Atlantic salmon
Encyclopedia
The Atlantic salmon is a species of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 in the family Salmonidae
Salmonidae
Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...

, which is found in the northern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 and in rivers that flow into the north Atlantic and (due to human introduction) the north Pacific.

It is also commercially known as bay salmon, black salmon, caplin-scull salmon, fiddler, grilse, grilt, kelt, landlocked salmon, ouananiche, outside salmon, parr, Sebago salmon, silver salmon, slink, smolt, spring salmon or winnish.

Life stages

Most Atlantic salmon follow an anadromous fish migration
Fish migration
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 thousands of kilometres...

 pattern, in that they undergo their greatest feeding and growth in salt water; however, adults return to spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

 in native freshwater
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 streams where the eggs hatch and juveniles grow through several distinct stages.

Atlantic salmon do not require salt water, however, and numerous examples of fully freshwater ("landlocked") populations of the species exist throughout the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

. In North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, the landlocked strains are frequently known as ouananiche.

Freshwater phase

The freshwater phases of Atlantic salmon vary between one and eight years, variably according to river location. While the young in southern rivers, such as those to the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...

, are only one year old when they leave, those further north, such as in Scottish
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 rivers, can be over four years old, and in Ungava Bay
Ungava Bay
Ungava Bay is a large bay in northeastern Canada separating Nunavik from Baffin Island. The bay is shaped like a rounded square with a side length of about and has an area of approximately...

, northern Quebec, smolts as old as 8 years have been encountered. The average age correlates to temperature exceeding 7 °C (44.6 °F).

The first phase is the alevin stage, when the fish stay in the breeding ground and use the remaining nutrients in their yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...

. During this developmental stage, the young gills develop and they become active hunters. Next is the fry
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

 stage, where the fish grow and subsequently leave the breeding ground in search of food. During this time, they move to areas with higher prey concentration. The final freshwater stage is when they develop into parr, in which they prepare for the trek to the Atlantic Ocean.

During these times, the Atlantic salmon are very susceptible to predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

. Nearly 40% are eaten by trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

 alone. Other predators include other fish and bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s.

Saltwater phases

When parr develop into smolt
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

, they begin the trip to the ocean, which predominantly happens between March and June. Migration allows acclimation to the changing salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

. Once ready, young smolt leave, preferring an ebb tide
Ebb Tide
"Ebb Tide" is a popular song, written in 1953 by the lyricist Carl Sigman and composer Robert Maxwell.-Recordings:* The best-known versions are by Frank Chacksfield & His Orchestra , Vic Damone , Roy Hamilton , Frank Sinatra , The Platters , Lenny Welch and the Righteous Brothers...

.

Having left their natal streams, they experience a period of rapid growth during the one to four years they live in the ocean. Typically, Atlantic salmon migrate from their home streams to an area on the continental plate off West Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

. During this time, they face predation from humans, Seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

, Greenland shark
Greenland shark
The Greenland shark, Somniosus microcephalus, also known as the sleeper shark, gurry shark, ground shark, grey shark, or by the Inuit languages name Eqalussuaq, is a large shark native to the waters of the North Atlantic Ocean around Greenland and Iceland. These sharks live farther north than any...

s, skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....

, cod
Cod
Cod is the common name for genus Gadus, belonging to the family Gadidae, and is also used in the common name for various other fishes. Cod is a popular food with a mild flavor, low fat content and a dense, flaky white flesh. Cod livers are processed to make cod liver oil, an important source of...

, and halibut
Halibut
Halibut is a flatfish, genus Hippoglossus, from the family of the right-eye flounders . Other flatfish are also called halibut. The name is derived from haly and butt , for its popularity on Catholic holy days...

. Some dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s have been noticed playing with dead salmon, but it is still unclear whether they consume them.

Once large enough, Atlantic salmon change into the grilse phase, where they become ready to return to precise fresh water tributary in which they were born. After returning to their natal streams, the salmon will cease eating altogether prior to spawning. Although largely unknown, odor — the exact chemical signature of that stream — is suspected to play an important role in how salmon return to the area where they hatched. Once above around 250 g
Gram
The gram is a metric system unit of mass....

, the fish no longer become prey for birds and many fish, although seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

 do prey upon them. Seals that commonly eat Atlantic salmon are the gray
Grey Seal
The grey seal is found on both shores of the North Atlantic Ocean. It is a large seal of the family Phocidae or "true seals". It is the only species classified in the genus Halichoerus...

 and common seals. Survivability to this stage has been estimated at between 14 and 53%.

Nomenclature

The Atlantic salmon was given its scientific binomial name by zoologist
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

 and taxonomist
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 Carl Linnaeus in 1758. It was not until later, however, that the differently coloured smolts were found to be the same species.

The name, Salmo salar, is from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 "Salmo", meaning salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...

, and "salar", meaning "leaper
Jumping
Jumping or leaping is a form of locomotion or movement in which an organism or non-living mechanical system propels itself through the air along a ballistic trajectory...

," according to M. Barton, but more likely meaning "resident of salt water." Lewis and Short's Latin Dictionary (Clarendon Press, Oxford, 1879) translates `salar' as meaning `a kind of trout' from its use in the `Idylls' of the poet Ausonius (4th Century CE).

Physiology

The colouration of young Atlantic salmon does not resemble their adult stage. While they live in freshwater, they have blue and red spots. While they mature, they take on a silver blue sheen. When adult, the easiest way of identifying them is by the black spots predominantly above the lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

, although the caudal fin is usually unspotted. When they reproduce, males take on a slight green or red colouration. The salmon has a fusiform body, and well-developed teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...

. All fins, save the adipose, are bordered with black.

Distribution and habitat

Beginning around 1990 the rates of Atlantic salmon mortality at sea more than doubled, and by 2000 the numbers of Atlantic salmon had dropped to critically low levels. In the western Atlantic fewer than 100,000 of the important multi-sea-winter salmon were returning. Rivers of the coast of Maine, plus southern New Brunswick and much of mainland Nova Scotia saw runs drop precipitously, and even disappear.

Beginning in the mid-1990s the Atlantic Salmon Federation in cooperation with partners were developing sonic tracking technology, and by 2008 the salmon have been tracked from rivers such as the Restigouche and the Miramichi as far along their migration routes as the Strait of Belle Isle, between Labrador and Newfoundland - and half way to feeding grounds in Greenland.

For whatever reasons, possibly related to improvements in ocean feeding grounds, returns in 2008 have been very positive. On the Penobscot returns had been about 940 in 2007, and by mid-July 2008 the return was 1,938. Similar stories were played out in rivers from Newfoundland to Quebec.

The problems at sea remain, and there is a concerted international effort called SALSEA, to find out more about the mortality at sea. It is organized by the North Atlantic Salmon Conservation Organization (NASCO).

Around the North Atlantic, efforts to restore salmon to their native habitats are underway and there is some slow but steady progress. Restoration and protection of the habitat itself is key to this process but issues of excessive harvest and competition with farmed and escaped salmon are also primary considerations. In the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

, Atlantic salmon have been introduced successfully, but the actual percentage of salmon reproducing naturally is very low. Most are stocked annually. Atlantic salmon were native to Lake Ontario
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north and southwest by the Canadian province of Ontario, and on the south by the American state of New York. Ontario, Canada's most populous province, was named for the lake. In the Wyandot language, ontarío means...

 but were extirpated by habitat loss and overfishing in the late 19th century. The state of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 has since been annually stocking its adjoining rivers and tributaries with the fish and in many cases does not allow active pursuit of the species. Wild salmon on entering rivers as adults have characteristically pointed fins which help scientists distinguish from farmed or escaped salmon.

Diet

Young salmon begin a feeding response within a few days. After the yolk sac is absorbed by the body, they begin to hunt. Juveniles start with tiny invertebrates, but as they mature, they may occasionally eat small fish. During this time, they hunt both in the substrate
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....

 and in the current. Some have been known to eat salmon eggs. The most commonly eaten foods include caddisflies, blackflies
Black fly
A black fly is any member of the family Simuliidae of the Culicomorpha infraorder. They are related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. There are over 1,800 known species of black flies . Most species belong to the immense genus Simulium...

, mayflies
Mayfly
Mayflies are insects which belong to the Order Ephemeroptera . They have been placed into an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies...

, and stoneflies.

As adults, the fish feed on much larger food: Arctic squid, sand eel
Sand Eel
Sand eel or sandeel is the common name used for a considerable number of species of fish. Most of them are sea fish of the genera Hyperoplus , Gymnammodytes or Ammodytes...

s, amphipods, Arctic shrimp, and sometimes herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

, and the fishes' size increases dramatically.

Behaviour

Fry and parr have been said to be territorial, but evidence showing that they guard territories is inconclusive. While they may occasionally be aggressive towards each other, the social hierarchy
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

 is still unclear. Many have been found to school
Swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...

, especially when leaving the estuary.

Adult Atlantic salmon are considered much more aggressive than other salmon and are more likely to attack other fish than others. Where they have become an invasive
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 threat it has become a concern that they are attacking native salmon such as Chinook salmon
Chinook salmon
The Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...

 and Coho salmon
Coho salmon
The Coho salmon, Oncorhynchus kisutch, is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers". It is the state animal of Chiba, Japan.-Description:...

.

Breeding

Atlantic salmon breed in the rivers of: Western Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 from Northern Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

 north to Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

, Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

, and the east coast of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 from Connecticut
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...

 in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 north to northern Labrador
Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...

 and Arctic Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. Atlantic salmon which have escaped from the aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...

 industry have also been found breeding in rivers tributary to the Pacific Ocean in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

 on Canada's west coast. The species constructs a nest or "redd" in the gravel bed of a stream. The female creates a powerful downdraught of water with her tail near the gravel to excavate a depression. After she and a male fish have respectively shed eggs and milt (sperm) upstream of the depression, the female again uses her tail, this time to shift gravel to cover the eggs and milt which have lodged in the depression. At sea, the species is found mainly in the waters off Greenland and in migrations to and from its natal streams. Until the early 19th century, Atlantic salmon were native to the waters of central New York. When dams were constructed on the Oswego River
Oswego River (New York)
The Oswego River is a river in upstate New York in the United States. This river is the second-largest river flowing into Lake Ontario. James Fenimore Cooper’s novel The Pathfinder, or The Inland Sea is set in the Oswego River valley...

, their spawning areas were cut off and they went extinct locally.

Unlike the various Pacific salmon species which die after spawning semelparous, the Atlantic salmon is iteroparous, which means the fish does not automatically die after spawning, and may recondition themselves, return to the sea to repeat the migration and spawning pattern several times, although most spawn once or twice. Nevertheless, migration and spawning exact an enormous physiological toll on the individual fish, such that repeat spawners are by far the exception rather than the norm. Atlantic salmon show high diversity in age of maturity and may mature as parr, 1–5 sea-winter fish, and in rare instances, at older sea ages. All these ages at maturity may occur in the same population, constituting a ‘bet hedging’ strategy against variation in stream flows.

Aquaculture

In its natal streams, Atlantic salmon are considered a prized recreational fish, pursued by avid fly anglers
Fly fishing
Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...

 during its annual runs. At one time, the species supported an important commercial fishery and a supplemental food fishery. However, the wild Atlantic salmon fishery is commercially dead; after extensive habitat damage and overfishing, wild fish make up only 0.5% of the Atlantic salmon available in world fish markets. The rest are farmed, predominantly from aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...

 in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Faroe Islands
Faroe Islands
The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 and Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

 in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. Sport fishing communities, mainly from Iceland and Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

, have joined in the North Atlantic Salmon Fund (NASF) to buy away commercial quotas in an effort to save the wild species of Salmo salar.

Aquaculture techniques

Adult male and female fish are anaesthetised
Anesthesia
Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...

. Eggs and sperm are "stripped", after the fish are cleaned and cloth dried. Sperm and eggs are mixed, washed, and placed into fresh water. Adults recover in flowing, clean, well-aerated
Aeration
Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or substance.-Aeration of liquids:-Methods:Aeration of liquids is achieved by:...

 water. Some researchers have even studied cryopreservation of their eggs.

Fry are generally reared in large freshwater tanks for 12 to 20 months. Once the fish have reached the smolt phase, they are taken out to sea, where they are held for up to two years. During this time the fish grow and mature in large cages off the coasts of Canada, the USA, or parts of Europe.

Generally, cages are made of two nets. Inner nets, which wrap around the cages, hold the salmon. Outer nets, which are held by floats, keep predators out.

Controversy

In the past some Atlantic salmon have escaped from cages at sea. In the Atlantic Ocean this has resulted in some breeding with native populations but generally most surviving offspring were from the domesticated Atlantics, not hybrids.

On the West Coast of Northern America, Aquaculturists have taken great care to ensure the non-native salmon cannot escape from their open net pens and it is now not considered a major concern. There is no evidence that Atlantic salmon can survive and establish wild populations in the Pacific. "From 1905 until 1935 in excess of 8.6 million Atlantic salmon of various life stages (predominantly advanced fry) were intentionally introduced to more than 60 individual B.C. lakes and streams. Historical records indicate that in a few instances mature sea-run Atlantic salmon were captured in the Cowichan River, however a self-sustaining population never materialized. Environmental assessments by the U.S. National Marine Fisheries Service, the Washington Department of Fish and Wildlife and the B.C. Environmental Assessment Office have concluded that the potential risk of Atlantic salmon colonization in the Pacific Northwest is low.

Human impact

Salmon decline in Lake Ontario
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north and southwest by the Canadian province of Ontario, and on the south by the American state of New York. Ontario, Canada's most populous province, was named for the lake. In the Wyandot language, ontarío means...

 goes back to the 18th-19th centuries, due to logging and soil erosion, as well as dam and mill construction. By 1896, the species was declared extirpated from the lake.

In the 1950s, salmon from rivers in the US and Canada, as well as from Europe, were discovered to gather in the sea around Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

 and the Faroe Islands
Faroe Islands
The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...

. A massive commercial fishing industry was established, taking salmon in drift net
Drift net
Drift netting is a fishing technique where nets, called drift nets, are allowed to float freely at the surface of a sea or lake. Usually a drift net is a gill net with floats attached to a rope along the top of the net, and weights attached to another rope along the foot of the net to keep the net...

s. After an initial series of record annual catches, the numbers crashed: between 1979 and 1990, catches fell from four million to 700,000.

Currently, overfishing, habitat loss and aquacultured salmon escapes are the greatest threats to natural Atlantic salmon populations. Overfishing at sea is generally considered the primary negative factor, however, even though marine exploitation rates estimated for various Newfoundland stocks for the period 1984–1991 averaged 45% on small (<63 cm) salmon and 74.2% on large salmon (>63 cm), closure of the Newfoundland commercial salmon fishery beginning in 1992 has not resulted in general increases in salmon populations through the present.

In New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...

, many efforts are underway to restore salmon to the region by knocking down obsolete dams and updating others with fish ladder
Fish ladder
A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial barriers to facilitate diadromous fishes' natural migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps into the waters on...

s and other contraptions that have proven effective in the West with Pacific salmon. There is some success thus far, with populations growing in the Penobscot
Penobscot River
The Penobscot River is a river in the U.S. state of Maine. Including the river's West Branch and South Branch increases the Penobscot's length to , making it the second longest river system in Maine and the longest entirely in the state. Its drainage basin contains .It arises from four branches...

 and Connecticut River
Connecticut River
The Connecticut River is the largest and longest river in New England, and also an American Heritage River. It flows roughly south, starting from the Fourth Connecticut Lake in New Hampshire. After flowing through the remaining Connecticut Lakes and Lake Francis, it defines the border between the...

s. In Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

, the Atlantic Salmon Restoration Program was started in 2006, and is one of the largest freshwater conservation programs in North America. It has stocked Lake Ontario
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north and southwest by the Canadian province of Ontario, and on the south by the American state of New York. Ontario, Canada's most populous province, was named for the lake. In the Wyandot language, ontarío means...

 with over 700,000 young Atlantic salmon. In October 2007 salmon was video recorded running in Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

's Humber River
Humber River (Ontario)
The Humber River is one of two major rivers on either side of Toronto, Ontario, Canada, the other being the Don River to the east. It was designated a Canadian Heritage River on September 24, 1999....

 by the Old Mill
Old Mill Inn & Spa
The Old Mill Inn and Spa is an English-style inn and restaurant in The Kingsway neighbourhood of the Toronto suburb of Etobicoke. It is located off Bloor Street, overlooking the Humber River along 2.5 hectares, at 21 Old Mill Road...

. In November 2007, a migrating salmon was observed in the Credit River
Credit River
The Credit River is a river in southern Ontario which flows from headwaters above the Niagara Escarpment to empty into Lake Ontario at Port Credit, Mississauga. It drains an area of approximately 1,000 km²...

. There has also been some success in establishing Atlantic salmon in Fish Creek, a tributary of Oneida Lake
Oneida Lake
Oneida Lake is the largest lake entirely within New York State . The lake is located northeast of Syracuse and near the Great Lakes. It serves as one of the links in the Erie Canal. It empties into the Oneida River which flows into the Oswego River which in turn flows into Lake Ontario...

 in central New York.

Atlantic salmon however, remains a popular fish for human consumption. It is commonly sold fresh, canned, or frozen.

Beaver impact

The decline in anadromous salmonid species over the last two to three centuries is correlated with the decline in the North American beaver and European beaver
European Beaver
The Eurasian beaver or European beaver is a species of beaver, which was once widespread in Eurasia, where it was hunted to near extinction both for fur and for castoreum, a secretion of its scent gland believed to have medicinal properties...

, although some fish and game departments continue to advocate removal of beaver dams as potential barriers to spawning runs. Migration of adult Atlantic salmon may be limited by beaver dams during periods of low stream flows, but the presence of juvenile Salmo salar upstream from the dams suggests the dams are penetrated by parr. Downstream migration of Atlantic salmon smolts was similarly unaffected by beaver dams, even in periods of low flows. A 2003 study of Atlantic salmon and sea trout (Salmo trutta morpha trutta) spawning in the Numedalslågen River
Numedalslågen
-Location:Numedalslågen stretches for over 250 kilometres through the counties of Vestfold and Buskerud, beginning at the Hardangervidda plateau and meeting the ocean at Larvik in Vestfold. Numedalslågen is one of Norway's longest rivers. The rivers runs through the municipalities Larvik, Lardal,...

 and 51 of its tributaries in southeastern Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 were unhindered by beaver. In a restored, third-order stream in northern Nova Scotia, beaver dams generally posed no barrier to Atlantic salmon migration except in the smallest upstream reaches in years of low flow where pools were not deep enough to enable the fish to leap the dam or without a column of water over-topping the dam for the fish to swim up. The importance of winter habitat to salmonids afforded by beaver ponds may be especially important (and underappreciated) in streams of northerly latitudes without deep pools where ice cover makes contact with the bottom of shallow streams. In addition, the up to 8 year long residence time of juveniles in freshwater may make beaver-created permanent summer pools a crucial success factor for Atlantic salmon populations. In fact, two year-old Atlantic salmon parr in beaver ponds in eastern Canada showed faster summer growth in length and mass and were in better condition than parr upstream or downstream from the pond.

England and Wales

Edward I
Edward I of England
Edward I , also known as Edward Longshanks and the Hammer of the Scots, was King of England from 1272 to 1307. The first son of Henry III, Edward was involved early in the political intrigues of his father's reign, which included an outright rebellion by the English barons...

 instituted a penalty for collecting salmon during certain times of the year. His son Edward II
Edward II of England
Edward II , called Edward of Caernarfon, was King of England from 1307 until he was deposed by his wife Isabella in January 1327. He was the sixth Plantagenet king, in a line that began with the reign of Henry II...

 continued, regulating the construction of weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...

s. Enforcement was overseen by those appointed by the Justices of the Peace. Because of confusing laws and the appointed conservators having little power, most laws were barely enforced.

Based upon this, a Royal Commission was appointed in 1860 to thoroughly investigate the Atlantic salmon and the laws governing the species, resulting in the 1861 Salmon Fisheries Act. The act placed enforcement of the laws under the Home Office
Home Office
The Home Office is the United Kingdom government department responsible for immigration control, security, and order. As such it is responsible for the police, UK Border Agency, and the Security Service . It is also in charge of government policy on security-related issues such as drugs,...

's control, but it was later taken from the Home Office and transferred to the Board of Trade
Board of Trade
The Board of Trade is a committee of the Privy Council of the United Kingdom, originating as a committee of inquiry in the 17th century and evolving gradually into a government department with a diverse range of functions...

, and then later to the Board of Agriculture and Fisheries
Minister of Agriculture, Fisheries and Food
The Minister of Agriculture, Fisheries and Food was a UK cabinet position, responsible for the Ministry of Agriculture, Fisheries and Food. The post was originally named President of the Board of Agriculture and was created in 1889...

.

Another act passed in 1865 imposed charges to fish and catch limits. It also caused the formation of local boards having jurisdiction over a certain river. The next significant act, passed in 1907, allowed the board to charge 'duties' to catch other freshwater fish, including trout.

Despite legislation, board effects decreased until, in 1948, the River Boards Act gave authority of all freshwater fish and the prevention of pollution to one board per river. In total, it created 32 boards.

In 1974, all the 32 boards were reduced to 10 regional water authorities (RWAs). Although only the Northumbria
Northumbria
Northumbria was a medieval kingdom of the Angles, in what is now Northern England and South-East Scotland, becoming subsequently an earldom in a united Anglo-Saxon kingdom of England. The name reflects the approximate southern limit to the kingdom's territory, the Humber Estuary.Northumbria was...

n, Welsh
Welsh people
The Welsh people are an ethnic group and nation associated with Wales and the Welsh language.John Davies argues that the origin of the "Welsh nation" can be traced to the late 4th and early 5th centuries, following the Roman departure from Britain, although Brythonic Celtic languages seem to have...

, northwest and southwest RWA's had considerable salmon populations, all ten also cared for trout and freshwater eels.

The Salmon and Freshwater Fisheries Act was passed in 1975. Among other things, it regulated fishing licences, seasons, and size limits, and banned obstructing the salmon's migratory paths.

Scotland

Legislation in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 to help Atlantic salmon began in 1318 by Alexander II
Alexander II of Scotland
Alexander II was King of Scots from1214 to his death.-Early life:...

. It prohibited certain types of traps in rivers.

During the 15th century, many laws were passed; many regulated fishing times, and worked to ensure smolts could safely pass downstream. James III
James III of Scotland
James III was King of Scots from 1460 to 1488. James was an unpopular and ineffective monarch owing to an unwillingness to administer justice fairly, a policy of pursuing alliance with the Kingdom of England, and a disastrous relationship with nearly all his extended family.His reputation as the...

 even closed a meal
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

 mill
Watermill
A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour, lumber or textile production, or metal shaping .- History :...

 because of its history of killing fish attracted to the wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

. Because the fish were held in such high regard, poachers
Poaching
Poaching is the illegal taking of wild plants or animals contrary to local and international conservation and wildlife management laws. Violations of hunting laws and regulations are normally punishable by law and, collectively, such violations are known as poaching.It may be illegal and in...

 were severely punished.

More recent legislation has established commissioners who manage districts. Furthermore, the Salmon and Freshwater Fisheries Act in 1951 required the Secretary of State
Secretary of State for Scotland
The Secretary of State for Scotland is the principal minister of Her Majesty's Government in the United Kingdom with responsibilities for Scotland. He heads the Scotland Office , a government department based in London and Edinburgh. The post was created soon after the Union of the Crowns, but was...

 be given data about the catches of salmon and trout to help establish catch limits.

United States

Several populations of Atlantic salmon are in serious decline, and are listed as endangered under the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

 (ESA). Currently, runs of 11 rivers in Maine are on the list - Kennebec, Androscoggin, Penoboscot, Sheepscot, Ducktrap, Cove Brook, Pleasant, Narraguagus, Machias, East Machias and Dennys. The Penobscot is the "anchor river" for Atlantic salmon populations in the US. Returns in 2008 have been around 2,000, more than double the 2007 return of 940.

Section 9 of the ESA makes it illegal to take an endangered species of fish or wildlife. The definition of "take" is to "harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct".

Canada

The federal government
Government of Canada
The Government of Canada, formally Her Majesty's Government, is the system whereby the federation of Canada is administered by a common authority; in Canadian English, the term can mean either the collective set of institutions or specifically the Queen-in-Council...

 has prime responsibility for protecting the Atlantic salmon, but over the last generation, there has been a continued effort to shift management as much as possible to provincial authorities
Provinces and territories of Canada
The provinces and territories of Canada combine to make up the world's second-largest country by area. There are ten provinces and three territories...

 through memoranda of understanding, for example. A new Atlantic salmon policy is in the works, and in the past three years there has been an attempt by government to pass a new version of the century-old Fisheries Act through Parliament.

Federal legislation regarding at-risk populations is weak. Inner Bay of Fundy
Bay of Fundy
The Bay of Fundy is a bay on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine...

 Atlantic salmon runs were declared endangered in 2000. As of 2008, no recovery plan is in place.

It takes constant pressure from nongovernmental organizations, such as the Atlantic Salmon Federation, for improvements in management, and for initiatives to be considered. For example, the technology for mitigation of acid rain
Acid rain
Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions . It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen...

-impacted rivers used in Norway is needed in 54 Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...

 rivers. Yet, an initiative of the ASF and the Nova Scotia Salmon Association raised the funds to get a project in place, in West River-Sheet Harbour.

In Quebec, the daily catch limit for Atlantic salmon is one fish over 63 cm (24.8 in), two fish under 63 cm or one fish over and one under 63 cm, provided the smaller fish was the first one caught (a provision designed to prevent an angler from continuing to fish if a large fish is already in possession). The annual catch limit is seven Atlantic salmon of any size.

NASCO

The North Atlantic Salmon Conservation Organization
North Atlantic Salmon Conservation Organization
The North Atlantic Salmon Conservation Organization is an international organization established under the Convention for the Conservation of Salmon in the North Atlantic Ocean from October 1 1983....

 (NASCO) is an international council made up of Canada, Denmark, the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

, Iceland, Norway, the Russian Federation
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, and the United States, with its headquarters in Edinburgh
Edinburgh
Edinburgh is the capital city of Scotland, the second largest city in Scotland, and the eighth most populous in the United Kingdom. The City of Edinburgh Council governs one of Scotland's 32 local government council areas. The council area includes urban Edinburgh and a rural area...

. It was established in 1983 to help protect Atlantic salmon stocks, through the cooperation between nations. They work to restore habitat and promote conservation of the salmon.

Sustainable consumption

In 2010, Greenpeace International has added the Atlantic salmon to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries".

External links

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