesh, although its feeding habits are destructive and sometimes cannibalistic. The candlefish (or eulachon), a smelt found from Oregon to Alaska, is named for the fact that it is so fat at spawning time that when dried and strung on a wick it can be burned as a primitive candle. In Alaska and NE Asia are found the northwestern smelt (or rainbow herring) and the pond smelt. The top smelt, Atherinops affinis, and jack smelt are Pacific silversides of the family Atherinidae, which belong to a different order. The deep-sea smelts, family Bathylagidae, are closely related to the true smelts. Deep-sea and true smelts are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Clupeiformes, families Bathylagidae and Osmeridae, respectively.
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