| Salmon | |
|---|---|
 | |
| Atlantic salmon,Salmo salar | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Salmoniformes |
| Family: | Salmonidae |
| Subfamily: | Salmoninae |
| Groups included | |
| Cladistically included but traditionally excluded taxa | |
all other members ofSalmoninae | |
Salmon (/ˈsæmən/;pl.: salmon) are any of severalcommercially importantspecies ofeuryhalineray-finned fish from thegeneraSalmo andOncorhynchus of thefamilySalmonidae, native totributaries of theNorth Atlantic (Salmo) andNorth Pacific (Oncorhynchus) basins.Salmon is a colloquial orcommon name used for fish in this group, but is not ascientific name. Other closely related fish in the same family includetrout,char,grayling,whitefish,lenok andtaimen, allcoldwater fish of thesubarctic and coolertemperate regions with some sporadicendorheic populations inCentral Asia.
Salmon are typicallyanadromous: they hatch in the shallowgravelbeds offreshwaterheadstreams and spend theirjuvenile years inrivers,lakes and freshwaterwetlands, migrate to theocean asadults and live likesea fish, thenreturn to their freshwater birthplace toreproduce. However, populations of several species are restricted to fresh waters (i.e. landlocked) throughout their lives.Folklore has it that the fish return to the exactstream where they themselves hatched tospawn, and tracking studies have shown this to be mostly true. A portion of a returningsalmon run may stray and spawn in different freshwater systems; the percent of straying depends on the species of salmon.[1] Homing behavior has been shown to depend onolfactory memory.[2][3]
Salmon are importantfood fish and are intensivelyfarmed in many parts of the world,[4] withNorway being the world's largest producer of farmed salmon, followed byChile.[5] They are also highly prizedgame fish forrecreational fishing, by both freshwater and saltwateranglers. Many species of salmon have since beenintroduced andnaturalized into non-native environments such as theGreat Lakes ofNorth America,Patagonia inSouth America andSouth Island ofNew Zealand.[6]
The Modern English termsalmon is derived fromMiddle English:samoun,samon andsaumon, which in turn are fromAnglo-Norman:saumon, fromOld French:saumon, and fromLatin:salmō (which in turn might have originated fromsalire, meaning "to leap".[7]). The unpronounced "l" absent from Middle English was later added as aLatinisation to make the word closer to its Latin root. The termsalmon has mostly displaced its now dialectal synonymlax, in turn fromMiddle English:lax, fromOld English:leax, fromProto-Germanic: *lahsaz fromProto-Indo-European:*lakso-.[8][9]
The seven commercially important species of salmon occur in two genera of thesubfamilySalmoninae. The genusSalmo contains theAtlantic salmon, found in both sides of theNorth Atlantic, as well as more than 40 other species commonly named astrout. The genusOncorhynchus contains 12 recognised species which occur naturally only in the North Pacific, six of which are known asPacific salmon while the remainder are considered trout. Outside their native habitats,Chinook salmon have been successfully introduced inNew Zealand andPatagonia, whilecoho,sockeye and Atlantic salmon have been established in Patagonia, as well.[10]
| Atlantic and Pacific salmon | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Genus | Image | 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 salarLinnaeus, 1758 | 150 cm (4 ft 11 in) | 120 cm (3 ft 11 in) | 46.8 kilograms (103 lb) | 13 years | 4.4 | [11] | [12] | [13] |  Near threatened[14] |
| Oncorhynchus (Pacific salmon) |   | Chinook salmon | Oncorhynchus tshawytscha(Walbaum, 1792) | 150 cm (4 ft 11 in) | 70 cm (2 ft 4 in) | 61.4 kilograms (135 lb) | 9 years | 4.4 | [15] | [16] | [17] |  Least concern[18] |
  | Chum salmon | Oncorhynchus keta(Walbaum, 1792) | 100 cm (3 ft 3 in) | 58 cm (1 ft 11 in) | 15.9 kilograms (35 lb) | 7 years | 3.5 | [19] | [20] | [21] | Least concern[22] | |
  | Coho salmon | Oncorhynchus kisutch(Walbaum, 1792) | 108 cm (3 ft 7 in) | 71 cm (2 ft 4 in) | 15.2 kilograms (34 lb) | 5 years | 4.2 | [23] | [24] | [25] | Least concern[26] | |
 | Masu salmon | Oncorhynchus masou(Brevoort, 1856) | 79 cm (2 ft 7 in) | 50 cm (1 ft 8 in) | 10.0 kilograms (22.0 lb) | 3 years | 3.6 | [27] | [28] | Not assessed | ||
  | Pink salmon | Oncorhynchus gorbuscha(Walbaum, 1792) | 76 cm (2 ft 6 in) | 50 cm (1 ft 8 in) | 6.8 kilograms (15 lb) | 3 years | 4.2 | [29] | [30] | [31] | Least concern[32] | |
  | Sockeye salmon | Oncorhynchus nerka(Walbaum, 1792) | 84 cm (2 ft 9 in) | 58 cm (1 ft 11 in) | 7.7 kilograms (17 lb) | 8 years | 3.7 | [33] | [34] | [35] | Least concern[36] | |
† Both theSalmo andOncorhynchus genera also contain a number oftrout species informally referred to as salmon. WithinSalmo, theAdriatic salmon (Salmo obtusirostris) andBlack Sea salmon (Salmo labrax) have both been named as salmon inEnglish, although they fall outside the generally recognized seven salmon species. Themasu salmon (Oncorhynchus masou) is actually considered a trout ("cherry trout") inJapan, withmasu actually being theJapanese word for trout. On the other hand, thesteelhead andsea trout, the anadromous forms ofrainbow trout andbrown trout respectively, are from the same genera as salmon and live identical migratory lives, but neither is termed "salmon" .
| This article is part of a series on |
| Commercial fish |
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| Large predatory |
| Forage |
| Demersal |
| Mixed |
The extinctEosalmo driftwoodensis, the oldest knownSalmoninae fish in thefossil record, helps scientists figure how the different species of salmon diverged from acommon ancestor. TheEocene salmon's fossil fromBritish Columbia provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis ofmitochondrial DNA suggest the divergence occurred 10 to 20 million years ago during theMiocene. This independent evidence fromDNA analysis and the fossil record indicate that salmon divergence occurred long before theQuaternary glaciation began the cycle ofglacial advance and retreat.[37]
There are several other species of fish which are colloquially called "salmon" but are not true salmon. Of those listed below, the Danube salmon orhuchen is a large freshwatersalmonid closely related (from the same subfamily) to the seven species of salmon above, but others are fishes of unrelatedorders, given the common name "salmon" simply due to similar shapes, behaviors andniches occupied:
| Some other fishes called salmon | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Common name | Scientific name | Order | Maximum length | Common length | Maximum weight | Maximum age | Trophic level | Fish Base | FAO | ITIS | IUCN status |
| Australian salmon | Arripis trutta(Forster, 1801) | Perciformes | 89 cm (2 ft 11 in) | 47 cm (1 ft 7 in) | 9.4 kilograms (21 lb) | 26 years | 4.1 | [38] | [39] | Not assessed | |
| Danube salmon | Hucho hucho(Linnaeus, 1758) | Salmoniformes | 150 cm (4 ft 11 in) | 70 cm (2 ft 4 in) | 52 kilograms (115 lb) | 15 years | 4.2 | [40] | [41] |  Endangered[42] | |
| Hawaiian salmon | Elagatis bipinnulata(Quoy & Gaimard, 1825) | Carangiformes | 180 cm (5 ft 11 in) | 90 cm (2 ft 11 in) | 46.2 kilograms (102 lb) | 6 years | 3.6 | [43] | [44] | [45] | Not assessed |
| Indian salmon | Eleutheronema tetradactylum(Shaw, 1804) | Perciformes | 200 cm (6 ft 7 in) | 50 cm (1 ft 8 in) | 145 kilograms (320 lb) | years | 4.4 | [46] | [47] | Not assessed | |
Salmon eggs are laid in freshwater streams typically at high latitudes. Theeggs 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 withscales that are easily rubbed off. Only 10% of all salmon eggs are estimated to survive to this stage.[59]
The smolt body chemistry changes, allowing them to live in salt water. While a few species of salmon remain in fresh water throughout their life cycle, the majority areanadromous and migrate to the ocean for maturation: in these species, smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed toosmoregulation in the ocean. This body chemistry change is hormone-driven, causing physiological adjustments in the function of osmoregulatory organs such as the gills, which leads to large increases in their ability to secrete salt.[60] Hormones involved in increasingsalinity tolerance includeinsulin-like growth factor I,cortisol, andthyroid hormones,[61] which permits the fish to endure the transition from a freshwater environment to the ocean.
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. Grilse may be present at spawning, and go unnoticed by large males, releasing their own sperm on the eggs.[62]
Prior to spawning, depending on thespecies, salmon undergo changes. They may grow a hump, develop canine-like teeth, or develop akype (a pronounced curvature of the jaws in male salmon). All 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 1,400 km (900 mi) and climb nearly 2,100 m (7,000 ft) 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 assemelparity. 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 herroe, 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 2.8 m2 (30 sq ft).[63] The eggs usually range from orange to red. One or more males approach the female in her redd, depositing sperm, or milt, over the roe.[57] 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 may make as many as seven redds before her supply of eggs is exhausted.[57]
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 theotolith (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 andestuaries provide important habitat for many salmon species. They feed onterrestrial andaquatic insects,amphipods, and othercrustaceans 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 associatedwetlands 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 ofcorticosteroids.
Salmon are mid-levelcarnivores whose diet change according to their life stage. Salmonfry predominantly feed uponzooplankton until they reachfingerling sizes, when they start to consume more aquaticinvertebrates such asinsect larvae, microcrustaceans andworms. Asjuveniles (parrs), they become more predatory and actively prey uponaquatic insects, small crustaceans,tadpoles and smallbait fishes. They are also known to breach the water to attack terrestrial insects such asgrasshoppers anddragonflies,[64] as well as consumingfish eggs (even those of other salmon).
As adults, salmon behave like other mid-sizedpelagic fish, eating a variety of sea creatures including smallerforage fish such aslanternfish,herrings,sand lances,mackerels andbarracudina. They also eatkrill,squid andpolychaete worms.[65]
In thePacific Northwest andAlaska, salmon arekeystone species.[66] The migrations of salmon represent a massive retrogradenutrient transfer, rich innitrogen,sulfur,carbon andphosphorus, from the ocean to the inlandfreshwater ecosystems. Predation bypiscivorous land animals (such asospreys,bears andotters) along the journey serve to transfer the nutrients from the water to land, anddecomposition of salmon carcasses benefits theforest ecosystem.
In the case ofPacific salmon, most (if not all) of the salmon that survive to reach theheadwater spawning grounds willdie after laying eggs and their dead bodies sink to cover the gravel beds, with the nutrients released from thebiodegradation of their corpses providing a significant boost to these otherwisebiomass-poor shallow streams.
Grizzly bears function asecosystem engineers, capturing salmon and carrying them into adjacent dry land to eat the fish. There they deposit nutrient-rich urine and feces and partially eaten carcasses. Bears preparing forhibernation tend to preferentially consume the more nutrient- andenergy-richsalmon roes andbrain over the actualflesh,[67] and are estimated to discard up to half the salmon they've harvested uneaten on the forest floor,[68][69] in densities that can reach 4,000 kg (8,800 lb) per hectare,[70] providing as much as 24% of the total nitrogen available to theriparianwoodlands. The foliage ofspruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from the fished salmon.[71]
Beavers also function as ecosystem engineers; in the process of tree-cutting anddamming, beavers alter the local ecosystems extensively. Beaver ponds can provide critical habitat forjuvenile salmon.
An example of this was seen in the years following 1818 in theColumbia 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 (seeTreaty of 1818). At the time, theHudson's Bay Company sent word totrappers 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:[72][73][74]
Beaver dams are able to nurture salmon juveniles in estuarinetidal marshes where the salinity is less than 10 ppm. Beavers build small dams of generally less than 60 cm (2 ft) high in channels in themyrtle zone[clarification needed]. 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 by larger fish.[75]
It has been discovered that rivers which have seen a decline or disappearance of anadromouslampreys, loss of the lampreys also affects the salmon in a negative way. Like salmon, anadromous lampreys stop feeding and die after spawning, and their decomposing bodies release nutrients into the stream. Also, along with species likerainbow trout andSacramento sucker, lampreys clean the gravel in the rivers during spawning.[76] Their larvae, called ammocoetes, arefilter feeders which contribute to the health of the waters. They are also a food source for the young salmon, and being fattier and oilier, it is assumed predators prefer them over salmon offspring, taking off some of the predation pressure on smolts.[77][unreliable source?] Adult lampreys are also the preferred prey of seals and sea lions, which can eat 30 lampreys to every salmon, allowing more adult salmon to enter the rivers to spawn without being eaten by the marine mammals.[78][79]
According to Canadian biologist Dorothy Kieser, themyxozoan parasiteHenneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to theHaida 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 themyxosporean group have complex life cycles, where the salmon is one of two hosts. The fish releases the spores after spawning. In theHenneguya 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 causeswhirling disease in trout has a similar life cycle.[80] However, as opposed to whirling disease, theHenneguya 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 onHenneguya salminicola was done by scientists at the Pacific Biological Station in Nanaimo in the mid-1980s, in particular, an overview report[81] which states, "the fish that have the longest fresh water residence time as juveniles have the most noticeable infections. Hence in order ofprevalence, 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 asFraser,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 thatHenneguya, economically deleterious though it is, is harmless from the view ofpublic health. It is strictly afish parasite that cannot live in or affectwarm blooded animals, including man".
According to Klaus Schallie, Molluscan Shellfish Program Specialist with theCanadian 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 inBarkley Sound (southern B.C., west coast ofVancouver Island) are noted for their high incidence of infestation."[citation needed]
Sea lice, particularlyLepeophtheirus salmonis and variousCaligus species, includingC. clemensi andC. rogercresseyi, can cause deadly infestations of both farm-grown and wild salmon.[82][83] Sea lice areectoparasites 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.[84][85][86]
Large numbers of highly populated, open-net salmon farms[A]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.[88][89] Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable. On thePacific coast of Canada, the louse-induced mortality of pink salmon in some regions is commonly over 80%.[90]
The risk of injury caused byunderwater pile driving has been studied by Dr. Halvorsen and her co-workers.[91] The study concluded that the fish are at risk of injury if the cumulativesound exposure level exceeds 210dB relative to 1 μPa2 s.[clarification needed]
As can be seen from the production chart, the global capture reported by different countries to theFAO 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.[48]
Nearly all captured wild salmon arePacific salmon. The capture of wildAtlantic salmon has always been relatively small, and has declined steadily since 1990. In 2011 only 2,500 tonnes were reported.[12] In contrast, about half of all farmed salmon are Atlantic salmon.
Recreational salmon fishing can be a technically demanding kind ofsport fishing, not necessarily intuitive for beginning fishermen.[92] A conflict exists betweencommercial fishermen and recreational fishermen for the right to salmonstock resources. Commercial fishing inestuaries andcoastal 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 salmon sport fishing has completely replaced inshore commercial salmon fishing.[93] In most cases, the commercial value of a salmon sold asseafood can be several times less than the value attributed to the same fish caught by a sport fisherman. This is "a powerful economic argument for allocating stock resources preferentially to sport fishing".[93]
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Salmonaquaculture is a major contributor to the world production of farmed finfish, representing about US$10 billion annually. Other commonly cultured fish species includetilapia,catfish,sea bass,carp andbream. Salmon farming is significant inChile,Norway,Scotland, Canada and theFaroe Islands; it is the source for most salmon consumed in the United States and Europe. Atlantic salmon are also, in very small volumes, farmed in Russia andTasmania, Australia.
Salmon arecarnivorous, and need to be fed meals produced from catching other wildforage fish and other marine organisms. Salmon farming leads to a high demand for wildforage fish. As a predator, salmon require large nutritional intakes ofprotein, and farmed salmon consume more fish than they generate as a final product. On a dry weight basis, 2–4 kg of wild-caught fish are needed to produce one kilogram of salmon.[94] As the salmon farming industry expands, it requires more forage fish for feed, at a time when 75% of the world's monitored fisheries are already near to or have exceeded theirmaximum sustainable yield.[95] The industrial-scale extraction of wild forage fish for salmon farming affects the survivability of other wild predatory fish which rely on them for food. Research is ongoing into sustainable and plant-based salmon feeds.[96]
Intensive salmon farming uses open-net cages, which have low production costs. It has the drawback of allowing disease andsea lice to spread to local wild salmon stocks.[97]
Another form of salmon production, which is safer but less controllable, is to raise salmon inhatcheries until they are old enough to become independent. They are released into rivers in an attempt to increase the salmon population. This system is referred to asranching. It 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, a company is limited in benefiting financially from their investment.
Because of this, the ranching method has mainly been used by various public authorities and non-profit groups, such as theCook Inlet Aquaculture Association, as a way to increase salmon populations in situations where they have declined due tooverharvesting, construction ofdams andhabitat destruction orfragmentation. Negative consequences to this sort of population manipulation include genetic "dilution" of the wild stocks. Many jurisdictions are now beginning to discourage supplemental fish planting in favour of harvest controls, and habitat improvement and protection.
A variant method offish stocking, called ocean ranching, is under development inAlaska. 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 catch them.
An alternative method to hatcheries is to use spawning channels. These areartificial 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 that destroy natural redds also clean the regular streams. Spawning channels preserve the natural selection of natural streams, as there is no benefit, as in hatcheries, to use prophylactic chemicals to control diseases.[citation needed]
Farm-raised salmon are fed the carotenoidsastaxanthin andcanthaxanthin to match their flesh colour to wild salmon[98] to improve their marketability.[99] Wild salmon get thesecarotenoids, primarily astaxanthin, from eatingshellfish andkrill.
One proposed alternative to the use of wild-caught fish as feed for the salmon, is the use ofsoy-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. The fish omega-3 fatty acid content would be reduced compared to fish-fed salmon.
Another possible alternative is a yeast-based coproduct ofbioethanol production,proteinaceous fermentation biomass. Substituting such products for engineered feed can result in equal (sometimes enhanced) growth in fish.[100] With its increasing availability, this would address the problems of rising costs for buying hatcheryfish feed.
Yet another attractive alternative is the increased use ofseaweed. Seaweed provides essential minerals and vitamins for growing organisms. It offers the advantage of providing natural amounts ofdietary fiber and having a lowerglycemic load than grain-basedfish meal.[100] 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.[101][failed verification]
Salmonpopulation levels are of concern in the Atlantic and in some parts of the Pacific.[103] 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 theSnake and Columbia River systems in northwestern United States.
Alaska fishery stocks are still abundant, and catches have been on the rise in recent decades, after the state initiated limitations in 1972.[104][105][citation needed] Some of the most important Alaskan salmon sustainablewild fisheries are located near theKenai River,Copper River, and inBristol Bay.Fish farming of Pacific salmon is outlawed in the United StatesExclusive Economic Zone,[106] however, there is a substantial network of publicly fundedhatcheries,[107] and the State of Alaska'sfisheries management system is viewed as a leader in the management of wildfish stocks.
In Canada, returningSkeena River wild salmon supportcommercial,subsistence andrecreational 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.[108]
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.[109] Both Atlantic and Pacific salmon are popularsportfish.
Salmon populations have been established in all the Great Lakes. Coho stocks were planted by the state of Michigan in the late 1960s to control the growing population of non-nativealewife. 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.
Wild, self-sustaining Pacific salmon populations have been established in New Zealand, Chile, and Argentina.[110] They are highly prized by sport fishers, but others worry about displacing native fish species.[111] Also, and especially in Chile (Aquaculture in Chile), both Atlantic and Pacific salmon are used in net pen farming.
In 2020 researchers reported widespread declines in the sizes of four species of wildPacific salmon: Chinook, chum, coho, and sockeye. These declines have been occurring for 30 years, and are thought to be associated with climate change and competition with growing numbers of pink and hatchery salmon.[112][102]
Salmon is a popularfood fish. Classified as anoily fish,[113] salmon is considered to be healthy due to the fish's highprotein, highomega-3 fatty acids, and highvitamin D[114] content. Salmon is also a source ofcholesterol, with a range of23–214 mg/100 g depending on the species.[115] According to reports in the journalScience, farmed salmon may contain high levels ofdioxins.[medical citation needed] PCB (polychlorinated biphenyl) levels may be up to eight times higher in farmed salmon than in wild salmon,[116] but still well below levels considered dangerous.[117][118] Nonetheless, according to a 2006 study published in theJournal of the American Medical Association, the benefits of eating even farmed salmon still outweigh any risks imposed by contaminants.[119] Farmed salmon has a high omega-3 fatty acid content comparable to wild salmon.[120] The type of omega-3 present may not be a factor for other important health functions.[vague]
Salmon flesh is generally orange to red, although white-fleshed wild salmon with white-black skin colour occurs. The natural colour of salmon results fromcarotenoid pigments, largelyastaxanthin, but alsocanthaxanthin, in the flesh.[121] Wild salmon get these carotenoids from eatingkrill and other tinyshellfish.
The vast majority ofAtlantic salmon available in market around the world are farmed (almost 99%),[122] whereas the majority ofPacific salmon are wild-caught (greater than 80%). Canned salmon in the U.S. 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 calledgravlax). 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 containAnisakisnematodes, marineparasites that causeanisakiasis. Before the availability ofrefrigeration, theJapanese did not consume raw salmon. Salmon and salmonroe have only recently come into use in makingsashimi (raw fish) andsushi.[123]
To theIndigenous peoples of the Pacific Northwest Coast, salmon is considered a vital part of the diet. Specifically, the indigenous peoples ofHaida Gwaii, located near formerQueen Charlotte Island inBritish Columbia, rely on salmon as one of their main sources of food, although many other bands have fished Pacific waters for centuries.[124] Salmon are not only ancient and unique, but it is important because it is expressed in culture, art forms, and ceremonial feasts. Annually, salmon spawn in Haida, feeding on everything on the way upstream and down.[124] Within the Haida nation, salmon is referred to as"tsiin",[124] and is prepared in several ways including smoking, baking, frying, and making soup.
Historically, there has always been enough salmon, as traditionalsubsistence fishing methods did not result in overfishing, and people only took what they needed.[125] In 2003, a report onFirst Nations participation in commercial fisheries, including salmon, commissioned by BC'sMinistry of Agriculture and Food found that there were 595 First Nation-owned and operated commercial vessels in the province. Of those vessels, First Nations' members owned 564.[125] However, employment within the industry has decreased overall by 50% in the last decade, with 8,142 registered commercial fishermen in 2003. This has affected employment for many fisherman, who rely on salmon as a source of income.[relevant?]
Black bears also rely on salmon as food. The leftovers the bears leave behind are considered important nutrients for theCanadian forest, such as the soil, trees and plants. In this sense, the salmon feed the forest and in return receive clean water and gravel in which to hatch and grow, sheltered from extremes of temperature and water flow in times of high and low rainfall.[124] However, the condition of the salmon in Haida has been affected in recent decades. Due to logging and development, much of the salmon's habitat (i.e.,Ain River) has been destroyed, resulting in the fish being close to endangered.[124] For residents, this has resulted in limits on catches, which, in turn, has affected families' diets and cultural events such as feasts. Some of the salmon systems in danger include the Davidon, Naden, Mamim, and Mathers.[124]
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The salmon has long been at the heart of the culture and livelihood of coastal dwellers, which can be traced as far back as 5,000 years when archeologists discoveredNisqually tribe remnants.[126] The original distribution of the genusOncorhynchus covered the Pacific Rim coastline.[127] History shows salmon used tributaries, rivers and estuaries without regard to jurisdiction for 18–22 million years. Baseline data is near impossible to recreate based on the inconsistent historical data, but there has been massive depletion since the 1900s. ThePacific Northwest once sprawled with native inhabitants who ensured little degradation was caused by their actions to salmon habitats. Asanimists, the indigenous people relied not only for salmon for food, but spiritual guidance. The role of the salmon spirit guided the people to respect ecological systems such as the rivers and tributaries the salmon used for spawning. Natives often used the entire fish and left little waste by turning the bladder into glue, and using bones for toys and skin for clothing and shoes. The original salmon ceremony, introduced by indigenous tribes on the Pacific coast, consisted of three major parts. First was the welcoming of the first catch, and then the cooking of it. Finally the bones were returned to the sea to induce hospitality so other salmon would give their lives to the people of that village.[128]
Many tribes, such as theYurok, had ataboo against harvesting the first fish that swam upriver in summer, but once they confirmed that thesalmon run had returned in abundance they would begin to catch them in plentiful.[129] The indigenous practices were guided by deep ecological wisdom, which was eradicated when Euro-American settlements began to be developed.[130] Salmon have a much grander history than what is presently shown today. The salmon that once dominated the Pacific Ocean are now just a fraction in population and size. The Pacific salmon population is now less than 1–3% of what it was whenLewis and Clark arrived at the region.[131] In his 1908State of the Union address, U.S. PresidentTheodore Roosevelt observed that the fisheries were in significant decline:[132][133]
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 theColumbia River, theChief Joseph Dam completed in 1955 completely blocks salmon migration to the upper Columbia River system.
TheFraser River salmon population was affected by the 1914 slide caused by theCanadian Pacific Railway atHells Gate. The 1917 catch was one quarter of the 1913 catch.[134]
Theorigin of the word for "salmon" was one of the arguments about the location of the origin of theIndo-European languages.
The salmon is an important creature in several strands ofCeltic mythology and poetry, which often associated them with wisdom and venerability. In Irish folklore, fishermen associated salmon with fairies and thought it was unlucky to refer to them by name.[135] InIrish mythology, a creature called theSalmon of Knowledge[136] plays a key role in the taleThe Boyhood Deeds of Fionn. In the tale, the Salmon will grant powers of knowledge to whoever eats it, and is sought by poetFinn 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. In so doing, he inadvertently gains the Salmon's wisdom. Elsewhere in Irish mythology, the salmon is also one of the incarnations of bothTuan mac Cairill[137] andFintan mac Bóchra.[138]
Salmon also feature inWelsh mythology. In the prose taleCulhwch and Olwen, the Salmon of Llyn Llyw is the oldest animal in Britain, and the only creature who knows the location ofMabon ap Modron. After speaking to a string of other ancient animals who do not know his whereabouts,King Arthur's menCai andBedwyr are led to the Salmon of Llyn Llyw, who lets them ride its back to the walls of Mabon's prison inGloucester.[139]
InNorse mythology, afterLoki tricked the blind godHöðr into killing his brotherBaldr, Loki jumped into a river and transformed himself into a salmon to escape punishment from the othergods. When they held out a net to trap him he attempted to leap over it but was caught byThor who grabbed him by the tail with his hand, and this is why the salmon's tail is tapered.[140]
Salmon are central spiritually and culturally toNative American mythology on the Pacific coast, from theHaida andCoast Salish peoples, to theNuu-chah-nulth peoples inBritish Columbia.[141]
Text and images are available under aCreative Commons Attribution 4.0 International License.
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