Salmon farming is a profitable business because of consumer demand for salmon and the decline of commercially viable wild salmon fisheries. Unfortunately there are many problems associated with salmon aquaculture.
The most commonly farmed species of salmon is Atlantic salmon (Salmo salar)- in 1999 Atlantic salmon made up 80% of farmed salmon (Engle and Quagrainie, p. 24).
Typically young farmed salmon are raised in hatcheries. Salmon are then raised to marketable size in sea cages. These cages need to be located in select areas. Water currents have to be strong enough to prevent the accumulation of waste near to the cages. On the other hand, if the currents are too strong they can damage the cages and along the fish to escape.
Salmon farming has been implicated in the spread of several infectious diseases and parasites from farmed salmon to wild salmon. In the 1970s Gyrodactylus salaris (a parasitic fluke that infects fish) appeared in wild salmon populations in Norway. The source of the parasite was traced to farmed salmon from infected hatcheries. Within two decades the infection had wiped out 30 populations of wild salmon in Norway (Stead and Laird, p. 348).
Salmon farms have also been implicated in increased infections of sea lice in wild salmon populations near to the farms. Some have suggested that the abnormally high population densities of the fish farm cages supports larger numbers of sea lice. These unnaturally large sea lice populations then prey on nearby wild fish. On the west coast of Canada sea lice related to salmon farming has been implicated in the decline or extinction of local wild salmon populations.
Another problem associated with fish farming is the fact that farmed salmon have often escaped into the wild. Cages can become damaged by waves or storms, allowing fish to escape. In places where the farmed salmon are not native, escaped salmon compete with native salmon and other fish. For example, Atlantic salmon are farmed on the Pacific coast of North America, where they are not native. When these Atlantic salmon escape into the wild, they compete with local, native salmon species.
Farmed salmon are sometimes genetically modified. When genetically modified Atlantic salmon escape into the wild in areas where there are wild native Atlantic salmon populations, they can interbreed with wild fish, thereby altering the wild stocks. In some parts of Scandinavia a significant portion of the wild fish caught by fishermen were found to have originated in salmon farming operations. In short, genetically altered Atlantic salmon can escape and interbreed with, and alter their wild counterparts.
Another problem with salmon farming is that farmed salmon are fed with fish meal. Salmon feed is made from other fish. In order to produce farmed salmon, a significant amount of other fish are needed. In other words, salmon production is wasteful and contributes to over fishing.
Aside from environmental concerns, there is one other significant reason for consumers to avoid farmed salmon. Studies have shown that farmed salmon typically have higher levels of toxins than their wild counterparts. The concentrated fish meal used to feed farmed salmon causes the toxins that are present in the ocean food chain to build up in the fish’s bodies. The elevated danger that farmed salmon pose to the health of consumers is one compelling reason to avoid eating the fish, or at least to limit consumption.
The environmental and ecological problems associated with salmon farming, along with the elevated levels of toxins found in farmed salmon, are good reasons to avoid eating farmed salmon.
Carol R. Engle and Kwamena Quagrainie. Aquaculture Marketing Handbook. Ames, Iowa: Blackwell Publishing Professional, 2006.
Selina M. Stead and Lindsay Laird (editors). Handbook of Salmon Farming. Bodmin, Cornwall, UK: Praxis Publishing Ltd., 2002.