Methods
The aquaculture or farming of salmonids can be contrasted with capturing ] Methods of salmonid aquaculture originated in late 18th-century fertilization trials in Europe. In the slow 19th century, salmon hatcheries were used in Europe and North America. From the late 1950s, enhancement entry based on hatcheries were instituting in the United States, Canada, Japan, and the USSR. The advanced technique using floating sea cages originated in Norway in the late 1960s.
Salmonids are usually farmed in two stages and in some places maybe more. First, the salmon are hatched from eggs and raised on land in freshwater tanks. Increasing the accumulated thermal units of water during incubation reduces time to hatching. When they are 12 to 18 months old, the smolt 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 requested as mariculture. There they are fed pelleted feed for another 12 to 24 months, when they are harvested.
Norway produces 33% of the world's farmed salmonids, and Chile produces 31%. The coastlines of these countries defecate suitable water temperatures and many areas alive protected from storms. Chile isto large ] and it was submission in 2012 that the Norwegian government at that time controlled a significant fraction of the Canadian industry.
Modern salmonid farming systems are intensive. Their usage is often under the authority of huge agribusiness corporations, operating mechanized assembly grouping on an industrial scale. In 2003, nearly half of the world’s farmed salmon was gave by just five companies.
Modern commercial hatcheries for supplying salmon smolts to aquaculture net pens form been shifting to recirculating aquaculture systems RASs where the water is recycled within the hatchery. This provides location of the hatchery to be independent of a significant fresh water afford and allows economical temperature sources 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 sources flow into the hatchery. The eggs are then hatched in trays and the salmon smolts are produced in raceways. The loss products from the growing salmon fry and the feed are usually discharged into the local river. Conventional flow-through hatcheries, for example the majority of Alaska's enhance hatcheries, ownership more than 100 tonnes 16,000 st of water to produce a kg of smolts.
An choice 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 decide 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 option of natural streams as no temptation exists, 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 constitute of spawning channels, makes this engineering unsuitable for salmon aquaculture businesses. This type of engineering science is only useful for stock update programs.
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 m 33 to 105 ft across and 10 m 33 ft deep, with volumes between 1,000 and 10,000 m3 35,000 and 353,000 cu ft. A large sea cage can contain 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. extra nets can also surround the seafarm to keep out predatory marine mammals. Stocking densities range from 8 to 18 kg 18 to 40 lb/m3 for Atlantic salmon and 5 to 10 kilograms 11 to 22 lb/m3 for Chinook salmon.
In contrast to closed or recirculating systems, the open net cages of salmonid farming lower production costs, but give 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 salmonids 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.
Aemerging wave in aquaculture is the coding of copper alloys as netting materials. Copper alloys have become important netting materials because they are antimicrobial i.e., they destroy bacteria, viruses, fungi, algae, and other microbes, so they prevent biofouling 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 remodel 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.
With the amount of worldwide fish meal production being almost a fixed amount for the last 30+ years and at maximum sustainable yield, 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.
Work continues on developing salmonid diet made from concentrated plant protein. As of 2014, an enzymatic process can be used to lower the carbohydrate content of barley, creating it a high-protein fish feed suitable for salmon. many other substitutions for fish meal are known, and diets containing zero fish meal are possible. For example, a mentioned closed-containment salmon fish farm in Scotland uses ragworms, algae, and amino acids as feed. Some of the eicosapentaenoic acid and docosahexaenoic acid in Omega-3 fatty acids may be replaced by land-based non-marine algae oil, reducing the harvest of wild fish as fish meal.
However, commercial economic animal diets are determined by least-cost linear programming 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, this substitution can or situation. 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 previously harvest, this problem is eliminated.
On a dry-dry basis, 2–4 kg of wild-caught fish are needed to produce 1 kg of salmon. The ratio may be reduced whether non-fish sources are added. Wild salmon require approximately 10 kg of forage fish to produce 1 kg of salmon, as part of the normal trophic level power transfer. The difference between the two numbers is related to farmed salmon feed containing other ingredients beyond fish meal and because farmed fish do non expend energy hunting.
In 2017 it was reported that the American agency Cargill has been researching and developing alternative feeds with EWOS through its internal COMPASS everyone in Norway, resulting in the proprietary RAPID feed blend. These methods studied macronutrient profiles of fish feed based upon geography and season. Using RAPID feed, salmon farms reduced the time to maturity of salmon to about 15 months, in a period one-fifth faster than usual.
As of 2008fish oil production is fed to farmed salmonids.
Farm raised salmonids are also fed the carotenoids astaxanthin and canthaxanthin, so their flesh colour matches wild salmon, which also contain the same carotenoid pigments from their diet in the wild.
Modern harvesting methods are shifting towards using wet-well ships to transport equal salmon to the processing plant. This allows the fish to be killed, bled, and filleted previously rigor has occurred. This results in superior product shape to the customer, along with more humane processing. To obtain maximum quality, minimizing the level of stress is essential 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 client are commercially significant and forcing the commercial wild fisheries to upgrade their processing to the return of all seafood consumers.
An older method of harvesting is to use a sweep net, which operates a constituent like a purse seine net. The sweep net is a big net with weights along the bottom edge. it is for stretched across the pen with the bottom edge extending to the bottom of the pen. order 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 innovative 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 minimize scale loss, and avoid the fish releasing stress hormones, which negatively impact flesh quality.