In semi-intensive or intensive fish farms, fish are given supplementary feed, which may be of vegetable origin or may include wet fish, fish oil and/or fishmeal. Exceptions to this are filter feeders (such as silver carp, bighead carp, catla and rohu) in extensive systems where the fish feed entirely from the food web within the pond, which may be enhanced by the addition of fertilizer or manure. Farmed marine fishes, in contrast, are largely dependent on fish meal and/or fish oil feed. These include Atlantic salmon, gilthead seabeam and European seabass which, together with intensively farmed rainbow trout, dominate farmed fish production in the EU and Norway.
Fishmeal and fish oil are produced from purpose-caught feed fish combined with trimmings from food fish which comprise about 5 millions tonnes, according to the International Fishmeal and Fish Oil Association. Currently most fishmeal and fish oil are fed to farmed fish or shrimps, with most other fishmeal being fed to farmed pigs and poultry and most other fish oil consumed as food.
A study by Tacon and Metian1 found that, in 2006, industrially formulated feeds for farmed fish and crustaceans used 88.5% of fish oil, and 68.2% fishmeal, produced globally. This was equivalent to 16.6 million tonnes of small pelagic forage fish. A later paper by the same authors2 estimates that between 5.6 and 8.8 million (for which the mean is 7.2 million) tonnes of feed fish were fed directly to farmed fish in the same year, which suggests that fish oil and fishmeal aquaculture feeds accounted for 65-75%, or 70%, of the total wild fish tonnage fed to farmed fish and crustaceans.
In that year, farmed trout, salmon and other marine fish, comprising just 10.6% of total farmed fish and crustacean production tonnage, consumed over one third (39%) of the total fishmeal, and three quarters (76%) of the total fish oil, used in global aquaculture. Farmed salmon species comprising just 4.3% of the total farmed fish and crustacean production, consumed 43% of total fish oil and 15% of total fishmeal, used by aquaculture in 2006.
These figures show that most of the world’s fish oil production used in aquaculture, and much of the fishmeal used there, is fed to farmed carnivourous fish speices which comprise just a small proportion of total farmed fish and crustacean production.
A fully referenced discussion of the welfare issues in fish farmed is available in the following paper:
Study to estimate numbers of farmed fish killed in global aquaculture each year ( 540 KB) 40 pages. July 2012.
1. Tacon, A.G.J. and Metian, M. 2008. Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: Trends and future prospects. Aquaculture 285 (2008) 146–158. http://www.cnr.uidaho.edu/fish510/PDF/fishmeal.pdf.
2. Tacon, A.G.J. and Metian, M. 2009. Fishing for aquaculture: Nonfood use of small pelagic forage fish, a global perspective. Rev Fish Sci 17:305–317.