Salmon
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 |
| Commercial production of salmon in million tonnes 1950–2010 |
Salmon // is the common name for several species of
fish in the
family Salmonidae. Other fish in the same family include
trout,
char,
grayling and
whitefish. Various species of salmon display anadromous life strategies while others display freshwater resident life strategies. Salmon are native to tributaries of the North Atlantic (genus
Salmo) and Pacific Ocean (genus
Oncorhynchus). Many species of salmon have been introduced into non-native environments such as the
Great Lakes of North America and
Patagonia in South America. Salmon are intensively produced in
aquaculture in many parts of the world.
Typically, salmon are
anadromous: they are born in
fresh water, migrate to the ocean, then return to fresh water to
reproduce. However, populations of several species are restricted to fresh water through their lives.
Folklore has it that the fish return to the exact spot where they were born to
spawn; tracking studies have shown this to be true, and this homing behavior has been shown to depend on
olfactory memory.
Species
The term "salmon" comes from the
Latin salmo, which in turn may have originated from
salire, meaning "to leap".
[4] The nine commercially important species of salmon occur in two genera. The genus
Salmo contains the
Atlantic salmon, found in the north Atlantic, as well as many species commonly named
trout. The genus
Oncorhynchus contains eight species which occur naturally only in the north Pacific. As a group, these are known as
Pacific salmon.
Chinook salmon have been introduced in New Zealand and Patagonia. Coho, Kokanee and Atlantic salmon have been established in Patagonia as well.
| Atlantic and Pacific salmon |
|---|
| Genus | Common name | Scientific name | Maximum
length | Common
length | Maximum
weight | Maximum
age | Trophic
level | Fish
Base | FAO | ITIS | IUCN status |
Salmo
(Atlantic salmon) | Atlantic salmon | Salmo salar Linnaeus, 1758 | 150 cm | 120 cm | 46.8 kg | 13 years | 4.4 |
|
| [8] |  Least concern[9] |
Oncorhynchus
(Pacific salmon) | Chinook salmon | Oncorhynchus tshawytscha (Walbaum, 1792) | 150 cm | 70 cm | 61.4 kg | 9 years | 4.4 |
|
| [12] | Not assessed |
| Chum salmon | Oncorhynchus keta (Walbaum, 1792) | 100 cm | 58 cm | 15.9 kg | 7 years | 3.5 |
|
| [15] | Not assessed |
| Coho salmon | Oncorhynchus kisutch (Walbaum, 1792) | 108 cm | 71 cm | 15.2 kg | 5 years | 4.2 |
|
| [18] | Not assessed |
| Pink salmon | Oncorhynchus gorbuscha (Walbaum, 1792) | 76 cm | 50 cm | 6.8 kg | 3 years | 4.2 |
|
| [21] | Not assessed |
| Sockeye salmon | Oncorhynchus nerka (Walbaum, 1792) | 84 cm | 58 cm | 7.7 kg | 8 years | 3.7 |
|
| [24] | Least concern[25] |
| Masu salmon | Oncorhynchus masou (Brevoort, 1856) | 79.0 cm | cm | 10.0 kg | 3 years | 3.6 |
|
| [27] | Not assessed |
Both the Salmo and Oncorhynchus genera also contain a number of species referred to as trout. Within Salmo, additional minor taxa have been called salmon in English, i.e. the Adriatic salmon (Salmo obtusirostris) and Black Sea salmon (Salmo labrax). The steelhead anadromous form of the rainbow trout migrates to sea, but it is not termed "salmon".
There are also a number of other species whose common names refer to them as being salmon. Of those listed below, the Danube salmon or
huchen is a large freshwater
salmonid related to the salmon above, but others are marine fishes of the non-related
perciform-order:
| Some other fishes called salmon |
| Common name | Scientific name | Maximum
length | Common
length | Maximum
weight | Maximum
age | Trophic
level | Fish
Base | FAO | ITIS | IUCN status |
| Danube salmon | Hucho hucho (Linnaeus, 1758) | 150 cm | 70 cm | 52 kg | 15 years | 4.2 |
|
|
|  Endangered[30] |
| Australian salmon | Arripis trutta (Forster, 1801) | 89 cm | 47 cm | 9.4 kg | 26 years | 4.1 |
|
|
| Not assessed |
| Hawaiian salmon | Elagatis bipinnulata (Quoy & Gaimard, 1825) | 180 cm | 90 cm | 46.2 kg | years | 3.6 |
|
|
| Not assessed |
| Indian salmon | Eleutheronema tetradactylum (Shaw, 1804) | 200 cm | 50 cm | 145 kg | years | 4.4 |
|
|
| Not assessed |
Eosalmo driftwoodensis, the oldest known salmon in the fossil record, helps scientists figure how the different species of salmon diverged from a common ancestor. The British Columbia salmon fossil provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred by 10 to 20 million years ago. This independent evidence from DNA analysis and the fossil record reject the glacial theory of salmon divergence.
Distribution
- Atlantic salmon (Salmo salar) reproduces in northern rivers on both coasts of the Atlantic Ocean.
- Landlocked salmon (Salmo salar m. sebago) live in a number of lakes in eastern North America and in Northern Europe, for instance in lakes Sebago, Onega, Ladoga, Saimaa, Vänern and Winnipesaukee. They are not a different species from the Atlantic salmon, but have independently evolved a non-migratory life cycle, which they maintain even when they could access the ocean.
- Masu salmon or cherry salmon (Oncorhynchus masou) is found only in the western Pacific Ocean in Japan, Korea and Russia. A land-locked subspecies known as the Taiwanese salmon or Formosan salmon (Oncorhynchus masou formosanus) is found in central Taiwan's Chi Chia Wan Stream.
- Chinook salmon (Oncorhynchus tshawytscha) is also known in the US as king salmon or blackmouth salmon, and as spring salmon in British Columbia. Chinook are the largest of all Pacific salmon, frequently exceeding 30 lb (14 kg). The name Tyee is used in British Columbia to refer to Chinook over 30 pounds, and in Columbia River watershed, especially large Chinook were once referred to as June hogs. Chinook salmon are known to range as far north as the Mackenzie River and Kugluktuk in the central Canadian arctic, and as far south as the Central California Coast.
- Chum salmon (Oncorhynchus keta) is known as dog, keta, or calico salmon in some parts of the US. This species has the widest geographic range of the Pacific species: south to the Sacramento River in California in the eastern Pacific and the island of Kyūshū in the Sea of Japan in the western Pacific; north to the Mackenzie River in Canada in the east and to the Lena River in Siberia in the west.
- Coho salmon (Oncorhynchus kisutch) is also known in the US as silver salmon. This species is found throughout the coastal waters of Alaska and British Columbia and as far south as Central California (Monterey Bay). It is also now known to occur, albeit infrequently, in the Mackenzie River.
- Pink salmon (Oncorhynchus gorbuscha), known as humpies in southeast and southwest Alaska, are found from northern California and Korea, throughout the northern Pacific, and from the Mackenzie River in Canada to the Lena River in Siberia, usually in shorter coastal streams. It is the smallest of the Pacific species, with an average weight of 3.5 to 4.0 lb (1.6 to 1.8 kg).
- Sockeye salmon (Oncorhynchus nerka) is also known in the US as red salmon. This lake-rearing species is found south as far as the Klamath River in California in the eastern Pacific and northern Hokkaidō island in Japan in the western Pacific and as far north as Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. Although most adult Pacific salmon feed on small fish, shrimp and squid; sockeye feed on plankton they filter through gill rakers. Kokanee salmon is a land-locked form of sockeye salmon.
- The Danube salmon or huchen (Hucho hucho), is the largest permanent fresh water salmonid species.
Life cycle
Life cycle of Pacific salmon
Eggs in different stages of development: In some, only a few cells grow on top of the yolk, in the lower right, the blood vessels surround the yolk and in the upper left, the black eyes are visible, even the little lens.
Salmon fry hatching — the baby has grown around the remains of the yolk — visible are the arteries spinning around the yolk and little old drops, also the gut, the spine, the main caudal blood vessel, the bladder and the arcs of the gills
Salmon eggs are laid in freshwater streams typically at high latitudes. The
eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for six months to three years in their natal stream before becoming smolts, which are distinguished by their bright, silvery colour with
scales that are easily rubbed off. Only 10% of all salmon eggs are estimated to survive to this stage.
[48] The smolt body chemistry changes, allowing them to live in saltwater. Smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to
osmoregulation in the ocean.
Juvenile salmon, parr, grow up in the relatively protected natal river
The parr lose their camouflage bars and become smolt' as they become ready for the transition to the ocean
Male ocean phase adult sockeye
Male spawning phase adult sockeye
The salmon spend about one to five years (depending on the species) in the open ocean, where they gradually become sexually mature. The adult salmon then return primarily to their natal streams to spawn. Atlantic salmon spend between one and four years at sea. (When a fish returns after just one year's sea feeding, it is called a grilse in Canada, Britain and Ireland.) Prior to spawning, depending on the
species, salmon undergo changes. They may grow a hump, develop canine teeth, develop a kype (a pronounced curvature of the jaws in male salmon). All will change from the silvery blue of a fresh-run fish from the sea to a darker colour. Salmon can make amazing journeys, sometimes moving hundreds of miles upstream against strong currents and rapids to reproduce. Chinook and sockeye salmon from central Idaho, for example, travel over 900 miles (1,400 km) and climb nearly 7,000 feet (2,100 m) from the Pacific Ocean as they return to spawn. Condition tends to deteriorate the longer the fish remain in fresh water, and they then deteriorate further after they spawn, when they are known as kelts. In all species of Pacific salmon, the mature individuals die within a few days or weeks of spawning, a trait known as
semelparity. Between 2 and 4% of Atlantic salmon kelts survive to spawn again, all females. However, even in those species of salmon that may survive to spawn more than once (
iteroparity), postspawning mortality is quite high (perhaps as high as 40 to 50%.)
To lay her
roe, the female salmon uses her tail (caudal fin), to create a low-pressure zone, lifting gravel to be swept downstream, excavating a shallow depression, called a redd. The redd may sometimes contain 5,000 eggs covering 30 square feet (2.8 m
2). The eggs usually range from orange to red. One or more males will approach the female in her redd, depositing his sperm, or milt, over the roe. The female then covers the eggs by disturbing the gravel at the upstream edge of the depression before moving on to make another redd. The female will make as many as seven redds before her supply of eggs is exhausted.
Each year, the fish experiences a period of rapid growth, often in summer, and one of slower growth, normally in winter. This results in ring formation around an earbone called the
otolith, (annuli) analogous to the growth rings visible in a tree trunk. Freshwater growth shows as densely crowded rings, sea growth as widely spaced rings; spawning is marked by significant erosion as body mass is converted into eggs and milt.
Freshwater streams and estuaries provide important habitat for many salmon species. They feed on
terrestrial and
aquatic insects,
amphipods, and other
crustaceans while young, and primarily on other fish when older. Eggs are laid in deeper water with larger gravel, and need cool water and good water flow (to supply oxygen) to the developing embryos. Mortality of salmon in the early life stages is usually high due to natural predation and human-induced changes in habitat, such as siltation, high water temperatures, low oxygen concentration, loss of stream cover, and reductions in river flow.
Estuaries and their associated
wetlands provide vital nursery areas for the salmon prior to their departure to the open ocean. Wetlands not only help buffer the estuary from silt and pollutants, but also provide important feeding and hiding areas.
Salmon not killed by other means show greatly accelerated deterioration (
phenoptosis, or "programmed aging") at the end of their lives. Their bodies rapidly deteriorate right after they spawn as a result of the release of massive amounts of
corticosteroids.
Ecology
Bears and salmon
In the Pacific Northwest and Alaska, salmon are
keystone species, supporting wildlife such as birds, bears and otters. The bodies of salmon represent a transfer of nutrients from the ocean, rich in nitrogen, sulfur, carbon and phosphorus, to the
forest ecosystem.
Grizzly bears function as
ecosystem engineers, capturing salmon and carrying them into adjacent wooded areas. There they deposit nutrient-rich urine and faeces and partially eaten carcasses. Bears are estimated to leave up to half the salmon they harvest on the forest floor, in densities that can reach 4,000 kilograms per hectare,
providing as much as 24% of the total nitrogen available to the riparian woodlands. The foliage of
spruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from fished salmon.
Beavers and salmon
Sockeye salmon jumping over beaver dam
Beavers also function as ecosystem engineers; in the process of clear-cutting and damming, beavers alter their ecosystems extensively. Beaver ponds can provide critical habitat for
juvenile salmon. An example of this was seen in the years following 1818 in the Columbia River Basin. In 1818, the British government made an agreement with the U.S. government to allow U.S. citizens access to the Columbia catchment (see
Treaty of 1818). At the time, the
Hudson's Bay Company sent word to
trappers to extirpate all furbearers from the area in an effort to make the area less attractive to U.S. fur traders. In response to the elimination of beavers from large parts of the river system,
salmon runs plummeted, even in the absence of many of the factors usually associated with the demise of salmon runs. Salmon recruitment can be affected by beavers' dams because dams can:
- Slow the rate at which nutrients are flushed from the system; nutrients provided by adult salmon dying throughout the fall and winter remain available in the spring to newly hatched juveniles
- Provide deeper water pools where young salmon can avoid avian predators
- Increase productivity through photosynthesis and by enhancing the conversion efficiency of the cellulose-powered detritus cycle
- Create low-energy environments where juvenile salmon put the food they ingest into growth rather than into fighting currents
- Increase structural complexity with many physical niches where salmon can avoid predators
Beavers' dams are able to nurture salmon juveniles in estuarine tidal marshes where the salinity is less than 10 ppm. Beavers build small dams of generally less than 2 feet (60 cm) high in channels in the myrtle zone. These dams can be overtopped at high tide and hold water at low tide. This provides refuges for juvenile salmon so they do not have to swim into large channels where they are subject to predation.
Parasites
According to Canadian biologist Dorothy Kieser, the
myxozoan parasite
Henneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to the Haida Gwaii Islands. The fish responds by walling off the parasitic infection into a number of cysts that contain milky fluid. This fluid is an accumulation of a large number of parasites.
Henneguya and other parasites in the myxosporean group have complex life cycles, where the salmon is one of two hosts. The fish releases the spores after spawning. In the
Henneguya case, the spores enter a second host, most likely an invertebrate, in the spawning stream. When juvenile salmon migrate to the Pacific Ocean, the second host releases a stage infective to salmon. The parasite is then carried in the salmon until the next spawning cycle. The myxosporean parasite that causes whirling disease in trout has a similar life cycle. However, as opposed to whirling disease, the
Henneguya infestation does not appear to cause disease in the host salmon — even heavily infected fish tend to return to spawn successfully.
According to Dr. Kieser, a lot of work on
Henneguya salminicola was done by scientists at the Pacific Biological Station in Nanaimo in the mid-1980s, in particular, an overview report which states, "the fish that have the longest fresh water residence time as juveniles have the most noticeable infections. Hence in order of prevalence coho are most infected followed by sockeye, chinook, chum and pink." As well, the report says, at the time the studies were conducted, stocks from the middle and upper reaches of large river systems in British Columbia such as Fraser, Skeena, Nass and from mainland coastal streams in the southern half of B.C., "are more likely to have a low prevalence of infection." The report also states, "It should be stressed that
Henneguya, economically deleterious though it is, is harmless from the view of public health. It is strictly a fish parasite that cannot live in or affect warm blooded animals, including man".
According to Klaus Schallie, Molluscan Shellfish Program Specialist with the Canadian Food Inspection Agency, "
Henneguya salminicola is found in southern B.C. also and in all species of salmon. I have previously examined smoked chum salmon sides that were riddled with cysts and some sockeye runs in Barkley Sound (southern B.C., west coast of Vancouver Island) are noted for their high incidence of infestation."
Sea lice, particularly
Lepeophtheirus salmonis and various
Caligus species, including
C. clemensi and
C. rogercresseyi, can cause deadly infestations of both farm-grown and wild salmon. Sea lice are
ectoparasites which feed on mucus, blood, and skin, and migrate and latch onto the skin of wild salmon during free-swimming, planktonic nauplii and copepodid larval stages, which can persist for several days. Large numbers of highly populated, open-net salmon farms can create exceptionally large concentrations of sea lice; when exposed in river estuaries containing large numbers of open-net farms, many young wild salmon are infected, and do not survive as a result. Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable. On the
Pacific coast of Canada, the louse-induced mortality of pink salmon in some regions is commonly over 80%.
Wild fisheries
Wild fisheries - commercial capture of all true wild salmon species 1950–2010, as reported by the
FAO
Commercial
As can be seen from the production chart at the left, the global capture reported by different countries to the
FAO of commercial wild salmon has remained fairly steady since 1990 at about one million tonnes per year. This is in contrast to farmed salmon (below) which has increased in the same period from about 0.6 million tonnes to well over two million tonnes.
Nearly all captured wild salmon are Pacific salmon. The capture of wild Atlantic salmon has always been relatively small, and has declined steadily since 1990. In 2011 only 2,500 tonnes were reported. In contrast about half of all farmed salmon are Atlantic salmon.
Recreational
Recreational salmon fishing can be a technically demanding kind of
sport fishing, not necessarily congenial for beginning fishermen. A conflict exists between
commercial fishermen and recreational fishermen for the right to salmon
stock resources. Commercial fishing in
estuaries and
coastal areas is often restricted so enough salmon can return to their natal rivers where they can spawn and be available for sport fishing. On parts of the North American west coast sport salmon fishing completely replaces inshore commercial fishing. The commercial value of a salmon can be several times less than the value of the same fish caught by a sport fisherman. This is "a powerful economic argument for allocating stock resources preferentially to sport fishing."
Farmed salmon
Aquaculture production of all true salmon species 1950–2010,
as reported by the FAO
Salmon
aquaculture is a major contributor to the world production of farmed finfish, representing about US$10 billion annually. Other commonly cultured fish species include:
tilapia,
catfish,
sea bass,
carp and
bream. Salmon farming is significant in
Chile,
Norway,
Scotland, Canada and the
Faroe Islands, and is the source for most salmon consumed in America and Europe. Atlantic salmon are also, in very small volumes, farmed in Russia and the island of
Tasmania, Australia.
Salmon are
carnivorous and are currently fed a meal produced from catching other
wild fish and other marine organisms. Salmon farming leads to a high demand for wild
forage fish. Salmon require large nutritional intakes of protein, and consequently, farmed salmon consume more fish than they generate as a final product. To produce one pound of farmed salmon, products from several pounds of wild fish are fed to them. As the salmon farming industry expands, it requires more wild forage fish for feed, at a time when 75% of the world's monitored fisheries are already near to or have exceeded their
maximum sustainable yield. The industrial-scale extraction of wild forage fish for salmon farming then impacts the survivability of the wild predator fish which rely on them for food.
Work continues on substituting vegetable
proteins for animal proteins in the salmon diet. Unfortunately, though, this substitution results in lower levels of the highly valued
omega-3 fatty acid content in the farmed product.
Intensive salmon farming now uses open-net cages, which have low production costs, but have the drawback of allowing disease and
sea lice to spread to local wild salmon stocks.
On a dry weight basis, 2–4 kg of wild-caught fish are needed to produce one kg of salmon.
Another form of salmon production, which is safer but less controllable, is to raise salmon in
hatcheries until they are old enough to become independent. They are then released into rivers, often in an attempt to increase the salmon population. This system is referred to as
ranching, and was very common in countries such as Sweden before the Norwegians developed salmon farming, but is seldom done by private companies, as anyone may catch the salmon when they return to spawn, limiting a company's chances of benefiting financially from their investment. Because of this, the method has mainly been used by various public authorities and nonprofit groups such as the
Cook Inlet Aquaculture Association as a way of artificially increasing salmon populations in situations where they have declined due to
overharvesting, construction of dams, and
habitat destruction or
fragmentation. Unfortunately, there can be negative consequences to this sort of population manipulation, including genetic "dilution" of the wild stocks, and many jurisdictions are now beginning to discourage supplemental fish planting in favour of harvest controls and habitat improvement and protection. A variant method of fish stocking, called ocean ranching, is under development in
Alaska. There, the young salmon are released into the ocean far from any wild salmon streams. When it is time for them to spawn, they return to where they were released where fishermen can then catch them.
An alternative method to hatcheries is to use spawning channels. These are artificial streams, usually parallel to an existing stream with concrete or rip-rap sides and gravel bottoms. Water from the adjacent stream is piped into the top of the channel, sometimes via a header pond, to settle out sediment. Spawning success is often much better in channels than in adjacent streams due to the control of floods, which in some years can wash out the natural redds. Because of the lack of floods, spawning channels must sometimes be cleaned out to remove accumulated sediment. The same floods which destroy natural redds also clean them out. Spawning channels preserve the natural selection of natural streams, as there is no benefit, as in hatcheries, to use prophylactic chemicals to control diseases.
Farm-raised salmon are fed the
carotenoids astaxanthin and
canthaxanthin to match their flesh color to wild salmon.
One proposed alternative to the use of wild-caught fish as feed for the salmon, is the use of soy-based products. This should be better for the local environment of the fish farm, but producing soy beans has a high environmental cost for the producing region.
Another possible alternative is a yeast-based coproduct of
bioethanol production,
proteinaceous fermentation biomass. Substituting such products for engineered feed can result in equal (sometimes enhanced) growth in fish. With its increasing availability, this would address the problems of rising costs for buying hatchery fish feed.
Yet another attractive alternative is the increased use of seaweed. Seaweed provides essential minerals and vitamins for growing organisms. It offers the advantage of providing natural amounts of dietary fiber and having a lower glycemic load than grain-based fish meal. In the best-case scenario, widespread use of seaweed could yield a future in aquaculture that eliminates the need for land, freshwater, or fertilizer to raise fish.
Management
The population of wild salmon declined markedly in recent decades, especially North Atlantic populations, which spawn in the waters of western Europe and eastern Canada, and wild salmon in the Snake and Columbia River systems in northwestern United States.
Salmon
population levels are of concern in the Atlantic and in some parts of the Pacific.
Alaska fishery stocks are still abundant, and catches have been on the rise in recent decades, after the state initiated limitations in 1972. Some of the most important Alaskan salmon sustainable
wild fisheries are located near the
Kenai River,
Copper River, and in
Bristol Bay.
Fish farming of Pacific salmon is outlawed in the United States
Exclusive Economic Zone,
[citation needed] however, there is a substantial network of publicly funded
hatcheries, and the State of Alaska's
fisheries management system is viewed as a leader in the management of wild
fish stocks. In Canada, returning
Skeena River wild salmon support
commercial,
subsistence and
recreational fisheries, as well as the area's diverse wildlife on the coast and around communities hundreds of miles inland in the watershed. The status of wild salmon in Washington is mixed. Of 435 wild stocks of salmon and steelhead, only 187 of them were classified as healthy; 113 had an unknown status, one was extinct, 12 were in critical condition and 122 were experiencing depressed populations.
The commercial salmon fisheries in California have been either severely curtailed or closed completely in recent years, due to critically low returns on the Klamath and or Sacramento Rivers, causing millions of dollars in losses to commercial fishermen.
Both Atlantic and Pacific salmon are popular
sportfish.
Salmon populations now exist in all the Great Lakes. Coho stocks were planted in the late 1960s in response to the growing population of non-native
alewife by the state of Michigan. Now Chinook (king), Atlantic, and coho (silver) salmon are annually stocked in all Great Lakes by most bordering states and provinces. These populations are not self-sustaining and do not provide much in the way of a commercial fishery, but have led to the development of a thriving sport fishery.
As food
Main article:
Salmon (food)
Salmon is a popular food. Classified as an
oily fish, salmon is considered to be healthy due to the fish's high
protein, high
omega-3 fatty acids, and high
vitamin D content. Salmon is also a source of
cholesterol, with a range of 23–214 mg/100 g depending on the species.
According to reports in the journal
Science, however, farmed salmon may contain high levels of
dioxins. PCB (
polychlorinated biphenyl) levels may be up to eight times higher in farmed salmon than in wild salmon, but still well below levels considered dangerous. Nonetheless, according to a 2006 study published in the Journal of the American Medical Association, the benefits of eating even farmed salmon still outweigh any risks imposed by contaminants. The type of omega-3 present may not be a factor for other important health functions.
Salmon flesh is generally orange to red, although white-fleshed wild salmon occurs. The natural colour of salmon results from
carotenoid pigments, largely
astaxanthin, but also
canthaxanthin, in the flesh. Wild salmon get these carotenoids from eating
krill and other tiny
shellfish.
The vast majority of
Atlantic salmon available around the world are farmed (almost 99%), whereas the majority of
Pacific salmon are wild-caught (greater than 80%). Canned salmon in the US is usually wild Pacific catch, though some farmed salmon is available in canned form.
Smoked salmon is another popular preparation method, and can either be hot or cold
smoked.
Lox can refer to either cold-smoked salmon or salmon cured in a brine solution (also called
gravlax). Traditional canned salmon includes some skin (which is harmless) and bone (which adds calcium). Skinless and boneless canned salmon is also available.
Raw salmon flesh may contain
Anisakis nematodes, marine
parasites that cause
anisakiasis. Before the availability of
refrigeration, the
Japanese did not consume raw salmon. Salmon and salmon
roe have only recently come into use in making
sashimi (raw fish) and
sushi.
History
The salmon has long been at the heart of the culture and livelihood of coastal dwellers. Many people of the northern Pacific shore had a ceremony to honor the first return of the year. For many centuries, people caught salmon as they swam upriver to spawn. A famous
spearfishing site on the
Columbia River at
Celilo Falls was inundated after great dams were built on the river. The
Ainu, of northern Japan, trained dogs to catch salmon as they returned to their breeding grounds
en masse. Now, salmon are caught in bays and near shore.
The Columbia River salmon population is now less than 3% of what it was when
Lewis and Clark arrived at the river.
Salmon canneries established by settlers beginning in 1866 had a strong negative impact on the salmon population. In his 1908
State of the Union address, U.S. President
Theodore Roosevelt observed that the fisheries were in significant decline:
The salmon fisheries of the Columbia River are now but a fraction of what they were twenty—five years ago, and what they would be now if the United States Government had taken complete charge of them by intervening between Oregon and Washington. During these twenty—five years the fishermen of each State have naturally tried to take all they could get, and the two legislatures have never been able to agree on joint action of any kind adequate in degree for the protection of the fisheries. At the moment the fishing on the Oregon side is practically closed, while there is no limit on the Washington side of any kind, and no one can tell what the courts will decide as to the very statutes under which this action and non—action result. Meanwhile very few salmon reach the spawning grounds, and probably four years hence the fisheries will amount to nothing; and this comes from a struggle between the associated, or gill—net, fishermen on the one hand, and the owners of the fishing wheels up the river.
On the Columbia river the
Chief Joseph Dam completed in 1955 completely blocks salmon migration to the upper Columbia River system.
The
Fraser River salmon population was affected by the 1914 slide caused by the Canadian Pacific Railway at
Hells Gate. The 1917 catch was one quarter of the 1913 catch.
Mythology
Scales on the "Big Fish" or "Salmon of Knowledge" celebrates the return of fish to the
River Lagan
The salmon is an important creature in several strands of
Celtic mythology and poetry, which often associated them with wisdom and venerability. In
Irish mythology, a creature called the
Salmon of Knowledge plays key role in the tale
The Boyhood Deeds of Fionn. In the tale, the Salmon will grant powers of knowledge to whoever eats it, and is sought by poet
Finn Eces for seven years. Finally Finn Eces catches the fish and gives it to his young pupil,
Fionn mac Cumhaill, to prepare it for him. However, Fionn burns his thumb on the salmon's juices, and he instinctively puts it in his mouth. As such, he inadvertently gains the Salmon's wisdom. Elsewhere in Irish mythology, the salmon is also one of the incarnations of both
Tuan mac Cairill and
Fintan mac Bóchra.
Salmon also feature in
Welsh mythology. In the prose tale
Culhwch and Olwen, the Salmon of Llyn Llyw is the oldest animal in Britain, and the only creature who knows the location of
Mabon ap Modron. After speaking to a string of other ancient animals who do not know his whereabouts,
King Arthur's men
Cai and
Bedwyr are led to the Salmon of Llyn Llyw, who lets them ride its back to the walls of Mabon's prison in
Gloucester.
In
Norse mythology, after
Loki tricked the blind god
Höðr into killing his brother
Baldr, Loki jumped into a river and transformed himself into a salmon to escape punishment from the other
gods. When they held out a net to trap him he attempted to leap over it but was caught by
Thor who grabbed him by the tail with his hand, and this is why the salmon's tail is tapered.
Least concern[9]
Endangered[30]
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