Though people have raised fish in artificial ponds for millennia, it is only once since the 1960s that the pratice has been extended to shrimp. And farming these crustaceans has rapidly become big business. Some 1m tonnes are cultivated each year. In Ecuador, for instance, 230,000 people earn their livings working for shrimp farms, and a fifth of all the households in the country's coastal provinces are dependent on the farms for their income.