Aquaculture
Published: 28/01/2005Many hope that the cultivation of fish and shellfish will provide the solution to the rising demand for fish and other marine products. Indeed, aquaculture has grown by 9.6 per cent annually since 1984, and is today the world’s fastest-growing food production system. In Europe, the largest aquaculture branch is salmon farming, but tuna farming in the Mediterranean is on the rise with a 50 per cent increase in 2003.
This relatively young industry, however, has its own environmental problems. Fish farms are located in coastal areas, and can have detrimental effects in vulnerable areas. The release of nutrients, pathogens, chemicals and pharmaceuticals all make serious impacts on the marine environment. Dense farm populations provide an excellent environment for diseases and parasites, which may infect wild stocks in the surrounding waters.
Another problem is the introduction of exotic fish and shellfish species that escape and either compete with, infect or prey on native species. This has happened in the Barents Sea, where the voracious Kamchatka crab was introduced in the 1960’s to boost Russian food supply. Now, it is found along the Norwegian coast and even as far out at sea as the Lofoten Islands. The giant crabs, which eat fish eggs, snails, clams, shellfish and dead fish, reproduce exceptionally fast and their current population is estimated at more than 12 million in northern Europe.
Paradoxically, the cultivation of fish and shrimps also contributes directly to overfishing, as it is dependent on wild-caught fish for feed. For example, to produce one kilogram of salmon, an average of four kilograms of wild caught fish is needed. Increased cultivation therefore results in increased fishing pressure on the species exploited to produce feed. Furthermore, the unintended capture, illegal culling or disturbance of habitats of fish, mammals, birds or other animals can exert pressure on other species that play no role in aquaculture.
The explosive development of tuna farming in the Mediterranean, primarily to meet Japanese demand for sushi and sashimi, both threatens wild stocks of the endangered bluefin tuna in the Mediterranean and contributes to overfishing and bycatch of other species. This farming method depends on the catching of juveniles and adults for fattening in farms, as well as on wild-caught fish for feed.