Salmon aquaculture, or fish farming, is the industrial production of salmon from egg to market in a net-cage, pond or contained system. Most of the industry still uses open net-cages in the ocean.
Most of the world's farmed salmon comes from Scotland, Norway, Chile and British Columbia. In British Columbia, a great controversy has developed over how to utilize salmon and coastal resources. Many believe that fish farms wreak havoc with wild salmon populations as well as coastal ecosystems. Salmon farmers say they have greatly improved their management systems and also provide jobs.
Some wild Pacific salmon populations are endangered, mainly because of the loss of their fresh water habitat due to dams. Salmon have also been over-fished in some areas. The Atlantic species of wild salmon is almost non-existent in the U.S. Pacific salmon are still commercially fished in areas where their populations remain strong. Many of these sustainable, limited-entry fisheries, from Alaska to California, have been or are being certified for a consumer eco-label by the Marine Stewardship Council.
But almost all of salmon products sold in the U.S. are farm-raised Atlantic salmon grown in the Pacific waters of British Columbia and Chile. The open, net-cage has become very controversial because many believe salmon farms to pose a serious threat to wild salmon. One reason is because large numbers of farmed Atlantic salmon often escape their net-cages into the wild.
A salmon farm is likely to hold 500,000 to 750,000 fish in an area the size of four football fields. Salmon are carnivores. On average it takes 5 to 10 pounds of feed to produce two pounds of farmed salmon. In one study, over a billion sea lice eggs were produced by just twelve farms in a two week period. Infection with one to three sea lice can kill a wild juvenile pink salmon. In British Columbia alone there are approximately 136 salmon farm licenses with over 85 farms active at any given time. Canada and Chile are the two primary sources of farmed salmon for American consumers. Two-thirds of the salmon consumed by Americans is farm-raised.
Farm salmon are exposed to artificial processes to increase their growth rate rapidly marketable size. As smolts they are transported to sea in well-boats, or slung in containers beneath a helicopter. The life span of a standard farmed salmon ranges from 18 months to 2 years, and up to 2 to 3 years for a so-called organic salmon. By slaughter-time farm fish weigh approximately 6lb and measure upwards of 24 inches in length. Wild salmon of the same age are still in their natal stream and weigh only a few ounces.
Farm salmon’s flesh can be flabby because they have food delivered to their mouths and little danger of being attacked by predators. A wild salmon’s flesh is firmer because of its natural life-style. Fat lines on a farmed salmon are whiter and wider than those on a wild salmon. Wild salmon gets a lot of exercise migrating thousands of miles from the streams that gave them birth to their Greenland feeding grounds.
Farmed salmon are thought to have diseases and parasites such as sea-lice. Escapes of farmed salmon have damaged wild salmon and sea-trout populations in the West Highlands and Island of Scotland.
Each year hundreds of thousands of farmed salmon escape from their cages. These farmed fish compete with wild salmon for food and spawning resources. Initial research has shown that in a few generations escaped farm salmon will out compete and replace wild salmon.
Sea lice that have attached themselves to a wild fish die when the host fish enters fresh water. Farmed salmon never enter fresh water. A salmon farm site may hold twenty cages containing more that 1 million fish. Cages act as a magnet for sea lice and they breed there in their billions. Sea lice are free-swimming and move on tidal currents. Therefore, as wild fish pass by the cages they are confronted with clouds of sea lice which then attach themselves to the wild fish. Sea lice can kill a wild fish. Sea-trout are at greater risk because they do not migrate.
From birth to slaughter, farmed salmon are treated with a range of chemicals to protect them from disease and to make them more attractive to consumers. Wild salmon are naturally pink, because of their diet. Farmed salmon flesh, however, is muddy grey in colour. Most farm salmon are fed a manufactured colorant in their food to make it appealing to consumers.
Common diseases on fish farms include Salmon Anaemia, Bacterial Kidney Disease and Infectious Pancreatic Necrosis, all of which can be fatal to caged salmon. Because of the numbers of fish stocked into each cage disease spreads rapidly and is as quickly transferred to adjacent cages in the same sea loch.
Factory-farmed salmon have been identified by scientists as containing potentially harmful levels of PCB’s and dioxins. A recent report advised people to limit the quantity of farmed salmon they ate to no more than four meals a year.