For most of man's existence he has been a hunter-gatherer. These days, however, it is as a farmer that he harvests almost all his food from the land. Now he has started farming the sea, too. The world produced 48 billion tonnes of farmed fish in 2005, worth $71 billion. That was 34% of the total, a proportion that is likely to rise to half by 2010. A huge variety of fish, including cod, crayfish, bream, halibut, mussels, salmon, sea bass and sturgeon, are all farmed, providing jobs and food for people all over the world.rnUnfortunately, fish farming is still in its infancy and in some places may do more harm than good. In Indonesia, Thailand, Vietnam and other parts of Asia, huge swathes of coastline have been denuded of trees to make way for ponds and pens. Many fish farms create pollution, too. Even if the water in which the fish are reared starts out fresh, the build-up of faeces and uneaten food soon makes it foul. The mix is made even nastier by the pesticides and antibiotics needed to keep the crop alive. And to cap it all, aquaculture produces CO_2 and gobbles up energy.
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