Aquaculture of salmon - AbsoluteAstronomy.com

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...

, along with 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...

, are the two most important fish groups in aquaculture

Aquaculture

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

. In 2007, the aquaculture of salmon and salmon trout was worth US$10.7 billion. The most commonly farmed salmon is the 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....

. Other commonly farmed fish groups 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...

, 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 aquaculture production grew over ten-fold during the 25 years from 1982 to 2007. Leading producers of farmed salmon are Norway with 33 percent, Chile with 31 percent, and other European producers with 19 percent.

There is currently much controversy about the ecological and health impacts of intensive salmon aquaculture. There are particular concerns about the impacts on wild salmon and other marine life. Some of this controversy is part of a major commercial competitive fight for market share and price between Alaska commercial salmon fishermen and the rapidly evolving salmon aquaculture industry.

Methods

The aquaculture

Aquaculture

of salmon is the farming and harvesting of salmon under controlled conditions. Farmed salmon can be contrasted with wild salmon captured using commercial fishing

Commercial fishing

Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...

techniques. However, the concept of "wild" salmon as used by the Alaska Seafood
Marketing Institute includes stock enhancement fish produced in hatcheries that have historically been considered ocean ranching

Aquaculture

. The percentage of the Alaska salmon harvest resulting from ocean ranching depends upon the species of salmon and location, Alaska Department of Fish and Game http://www.cf.adfg.state.ak.us/geninfo/enhance/enhance.php however it is all marketed as "wild Alaska salmon".

Methods of salmon aquaculture originated in late 18th century fertilization trials in Europe. In the late 19th century, salmon hatcheries

Fish hatchery

A fish hatchery is a "place for artificial breeding, hatching and rearing through the early life stages of animals, finfish and shellfish in particular". Hatcheries produce larval and juvenile fish primarily to support the aquaculture industry where they are transferred to on-growing systems...

were used in Europe and North America. From the late 1950s, enhancement programs based on hatcheries were established in the United States, Canada, Japan and the USSR. The contemporary technique using floating sea cages originated in Norway in the late 1960s.

Salmon are usually farmed in 2 stages and in some places maybe more. First, the salmon are hatched from eggs and raised on land in freshwater tanks. When they are 12 to 18 months old, the smolt

Spawn (biology)

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

(juvenile salmon) are transferred to floating sea cages or net pens anchored in sheltered bays or fjords along a coast. This farming in a marine environment is known as mariculture

Mariculture

Mariculture is a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish,...

. There they are fed pelleted feed for another 12 to 24 months, when they are harvested.

Norway produces 33 percent of the world's farmed salmon, and Chile produces 31 percent. The coastlines of these countries have suitable water temperatures and many areas well protected from storms. Chile is close to large 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...

eries which supply fish meal

Fish meal

Fish meal, or fishmeal, is a commercial product made from both whole fish and the bones and offal from processed fish. It is a brown powder or cake obtained by rendering pressing the cooked whole fish or fish trimmings to remove most of the fish oil and water, and then ground...

for salmon aquaculture. Scotland and Canada are also significant producers.

Modern salmon farming systems are intensive and not usually owned by small scale operators. Their ownership is often under the control of agribusiness

Agribusiness

In agriculture, agribusiness is a generic term for the various businesses involved in food production, including farming and contract farming, seed supply, agrichemicals, farm machinery, wholesale and distribution, processing, marketing, and retail sales....

corporations, operating mechanised assembly lines on an industrial scale producing standardised products. In 2003, nearly half of the world’s farmed salmon was produced by just five companies.

Hatcheries

Modern commercial hatcheries for supplying salmon smolts to aquaculture net pens have been shifting to Recycle Aquaculture

Aquaculture

Systems (RAS) where the water is recycled within the hatchery. This allows location of the hatchery to be independent of a significant fresh water supply and allows economical temperature control to both speed up and slow down the growth rate to match the needs of the net pens.

Conventional hatchery systems operate flow through where spring water or other water source flow into the hatchery. The eggs are then hatched in trays and the salmon smolts produced in raceways. The waste products from the growing salmon fry and the feed are usually discharged into the local river. Conventional flow through hatcheries, such as are being used by most of the Alaska ocean ranching

Aquaculture

enhancement hatcheries use more than 100 tons of water to produce to produce a kg of smolts.
An alternative method to hatching in freshwater tanks 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 temptation, as in hatcheries, to use prophylactic chemicals to control diseases. However, exposing fish to wild parasites and pathogens using uncontrolled water supplies, combined with the high cost of spawning channels, makes this technology unsuitable for salmon aquaculture businesses. This type of technology is only useful for stock enhancement programs.

Sea cages

Sea cages, also called sea pens or net pens, are usually made of mesh framed with steel or plastic. They can be square or circular, 10 to 32 metres across and 10 metres deep, with volumes between 1,000 and 10,000 cubic metres. A large sea cage can house up to 90,000 fish.

They are usually placed side by side to form a system called a seafarm or seasite, with a floating wharf and walkways along the net boundaries. Additional nets can also surround the seafarm to keep out predatory marine mammals. Stocking densities range from 8 to 18 kilograms per cubic metre for Atlantic salmon and 5 to 10 kilograms per cubic metre for Chinook salmon.

In contrast to closed or recirculating systems, the open net cages of salmon farming lower production costs, but provide no effective barrier to the discharge of wastes, parasites and disease into the surrounding coastal waters. Farmed salmon in open net cages can escape into wild habitats, for example, during storms.

An emerging wave in aquaculture is applying the same farming methods used for salmon to other carnivorous finfish species, such as cod, bluefin tuna, halibut and snapper. However, this is likely to have the same environmental drawbacks as salmon farming.
A second emerging wave in aquaculture is the development of copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

alloys as netting materials. Copper alloys have become important netting materials because they are antimicrobial (i.e., they destroy bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, viruses, fungi, algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, and other microbes) and they therefore prevent biofouling

Biofouling

Biofouling or biological fouling is the undesirable accumulation of microorganisms, plants, algae, or animals on wetted structures.-Impact:...

(i.e., the undesirable accumulation, adhesion, and growth of microorganisms, plants, algae, tubeworms, barnacles, mollusks, and other organisms). By inhibiting microbial growth, copper alloy aquaculture cages avoid costly net changes that are necessary with other materials. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive.

Feeding

Salmon are carnivorous and are currently being fed compound fish feeds containing fish meal

Fish meal

and other feed ingredients, ranging from wheat

Wheat

Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

byproducts to soybean meal

Soybean meal

Soybean meal also known as Soyabean Oil Cake is a flour made by grinding the solid residue of soybean oil production. It is widely used as a filler and source of protein in animal diets, including pig, chicken, cattle, horse, sheep, and fish feed....

and feather meal

Feather meal

Feather meal is made from poultry feathers by partially hydrolyzing under elevated heat and pressure and then grinding. Although total nitrogen levels are fairly high, the bioavailability of this nitrogen may be low...

. Being an aquatic carnivore

Carnivore

A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

, salmon don't tolerate or properly metabolize many plant based carbohydrates and use fats instead of carbohydrates as a primary energy source. With the amount of world wide fish meal production being almost a constant amount for the last 30+ years and at 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...

(MSY), much of the fish meal market has shifted from chicken and pig feed to fish and shrimp feeds as aquaculture has grown in this time period Ocean Stewards report with graph on supply as a function of time http://www.oceanstewards.org/pdf/Fishmeal%20Industry%20Overview.pdf . 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 and protein concentrates for fish meal

Fish meal

in the salmon diet. Many substitutions for fish meal are known and diets containing zero fish meal are possible. However, commercial economic animal diets are determined by least cost linear programming

Linear programming

Linear programming is a mathematical method for determining a way to achieve the best outcome in a given mathematical model for some list of requirements represented as linear relationships...

models that are effectively competing with similar models for chicken and pig feeds for the same feed ingredients and these models show that fish meal is more useful in aquatic diets than in chicken diets, where they can make the chickens taste like fish. Unfortunately though, this substitution can result in lower levels of the highly valued omega-3 content in the farmed product. However, when vegetable oil is used in the growing diet as an energy source and a different finishing diet containing high omega-3 content fatty acids from either fish oil, algae oils or some vegetable oils are used a few months before harvest, this problem is eliminated. At the present time, more than 50 percent of the world fish oil

Fish oil

Fish oil is oil derived from the tissues of oily fish. Fish oils contain the omega-3 fatty acids eicosapentaenoic acid , and docosahexaenoic acid , precursors of certain eicosanoids that are known to reduce inflammation throughout the body, and are thought to have many health benefits.Fish do not...

production is feed to farmed salmon. Farm raised salmon are also 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...

, so that their flesh color matches wild salmon, which also contain the same carotenoid

Carotenoid

pigments from their diet in the wild. On a dry-dry basis, it takes 2–4 kg of wild caught fish to produce one kg of salmon. Wild salmon require about 10kg of forage fish to produce a kg of salmon, as part of the normal trophic level

Trophic level

The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism...

energy transfer. The difference between the two numbers is related to farmed salmon feed containing other ingredients beyond fish meal and the fact that farmed fish don't spend a lot of metabolic energy catching a dinner that doesn't want to be caught.

Harvesting

Modern harvesting methods are shifting towards using wet well ships to transport the live salmon to the processing plant. This allows the fish to be killed, bleed, and filleted before rigor has occurred. This results in superior product quality to the customer along with more humane processing. To obtain maximum quality, it is necessary to minimize the level of stress in the live salmon until actually being electrically and percussively killed and the gills slit for bleeding. These improvements in processing time and freshness to the final customer are commercially significant and forcing the commercial wild fisheries to upgrade their processing to the benefit of all seafood consumers.
An older method of harvesting is to use a sweep net, which operates a bit like a purse seine net. The sweep net is a big net with weights along the bottom edge. It is stretched across the pen with the bottom edge extending to the bottom of the pen. Lines attached to the bottom corners are raised, herding some fish into the purse, where they are netted. Before killing, the fish are usually rendered unconscious in water saturated in carbon dioxide, although this practice is being phased out in some countries due to ethical and product quality concerns. More advanced systems use a percussive-stun harvest system that kills the fish instantly and humanely with a blow to the head from a pneumatic piston. They are then bled by cutting the gill arches and immediately immersing them in iced water. Harvesting and killing methods are designed to minimise scale loss, and avoid the fish releasing stress hormones, which negatively affect flesh quality.

Wild versus farmed

Wild salmon are captured from wild habitats using commercial fishing

Commercial fishing

techniques. Most wild salmon is caught in North American, Japanese and Russian fisheries. The following table shows the changes in production of wild salmon and farmed salmon over a period of 25 years, as reported by the FAO

Fão

Fão is a town in Esposende Municipality in Portugal....

. Russia, Japan and Alaska all operate major hatchery based stock enhancement programs that are really ocean ranching

Aquaculture

. The resulting fish hatchery fish are defined as "wild" for FAO and marketing purposes.

Salmon production in tonnes by species
	1982		2007
Species	Wild	Farmed	Wild	Farmed
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....	10,326	13,265	2,989	1,433,708
Salmon trout		171,946		604,695
Coho salmon Coho salmon The Coho salmon, Oncorhynchus kisutch, is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers". It is the state animal of Chiba, Japan.-Description:...	42,281	2,921	17,200	115,376
Chinook salmon Chinook salmon The Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...	25,147		8,906	11,542
Pink salmon Pink salmon Pink 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 :...	170,373		495,986
Chum salmon Chum salmon The 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...	182,561		303,205
Sockeye salmon Sockeye salmon Sockeye 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...	128,176		164,222

Total salmon production
	1982		2007
	tonnes	percent	tonnes	percent
Wild	558,864	75	992,508	31
Farmed	188,132	25	2,165,321	69
Overall	746,996		3,157,831

Issues

There is currently much controversy about the ecological and health impacts of intensive salmon aquaculture. There are particular concerns about the impacts on wild salmon and other marine life and on the incomes of commercial salmon fishermen. The interest of the commercial fishermen are trying to prevent competition.

Disease and parasites

In 1972, Gyrodactylus, a monogenea

Monogenea

Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....

n parasite, spread from Norwegian hatcheries to wild salmon, and devastated some wild salmon populations.

In 1984, infectious salmon anemia (ISAv) was discovered in Norway in an Atlantic salmon hatchery. Eighty percent of the fish in the outbreak died. ISAv, a viral disease, is now a major threat to the viability of Atlantic salmon farming. It is now the first of the diseases classified on List One of the European Commission

European Commission

The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....

’s fish health regime. Amongst other measures, this requires the total eradication of the entire fish stock should an outbreak of the disease be confirmed on any farm. ISAv seriously affects salmon farms 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

Norway

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

, 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...

and Canada

Canada

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

, causing major economic losses to infected farms. As the name implies, it causes severe anemia

Anemia

Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

of infected fish

Fish

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

. Unlike mammals, the red blood cells of fish have DNA, and can become infected with viruses. The fish develop pale gill

Gill

A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

s, and may swim close to the water surface, gulping for air. However, the disease can also develop without the fish showing any external signs of illness, the fish maintain a normal appetite, and then they suddenly die. The disease can progress slowly throughout an infected farm and, in the worst cases, death rates may approach 100 percent. It is also a threat to the dwindling stocks of wild salmon. Management strategies include developing a vaccine and improving genetic resistance to the disease.

In the wild, diseases and parasites are normally at low levels, and kept in check by natural predation on weakened individuals. In crowded net pens they can become epidemics. Diseases and parasites also transfer from farmed to wild salmon populations. A recent study in British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

links the spread of parasitic 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...

from river salmon farms to wild pink salmon in the same river. The European Commission

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 extinction

Extinction

In 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 lice from nearby salmon farms. These predictions have been disputed by other scientists and recent harvests have indicated that the predictions were in error. Antibiotics and pesticides are often used to control the diseases and parasites.

Pollution and toxins

Salmon farms are typically sited in marine ecosystems with good water quality, high water exchange rates, current speeds fast enough to prevent pollution of the bottom but slow enough to prevent pen damage, protection from major storms, reasonable water depth and a reasonable distance from major infrastructure such as ports, processing plants and logistical facilities like airports. Logistical considerations are significant and feed and maintenance labor must be transported to the facility and the product returned. Siting decisions are complicated by complex politically driven permitting problems in many countries that prevents optimal locations for the farms.

In sites without adequate currents there can be an accumulation of heavy metals

Heavy metals

A heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,...

on the benthos

Benthos

Benthos is the community of organisms which live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.Many organisms...

(seafloor) near the salmon farms, particularly copper and zinc.

Toxins are also found in the flesh of farmed salmon. A 2004 study, reported in Science, analysed farmed and wild salmon for organochlorine contaminants. They found the contaminants were higher in farmed salmon. Within the farmed salmon, European (particularly Scottish) salmon had the highest levels, and Chilean salmon the lowest. A follow up study confirmed this, and found levels of dioxin

Dioxins and dioxin-like compounds

Dioxins and dioxin-like compounds are by-products of various industrial processes, and are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants . They include:...

s, chlorinated pesticides, PCB

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...

s and other toxins up to ten times greater in farmed salmon than wild Pacific salmon. On a positive note, further research using the same fish samples used in the previous study, showed that farmed salmon contained levels of beneficial fatty acids that were two to three times higher than wild salmon. A follow up benefit-risk analysis on salmon consumption balanced the cancer risks with the (n-3) fatty acid advantages of salmon consumption. They found that recommended levels of (n-3) fatty acid consumption can be achieved eating farmed salmon with acceptable carcinogenic risks, but recommended levels of EPA+DHA intake cannot be achieved solely from farmed (or wild) salmon without unacceptable carcinogenic risks. The conclusions were that

"...consumers should not eat farmed fish from Scotland, Norway and eastern Canada more than three times a year; farmed fish from Maine, western Canada and Washington state no more than three to six times a year; and farmed fish from Chile no more than about six times a year. Wild chum salmon can be consumed safely as often as once a week, pink salmon, Sockeye and Coho about twice a month and Chinook just under once a month."

Impact on wild salmon

Farmed salmon can, and often do, escape from sea cages. If the farmed salmon is not native, it can compete with native wild species for food and habitat. If the farmed salmon is native, it can interbreed with the wild native salmon. Such interbreeding can reduce genetic diversity, disease resistance and adaptability. In 2004, about 500,000 salmon and trout escaped from ocean net pens off Norway. Around Scotland, 600,000 salmon were released during storms. Commercial fishermen targeting wild salmon not infrequently catch escaped farm salmon. At one stage, in the Faroe Islands

Faroe Islands

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

, 20 to 40 percent of all fish caught were escaped farm salmon.

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 Caligus clemensi and Caligus rogercresseyi, can cause deadly infestations of both farm-grown and wild salmon. Sea lice are ectoparasites which feed on mucous, 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%.

A 2008 meta-analysis of available data shows that salmon farming reduces the survival of associated wild salmon populations. This relationship has been shown to hold for Atlantic, steelhead, pink, chum, and coho salmon. The decrease in survival or abundance often exceeds 50 percent. However, these studies are all correlation analysis and correlation doesn't equal causation, especially when similar salmon declines were occurring in Oregon and California, which have no salmon aquaculture or marine net pens. Independent of the predictions of the failure of salmon runs in Canada indicated by these studies, the wild salmon run in 2010 was a record harvest.

Wild salmon are anadromous. They spawn inland in fresh water and when young migrate

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...

to the ocean where they grow up. Most salmon return to the river where they were born, although some stray to other rivers. There is concern about of the role of genetic diversity within salmon runs. The resilience of the population depends on some fish being able to survive environmental shocks, such as unusual temperature extremes. It is also unclear what the effect of hatchery production has been on the genetic diversity of salmon.

Genetic modification

Salmon have been genetically modified in laboratories so they can grow faster. There is opposition to the commercial use of these fish, and, so far, no approval has been given. A Canadian company, Aqua Bounty Farms, has developed a modified Atlantic salmon which grows several times faster, and is more disease resistant and cold tolerant. This was achieved using a chinook salmon gene sequence affecting growth hormones, and a promoter sequence from the ocean pout

Ocean pout

The ocean pout is an eelpout in the family Zoarcidae. It is found in the Northwest Atlantic Ocean, off the coast of New England and eastern Canada...

affecting antifreeze production. Normally, salmon produce growth hormone

Growth hormone

Growth hormone is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior...

s only in the presence of light. The modified salmon doesn't switch growth hormone production off. The company first submitted the salmon for FDA approval in 1996. A concern with transgenic salmon is what might happen if they escape into the wild. One study, in a laboratory setting, found that modified salmon mixed with their wild cohorts were aggressive in competing, but ultimately failed.

Impact on forage fish

The use of forage fish for fish meal production has been almost a constant for the last thirty years and at the 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...

, while the market for fish meal has shifted from chicken, pig and pet food to aquaculture diets. Ocean Stewards report with graph on supply as a function of time http://www.oceanstewards.org/pdf/Fishmeal%20Industry%20Overview.pdf The fact that this market shift at constant production is an economic decision having no impact on the forage fish harvest rates for fish meal implies that the development of salmon aquaculture had no impact on forage fish harvest rates.

Fish do not actually produce omega-3 fatty acids, but instead accumulate them from either consuming microalgae that produce these fatty acids, as is the case with forage fish like herring

Herring

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

and sardines, or, as is the case with fatty predatory fish

Predatory fish

Predatory fish are fish that predate upon other fish or animals. Some predatory fish include perch, muskie , pike, walleye, salmon.Levels of large predatory fish in the global oceans are estimated to be about 10% of their pre-industrial levels...

, like salmon, by eating prey fish that have accumulated omega-3 fatty acid

Omega-3 fatty acid

N−3 fatty acids are essential unsaturated fatty acids with a double bond starting after the third carbon atom from the end of the carbon chain....

s from microalgae. To satisfy this requirement, more than 50 percent of the world fish oil

Fish oil

production is fed to farmed salmon.

In addition, salmon require nutritional intakes of protein, protein which is often supplied to them in the form of fish meal as the lowest cost alternative protein. 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 a higher percentage of the wild forage fish for feed, at a time when seventy five percent of the worlds 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...

Salmon Aquaculture Dialogue

In 2004 the World Wide Fund for Nature

World Wide Fund for Nature

The World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...

(WWF) initiated the Salmon Aquaculture Dialogue. The aim of the dialogue is to produce an environmental standard for farmed salmon by 2010. The WWF have identified what they call "seven key environmental and social impacts", which they characterise as follows

Hatch and release

Another form of salmon production, which is safer but less controllable, is to raise salmon in 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...

until they are old enough to become independent. They are then released into rivers, often in an attempt to increase the salmon population. This practice was very common in countries like Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

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 non profit groups like 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 overharvest, construction of dams, and habitat destruction or disruption. 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.

Atlantic salmon

In their natal streams, 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....

are considered a prized recreational fish, pursued by avid fly anglers

Fly fishing

Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...

during its annual runs. At one time, the species supported an important commercial fishery and a supplemental food fishery. However, the wild Atlantic salmon fishery is commercially dead; after extensive habitat damage and overfishing, wild fish make up only 0.5% of the Atlantic salmon available in world fish markets. The rest are farmed, predominantly from aquaculture

Aquaculture

in Chile

Chile

, Canada, Norway, Russia

Russia

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

, the UK

United Kingdom

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

and Tasmania

Tasmania

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

in Australia

Australia

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

.

Atlantic salmon is, by far, the species most often chosen for farming. It is easy to handle, it grows well in sea cages, commands a high market value and it adapts well to being farmed away from its native habitats.

Adult male and female fish are anaesthetised

Anesthesia

Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...

. Eggs and sperm are "stripped", after the fish are cleaned and cloth dried. Sperm and eggs are mixed, washed, and placed into fresh water. Adults recover in flowing, clean, well aerated

Aeration

Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or substance.-Aeration of liquids:-Methods:Aeration of liquids is achieved by:...

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

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

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

Many Atlantic salmon escape from cages at sea. Those salmon who further breed tend to lessen the genetic

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

diversity of the species leading to lower survival rates, and lower catch rates. On the West Coast of Northern America, the non-native salmon can be an invasive threat, especially in Alaska

Alaska

and parts of Canada. This causes them to compete with native salmon for resources. Extensive efforts are underway to prevent escapes and the spread of Atlantic salmon in the Pacific and elsewhere.

Atlantic salmon which have escaped from the aquaculture

Aquaculture

industry have also been found breeding in rivers tributary to the Pacific Ocean in British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

on Canada's west coast.

Worldwide, in 2007, 1,433,708 tonnes of Atlantic salmon were harvested with a value of 7.578 billion US dollars.

Salmon trout

In 1992 the salmon trout, Salmo gairdneri, was reclassified as a true salmon, Oncorhynchus mykiss. Salmon trout take an anadromous form and a non-anadromous form. The anadromous form, who migrate between lakes and rivers and the ocean, are known as steelhead salmon or ocean trout, while the non-anadromous form, who spend their entire life in freshwater, are known as rainbow trout.

Salmon trout are raised in many countries throughout the world. Since the 1950s production has grown exponentially, particularly in Europe and recently in Chile. Worldwide, in 2007, 604,695 tonnes of farmed salmon trout were harvested with a value of 2.589 billion US dollars. The largest producer is Chile. In Chile and Norway, the ocean cage production of steelhead has expanded to supply export markets. Inland production of rainbow trout to supply domestic markets has increased strongly in countries such as Italy, France, Germany, Denmark and Spain. Other significant producing countries include the USA, Iran, Germany and the UK.

Salmon trout have tender flesh and a mild, somewhat nutty flavour. Steelhead meat is pink like that of other salmon, and is more flavourful than the light-coloured meat of rainbow trout. Both are highly desired food. However, farmed trout and those taken from certain lakes have a pronounced earthy flavour which many people find unappealing; many shoppers therefore make it a point to ascertain the source of the fish before buying. Salmon trout that are wild have a diet of scuds (freshwater shrimp), insects such as flies, and crayfish

Crayfish

Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...

are the most appealing. Dark red/orange meat indicates that it is either an anadromous steelhead or a farmed rainbow trout given a supplemental diet with a high iodine content. The resulting pink flesh is marketed under monikers like Ruby Red or Carolina Red.

The salmon trout is especially susceptible to enteric redmouth disease

Enteric redmouth disease

-Introduction:Enteric redmouth disease, or simply redmouth disease is a bacterial infection of freshwater and marine fish caused by the pathogen Yersinia ruckeri. It is primarily found in rainbow trout and other cultured salmonids. The disease is characterized by subcutaneous hemorrhaging of the...

. There has been considerable research conducted on redmouth disease, as its implications for salmon trout farmers are significant. The disease does not affect humans.

Coho salmon

The Coho salmon

Coho salmon

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

is the state animal of Chiba

Chiba Prefecture

is a prefecture of Japan located in the Kantō region and the Greater Tokyo Area. Its capital is Chiba City.- History :Chiba Prefecture was established on June 15, 1873 with the merger of Kisarazu Prefecture and Inba Prefecture...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.

Coho salmon mature after only one year in the sea, so two separate broodstock

Broodstock

Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers. These are generally kept in ponds or tanks in which...

s (spawners) are needed, alternating each year. Broodfish are selected from the salmon in the seasites and transferred to freshwater tanks for maturation and spawning."

Worldwide, in 2007, 115,376 tonnes of farmed Coho salmon were harvested with a value of 456 million US dollars. Chile, with about 90 percent of word production, is the primary producer with Japan and Canada producing the rest.

Chinook salmon

In Alaska, Chinook salmon

Chinook salmon

The Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...

are the state fish, and are known as "king salmon" because of their large size and flavoursome flesh. Those from the 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...

in Alaska are particularly known for their colour, rich flavour, firm texture, and high Omega-3 oil content.

Worldwide, in 2007, 11,542 tonnes of farmed Chinook salmon were harvested with a value of 83 million US dollars. New Zealand is the largest producer of farmed king salmon, accounting for over half of world production (7,400 tonnes in 2005). Most of the salmon are farmed in the sea (mariculture

Mariculture

) using a method sometimes called sea-cage ranching. Sea-cage ranching takes place in large floating net cages, about 25 metres across and 15 metres deep, moored to the sea floor in clean, fast-flowing coastal waters. Smolt

Spawn (biology)

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

(young fish) from freshwater hatcheries are transferred to cages containing several thousand salmon, and remain there for the rest of their life. They are fed fishmeal pellets high in protein and oil.

King salmon are also farmed in net cages placed in freshwater rivers or raceways

Raceway (aquaculture)

A raceway, also known as a flow-through system, is an artificial channel used in aquaculture to culture aquatic organisms. Raceway systems are among the earliest methods used for inland aquaculture. A raceway usually consists of rectangular basins or canals constructed of concrete and equipped with...

, using techniques similar to those used for sea-farmed salmon. A unique form of freshwater salmon farming occurs in some hydroelectric canals. A site in Tekapo, fed by fast cold waters from the Southern Alps

Southern Alps

The Southern Alps is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the island's western side...

, is the highest salmon farm in the world, 677 metres above sea level.

Before they are killed, cage salmon are anaesthetised with a herbal extract. They are then spiked in the brain

Ike jime

or is a method of paralyzing and bleeding fish to maintain its quality. The technique originated in Japan, but is now in widespread use. It involves the insertion of a spike quickly and directly into the hind brain, thereby causing immediate brain death. A fish brain is usually located slightly...

. The heart beats for a time as the animal is bled from its sliced gills. Relaxing the salmon like this when it is killed produces firm, long-keeping flesh. Lack of disease in wild populations and low stocking densities used in the cages means that New Zealand salmon farmers do not use antibiotics and chemicals that are often needed elsewhere.

Timeline

1527: The life history of the Atlantic salmon is described by Hector Boece
Hector Boece
Hector Boece , known in Latin as Hector Boecius or Boethius, was a Scottish philosopher and first Principal of King's College in Aberdeen, a predecessor of the University of Aberdeen.-Biography:He was born in Dundee where he attended school...

of the University of Aberdeen
University of Aberdeen
The University of Aberdeen, an ancient university founded in 1495, in Aberdeen, Scotland, is a British university. It is the third oldest university in Scotland, and the fifth oldest in the United Kingdom and wider English-speaking world...

, Scotland.

1763: Fertilization trials for Atlantic salmon take place in Germany. Later biologists refined these in Scotland and France.
1854: Salmon spawing beds and rearing ponds built along the bank of a river by the Dohulla Fishery, Ballyconneely
Ballyconneely
Ballyconneely is a small ribbon development in west Connemara, County Galway, Ireland.Settlements are spread out north on the road to Clifden and south on the road to Roundstone...

, Ireland.
Late 19th century: Salmon hatcheries
Fish hatchery
A fish hatchery is a "place for artificial breeding, hatching and rearing through the early life stages of animals, finfish and shellfish in particular". Hatcheries produce larval and juvenile fish primarily to support the aquaculture industry where they are transferred to on-growing systems...

are used in Europe, North America, and Japan to enhance wild populations.
Late 1960s: First salmon farms established in Norway and Scotland.
Early 1970s: Salmon farms established in North America.
1975: Gyrodactylus, a small monogenea
Monogenea
Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....

n parasite, spreads from Norwegian hatcheries to wild salmon, probably by means of fishing gear, and devastates some wild salmon populations.
Late 1970s: Salmon farms established in Chile and New Zealand.
1984: Infectious salmon anemia, a viral disease, is discovered in a Norwegian salmon hatchery. Eighty percent of the involved fish die.
1985: Salmon farms established in Australia.
1987: First reports of escaped Atlantic salmon being caught in wild Pacific salmon fisheries.
1988: A storm hits the Faroes Islands releasing millions of Atlantic salmon.
1989: Furunculosis, a bacterial disease, spreads through Norwegian salmon farms and wild salmon.
Early 1990s: 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...

from Atlantic salmon farms infest wild sea trout around Ireland, resulting in the collapse of their fisheries.
1996: World farmed salmon production exceeds wild salmon harvest.
2007: A 10 square miles (25.9 km²) swarm of Pelagia noctiluca
Pelagia noctiluca
Pelagia noctiluca is a jellyfish in the family Pelagiidae. In Latin, Pelagia means "of the sea", nocti stands for night and luca means light thus Pelagia noctiluca can be described as a marine organism with the ability to glow in the dark.This species of jellyfish commonly known as the mauve...

jellyfish wipes out a 100,000 fish salmon farm in Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

.

External links

Aquaculture: Salmon - World Wildlife Fund
BC Salmon Facts Salmon farming industry site explaining salmon farming in British Columbia, Canada.
BC Salmon Farmers Association Association representing salmon farmers in British Columbia, Canada.
CAIA – Canadian Industry Aquaculture Association Canadian association representing all salmon farms in Canada.
Disease-Related Impacts of Salmon Aquaculture - World Wildlife Fund press release
Salmon Aquaculture – David Suzuki Foundation brochure
Watershed Watch Salmon Society
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.
Aquacultural Revolution: The scientific case for changing salmon farming - Watershed Watch Salmon Society. Short video documentary by filmmakers Damien Gillis and Stan Proboszcz. 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.
Positive Aquaculture Awareness Independent association which promotes salmon farming in British Columbia, Canada.
Farmed and dangerous - Salmon Farming Problems – Coastal Alliance for Aquaculture Reform
Sea Lice - Coastal Alliance for Aquaculture Reform. An overview of farmed- to wild-salmon interactive effects.
What about this fish? – Video extract from Harvest of Fear.
Fish farms drive wild salmon populations toward extinction Biology News Net. December 13, 2007.
Salmonid parasites University of St Andrews Marine Ecology Research Group.

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Methods

Hatcheries

Sea cages

Feeding

Harvesting

Wild versus farmed

Issues

Disease and parasites

Pollution and toxins

Impact on wild salmon

Genetic modification

Impact on forage fish

Salmon Aquaculture Dialogue

Hatch and release

Atlantic salmon

Salmon trout

Coho salmon

Chinook salmon

Timeline

Further reading

External links