Like the Atlantic salmon, the rainbow smelt is an anadromous species - it lives in the sea for part of its life cycle and reproduces in fresh water. It is primarily an inshore species, occurring in bays and estuaries along the North American Atlantic coast, from the Hamilton Inlet - Lake Melville estuary of Labrador, and it can be found along the eastern seaboard of North America, as far south as New Jersey. Smelts occur sparingly in Labrador but may be numerous at times in the coastal waters around Newfoundland. They can be found in most estuaries of the Gulf of St Lawrence region of Quebec (especially the North Shore), New Brunswick, and Nova Scotia; and around coastal Nova Scotia and the Bay of Fundy waters of Nova Scotia and New Brunswick. Smelt can also be found landlocked in many freshwater lakes of the coastal provinces of Canada and eastern North America where they can live successfully throughout the life cycle. In the Great lakes, populations have developed as a result of introductions into Crystal Lake, MI. The rainbow smelt has subsequently spread through the Great Lakes, where it is often an abundant species.
The rainbow smelt, is also commonly known as the American smelt, Atlantic smelt, leefish, frostfish, and icefish. They ascend freshwater streams in spring to spawn and are often seen in large shoals in estuaries and rivers during the spawning migrations. Smelt prefer cooler waters during the warm months and tend to move offshore to live in deeper water in summer. Little is known of the marine portion of the life history, although there is some evidence of migrations in the sea. One smelt, tagged at Portage Island in Miramichi Bay, NB, was caught 161 km away in upper Chaleur Bay. Smelt enter estuaries in the fall and late winter months where they may encounter very low temperatures and consequently produce antifreeze proteins.
Rainbow smelt are carnivorous and voracious fish, eating a variety of invertebrate species, and, as they grow, any available small fishes (eg. silversides, mummichogs, and herring). Most mature smelt are in the 12-20cm size range, although individuals greater than 35 cm have been reported.
Although the full seasonal cycle of antifreeze production in smelt has yet to be documented, measurements and sample collection from the wild suggest that smelt follow the typical pattern of antifreeze production seen in fish inhabiting temperate waters - production of antifreeze during the winter months, followed by its loss over the summer.
Ewart,K.V. and G.L.Fletcher. 1990. Isolation and characterization of antifreeze proteins from smelt (Osmerus mordax) and Atlantic herring (Clupea harengus harengus). Canadian Journal of Zoology. 68: 1652-1658.