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A unique form of freshwater salmon farming occurs in some hydroelectric canals in New Zealand. A site in Tekapo, fed by fast, cold waters from the Southern Alps, is the highest salmon farm in the world, 677 m (2,221 ft) above sea level. [117] Before they are killed, cage salmon are sometimes anaesthetised with a herbal extract.
Salmon farming leads to a high demand for wild forage fish. As a predator, salmon require large nutritional intakes of protein, and farmed salmon consume more fish than they generate as a final product. On a dry weight basis, 2–4 kg of wild-caught fish are needed to produce one kilogram of salmon. [89]
Farming carnivorous fish such as salmon, however, does not always reduce pressure on wild fisheries, such farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by the FAO totaled 33.8 million tonnes worth about US$60 billion. [6]
To produce one kilograms of farmed salmon, products from several kilograms of wild fish are fed to them – this can be described as the "fish-in-fish-out" (FIFO) ratio. In 1995, salmon had a FIFO ratio of 7.5 (meaning 7.5 kilograms of wild fish feed were required to produce one kilogram of salmon); by 2006 the ratio had fallen to 4.9. [103]
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To reduce the environmental impact of aquaculture and especially of salmon farming, researches are being conducted to find alternatives to existing technologies.For the time being the marine net-pens is the only technology that dominates the aquaculture system in Canada.
Wild salmon is more nutritionally dense than farm-raised salmon and can contain up to three times less fat, fewer calories, and more vitamins and minerals like iron, potassium, and b-12.
Mariculture, sometimes called marine farming or marine aquaculture, [1] is a branch of aquaculture involving the cultivation of marine organisms for food and other animal products, in seawater. Subsets of it include ( offshore mariculture ), fish farms built on littoral waters ( inshore mariculture ), or in artificial tanks , ponds or raceways ...