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Atlantic salmon

Atlantic salmon
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Salmo
Species: S. salar
Binomial name
Salmo salar
Linnaeus, 1758
Distribution of Atlantic salmon

The Atlantic salmon (Salmo salar) is a salmon in the family Salmonidae. It is found in the northern Atlantic Ocean, in rivers that flow into the north Atlantic and, due to human introduction, in the north Pacific.[2][3]

Other names used to reference Atlantic salmon are: bay salmon, black salmon, caplin-scull salmon, Sebago salmon, silver salmon, fiddler, or outside salmon. At different points in their maturation and life cycle, they are known as parr, smolt, grilse, grilt, kelt, slink, and spring salmon. Atlantic salmon that do not journey to sea, usually because of past human interference, are known as landlocked salmon or ouananiche.


  • Nomenclature 1
  • Description 2
  • Distribution and habitat 3
  • Diet 4
  • Behavior 5
  • Life stages 6
    • Freshwater phase 6.1
    • Saltwater phases 6.2
  • Breeding 7
  • Hybridization 8
  • Aquaculture 9
    • Process 9.1
    • Controversy 9.2
  • Human impact 10
  • Recovery 11
  • Beaver impact 12
  • Legislation 13
    • England and Wales 13.1
    • Scotland 13.2
    • United States 13.3
    • Canada 13.4
  • NASCO 14
  • Sustainable consumption 15
  • See also 16
  • Notes 17
  • References 18
  • External links 19


The Atlantic salmon was given its scientific binomial name by zoologist and taxonomist Carolus Linnaeus in 1758. Later, the differently coloured smolts were found to be the same species.

The name, Salmo salar, is from the Latin salmo, meaning salmon, and salar, meaning leaper, according to M. Barton,[4] but more likely meaning "resident of salt water". Lewis and Short's Latin Dictionary (Clarendon Press, Oxford, 1879) translates salar as a kind of trout from its use in the Idylls of the poet Ausonius (4th century CE).


Atlantic salmon are among the largest salmon species

Atlantic and Chinook salmon are the largest salmon. After two years at sea they average 71 to 76 cm (28 to 30 in) in length and 3.6 to 5.4 kg (7.9 to 11.9 lb) in weight.[5] But specimens can be much larger. An Atlantic salmon netted in 1960 in Scotland, in the estuary of the river Hope, was recorded as weighing 49.44 kg (109 lb), while another netted in 1925 in Norway was recorded at 160.65 cm (63.25 inches) in length.[6]

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

Distribution and habitat

Ocean migration of Atlantic salmon from Connecticut River[7]

The distribution of Atlantic salmon depends on water temperature. Because of global warming, some southern populations in Spain and other warm countries are expected to be extirpated soon. Before human influence, the natural breeding grounds of Atlantic Salmon were rivers in Europe and the eastern coast of North America. When North America was settled by Europeans, eggs were brought on trains to the west coast and introduced into the rivers there. Other attempts to bring Atlantic salmon to new settlements were made; e.g. New Zealand. But since there are no suitable ocean currents on New Zealand, most of these introductions failed. There is at least one landlocked population of Atlantic salmon on New Zealand, where the fish never go out to sea.

Young salmon spend 1–4 years in their natal river. When they are large enough (ca. 15 cm), they smoltify which means they undergo a physiological change where they change camouflage from stream-adapted with large gray spots to sea-adapted with shiny sides. They also undergo some endocrinological changes which means they adapt for the change in osmosis from freshwater to saltwater. Finally, the parr (young fish) will finish smoltification by swimming with the current instead of swimming against the current. When this change of behavior occurs, they are no longer called parr, but are referred to as smolt. When the smolt reach the sea, they follow sea surface currents and feed on plankton or fry from other fish species such as herring. During their time at sea, they can sense the change in the Earth magnetic field through iron in their lateral line.

When they have had a year of good growth, they will move to the sea surface currents that transport them back to their natal river. It is a major misconception that salmon swim thousands of kilometers at sea; instead they surf through sea surface currents. When they reach their natal river they find it by smell; only 5% of Atlantic salmon go up the wrong river. Thus, the habitat of Atlantic salmon is the river where they are born and the sea surface currents that are connected to that river in a circular path.

Wild salmon disappeared from many rivers during the twentieth century due to overfishing and habitat change.[2] By 2000 the numbers of Atlantic salmon had dropped to critically low levels.[8]


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 and in the current. Some have been known to eat salmon eggs. The most commonly eaten foods include caddisflies, blackflies, mayflies, and stoneflies.[2]

As adults, the fish feed on much larger food: Arctic squid, sand eels, amphipods, Arctic shrimp, and sometimes herring, and the fishes' size increases dramatically.[2]


Fry and parr have been said to be territorial, but evidence showing them to guard territories is inconclusive. While they may occasionally be aggressive towards each other, the social hierarchy is still unclear. Many have been found to school, 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. A matter of concern is where they have become an invasive threat, attacking native salmon, such as Chinook salmon and coho salmon.[2]

Life stages

Life cycle of the Atlantic salmon

Most Atlantic salmon follow an anadromous fish migration pattern,[3] in that they undergo their greatest feeding and growth in saltwater; however, adults return to spawn in native freshwater streams where the eggs hatch and juveniles grow through several distinct stages.

Atlantic salmon do not require saltwater. Numerous examples of fully freshwater (i.e., "landlocked") populations of the species exist throughout the Northern Hemisphere.[3] In North America, the landlocked strains are frequently known as ouananiche.

Freshwater phase

The freshwater phases of Atlantic salmon vary between one and eight years, according to river location.[9] While the young in southern rivers, such as those to the English Channel, are only one year old when they leave, those further north, such as in Scottish rivers, can be over four years old, and in Ungava Bay, northern Quebec, smolts as old as eight years have been encountered.[9] The average age correlates to temperature exceeding 7 °C (45 °F).[2]

The first phase is the alevin stage, when the fish stay in the breeding ground and use the remaining nutrients in their yolk sacs. During this developmental stage, their young gills develop and they become active hunters. Next is the fry 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. Nearly 40% are eaten by trout alone. Other predators include other fish and birds.

Saltwater phases

When parr develop into smolt, they begin the trip to the ocean, which predominantly happens between March and June. Migration allows acclimation to the changing salinity. Once ready, young smolt leave, preferring an ebb tide.

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. During this time, they face predation from humans, seals, Greenland sharks, skate, cod, and halibut. Some dolphins 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, when they become ready to return to the same freshwater tributary they departed from as smolts. 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 – may play an important role in how salmon return to the area where they hatched. Once heavier than about 250 g, the fish no longer become prey for birds and many fish, although seals do prey upon them. Grey and common seals commonly eat Atlantic salmon. Survivability to this stage has been estimated at between 14 and 53%.[2]


Fish ladder for Atlantic salmon constructed in the middle of a large weir

Atlantic salmon breed in the rivers of Western Europe from northern Portugal north to Norway, Iceland, and Greenland, and the east coast of North America from Connecticut in the United States north to northern Labrador and Arctic Canada.

Some Atlantic salmon escape from cages at sea. These salmon tend to lessen the genetic diversity of the species leading to lower survival rates, and lower catch rates. On the west coast of North America, the non-native salmon can be an invasive threat, especially in Alaska and parts of Canada. This causes them to compete with native salmon for resources. Extensive efforts are underway to prevent the spread of Atlantic salmon in the Pacific and elsewhere.[10]

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 eggs and milt (sperm), respectively, 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.

Unlike the various Pacific salmon species which die after spawning (semelparous), the Atlantic salmon is iteroparous, which means the fish may recondition themselves and return to the sea to repeat the migration and spawning pattern several times, although most spawn only once or twice.[3][11] Migration and spawning exact an enormous physiological toll on individuals, such that repeat spawners are the exception rather than the norm.[11] Atlantic salmon show high diversity in age of maturity and may mature as parr, one- to five-sea-winter fish, and in rare instances, at older sea ages. This variety of ages can occur in the same population, constituting a ‘bet hedging’ strategy against variation in stream flows. So in a drought year, some fish of a given age will not return to spawn, allowing that generation other, wetter years in which to spawn.[9]


When in shared breeding habitats, Atlantic salmon will hybridize with brown trout (Salmo trutta).[12][13][14] Hybrids between Atlantic salmon and brown trout were detected in two of four watersheds studied in northern [Spain]. The proportions of hybrids in samples of 'salmon' ranged from 0 to 7-7% but they were not significantly heterogeneous among locations, resulting in a mean hybridization rate of 2-3%. This is the highest rate of natural hybridization so far reported and is significantly greater than rates observed elsewhere in Europe.[15]


Atlantic salmon marine cages in the Faroe Islands
A salmon farm holds yearlings for up to two years; many hold broodstock for even longer in these conditions to help ensure large, sexually mature adults. As is the case with this British Columbia farm, a majority of salmon farms are located in waters where Atlantic salmon is not native and risk becoming an invasive species upon release or escape.

In its natal streams, Atlantic salmon are considered prized recreational fish, pursued by fly anglers 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 in Norway, Chile, Canada, the UK, Ireland, Faroe Islands, Russia and Tasmania in Australia. Sport fishing communities, mainly from Iceland and Scandinavia, have joined in the North Atlantic Salmon Fund to buy away commercial quotas in an effort to save the wild species of Salmo salar.[11]


Adult male and female fish are anaesthetised; their eggs and sperm are "stripped" after the fish are cleaned and cloth dried. Sperm and eggs are mixed, washed, and placed into freshwater. Adults recover in flowing, clean, well-aerated water.[16] Some researchers have even studied cryopreservation of their eggs.[17]

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.[11]

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.[16]


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 care to ensure the non-native salmon cannot escape from their open-net pens, and escape is no longer considered a major concern. Evidence of Atlantic salmon surviving and establishing wild populations in the Pacific is lacking.

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 BC lakes and streams. Historical records indicate, 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 US National Marine Fisheries Service (NMFS), the Washington Department of Fish and Wildlife and the BC Environmental Assessment Office have concluded the potential risk of Atlantic salmon colonization in the Pacific Northwest is low.[18]

Human impact

Seine fishing for salmon – Wenzel Hollar, 1607–1677

Atlantic salmon were once abundant throughout the North Atlantic. European fishermen gillnetted for Atlantic salmon in rivers using hand-made nets for at least several centuries.[19] Wood and stone weirs along streams and ponds were used for millennia to harvest salmon in the rivers of Maine and New England,[20] and gillnetting was an early fishing technology in colonial America.[21]

Human activities have heavily damaged salmon populations across their range. The major impacts were from overfishing and habitat change, and the new threat from competitive farmed fish. Salmon decline in Lake Ontario 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.[22] When dams were constructed on the Oswego River, their spawning areas were cut off and they went extinct locally.

In the 1950s, salmon from rivers in the United States and Canada, as well as from Europe, were discovered to gather in the sea around Greenland and the Faroe Islands. A commercial fishing industry was established, taking salmon using drift nets. After an initial series of record annual catches, the numbers crashed; between 1979 and 1990, catches fell from four million to 700,000.[23] Overfishing at sea is generally considered the primary factor.

Beginning around 1990, the rates of Atlantic salmon mortality at sea more than doubled. In the western Atlantic, fewer than 100,000 of the important multiple sea-winter salmon were returning. Rivers of the coast of

  • Atlantic Salmon Conservation Foundation
  • NOAA Fisheries Atlantic salmon page
  • Atlantic Salmon Federation
  • Issues salmon face – Smithsonian Ocean Portal
  • State of Maine, Atlantic Salmon Commission
  • University of Massachusetts information regarding Atlantic salmon
  • Atlantic salmon's page on World Wide Fund for Nature's website
  • Alaska Fish and Game Atlantic salmon page
  • Atlantic Salmon Trust, an organization working to protect the Atlantic salmon
  • Atlantic Salmon Fishing, Information about Atlantic Salmon Fishing
  • Ontario Ministry of Natural Resources, Information About Atlantic Salmon Restoration Program
  • Atlantic Salmon Fishing Reports & Images
  • Salmon Ireland, information on the salmon rivers

External links

  • Atlantic salmon NOAA FishWatch. Retrieved 4 November 2012.


  1. ^ World Conservation Monitoring Centre (1996). "Salmo salar".  
  2. ^ a b c d e f g h i Shearer, W. (1992). The Atlantic Salmon. Halstead Press. 
  3. ^ a b c d e f The Audubon Society Field Guide to North American Fishes, Whales & Dolphins. Chanticleer Press. 1983. p. 395. 
  4. ^ Barton, M.: "Biology of Fishes.", pages 198–202 Thompson Brooks/Cole 2007
  5. ^ "Atlantic salmon (Salmo salar)".  
  6. ^ "Buller F, The Domesday Book of Giant Salmon Volume 1 & 2. Constable (2007) & Constable (2010)
  7. ^ Atlantic Salmon Life Cycle Connecticut River Coordinator's Office, U.S. Fish and Wildlife Service. Updated: 13 September 2010.
  8. ^ B. Dempson, C. J. Schwarz, D. G. Reddin, M. F. O’Connell, C. C. Mullins, and C. E. Bourgeois (2001). "Estimation of marine exploitation rates on Atlantic salmon (Salmo salar L.) stocks in Newfoundland, Canada" (PDF). ICES Journal of Marine Science: 331–341.  
  9. ^ a b c Klemetsen A, Amundsen P-A, Dempson JB, Jonsson B, Jonsson N, O’Connell MF, Mortensen E (2003). "Atlantic salmon Salmo salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.): a review of aspects of their life histories". Ecology of Freshwater Fish.  
  10. ^ a b Mills, D. (1989). Ecology and Management of Atlantic Salmon.  
  11. ^ a b c d Heen, K. (1993). Salmon Aquaculture. Halstead Press. 
  12. ^ Youngson, A. F., Webb, J. H., Thompson, C. E., and Knox, D. 1993. Spawning of escaped farmed Atlantic salmon (Salmo salar): hybridization of females with brown trout (Salmo trutta). Canadian Journal of Fisheries and Aquatic Sciences, 50:1986-1990.
  13. ^ Matthews, M. A., Poole, W. R., Thompson, C. E., McKillen, J., Ferguson, A., Hindar, K., and Wheelan, K. F. 2000. Incidence of hybridization between Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in Ireland. Fisheries Management and Ecology, 7:337-347.
  14. ^ Seawater tolerance in Atlantic salmon, Salmo salar L., brown trout, Salmo trutta L., and S. salar × S. trutta hybrids smolt. Urke HA, Koksvik J, Arnekleiv JV, Hindar K, Kroglund F, Kristensen T. Source Norwegian Institute of Water Research, 7462, Trondheim, Norway. henning.urke(@)
  15. ^ ) in northern Spain by Carlos Garcia de LeanizSalmo trutta) and brown trout (Salmo salarNatural hybridization between Atlantic salmon (
  16. ^ a b c Sedgwick, S. (1988). Salmon Farming Handbook. Fishing News Books LTD. 
  17. ^ N. Bromage (1995). Broodstock Management and Egg and Larval Quality.  
  18. ^ R. M. J. Ginetz (May 2002). "On the Risk of Colonization by Atlantic Salmon in BC waters" (PDF). B.C. Salmon Farmers Association. 
  19. ^ Jenkins, J. Geraint (1974). Nets and Coracles, p. 68. London, David and Charles.
  20. ^ "The River". The Penobscot River Restoration Trust. Retrieved 19 November 2013. 
  21. ^ Netboy, Anthony (1973) The Salmon: Their Fight for Survival, pp. 181-182. Boston, Houghton Mifflin.
  22. ^ a b Harb, M. "Upstream Battle", Canadian Geographic Magazine, June 2008, p. 24
  23. ^ "Salmon campaigner lands top award". BBC News. 22 April 2007. 
  24. ^ "Atlantic Salmon". Retrieved 19 November 2013. 
  25. ^ Carpenter, Murray (26 December 2011). "Shiny Patches in Maine’s Streambeds Are Bright Sign for Salmon". The New York Times. Retrieved February 2012. 
  26. ^ Atlantic Salmon Restoration Program
  27. ^ a b c P. Collen & R. J. Gibson (2001). spp.), as related to their influence on stream ecosystems and riparian habitats, and the subsequent effects on fish – a review"Castor"The general ecology of beavers ( (PDF).  
  28. ^ Howard Park & Øystein Cock Rønning (2007). "Low potential for restraint of anadromous salmonid reproduction by beaver Castor fiber in the Numedalslågen river catchment, Norway".  
  29. ^ Barry A. Taylor, Charles MacInnis, Trevor A. Floyd (2010). "Influence of Rainfall and Beaver Dams on Upstream Movement of Spawning Atlantic Salmon in a Restored Brook in Nova Scotia, Canada". River Research and Applications: 183–193.  
  30. ^ Douglas B. Sigourney, Benjamin H. Letcher & Richard A. Cunjak (2006). "Influence of beaver activity on summer growth and condition of age-2 Atlantic salmon parr".  
  31. ^ (16 U.S.C. 1532(19))
  32. ^ "Frequently Asked Questions (FAQ)". Bring Back the Salmon Lake Onterio. Retrieved 17 September 2015. 
  33. ^ "Endangered Populations". Atlantic Salmon Federation. Retrieved 17 September 2015. 
  34. ^ "NASCO ~ The North Atlantic Salmon Conservation Organization". Retrieved 11 February 2012. 
  35. ^ Greenpeace International Seafood Red list


See also

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".[35]

Sustainable consumption

The European Union, Iceland, Norway, the Russian Federation, and the United States, with its headquarters in Edinburgh.[34] 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.


In Lake Ontario, the historic populations of Atlantic Salmon went extinct, and cross-national efforts have been under way to reintroduce the species, with some areas already having restocked naturally reproducing populations.[32][33]

In Quebec, the daily catch limit for Atlantic salmon is one fish over 63 cm (25 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.

It takes constant pressure from acid rain-affected rivers used in Norway is needed in 54 Nova Scotia 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.

Federal legislation regarding at-risk populations is weak. Inner Bay of Fundy Atlantic salmon runs were declared endangered in 2000. As of 2008, no recovery plan is in place.

The federal government has prime responsibility for protecting the Atlantic salmon, but over the last generation, effort has continued to shift management as much as possible to provincial authorities through memoranda of understanding, for example. A new Atlantic salmon policy is in the works, and in the past three years, the government has attempted to pass a new version of the century-old Fisheries Act through Parliament.


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".[31]

Several populations of Atlantic salmon are in serious decline, and are listed as endangered under the Endangered Species Act (ESA). Currently, runs of 11 rivers in Maine are on the list – Kennebec, Androscoggin, Penobscot, 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.

United States

More recent legislation has established commissioners who manage districts. Furthermore, the Salmon and Freshwater Fisheries Act in 1951 required the Secretary of State be given data about the catches of salmon and trout to help establish catch limits.[2][16]

During the 15th century, many laws were passed; many regulated fishing times, and worked to ensure smolts could safely pass downstream. James III even closed a meal mill because of its history of killing fish attracted to the wheel. Because the fish were held in such high regard, poachers were severely punished.

Legislation in Scotland to help Atlantic salmon began in 1318 by Alexander II. It prohibited certain types of traps in rivers.


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.[2]

In 1974, the 32 boards were reduced to 10 regional water authorities (RWAs). Although only the Northumbrian, Welsh, northwest and southwest RWA's had considerable salmon populations, all ten also cared for trout and freshwater eels.

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.

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.

Based on 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's control, but it was later transferred to the Board of Trade, and then later to the Board of Agriculture and Fisheries.

Edward I instituted a penalty for collecting salmon during certain times of the year. His son Edward II continued, regulating the construction of weirs. 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.

England and Wales

The first laws regarding the Atlantic salmon were started nearly 800 years ago.


The importance of winter habitat to salmonids afforded by beaver ponds may be especially important in streams of northerly latitudes without deep pools where ice cover makes contact with the bottom of shallow streams.[27] In addition, the up to eight-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.[30]

A 2003 study of Atlantic salmon and sea-run brown trout/sea trout spawning in the Numedalslågen River and 51 of its tributaries in southeastern Norway were unhindered by beaver.[28] 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.[29]

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, 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.[27] Downstream migration of Atlantic salmon smolts was similarly unaffected by beaver dams, even in periods of low flows.[27]

Beaver impact

Atlantic salmon still remains a popular fish for human consumption.[3] It is commonly sold fresh, canned, or frozen.

In New England, many efforts are underway to restore salmon to the region by knocking down obsolete dams and updating others with fish ladders and other techniques that have proven effective in the West with Pacific salmon. There is some success thus far, with populations growing in the Penobscot and Connecticut Rivers. Lake Champlain now has Atlantic salmon. In Ontario, the Atlantic Salmon Restoration Program[26] was started in 2006, and is one of the largest freshwater conservation programs in North America. It has stocked Lake Ontario with over 700,000 young Atlantic salmon. In October 2007, salmon were video-recorded running in Toronto's Humber River by the Old Mill. In November 2007, a migrating salmon was observed in the Credit River.[22] There has also been some success in establishing Atlantic salmon in Fish Creek, a tributary of Oneida Lake in central New York.

Around the North Atlantic, efforts to restore salmon to their native habitats are underway, with slow progress. Habitat restoration and protection are key to this process, but issues of excessive harvest and competition with farmed and escaped salmon are also primary considerations. In the Great Lakes, Atlantic salmon have been introduced successfully, but the percentage of salmon reproducing naturally is very low. Most are stocked annually. Atlantic salmon were native to Lake Ontario, but were extirpated by habitat loss and overfishing in the late 19th century. The state of New York has since stocked its adjoining rivers and tributaries, and in many cases does not allow active fishing.[3][10]


Possibly because of improvements in ocean feeding grounds, returns in 2008 were positive. On the Penobscot River in Maine, returns were about 940 in 2007, and by mid-July 2008, the return was 1,938. Similar stories were reported in rivers from Newfoundland to Quebec. In 2011, more than 3,100 salmon returned to the Penobscot, the most since 1986, and nearly 200 ascended the Narraguagus River, up from the low two digits just a decade before.[25]


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