One of the most prominent members of the Osmeridae family of smelt, the rainbow smelt is an important forage species for predatory fish and a principal target for inland and coastal commercial fishing.
It is a close relative of the eulachon of the Pacific, the pond smelt (Hypomesus olidus) of the western Arctic, the capelin of the Atlantic, and the European smelt (Osmerus eperlanus).
Other NamesAmerican smelt, frostfish, leefish, toothed smelt, freshwater smelt; French: éperlan du nord.
IdentificationThe rainbow smelt is a slender, silver fish, with a pale green or olive-green back. Fresh from the water, the sides of the fish take on a purple, blue, or pink iridescent hue. The scales on the rainbow smelt are large and easily detached, and at spawning time those on the males develop small tubercles, resembling tiny buttons that serve as a mark of their sex.
The lower jaw of the fish projects beyond the upper one, and the entire mouth extends beyond the middle of each eye. On the tip of the tongue are large teeth. One large dorsal fin is located about halfway along the back, and behind that is a small adipose fin.
Size/AgeMost rainbow smelt are less than 8 inches long, although some coastal specimens have measured 14 inches. They may live for at least 6 years.
Spawning behaviorIn the spring, anadromous adult rainbow smelt migrate upstream to freshwater spawning grounds. Spawners reach the tide head in the main tributaries when the water temperature is only 39° to 41°F. Spawning occurs at night, typically over a gravelly bottom.
Rainbow smelt remain at spawning sites for a number of days before migrating downstream. Shortly after spawning, many males die. Some rainbow smelt are mature at 2 years of age, and all are mature at age 3.