- Rainbow smelt
Rainbow smelt Conservation status Scientific classification Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Osmeriformes Family: Osmeridae Genus: Osmerus Species: O. mordax Binomial name Osmerus mordax
Osmerus mordax mordax
Osmerus mordax dentex
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), and ones over 12 inches (30 cm) are known.
Distribution and habitat
The rainbow smelt's distribution extends from New Jersey to Labrador on the east coast and from Vancouver Island to the Arctic Ocean on the west coast. It has been introduced to the Great Lakes, and from there has made its way to various other inland bodies of water in Ontario and the midwestern United States. It occurs in rivers, coastal areas and ponds.
They eat zooplankton, invertebrates and other fish, including small smelt, sculpins, burbot, and whitefish. They are preyed upon by larger predatory fish such as coho salmon, burbot, trout, walleye, and yellow perch.
In their anadromous territories, they spend the summers along the coast, normally in waters no more than 20 feet (6.1 m) deep and no more than 1 mile (1.6 km) from shore. They overwinter under the ice in estuaries, producing an antifreeze protein and glycerol. In the spring, they spawn at night in small streams, often ones that go dry in the summer. Landlocked populations were historically known in Maine, and it was from one of these that they were introduced to one of the lakes in Michigan known as Crystal Lake, and then spread to the Great Lakes.
Since being introduced to the Great Lakes, rainbow smelt have been considered an invasive species and though they provide food for many native species of larger game fish, they also prey upon the young of these and other fish. They have been found to impact populations of lake herring, yellow perch, whitefish, bloaters, alewives, slimy sculpin, walleye, and lake trout.
Rainbow smelt are fished both commercially and for sport. Commercial harvests are down from historic levels; for example around 1850 an annual harvest from the Charles River alone was around 9 million fish. They are commonly processed into animal feed, but are also eaten by humans. They are a popular winter game fish and the spring smelt run is a tradition in many parts of their distribution.
Fishing for rainbow smelt using a gill net is a popular activity along the city of Chicago's lakefront. The season is open during the month of April. Superstition dictates that the fisherman must bite the head off the first fish of the season to have a good catch.
Rainbow smelt are spring spawners and prefer clean streams with light flow and light siltation. They face several barriers to migration, being weak swimmers they cannot overcome most fish ladders. This prevents them from making it past the dams to the headwater streams where they need to spawn. The rise in erosion and dams help to decimate the smelt population in the 1980s. Right now there are plans to try to reduce damming and to help control erosion. With current efforts to reduce the human impact on these and many other affected species the population is back on the rise. Future management recommendations are to continue to protect these streams from erosion and also to find ways to make the streams that do have dams more accessible to smaller, weaker swimming fish. With these things happening the population will thrive. Eventually these fish may become over populated and small-scale removal may be necessary.
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