The rainbow smelt (''Osmerus mordax'') is a North American

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Osmeridae Smelts are a family of small fish, the Osmeridae, found in the North Atlantic and North Pacific Oceans, as well as rivers, streams and lakes in Europe, North America and Northeast Asia. They are also known as freshwater smelts or typical smelts ...

Walleye The walleye (''Sander vitreus'', synonym ''Stizostedion vitreum''), also called the yellow pike or yellow pickerel, is a freshwater perciform fish native to most of Canada and to the Northern United States. It is a North American close relat ...

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...

, and other larger fish prey on these smelt. The rainbow smelt prefer juvenile

ciscoes The ciscoes (or ''ciscos'') are salmonid fish that differ from other members of the genus in having upper and lower jaws of approximately equal length and high gill raker counts. These species have been the focus of much study recently, as resea ...

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

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 Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

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. There are currently plans to try to reduce damming and to help control erosion.

Description

The body of the rainbow smelt is slender and cylindrical. It has a silvery, pale green back and is

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...

purple, blue, and pink on the sides, with a light underside. When full grown, the rainbow smelt is between long and weighs about . Individuals over long are known.

Distribution and habitat

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 New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delawa ...

and

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

to Arctic drainages, and the Pacific drainages as far south as

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest by ...

. 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.Fuller P. and E. Maynard (2011) ''Osmerus mordax''. USGS Nonindiginous Aquatic Species Database. nas.er.usgs.gov. Rainbow smelt (Goulais B) 2

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 Lake Michigan is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and the third-largest by surface area (), after Lake Superior and Lake Huron. To the east, its basin is conjoined with that o ...

, 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 Erie ( "eerie") is the fourth largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also ha ...

Lake Huron Lake Huron ( ) is one of the five Great Lakes of North America. Hydrologically, it comprises the easterly portion of Lake Michigan–Huron, having the same surface elevation as Lake Michigan, to which it is connected by the , Straits of Mack ...

Lake Ontario Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border sp ...

, and

Lake Superior Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...

. Rainbow smelt were first reported from Lake Ontario in 1929, and probably reached it by dispersal along natural waterways from the

Finger Lakes The Finger Lakes are a group of eleven long, narrow, roughly north–south lakes located south of Lake Ontario in an area called the ''Finger Lakes region'' in New York, in the United States. This region straddles the northern and transitional ...

, New York, where they were intentionally introduced in 1917. The ability of rainbow smelt to disperse is determined by the connectivity of lakes, the ability of smelt to move through connecting streams, and the suitability of connected lakes as habitat. Rainbow smelt are weak swimmers so they cannot make it over fish ladders. This has helped to prevent an even wider spread of their range. Rainbow smelt occur in rivers, coastal areas and ponds. In their anadromous territories, they spend the summers along the coast, normally in waters no more than deep and no more than from shore. They overwinter under the ice in estuaries, producing an antifreeze protein and

glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...

. In the spring, they spawn at night in small streams, often ones that go dry in the summer.

Ecology

In 1883 Stedman and Argyle found that the rainbow smelt consumed bloaters (''Coregonus hoyi'') and alewives (''Alosa pseudoharengus''). However, they also stated that this predator had not affected the population of bloaters but that impact could be a possibility. A 2003 study by Horppila et al. shows that smelt densities can exceed 40,000 individuals per hectare and may create a large predation pressure on the lake. Horppila et al. also states that a single smelt can consume between 0.12–0.14 grams food wet weight per day. Another study showed that in Lake Ontario the primary food sources for rainbow smelt were slimy sculpins (''Cottus cognatus'') and

opossum shrimp Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this ...

(''Mysis relicta''), but nothing was said on whether this predation had significant impact on the populations. In 1973 Havey reported that there was increased growth in landlocked

Atlantic salmon The Atlantic salmon (''Salmo salar'') is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlantic salmon are ...

populations after the introduction of the smelt. It was also shown by Brandt and Madon in 1986 that adult

lake trout The lake trout (''Salvelinus namaycush'') is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, it can also ...

(''Salvalinus namaycush'') could be a keystone predator species for the smelt. Hrabik et al. (1998) found evidence of competition for food between introduced rainbow smelt and native

yellow perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch, American river perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Sam ...

(''Perca flavescens'') in Wisconsin lake habitats, and smelt may be partially responsible for the decline of Great Lakes whitefish (''

Coregonus ''Coregonus'' is a diverse genus of fish in the salmon family ( Salmonidae). The ''Coregonus'' species are known as whitefishes. The genus contains at least 68 described extant taxa, but the true number of species is a matter of debate. The typ ...

'' spp.). The U.S. EPA stated in 2008 that they believe the smelt contributed to the extinction of the

blue pike The blue walleye (''Sander vitreus'' var. ''glaucus''), also called the blue pike, was a unique color morph (formerly considered a subspecies) of walleye which was endemic to the Great Lakes of North America. Morphometric studies led biologi ...

(''Stizostedion vitreum glaucum'') by outcompeting for food. Acidity may alter smelt distributions because they were not found in small lakes with pH less than 6.0 in several surveys. Because of snowmelt, rainbow smelt eggs might be exposed to lethal pH decreases in poorly buffered lakes.

Life history

Rainbow smelt are

, ascending from saltwater to freshwater to spawn. Smelt are also capable of completing their life history exclusively in freshwater. Landlocked adult rainbow smelt spawn shortly after ice-off at night in the lower reaches of streams. Shaw found in his research that no shoreline spawning had ever occurred. McKenzie states that the number of eggs extruded by a female is positively related to its size and Nellbring stated in his 1989 research that the eggs are adhesive and attach to substrates such as gravel, sand, mud, or submerged vegetation. Eggs are left unattended and hatch in 1–4 weeks, depending on water temperature. The time to sexual maturity is dependent on food supply and water temperature and abundant food and warmer temperatures encourage faster growth. Crossman and Scott state that in optimal conditions and large lakes, rainbow smelt may reach and can live for over seven years.

Fishing

Rainbow smelt are fished both commercially and for sport. Commercial harvests are down from historic levels; for example around 1880 an annual harvest from the

Charles River The Charles River ( Massachusett: ''Quinobequin)'' (sometimes called the River Charles or simply the Charles) is an river in eastern Massachusetts. It flows northeast from Hopkinton to Boston along a highly meandering route, that doubles bac ...

alone was around 9 million fish, while today few smelt are found in the Charles River. They are commonly processed into animal feed, but are also eaten by humans. They are a popular winter

game fish Game fish, sport fish or quarry refer to popular fish pursued by recreational anglers, and can be freshwater or saltwater fish. Game fish can be eaten after being caught, or released after capture. Some game fish are also targeted commercial ...

and the spring smelt run is a tradition in many parts of their distribution. Fishing for rainbow smelt using a gill net has historically been a popular activity along the City of Chicago's lakefront.

Management

The populations of the rainbow smelt in areas where it has been introduced, such as the Great Lakes, have been increasing in many regions, even with efforts to control its spread. Several things are being done to manage this species. Massive fish removal by over-fishing reduced the rainbow smelt populations in some lakes by the 1980s. Some people are taking a chemical approach to this growing problem, using Rotenone. While this is effective, it also harms other organisms and is unpopular with the public. Cox and Kitchell state that declines in smelt numbers, following natural recovery or stocking of grown predator fish, have been reported from lakes ranging in size from Lake Superior and Hessen. Additionally, similar results were found in a small pond near

Lillehammer Lillehammer () is a municipality in Innlandet county, Norway. It is located in the traditional district of Gudbrandsdal. The administrative centre of the municipality is the town of Lillehammer. Some of the more notable villages in the munic ...

, Norway in 1983. This research shows that the reintroduction of large piscivores such as walleye can help lead to the reduction of chemicals and poison needing to be used. The rainbow smelt is a U.S.

National Marine Fisheries Service The National Marine Fisheries Service (NMFS), informally known as NOAA Fisheries, is a United States federal agency within the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) that is responsible for the stew ...

Species of Concern, one of those species about which the U.S. Government's

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...

has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S.

Endangered Species Act The Endangered Species Act of 1973 (ESA or "The Act"; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of ec ...

(ESA).Species of Concern

NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

References

Other references

External links

Gulf of Maine Rainbow Smelt Information and Population Trends

Nova Scotia Department of Agriculture and Fisheries factsheet

U.S. Geologic Survey Nonindigenous Aquatic Species page
{{Taxonbar, from=Q2641362 Osmerus Freshwater fish of the Arctic Freshwater fish of North America Fish of the Great Lakes Fish of the United States Fish described in 1814 Taxa named by Samuel L. Mitchill