Rainbow smelt

Description

The rainbow smelt (Osmerus mordax) is a North American species of fish of the family Osmeridae. Walleye, trout, and other larger fish prey on these smelt. The rainbow smelt prefer juvenile ciscoes, zooplankton such as calanoid copepods (Leptodiaptomus ashlandi, L. minutus, L. sicilis), and other small organisms, but are aggressive and will eat almost any fish they find. They are anadromous spring spawners and prefer clean streams with light flow and light siltation. The rainbow smelt face several barriers. They are weak swimmers and struggle to navigate fish ladders preventing them from making it past dams to the headwater streams where they spawn. The rise in erosion and dams helped to decimate the smelt population in the 1980s. The body of the rainbow smelt is slender and cylindrical. It has a silvery, pale green back and is iridescent purple, blue, and pink on the sides, with a light underside. When full grown, the rainbow smelt is between 7 and 9 inches (18 and 23 cm) long and weighs about 3 ounces (85 g). Individuals over 12 inches (30 cm) long are known. The rainbow smelt is widespread across North American watersheds. The North American native range of the rainbow smelt extends through the Atlantic drainages between New Jersey and Labrador to Arctic drainages, and the Pacific drainages as far south as Vancouver Island. The rainbow smelt has been introduced into water bodies in the U.S. states of Colorado, Connecticut, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New York, North Carolina, North Dakota, Ohio, Pennsylvania, South Dakota, Tennessee, Vermont, Virginia, and Wisconsin. Rainbow smelt invaded the Great Lakes watershed through the intentional introduction of eggs from historically known landlocked populations in Maine to Crystal Lake, Michigan in 1912. This lake drains into Lake Michigan, from which fish escaped into Lake Michigan and spread quickly throughout the Great Lakes and their tributaries. Early records documenting the smelt's range expansion in the Great Lakes include Lake Michigan, Lake Erie, Lake Huron, Lake Ontario, and Lake Superior. Rainbow smelt were first reported from Lake Ontario in 1929, and probably reached it by dispersal along natural waterways from the Finger Lakes, New York, where they were intentionally introduced in 1917.