Salmon
Encyclopedia
Salmon is the common name for several species of fish in the family
Salmonidae
. Several other fish in the same family are called trout
; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true. Salmon live along the coasts of both the North Atlantic (one migratory species Salmo salar
) and Pacific Oceans (approximately a dozen species of the genus Oncorhynchus
), and have also been introduced into the Great Lakes
of North 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, there are populations of several species that are restricted to fresh water through their life. 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
.
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. It is estimated that only 10% of all salmon eggs survive to this stage. The smolt body chemistry changes, allowing them to live in salt water. Smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation
in 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 stream to spawn. In Alaska, the crossing-over to other streams allows salmon to populate new streams, such as those that emerge as a glacier
retreats. The precise method salmon use to navigate has not been established, though their keen sense of smell is involved. 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, Britian 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 (1,448.4 km) and climb nearly 7000 feet (2,133.6 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), post-spawning 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 m²). 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 associations 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 that are 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 corticosteroid
s.
Eosalmo driftwoodensis, the oldest known salmon fossil 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 that 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.
The Atlantic Ocean has only one species of salmon, in the genus Salmo
:
, some examples include;
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.
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
, 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 stock
s. 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. Out of 435 wild stocks of salmon and steelhead, only 187 of them were classified as healthy; 113 had an unknown status, 1 was extinct, 12 were in critical condition and 122 were experiencing depressed populations. The Columbia River salmon population is now less than 3% of what it was when Lewis and Clark
arrived at the river. 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 sportfishery.
Salmon aquaculture
is the major economic contributor to the world production of farmed fin-fish, representing over US$1 billion annually. Other commonly cultured fish species include: tilapia
, catfish
, sea bass
, carp
, bream, and trout
. 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 who rely on them for food.
Work continues on substituting vegetable protein
s 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 carotenoid
s astaxanthin
and canthaxanthin
to match their flesh color to wild salmon.
According to Canadian biologist Dorothy Kieser, the myxozoa
n parasite Henneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to the Queen Charlotte 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 a complex life cycle, 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 that "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 that, 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%.
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 system in northwestern United States. The decline is attributed to the following factors:
Several governments and nongovernmental organizations (NGOs) are sharing in research and habitat restoration efforts to relieve this situation.
Results overall show estuary problems exist for some rivers, but issues involving feeding grounds at sea are impacting populations as well. In 2008, returns were markedly improved for Atlantic salmon on both sides of the Atlantic Ocean, but no one knows if this is a temporary improvement or sign of a trend.
sockeye to determine age and size at maturity trends attributable to the selectivity of commercial gillnet harvests. The study found that the larger females (>550 mm) of all age classes were most susceptible to harvest. The study suggests that smaller, younger fish were more likely to successfully traverse the gillnet fishery and reproduce than the larger fish. The study also found that the average length of sockeye harvested from 1946–2005 was 8 mm larger than the sockeye who escaped the gillnet fishery to spawn, reducing the fecundity of the average female by 5%, or 104 eggs.
s are archetypal ecosystem engineer
s; in the process of clear cutting and damming, beavers alter their ecosystem 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 run
s 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:
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 (61 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.
, 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. Omega-3 content may also be lower than in wild-caught specimens, and in a different proportion to what is found naturally. Omega-3 comes in three types, alpha-linolenic acid
(ALA), docosahexaenoic acid
(DHA) and eicosapentaenoic acid
(EPA); wild salmon has traditionally been an important source of DHA and EPA, which are important for brain function and structure, among other things. The body can itself convert ALA omega-3 into DHA and EPA, but at a very inefficient rate (2–15%). 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.
A simple rule of thumb is that the vast majority of Atlantic salmon
available on the world market are farmed (greater than 99%), whereas the majority of Pacific salmon
are wild caught (greater than 80%). Farmed Atlantic salmon outnumber wild Atlantic salmon 85-to-1.
Salmon flesh is generally orange to red, although there are some examples of white-fleshed wild salmon. 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
. Because consumers have shown a reluctance to purchase white-fleshed salmon, astaxanthin (E161j), and very minutely canthaxanthin (E161g), are added as artificial colorants to the feed of farmed salmon, because prepared diets do not naturally contain these pigments. In most cases, the astaxanthin is made chemically; alternatively it is extracted from shrimp flour. Another possibility is the use of dried red yeast, which provides the same pigment. However, synthetic mixtures are the least expensive option. Astaxanthin is a potent antioxidant
that stimulates the development of healthy fish nervous system
s and enhances the fish's fertility and growth rate. Research has revealed canthaxanthin may have negative effects on the human eye, accumulating in the retina at high levels of consumption. Today, the concentration of carotenoids (mainly canthaxanthin and astaxanthin) exceeds 8 mg/kg of flesh, and all fish producers try to reach a level that represents a value of 16 on the "Roche Color Card", a colour card used to show how pink the fish will appear at specific doses. This scale is specific for measuring the pink colour due to astaxanthin and is not for the orange hue obtained with canthaxanthin. The development of processing and storage operations, which can be detrimental on canthaxanthin flesh concentration, has led to an increased quantity of pigments added to the diet to compensate for the degrading effects of the processing. In wild fish, carotenoid levels of up to 25 mg are present, but levels of canthaxanthin are, in contrast, minor.
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 either to cold smoked salmon or to 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
nematode
s, marine parasites that cause Anisakiasis. Before the availability of refrigeration
, Japanese did not consume raw salmon. Salmon and salmon roe
have only recently come into use in making sashimi
(raw fish) and sushi
.
and poetry, which often associated them with wisdom and venerability. In Irish mythology
, a creature called the Salmon of Wisdom
(or the Salmon of Knowledge) plays key role in the tale known as The Boyhood Deeds of Fionn
. The Salmon will grant powers of knowledge to whoever eats it, and has been sought by the 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 in order 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.
Salmon are central to Native American mythology
on the Pacific coast, from the Haida to the Nootka.
Partnership. The Puget Sound Partnership is currently working to implement policy change at the local level to alter the fate of salmon. Salmon recovery is guided by implementation of the Puget Sound Salmon Recovery Plan, adopted by the National Oceanic and Atmospheric Administration (NOAA) in January 2007. This recovery plan was developed by Shared Strategy, a grassroots collaborative effort to protect and restore salmon runs across Puget Sound. The Puget Sound Partnership has now rehabilitated over 800 acres of salmon habitat and it plans to continue to fight nearshore development and human impact affecting important salmon ecosystems. The Partnership's Action Agenda plans to instigate the Elwha Dam
removal, begin restoration of the Nisqually Estuary and removal of derelict Fishing gear, and continue with the current salmon Recovery Plan. In order to ensure the future of Pacific Northwest salmon, the Partnership continues to encourage Stormwater & Low Impact Development
, and advocates the "Puget Sound Starts Here" public education program.
Another notable local relief effort is the People for Puget Sound. People for Puget Sound is a citizen group founded by Kathy Fletcher in 1991 working to restore the health of our local land and waters with help from volunteers in the Puget Sound basin.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Salmonidae
Salmonidae
Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...
. Several other fish in the same family are called trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true. Salmon live along the coasts of both the North Atlantic (one migratory species Salmo salar
Atlantic salmon
The Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
) and Pacific Oceans (approximately a dozen species of the genus Oncorhynchus
Oncorhynchus
Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...
), and have also been introduced into the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
of North America. Salmon are intensively produced in aquaculture in many parts of the world.
Typically, salmon are anadromous
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
: they are born in fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
, migrate to the ocean, then return to fresh water to reproduce. However, there are populations of several species that are restricted to fresh water through their life. Folklore
Folklore
Folklore consists of legends, music, oral history, proverbs, jokes, popular beliefs, fairy tales and customs that are the traditions of a culture, subculture, or group. It is also the set of practices through which those expressive genres are shared. The study of folklore is sometimes called...
has it that the fish return to the exact spot where they were born to spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
; tracking studies have shown this to be true, and this homing behavior has been shown to depend on olfactory memory
Olfactory memory
Olfactory memory refers to the recollection of odours. Studies have found various characteristics of common memories of odour memory including persistence and high resistance to interference...
.
Life cycle
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. It is estimated that only 10% of all salmon eggs survive to this stage. The smolt body chemistry changes, allowing them to live in salt water. Smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...
in 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 stream to spawn. In Alaska, the crossing-over to other streams allows salmon to populate new streams, such as those that emerge as a glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
retreats. The precise method salmon use to navigate has not been established, though their keen sense of smell is involved. 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, Britian and Ireland.) Prior to spawning, depending on the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, 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 (1,448.4 km) and climb nearly 7000 feet (2,133.6 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), post-spawning mortality is quite high (perhaps as high as 40 to 50%.)
To lay her roe
Roe
Roe or hard roe is the fully ripe internal egg masses in the ovaries, or the released external egg masses of fish and certain marine animals, such as shrimp, scallop and sea urchins...
, 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 m²). 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.
Otolith
An otolith, , also called statoconium or otoconium is a structure in the saccule or utricle of the inner ear, specifically in the vestibular labyrinth of vertebrates. The saccule and utricle, in turn, together make the otolith organs. They are sensitive to gravity and linear acceleration...
, (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
Aquatic insects
Aquatic insects live some portion of their life cycle in the water. They feed in the same ways as other insects. Some diving insects, such as predatory diving beetles, can hunt for food underwater where land-living insects cannot compete.-Breathing:...
, 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 associations 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 that are not killed by other means show greatly accelerated deterioration (phenoptosis
Phenoptosis
Phenoptosis signifies the phenomenon of programmed cell death of an organism, ie that an organism's biology includes features that under certain circumstances will cause it to rapidly degenerate and die off...
, 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 corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s.
Species
The various species of salmon have many names, and varying behaviors.Eosalmo driftwoodensis, the oldest known salmon fossil 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 that 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.
Atlantic Ocean species
Salmo
Salmo is a genus of fish in the salmon family that includes the familiar species Atlantic salmon and brown trout . The natural distribution of the genus is chiefly European. Only the range of the Atlantic salmon extends to northern North America...
:
- Atlantic salmonAtlantic salmonThe Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
, or salmon, (Salmo salar) reproduce in northern rivers on both coasts of the ocean.- Land-locked salmon (Salmo salar m. sebago) live in a number of lakes in eastern North America and in Northern Europe, for instance in lakes Great LakesGreat LakesThe Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
, OnegaLake OnegaLake Onega is a lake in the north-west European part of Russia, located on the territory of Republic of Karelia, Leningrad Oblast and Vologda Oblast. It belongs to the basin of Baltic Sea, Atlantic Ocean, and is the second largest lake in Europe after Lake Ladoga...
, LadogaLake LadogaLake Ladoga is a freshwater lake located in the Republic of Karelia and Leningrad Oblast in northwestern Russia, not far from Saint Petersburg. It is the largest lake in Europe, and the 14th largest lake by area in the world.-Geography:...
, SaimaaSaimaaSaimaa is a lake in southeastern Finland. At approximately , it is the largest lake in Finland, and the fourth largest in Europe. It was formed by glacial melting at the end of the Ice Age. Major towns on the lakeshore include Lappeenranta, Imatra, Savonlinna, Mikkeli, Varkaus, and Joensuu. The...
and VänernVänernVänern is the largest lake in Sweden, the largest lake in the EU and the third largest lake in Europe after Ladoga and Onega in Russia. It is located in the provinces of Västergötland, Dalsland, and Värmland in the southwest of the country.- History :...
. 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 can access the ocean.
- Land-locked salmon (Salmo salar m. sebago) live in a number of lakes in eastern North America and in Northern Europe, for instance in lakes Great Lakes
Pacific Ocean species
Pacific species belong to the genus OncorhynchusOncorhynchus
Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...
, some examples include;
- Cherry salmon or seema (Oncorhynchus masou) is found only in the western Pacific Ocean in Japan, Korea and Russia. There is also a land-locked subspecies known as the Taiwanese salmon or Formosan salmon (Oncorhynchus masou formosanum) in central Taiwan's Chi Chia Wan Stream.
- Chinook salmonChinook salmonThe Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...
(Oncorhynchus tshawytscha) is also known in the US as king or blackmouth salmon, and as spring salmon in British Columbia. Chinook are the largest of all Pacific salmon, frequently exceeding 30 lb (13.6 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 HogsJune HogsIn the parlance of the Pacific Northwest of the United States, June Hogs were the largest Chinook salmon caught in the summer migratory runs of the fish...
. Chinook salmon are known to range as far north as the Mackenzie River and Kugluktuk in the central Canadian arctic. - Chum salmonChum salmonThe chum salmon, Oncorhynchus keta, is a species of anadromous fish in the salmon family. It is a Pacific salmon, and may also be known as dog salmon or Keta salmon, and is often marketed under the name Silverbrite 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 RiverSacramento RiverThe Sacramento River is an important watercourse of Northern and Central California in the United States. The largest river in California, it rises on the eastern slopes of the Klamath Mountains, and after a journey south of over , empties into Suisun Bay, an arm of the San Francisco Bay, and...
in California in the eastern Pacific and the island of KyūshūKyushuis the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include , , and . The historical regional name is referred to Kyushu and its surrounding islands....
in the Sea of JapanSea of JapanThe Sea of Japan is a marginal sea of the western Pacific Ocean, between the Asian mainland, the Japanese archipelago and Sakhalin. It is bordered by Japan, North Korea, Russia and South Korea. Like the Mediterranean Sea, it has almost no tides due to its nearly complete enclosure from the Pacific...
in the western Pacific; north to the Mackenzie RiverMackenzie RiverThe Mackenzie River is the largest river system in Canada. It flows through a vast, isolated region of forest and tundra entirely within the country's Northwest Territories, although its many tributaries reach into four other Canadian provinces and territories...
in Canada in the east and to the Lena RiverLena RiverThe Lena is the easternmost of the three great Siberian rivers that flow into the Arctic Ocean . It is the 11th longest river in the world and has the 9th largest watershed...
in Siberia in the west.
- Coho salmonCoho salmonThe Coho salmon, Oncorhynchus kisutch, is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers". It is the state animal of Chiba, Japan.-Description:...
(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 up most clear-running streams and rivers. It is also now known to occur, albeit infrequently, in the Mackenzie River. - Pink salmonPink salmonPink salmon or humpback salmon, Oncorhynchus gorbuscha, is a species of anadromous fish in the salmon family. It is the smallest and most abundant of the Pacific salmon.- Appearance :...
(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 RiverMackenzie RiverThe Mackenzie River is the largest river system in Canada. It flows through a vast, isolated region of forest and tundra entirely within the country's Northwest Territories, although its many tributaries reach into four other Canadian provinces and territories...
in Canada to the Lena RiverLena RiverThe Lena is the easternmost of the three great Siberian rivers that flow into the Arctic Ocean . It is the 11th longest river in the world and has the 9th largest watershed...
in Siberia, usually in shorter coastal streams. It is the smallest of the Pacific species, with an average weight of 3+1/2 to-. - Sockeye salmonSockeye salmonSockeye salmon , also called red salmon or blueback salmon in the USA, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it...
(Oncorhynchus nerka) is also known in the US as red salmon. This lake-rearing species is found south as far as the Klamath RiverKlamath RiverThe Klamath River is an American river that flows southwest through Oregon and northern California, cutting through the Cascade Range to empty into the Pacific Ocean. The river drains an extensive watershed of almost that stretches from the high desert country of the Great Basin to the temperate...
in California in the eastern Pacific and northern HokkaidōHokkaido, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island; it is also the largest and northernmost of Japan's 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaido from Honshu, although the two islands are connected by the underwater railway Seikan Tunnel...
island in Japan in the western Pacific and as far north as Bathurst InletBathurst InletBathurst Inlet is a deep inlet located along the northern coast of the Canadian mainland, into which the Burnside and Western Rivers empty. The name, or its native equivalent Kingoak , is also used to identify the community of Bathurst Inlet located on the shore.-Plans for a deep-water port:A...
in the Canadian Arctic in the east and the Anadyr RiverAnadyr RiverAnadyr is a river in the far northeast Siberia which flows into Anadyr Bay of the Bering Sea and drains much of the interior of Chukotka Autonomous Okrug. Its basin corresponds to the Anadyrsky District of Chukotka....
in SiberiaSiberiaSiberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
in the west. Although most adult Pacific salmon feed on small fish, shrimp and squid; sockeye feed on planktonPlanktonPlankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
that they filter through gill rakers. Kokanee salmon is a land-locked form of sockeye salmon.
Other species
- The huchenHuchenThe huchen or Danube salmon is a species of freshwater fish in the salmon family of order Salmoniformes. It is the type species of its genus...
or Danube salmon (Hucho hucho), the largest permanent fresh water salmonid species.
Salmon fisheries
Spearfishing
Spearfishing is an ancient method of fishing that has been used throughout the world for millennia. Early civilizations were familiar with the custom of spearing fish from rivers and streams using sharpened sticks....
site on the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
at Celilo Falls
Celilo Falls
Celilo Falls was a tribal fishing area on the Columbia River, just east of the Cascade Mountains, on what is today the border between the U.S. states of Oregon and Washington...
was inundated after great dams were built on the river. The Ainu
Ainu people
The , also called Aynu, Aino , and in historical texts Ezo , are indigenous people or groups in Japan and Russia. Historically they spoke the Ainu language and related varieties and lived in Hokkaidō, the Kuril Islands, and much of Sakhalin...
, 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.
Salmon population levels
Population dynamics of fisheries
A fishery is an area with an associated fish or aquatic population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed. Population dynamics describes the ways in which a given population grows and shrinks over time, as controlled by birth, death, and...
are of concern in the Atlantic and in some parts of the Pacific. Alaska fishery
Alaska salmon fishery
The Alaskan salmon fishery was saved due to strict mitigation measures and the implementation of policies. Alaska's successful conservation of their salmon resources is reflected in recent healthy and abundant salmon runs...
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
Wild fisheries of the world
A fishery is an area with an associated fish or aquatic population which is harvested for its commercial value. Fisheries can be marine or freshwater. They can also be wild or farmed. This article is an overview of the habitats occupied by the worlds' wild fisheries, and the human impacts on those...
are located near the Kenai River
Kenai River
The Kenai River called Kakny in the Dena'ina language, is a river in the Kenai Peninsula of south central Alaska. It runs westward from Kenai Lake in the Kenai Mountains, through the Kenai National Wildlife Refuge and Skilak Lake to its outlet into the Cook Inlet of the Pacific Ocean near Kenai...
, Copper River
Copper River (Alaska)
The Copper River or Ahtna River is a 300-mile river in south-central Alaska in the United States. It drains a large region of the Wrangell Mountains and Chugach Mountains into the Gulf of Alaska...
, and in Bristol Bay
Bristol Bay
Bristol Bay is the eastern-most arm of the Bering Sea, at 57° to 59° North 157° to 162° West in Southwest Alaska. Bristol Bay is 400 km long and 290 km, wide at its mouth...
. Fish farming
Fish farming
Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young fish into the wild for recreational fishing or to supplement a species'...
of Pacific salmon is outlawed in the United States Exclusive Economic Zone
Exclusive Economic Zone
Under the law of the sea, an exclusive economic zone is a seazone over which a state has special rights over the exploration and use of marine resources, including production of energy from water and wind. It stretches from the seaward edge of the state's territorial sea out to 200 nautical...
, however, there is a substantial network of publicly funded hatcheries
Hatchery
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons A hatchery is a...
, and the State of Alaska's fisheries management
Fisheries management
Fisheries management draws on fisheries science in order to find ways to protect fishery resources so sustainable exploitation is possible. Modern fisheries management is often referred to as a governmental system of appropriate management rules based on defined objectives and a mix of management...
system is viewed as a leader in the management of wild fish stock
Fish stock
Fish stocks are subpopulations of a particular species of fish, for which intrinsic parameters are the only significant factors in determining population dynamics, while extrinsic factors are considered to be insignificant.-The stock concept:All species have geographic limits to their...
s. In Canada, returning Skeena River
Skeena River
The Skeena River is the second longest river entirely within British Columbia, Canada . The Skeena is an important transportation artery, particularly for the Tsimshian and the Gitxsan - whose names mean "inside the Skeena River" and "people of the Skeena River" respectively, and also during the...
wild salmon support commercial, subsistence
Artisan fishing
Artisan fishing is a term used to describe small scale low-technology commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and traditional...
and recreational fisheries
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
, 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. Out of 435 wild stocks of salmon and steelhead, only 187 of them were classified as healthy; 113 had an unknown status, 1 was extinct, 12 were in critical condition and 122 were experiencing depressed populations. The Columbia River salmon population is now less than 3% of what it was when Lewis and Clark
Lewis and Clark Expedition
The Lewis and Clark Expedition, or ″Corps of Discovery Expedition" was the first transcontinental expedition to the Pacific Coast by the United States. Commissioned by President Thomas Jefferson and led by two Virginia-born veterans of Indian wars in the Ohio Valley, Meriwether Lewis and William...
arrived at the river. 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
Alewife
The alewife is a species of herring. There are anadromous and landlocked forms. The landlocked form is also called a sawbelly or mooneye...
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 sportfishery.
Aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
is the major economic contributor to the world production of farmed fin-fish, representing over US$1 billion annually. Other commonly cultured fish species include: tilapia
Tilapia
Tilapia , is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats, including shallow streams, ponds, rivers and lakes. Historically, they have been of major importance in artisan fishing in Africa and the...
, catfish
Catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
, sea bass
Sea bass
-Family Serranidae:* Barred sand bass , lives mainly off the coast of California* Black sea bass , whose range is the eastern coast of the United States...
, carp
Carp
Carp are various species of oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes, Siluriformes and Gymnotiformes to create the superorder Ostariophysi, since these groups have certain...
, bream, and trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
. Salmon farming is significant in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, Norway, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, 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
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
, 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
Forage fish
Forage fish, also called prey fish or bait fish, are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding...
. 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
Maximum sustainable yield
In population ecology and economics, maximum sustainable yield or MSY is, theoretically, the largest yield that can be taken from a species' stock over an indefinite period...
. The industrial scale extraction of wild forage fish for salmon farming then impacts the survivability of the wild predator fish who rely on them for food.
Work continues on substituting vegetable protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s 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
Sea lice
The sea louse is a copepod within the order Siphonostomatoida, family Caligidae. There are 36 genera within this family which include approximately 42 Lepeophtheirus and 300 Caligus species...
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.
Hatchery
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons A hatchery is a...
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
Cook Inlet Aquaculture Association
The Cook Inlet Aquaculture Association or CIAA is a non-profit organization based in Kenai, Alaska that works to create sustainable salmon stocks in the Cook Inlet area...
as a way of artificially increasing salmon populations in situations where they have declined due to overharvesting, construction of dams, and habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
or fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population 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
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. 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 carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
s astaxanthin
Astaxanthin
Astaxanthin is a carotenoid. It belongs to a larger class of phytochemicals known as terpenes. It is classified as a xanthophyll, which means "yellow leaves". Like many carotenoids, it is a colorful, lipid-soluble pigment. Astaxanthin is found in microalgae, yeast, salmon, trout, krill, shrimp,...
and canthaxanthin
Canthaxanthin
Canthaxanthin is a carotenoid pigment widely distributed in nature. Carotenoids belong to a larger class of phytochemicals known as terpenoids. The chemical formula of canthaxanthin is C40H52O2. It has E number E161g and is approved for use in the EU and USA however it is not approved for usage in...
to match their flesh color to wild salmon.
Diseases and parasites
Myxozoa
The Myxozoa are a group of parasitic animals of aquatic environments. Over 1300 species have been described and many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan. The average size of a Myxosporea spore usually ranges from 10 μm to 20 μm and Malacosporea up...
n parasite Henneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to the Queen Charlotte 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 a complex life cycle, 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 that "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 that, 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
Sea lice
The sea louse is a copepod within the order Siphonostomatoida, family Caligidae. There are 36 genera within this family which include approximately 42 Lepeophtheirus and 300 Caligus species...
, 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%.
Environmental pressures
- Sea lice - transfer of parasites from open-net cage salmon farming, especially sea lice, has reduced numbers. The European Commission (2002) concluded, "The reduction of wild salmonid abundance is also linked to other factors but there is more and more scientific evidence establishing a direct link between the number of lice-infested wild fish and the presence of cages in the same estuary." It is reported that wild salmon on the west coast of Canada are being driven to extinctionExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
by sea liceSea liceThe sea louse is a copepod within the order Siphonostomatoida, family Caligidae. There are 36 genera within this family which include approximately 42 Lepeophtheirus and 300 Caligus species...
from nearby salmon farms. For Atlantic salmon smolts, it takes as few as eight sea lice to kill the fish. On the Pacific Coast where the smolt are much smaller, only one or two can be critical, often resulting in death. In the Atlantic, sea lice have been a proven factor in both Norwegian and Scottish salmon declines. In the Western Atlantic, there has been little research at sea, but sea lice numbers in the period after 2000 do not appear to be a significant factor in the critical decline of endangered inner Bay of Fundy salmon. The situation may have been different in the 1980s and 1990s, but we are unlikely ever to know the factual history in that regard. - Overfishing - in general, has reduced populations, especially commercial netting in the Faroes and GreenlandGreenlandGreenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
. Several seafood sustainability guides have recommendations on which salmon fisheries are sustainable and which have negative impacts on salmon populations. - Warming in ocean and river water can delay spawning and accelerate the transition to smolting.
- Ulcerative dermal necrosisUlcerative dermal necrosisUlcerative dermal necrosis is a chronic dermatological disease of cold water salmonid fish that had a severe impact on north Atlantic Salmon and sea trout stocks in the late 1960s, the 1970s and 1980....
- (UDN) infections of the 1970s and 1980s severely affected adult salmon in freshwater rivers. - Habitat - the loss of suitable freshwater habitat, especially degradation of stream poolStream poolA stream pool, in hydrology, is a stretch of a river or stream in which the water depth is above average and the water velocity is quite below average.-Formation:...
s and reduction of suitable material for the excavation of redds has caused a reduction in spawning. Historically, stream pools were, to a large extent, created by beaverBeaverThe beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
s (see section below). With their extirpation, the nurturing function of these ponds was lost. Reduced retention of the nutrients brought by the returning adult salmon in stream pools has lowered populations. Without stream pools, dead adult salmon tend to be washed straight back down the streams and rivers, so the nutrients are not available for the hatchlings. The construction of dams, weirs, barriers and other "flood prevention" measures bring severe adverse impacts to river habitat and on the accessibility of those habitats to salmon, particularly in the northwest USA, where large numbers of dams have been built in many river systems, including over 400 in the Columbia River Basin. Other environmental factors, such as light intensity, water flow, or change in temperature, dramatically affects salmon during their migration season. Modern farmFarmA farm is an area of land, or, for aquaculture, lake, river or sea, including various structures, devoted primarily to the practice of producing and managing food , fibres and, increasingly, fuel. It is the basic production facility in food production. Farms may be owned and operated by a single...
ing methods and various sources of pollutionPollutionPollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
have resulted in loss of invertebrate diversity and population density in rivers, thus reducing food availability. Reduction in freshwater base flow in rivers and disruption of seasonal flows, because of diversions and extractions, hydroelectric powerHydroelectricityHydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
generation, irrigationIrrigationIrrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
schemes, bargeBargeA barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. Some barges are not self-propelled and need to be towed by tugboats or pushed by towboats...
transportation, and slackwater reservoirs, inhibit normal migratory processes and increase predation for salmon. Agricultural practices, such as the removal of riparian plants, destabilization of stream banks by livestock and irrigation processes, result in a loss of suitable low-gradient stream habitats.
Several governments and nongovernmental organizations (NGOs) are sharing in research and habitat restoration efforts to relieve this situation.
- In the western Atlantic, the Atlantic Salmon Federation has developed a major sonic tracking technology program to understand the high at-sea mortality since the early 1990s. Ocean arrays are deployed across the Baie des Chaleurs and between Newfoundland and Labrador at the Strait of Belle Isle. Salmon have now been tracked half way from rivers, such as the Restigouche, to Greenland feeding grounds. Now, the first line of the Ocean Tracking Network initiative is installed by DFO and Dalhousie University of Halifax, from Halifax to the edge of the continental shelf. First results include Atlantic salmon travelling from the Penobscot River in Maine, the "anchor river" for US Atlantic salmon populations.
- In the northern Atlantic, the North Atlantic Salmon Fund, led by Icelandic entrepreneur Orri VigfússonOrri VigfússonOrri Vigfússon is an Icelandic entrepreneur and environmentalist. In 2004 Time Magazine named him a "European Hero". He was awarded the Goldman Environmental Prize in 2007 for his efforts on saving endangered species...
, has worked closely since 1989 with governments and fishermen for conservation. The conservation efforts are not limited to oceans, and a sustainable angling scheme has been developed in rivers, notably in VopnafjörðurVopnafjörðurVopnafjörður is a village and municipality in Northeast Iceland, standing on a peninsula in the middle of a mountainous bay by the same name. The main industries of Vopnafjordur are fish processing, agriculture, and tourism and other services....
, IcelandIcelandIceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
. - Throughout the Pacific Rim, the Wild Salmon CenterWild Salmon CenterThe Wild Salmon Center is an international non-profit organization that works to protect wild salmon, steelhead, char, trout and the ecosystems on which these species depend. Headquartered in Portland, Oregon, United States, the WSC partners with communities, businesses, governments, and other...
partners with communities, businesses, governments, and other non-profits to protect and preserve healthy salmon ecosystems and the biodiversityBiodiversityBiodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
on which these ecosystems depend.
Results overall show estuary problems exist for some rivers, but issues involving feeding grounds at sea are impacting populations as well. In 2008, returns were markedly improved for Atlantic salmon on both sides of the Atlantic Ocean, but no one knows if this is a temporary improvement or sign of a trend.
- NOAA's Office of Protected Resources maintains a list of Endangered Species, the Endangered Species ActEndangered Species ActThe Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
. - Sweden has generated a protection program as part of its Biodiversity Action PlanBiodiversity Action PlanA Biodiversity Action Plan is an internationally recognized program addressing threatened species and habitats and is designed to protect and restore biological systems. The original impetus for these plans derives from the 1992 Convention on Biological Diversity...
. - State of Salmon maintains an IUCN redlist of endangered salmon.
- The Kamchatka PeninsulaKamchatka PeninsulaThe Kamchatka Peninsula is a peninsula in the Russian Far East, with an area of . It lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west...
, in the Russian Far EastRussian Far EastRussian Far East is a term that refers to the Russian part of the Far East, i.e., extreme east parts of Russia, between Lake Baikal in Eastern Siberia and the Pacific Ocean...
, contains the world's greatest salmon sanctuary. - Bear LakeBear Lake (Alaska)Bear Lake is near the town of Seward and Resurrection Bay, in the Kenai Peninsula Borough on the Kenai Peninsula in the U.S. state of Alaska. It is accessible from Bear Creek Road, which connects it to the Seward Highway. It is the site of salmon enhancement activities since 1962...
, AlaskaAlaskaAlaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, has been the site of salmon enhancement activities since 1962.
Alternative feed for hatcheries
One proposed alternative to fish feed from wild-caught fish is the use of soy-based products, which have the potential to promote healthy fish growth and have positive effects on the environment. Of particular interest is taurine. As one of the most abundant amino acids available, it would serve as a nutritious growth promoter for young hatchery fish. Another promising alternative is a yeast-based, proteinaceous fermentation biomass (PFB). PFB is a co-product of bio-ethanol production. Already, studies have shown that the substitution of PFB products for engineered feed have resulted 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. In the natural environment, seaweed provides essential minerals and vitamins for growing organisms. They offer a tremendous advantage to raising healthy young fish, as they provide natural amounts of dietary fiber and generally have 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 fishFishery pressures
A great threat to Pacific salmon conservation is commercial fishing. There are many methods of harvest for the commercial salmon fishing industry, such as trolling, seining, and gillnetting. Gillnets are an extremely size-selective method of harvest, where a long net is placed in the path of the salmon’s migration to their natal stream in hopes of entangling the salmon for commercial harvest. Fish too small to be caught pass through the net, fish too large cannot be entangled, only catching fish that fall somewhere in between. By selectively harvesting certain sizes of fish, governed by the mesh-size of the gillnet, some age-class and length-class fish are selectively removed from the population, progressively leaving phenotypically smaller spawners. Fecundity generally decreases with length. So, smaller fish produce fewer eggs than larger fish. There is also concern regarding the genetic information passed down from the fish. If the majority of spawning fish in a particular salmon run has gotten smaller due to the size-selective fishing methods, the run could eventually evolve to become smaller.Gillnet size selectivity
Gillnets are designed to harvest a specific sized fish. For example, Washington Department of Fish and Wildlife's 2010 Commercial Regulations had a 7 inches (177.8 mm) minimum mesh size restriction for Chinook, and a 5 inches (127 mm) minimum – 5.5 inches (139.7 mm) maximum for sockeye. Possible problems arising from this selective harvest are smaller reproducing adult fish, as well as the unexpected mortality of the fish which sustain injuries from the gillnet but are not retained in the fishery. Most salmon populations include several age classes, allowing for fish of different ages, and sizes, to reproduce with each other. A recent 2009 study looked at 59 years of catch and escapement data of Bristol BayBristol Bay
Bristol Bay is the eastern-most arm of the Bering Sea, at 57° to 59° North 157° to 162° West in Southwest Alaska. Bristol Bay is 400 km long and 290 km, wide at its mouth...
sockeye to determine age and size at maturity trends attributable to the selectivity of commercial gillnet harvests. The study found that the larger females (>550 mm) of all age classes were most susceptible to harvest. The study suggests that smaller, younger fish were more likely to successfully traverse the gillnet fishery and reproduce than the larger fish. The study also found that the average length of sockeye harvested from 1946–2005 was 8 mm larger than the sockeye who escaped the gillnet fishery to spawn, reducing the fecundity of the average female by 5%, or 104 eggs.
Gillnet-Related Mortality
If a salmon enters a gillnet, but manages to escape, it often sustains injuries. These injuries can lead to a lower degree of reproductive success. A study aimed at quantifying mortality of Bristol Bay sockeye salmon due to gillnet-related injuries found that 11 - 29% of sockeye sustained fishery-related injuries attributable to gillnets, 51% of those fish were expected to not reproduce.Salmon and beavers
BeaverBeaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
s are archetypal ecosystem engineer
Ecosystem engineer
An ecosystem engineer is any organism that creates or modifies habitats. Jones et al. identified two different types of ecosystem engineers:...
s; in the process of clear cutting and damming, beavers alter their ecosystem 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
Treaty of 1818
The Convention respecting fisheries, boundary and the restoration of slaves between the United States of America and the United Kingdom of Great Britain and Ireland, also known as the London Convention, Anglo-American Convention of 1818, Convention of 1818, or simply the Treaty of 1818, was a...
). At the time, the Hudson's Bay Company
Hudson's Bay Company
The Hudson's Bay Company , abbreviated HBC, or "The Bay" is the oldest commercial corporation in North America and one of the oldest in the world. A fur trading business for much of its existence, today Hudson's Bay Company owns and operates retail stores throughout Canada...
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 run
Salmon run
The salmon run is the time at which salmon swim back up the rivers in which they were born to spawn. All Pacific salmon die after spawning. While most Atlantic salmon die after their first spawn, about 5-10% return to the sea to feed between spawnings. The annual run is a major event for sport...
s 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 (61 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.
Salmon as food
Salmon is a popular food. Classified as an "oily fish", salmon is considered to be healthy due to the fish's high proteinProtein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, high omega-3 fatty acids, and high vitamin D
Vitamin D
Vitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
content. Salmon is also a source of cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
, with a range of 23–214 mg/100 g depending on the species. According to reports in the journal Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
, however, farmed salmon may contain high levels of dioxins. PCB (polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...
) levels may be up to eight times higher in farmed salmon than in wild salmon. Omega-3 content may also be lower than in wild-caught specimens, and in a different proportion to what is found naturally. Omega-3 comes in three types, alpha-linolenic acid
Alpha-linolenic acid
α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 ....
(ALA), docosahexaenoic acid
Docosahexaenoic acid
Docosahexaenoic acid is an omega-3 fatty acid that is a primary structural component of the human brain and retina. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain and six cis double bonds; the first double bond is located at the third carbon from the omega end...
(DHA) and eicosapentaenoic acid
Eicosapentaenoic acid
Eicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5. It also has the trivial name timnodonic acid...
(EPA); wild salmon has traditionally been an important source of DHA and EPA, which are important for brain function and structure, among other things. The body can itself convert ALA omega-3 into DHA and EPA, but at a very inefficient rate (2–15%). 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.
A simple rule of thumb is that the vast majority of Atlantic salmon
Atlantic salmon
The Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
available on the world market are farmed (greater than 99%), whereas the majority of Pacific salmon
Oncorhynchus
Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...
are wild caught (greater than 80%). Farmed Atlantic salmon outnumber wild Atlantic salmon 85-to-1.
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
pigments, largely astaxanthin
Astaxanthin
Astaxanthin is a carotenoid. It belongs to a larger class of phytochemicals known as terpenes. It is classified as a xanthophyll, which means "yellow leaves". Like many carotenoids, it is a colorful, lipid-soluble pigment. Astaxanthin is found in microalgae, yeast, salmon, trout, krill, shrimp,...
but also canthaxanthin
Canthaxanthin
Canthaxanthin is a carotenoid pigment widely distributed in nature. Carotenoids belong to a larger class of phytochemicals known as terpenoids. The chemical formula of canthaxanthin is C40H52O2. It has E number E161g and is approved for use in the EU and USA however it is not approved for usage in...
, in the flesh. Wild salmon get these carotenoids from eating krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
and other tiny shellfish
Shellfish
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
. Because consumers have shown a reluctance to purchase white-fleshed salmon, astaxanthin (E161j), and very minutely canthaxanthin (E161g), are added as artificial colorants to the feed of farmed salmon, because prepared diets do not naturally contain these pigments. In most cases, the astaxanthin is made chemically; alternatively it is extracted from shrimp flour. Another possibility is the use of dried red yeast, which provides the same pigment. However, synthetic mixtures are the least expensive option. Astaxanthin is a potent antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
that stimulates the development of healthy fish nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
s and enhances the fish's fertility and growth rate. Research has revealed canthaxanthin may have negative effects on the human eye, accumulating in the retina at high levels of consumption. Today, the concentration of carotenoids (mainly canthaxanthin and astaxanthin) exceeds 8 mg/kg of flesh, and all fish producers try to reach a level that represents a value of 16 on the "Roche Color Card", a colour card used to show how pink the fish will appear at specific doses. This scale is specific for measuring the pink colour due to astaxanthin and is not for the orange hue obtained with canthaxanthin. The development of processing and storage operations, which can be detrimental on canthaxanthin flesh concentration, has led to an increased quantity of pigments added to the diet to compensate for the degrading effects of the processing. In wild fish, carotenoid levels of up to 25 mg are present, but levels of canthaxanthin are, in contrast, minor.
Canned salmon in the U.S. is usually wild Pacific catch, though some farmed salmon is available in canned form. Smoked salmon
Smoked salmon
Smoked salmon is a preparation of salmon, typically a fillet that has been cured and then hot or cold smoked. Due to its moderately high price, smoked salmon is considered a delicacy.-Presentation:...
is another popular preparation method, and can either be hot or cold smoked. Lox can refer either to cold smoked salmon or to salmon cured in a brine solution (also called gravlax
Gravlax
Gravlax or gravad lax , gravet laks , gravlaks , graavilohi , graavilõhe , graflax is a Nordic dish consisting of raw salmon, cured in salt, sugar, and dill...
). 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
Anisakis
Anisakis is a genus of parasitic nematodes, which have a life cycle involving fish and marine mammals. They are infective to humans and cause anisakiasis...
nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s, marine parasites that cause Anisakiasis. Before the availability of refrigeration
Refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...
, Japanese did not consume raw salmon. Salmon and salmon roe
Roe
Roe or hard roe is the fully ripe internal egg masses in the ovaries, or the released external egg masses of fish and certain marine animals, such as shrimp, scallop and sea urchins...
have only recently come into use in making sashimi
Sashimi
Sashimi is a Japanese delicacy. It consists of very fresh raw meat, most commonly fish, sliced into thin pieces.-Origin:The word sashimi means "pierced body", i.e...
(raw fish) and sushi
Sushi
is a Japanese food consisting of cooked vinegared rice combined with other ingredients . Neta and forms of sushi presentation vary, but the ingredient which all sushi have in common is shari...
.
Nutritional information
159g (0.5fillet) of raw salmon contains:- Calories :202
- Fat(g): 7
- Carbohydrates(g): 0
- Fibers(g): 0
- Protein(g): 32.59
- Cholesterol(mg): 73
Salmon in mythology
The salmon is an important creature in several strands of Celtic mythologyCeltic mythology
Celtic mythology is the mythology of Celtic polytheism, apparently the religion of the Iron Age Celts. Like other Iron Age Europeans, the early Celts maintained a polytheistic mythology and religious structure...
and poetry, which often associated them with wisdom and venerability. In Irish mythology
Irish mythology
The mythology of pre-Christian Ireland did not entirely survive the conversion to Christianity, but much of it was preserved, shorn of its religious meanings, in medieval Irish literature, which represents the most extensive and best preserved of all the branch and the Historical Cycle. There are...
, a creature called the Salmon of Wisdom
Salmon of Wisdom
The Salmon of Knowledge is a creature figuring in the Fenian Cycle of Irish mythology. This salmon was sometimes called Fintan, or Finntan, in ancient times and is sometimes confused with Fintan mac Bóchra who was also known as, "The Wise" and once transformed into a salmon...
(or the Salmon of Knowledge) plays key role in the tale known as The Boyhood Deeds of Fionn
The Boyhood Deeds of Fionn
The Boyhood Deeds of Fionn is a medieval Irish narrative belonging to the Fenian Cycle of Irish mythology. As its title implies, it recounts the boyhood exploits of Fionn mac Cumhaill, the cycle's central figure...
. The Salmon will grant powers of knowledge to whoever eats it, and has been sought by the poet Finn Eces
Finn Eces
Finn Eces is a legendary Irish poet and sage, according to the Fenian Cycle of Irish mythology. He is the teacher of Fionn mac Cumhaill, according to the tale The Boyhood Deeds of Fionn. For years he tries to catch the Salmon of Wisdom, a fish that will grant all the world's knowledge to whoever...
for seven years. Finally Finn Eces catches the fish and gives it to his young pupil, Fionn mac Cumhaill
Fionn mac Cumhaill
Fionn mac Cumhaill , known in English as Finn McCool, was a mythical hunter-warrior of Irish mythology, occurring also in the mythologies of Scotland and the Isle of Man...
, 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
Tuan mac Cairill
In Irish mythology Tuan mac Cairill was a follower of Partholon who alone survived the plague that killed the rest of his people. Through a series of animal transformations he survived into Christian times, and told the story of his people to St. Finnian....
and Fintan mac Bóchra.
Salmon also feature in Welsh mythology
Welsh mythology
Welsh mythology, the remnants of the mythology of the pre-Christian Britons, has come down to us in much altered form in medieval Welsh manuscripts such as the Red Book of Hergest, the White Book of Rhydderch, the Book of Aneirin and the Book of Taliesin....
. In the prose tale Culhwch and Olwen
Culhwch and Olwen
Culhwch and Olwen is a Welsh tale about a hero connected with Arthur and his warriors that survives in only two manuscripts: a complete version in the Red Book of Hergest, ca. 1400, and a fragmented version in the White Book of Rhydderch, ca. 1325. It is the longest of the surviving Welsh prose...
, the Salmon of Llyn Llyw is the oldest animal in Britain, and the only creature who knows the location of Mabon ap Modron
Mabon ap Modron
Mabon ap Modron is a prominent figure from Welsh literature and mythology, the son of Modron and a member of Arthur's warband. Both he and his mother were likely deities in origin, descending from a divine mother–son pair. His name is related to the Romano-British god Maponos, whose name means...
. After speaking to a string of other ancient animals who do not know his whereabouts, King Arthur
King Arthur
King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to Medieval histories and romances, led the defence of Britain against Saxon invaders in the early 6th century. The details of Arthur's story are mainly composed of folklore and literary invention, and...
's men Cai
Sir Kay
In Arthurian legend, Sir Kay is Sir Ector's son and King Arthur's foster brother and later seneschal, as well as one of the first Knights of the Round Table. In later literature he is known for his acid tongue and bullying, boorish behavior, but in earlier accounts he was one of Arthur's premier...
and Bedwyr
Bedivere
In Arthurian legend, Sir Bedivere is the Knight of the Round Table who returns Excalibur to the Lady of the Lake. He serves as King Arthur's marshal and is frequently associated with Sir Kay...
are led to the Salmon of Llyn Llyw, who lets them ride its back to the walls of Mabon's prison in Gloucester
Gloucester
Gloucester is a city, district and county town of Gloucestershire in the South West region of England. Gloucester lies close to the Welsh border, and on the River Severn, approximately north-east of Bristol, and south-southwest of Birmingham....
.
In Norse mythology
Norse mythology
Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...
, after Loki
Loki
In Norse mythology, Loki or Loke is a god or jötunn . Loki is the son of Fárbauti and Laufey, and the brother of Helblindi and Býleistr. By the jötunn Angrboða, Loki is the father of Hel, the wolf Fenrir, and the world serpent Jörmungandr. By his wife Sigyn, Loki is the father of Nari or Narfi...
tricked the blind god Höðr
Höðr
Höðr is the brother of Baldr in Norse mythology. Guided by Loki he shot the mistletoe missile which was to slay the otherwise invulnerable Baldr....
into killing his brother Baldr, Loki jumped into a river and transformed himself into a salmon in order to escape punishment from the other gods
Æsir
In Old Norse, áss is the term denoting a member of the principal pantheon in Norse paganism. This pantheon includes Odin, Frigg, Thor, Baldr and Tyr. The second pantheon comprises the Vanir...
. When they held out a net to trap him he attempted to leap over it but was caught by Thor
Thor
In Norse mythology, Thor is a hammer-wielding god associated with thunder, lightning, storms, oak trees, strength, the protection of mankind, and also hallowing, healing, and fertility...
who grabbed him by the tail with his hand, and this is why the salmon's tail is tapered.
Salmon are central to Native American mythology
Native American mythology
Native American mythology is the body of traditional narratives associated with Native American religion from a mythographical perspective. Native American belief systems include many sacred narratives. Such spiritual stories are deeply based in Nature and are rich with the symbolism of seasons,...
on the Pacific coast, from the Haida to the Nootka.
Relief efforts
In the Pacific Northwest, one of the most notable relief efforts is the Puget SoundPuget Sound
Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...
Partnership. The Puget Sound Partnership is currently working to implement policy change at the local level to alter the fate of salmon. Salmon recovery is guided by implementation of the Puget Sound Salmon Recovery Plan, adopted by the National Oceanic and Atmospheric Administration (NOAA) in January 2007. This recovery plan was developed by Shared Strategy, a grassroots collaborative effort to protect and restore salmon runs across Puget Sound. The Puget Sound Partnership has now rehabilitated over 800 acres of salmon habitat and it plans to continue to fight nearshore development and human impact affecting important salmon ecosystems. The Partnership's Action Agenda plans to instigate the Elwha Dam
Elwha Dam
The Elwha Dam is a 108-ft high dam located in the United States, in the state of Washington, on the Elwha River approximately upstream from the mouth of the river on the Strait of Juan de Fuca. The dam was built under the direction of Thomas Aldwell...
removal, begin restoration of the Nisqually Estuary and removal of derelict Fishing gear, and continue with the current salmon Recovery Plan. In order to ensure the future of Pacific Northwest salmon, the Partnership continues to encourage Stormwater & Low Impact Development
Low impact development
Low-impact development is a term used in the United States to describe a land planning and engineering design approach to managing stormwater runoff. LID emphasizes conservation and use of on-site natural features to protect water quality...
, and advocates the "Puget Sound Starts Here" public education program.
Another notable local relief effort is the People for Puget Sound. People for Puget Sound is a citizen group founded by Kathy Fletcher in 1991 working to restore the health of our local land and waters with help from volunteers in the Puget Sound basin.
See also
- Alaska salmon fisheryAlaska salmon fisheryThe Alaskan salmon fishery was saved due to strict mitigation measures and the implementation of policies. Alaska's successful conservation of their salmon resources is reflected in recent healthy and abundant salmon runs...
- Aquaculture of salmonAquaculture of salmonSalmon, along with carp, are the two most important fish groups in aquaculture. In 2007, the aquaculture of salmon and salmon trout was worth US$10.7 billion. The most commonly farmed salmon is the Atlantic salmon. Other commonly farmed fish groups include tilapia, catfish, sea bass, bream and...
- Atlantic salmonAtlantic salmonThe Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
- Fish diseases and parasitesFish diseases and parasitesLike humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth...
- Pacific salmon
- Salmon runSalmon runThe salmon run is the time at which salmon swim back up the rivers in which they were born to spawn. All Pacific salmon die after spawning. While most Atlantic salmon die after their first spawn, about 5-10% return to the sea to feed between spawnings. The annual run is a major event for sport...
- Salmon louseSalmon louseThe salmon louse, Lepeophtheirus salmonis, is a species of copepod in the genus Lepeophtheirus.It is a sea louse, a parasite living on salmon. It lives off the mucus, skin and blood of the fish....
- Sea louse
- Wild Salmon CenterWild Salmon CenterThe Wild Salmon Center is an international non-profit organization that works to protect wild salmon, steelhead, char, trout and the ecosystems on which these species depend. Headquartered in Portland, Oregon, United States, the WSC partners with communities, businesses, governments, and other...
Further reading
- Atlas of Pacific Salmon, Xanthippe Augerot and the State of the Salmon Consortium, University of California Press, 2005, hardcover, 152 pages, ISBN 0-520-24504-0
- Making Salmon: An Environmental History of the Northwest Fisheries Crisis, Joseph E. Taylor III, University of Washington Press, 1999, 488 pages, ISBN 0-295-98114-8
- Trout and Salmon of North America, Robert J. Behnke, Illustrated by Joseph R. Tomelleri, The Free Press, 2002, hardcover, 359 pages, ISBN 0-7432-2220-2
- Come back, salmon, By Molly Cone, Sierra Club BooksSierra Club BooksSierra Club Books is the publishing division of the Sierra Club, founded in 1960 by then Sierra Club President David Brower. Volumes intended for club members had been published prior to 1960. In addition, books under their name had been published before 1960, but done through already established...
, 48 pages, ISBN 0-87156-572-2 - A book for juveniles describes the restoration of 'Pigeon Creek'. - The salmon: their fight for survival, By Anthony Netboy, 1973, Houghton Mifflin Co., 613 pages, ISBN 0-395-14013-7
- A River Lost, by Blaine Harden, 1996, WW Norton Co., 255 pages, ISBN 0-393-31690-4. (Historical view of the Columbia River system).
- River of Life, Channel of Death, by Keith C. Peterson, 1995, Confluence Press, 306 pages, ISBN 978-0-87071-496-2. (Fish and dams on the Lower Snake river.)
- Salmon, by Dr Peter Coates, 2006, ISBN 1-86189-295-0
- NEWS January 31, 2007: U.S. Orders Modification of Klamath River - Dams Removal May Prove More Cost-Effective for allowing the passage of Salmon
- Salmon age and sex composition and mean lengths for the Yukon River area, 2004 / by Shawna Karpovich and Larry DuBois. Hosted by Alaska State Publications Program.
- Trading Tails: Linkages Between Russian Salmon Fisheries and East Asian Markets. Shelley Clarke. (November 2007). 120pp. ISBN 978-1-85850-230-4.
- The Salmons Tale one of the twelve Ionan Tales by Jim MacCool
- "Last Stand of the American Salmon," G. Bruce Knecht for Men's Journal
- Sea Lice and Salmon: Elevating the dialogue on the farmed-wild salmon story Watershed Watch Salmon Society, 2004.
External links
- Plea for the Wanderer, an NFB documentary on West Coast salmon
- Fish farms drive wild salmon populations toward extinction Biology News Net. December 13, 2007.
- Salmonid parasites University of St Andrews Marine Ecology Research Group.
- Watershed Watch Salmon Society A British Columbia advocacy group for wild salmon
- Wild Salmon in Trouble: The Link Between Farmed Salmon, Sea Lice and Wild Salmon - Watershed Watch Salmon Society. Animated short video based on peer-reviewed scientific research, with subject background article Watching out for Wild Salmon.
- Aquacultural Revolution: The scientific case for changing salmon farming - Watershed Watch Salmon Society. Short video documentary. Prominent scientists and First Nation representatives speak their minds about the salmon farming industry and the effects of sea lice infestations on wild salmon populations.
- Genetic Status of Atlantic Salmon in Maine: Interim Report (2002) Online book
- University of Washington Libraries Digital Collections – Salmon Collection A collection of documents describing salmon of the Pacific Northwest.
- Canned Salmon Recipes by Alaska Packers' Association, 1900 e-book with color illustrations, available from Internet Archive
- Epicurean.com Salmon Recipes Collected recipes using Salmon at epicurean.com
- Low Sodium Salmon Recipe Recipe to make smoked salmon mousse.
- Salmon-omics: Effect of Pacific Decadal Oscillation on Alaskan Chinook Harvests and Market Price Kevin Ho, Columbia University, 2005.
- Salmon Nation A movement to create a bioregional community, based on the historic spawning area of Pacific salmon (CA to AK).
- The Distribution of Pacific Salmon (Oncorhynchus spp.) in the Canadian Western Arctic, by S. A. Stephenson
- Sea Lice - Coastal Alliance for Aquaculture Reform. An overview of farmed- to wild-salmon interactive effects.
- Salmon Farming Problems - Coastal Alliance for Aquaculture Reform. An overview of environmental impacts of salmon farming.
- nutrition facts