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Myth #1: Aquaculture is animals kept in mass stock under water
Aquaculture is often accused of crowding large quantities of fish into a small space resulting in poor animal welfare conditions. In reality, the amount of fish (or crustaceans) stocked in a net pen or pond is dependent upon many different factors and is called the stocking density. Stocking density varies according to species of fish/shellfish, water conditions at the farm and method of production.
Many studies have demonstrated diminishing returns once stocking densities exceed the carrying capacity. Carrying capacity in this regard is the number or quantity of animals that can be raised under appropriate animal welfare conditions. If the carrying capacity of a farm is exceeded, disease can set in, thus causing mortalities. There is therefore an incentive not to exceed the carrying capacity of a farm.
Let’s take a look at how stocking density is applied to salmon. Salmon are typically raised in pens that are 50 meters in diameter and over 20 meters deep. Stocking densities may be limited by local and national regulations. For example, in Norway the maximum stocking density is 25 kg per m3 (cubic meter). For 5 fully grown salmon this equates to approximately 200 liters of seawater per fish. In Scotland, many farms limit stocking density to 15 kg per m3 to comply with the Royal Society for the Prevention of Cruelty to Animals (RSCPA) Freedom Food animal welfare standard. To put this in perspective, the RSCPA Freedom Food animal welfare standard for a free range chicken shelter is 27.5 kg per m2 (square meter) and a maximum of 13 birds. That is 12.5 kg more than for salmon!
Limits to stocking density are not sufficient by themselves to assure appropriate animal welfare conditions. The GLOBALG.A.P. Aquaculture standard have 51 animal welfare control points to assist in ensuring stocking densities do not exceed carrying capacities, and the entire farm infrastructure is designed to respect animal welfare and to avoid unnecessary stress.