Canada is the fourth largest producer of farmed salmon in the world behind Norway, Chile and the UK, having produced a total value of $543 million in 2005. Of the aquaculture production in Canada, 48 per cent is in the waters of British Columbia with 24 per cent of the production centred in New Brunswick.
The 1980s saw a tremendous boom in all aquaculture production, with a fourfold increase from 11.4 tonnes to 45.7 tonnes from 1985 to 2000. Salmon farming mirrored this growth with increases in production from fewer than 50,000 tonnes in 1985 to more than one million tonnes in 2000, surpassing the wild capture of salmon.
In 1984, Ottawa encouraged foreign investment in the industry, paving the way for multi-national corporations to build salmon farms in the waters of B.C. With Norwegian investment, a shift from farms growing predominantly Pacific salmon to farming Atlantic salmon occurred in BC waters. Atlantic salmon continue to dominate the BC salmon farming industry representing 80 per cent of the market. Nearly all salmon farming is done in net-pens floating in the ocean, often in protected bays and coves at the mouths of rivers. These open systems, which often hold up to 700,000 fish in 12,000 square metres, are where many of the environmental issues arise.
The farm benefits from the circulation of clean oxygenated water and free removal of wastes into the surrounding waters. This pollution from waste feed and feces can smother bottom-dwelling marine life under the netpens and the excess nutrients can lead to harmful algal blooms.
Organic waste is not the only problem. Antibiotics and pesticides given to the fish and anti-fouling paints used on the pens release harmful materials into the surrounding waters. With high densities of fish, disease and parasites are often problems. These diseases can threaten wild populations of salmon as seen with the breakout of infectious salmon anemia in the Bay of Fundy in 1997. Sea lice, a marine parasite, are another significant problem as an infestation can both lower the value of the harvested fish and harm wild juvenile salmon migrating from the river to the ocean.