Rainbow Smelt
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The rainbow smelt (''Osmerus mordax'') is a North American
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
of the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Osmeridae.
Walleye The walleye (''Sander vitreus'', Synonym (taxonomy), synonym ''Stizostedion vitreum''), also called the walleyed pike, yellow pike, yellow pikeperch or yellow pickerel, is a freshwater perciform fish native to most of Canada and to the Northern ...
,
trout Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...
, and other larger fish prey on these smelt. The rainbow smelt prefer juvenile ciscoes,
zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...
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 gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstruc ...
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 U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...
and
Labrador Labrador () is a geographic and cultural region within the Canadian province of Newfoundland and Labrador. It is the primarily continental portion of the province and constitutes 71% of the province's area but is home to only 6% of its populatio ...
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 ...
. 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 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 depth () after Lake Superior and the third-largest by surface area (), after Lake Superior and Lake Huron. To the ...
, 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 ( ) 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 also has the shortest avera ...
,
Lake Huron Lake Huron ( ) is one of the five Great Lakes of North America. It is shared on the north and east by the Canadian province of Ontario and on the south and west by the U.S. state of Michigan. The name of the lake is derived from early French ex ...
,
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 (state), New York. The Canada–United Sta ...
, and
Lake Superior Lake Superior is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. Lake Michigan–Huron has a larger combined surface area than Superior, but is normally considered tw ...
. 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 directly south of Lake Ontario in an area called the ''Finger Lakes region'' in New York (state), New York, in the United States. This region straddles th ...
, 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 () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...
. 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 and 0.14 grams food wet weight per day. Another study showed that in Lake Ontario the primary food sources for rainbow smelt were
slimy sculpin The slimy sculpin (''Cottus cognatus'') is a freshwater species of fish belonging to the family Cottidae, which is the largest sculpin family. They usually inhabit cold rocky streams or lakes across North America, ranging from the Great Lakes, s ...
s (''Cottus cognatus'') and opossum shrimp (''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 Hucho taimen, Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlan ...
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 Salvelinus, char living mainly in lakes in Northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, laker, and grey trout. In Lake Sup ...
(''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 or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Samuel Latham Mitchill fr ...
(''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 type ...
'' spp.). The U.S. EPA stated in 2008 that they believe the smelt contributed to the extinction of the blue pike (''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
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 ...
, 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 language, Massachusett: ), sometimes called the River Charles or simply the Charles, is an river in eastern Massachusetts. It flows northeast from Hopkinton, Massachusetts, Hopkinton to Boston along a highly me ...
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 species pursued by recreational fishing, recreational fishers (typically angling, anglers), and can be freshwater fish, freshwater or saltwater fish. Game fish can be fish as food, eaten aft ...
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 Rotenone is an odorless, colorless, crystalline isoflavone. It occurs naturally in the seeds and stems of several plants, such as the jicama vine, and in the roots of several other members of the Fabaceae. It was the first-described member of the ...
. 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 munici ...
, 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 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 (NOAA ) is an American scientific and regulatory agency charged with Weather forecasting, forecasting weather, monitoring oceanic and atmospheric conditions, Hydrography, charting the seas, ...
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; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...
(ESA).Species of Concern
NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...


See also

*
Smelt (fish) 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 ...
* Pacific rainbow smelt


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
{{Authority control 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