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Under international pressure, Chile introduced strict new regulations in January. But the problems surrounding fish farming are complex, and some are only dimly understood. Daniel Pauly, 55, a professor of fisheries science at the University of British Columbia, has calculated that it takes 2 to 5 lbs. of anchovies, sardines, menhaden and the other oily fish that comprise fish meal to produce 1 lb. of farmed salmon, which he says makes no sense in a world trying to increase the amount of available protein. Kentucky State University biologist James Tidwell, 47, a former president of the World Aquaculture Society, points out, however, that wild salmon are bigger eaters than that--consuming at least 10 lbs. of fish to add 1 lb. in weight--and argues that harvesting large amounts of short-lived species like menhaden is no more harmful than mowing the lawn. "Fish-meal fish are nature's forage," he says. "Cropping them merely increases their productivity."
Disease is always a problem when fish are raised in close quarters. After a 1999 outbreak of infectious salmon anemia in fish farms in Scotland, all the farm-grown fish within 25 miles were slaughtered. A similar anemia outbreak in Maine two years ago led to the destruction of more than 2.5 million fish--and to federal insurance payouts totaling $16 million. "The more aquaculture there is," warns Callum Roberts, senior lecturer in marine conservation at the University of York in England, "the more disease there will be."
Some of the antibiotics that fish farmers give their stock to minimize disease pass easily into the surrounding environment, and some are highly toxic. Last year traces of the banned drug nitrofuran, which is dangerous to humans, were found by European Union inspectors in shrimp from Myanmar, Thailand and Vietnam. According to Wang Sihe, an expert with the Jiangsu Seawater Fisheries Research Institute, Chinese shrimp farms have mixed fish food with antibiotics and dumped it into fish ponds. Chloramphenicol, an antibiotic that can cause fatal anemia in humans, has also been used.
The fetid water that runs off shrimp farms is particularly damaging to the environment. Thailand, with 25,000 coastal shrimp farms, is the world's largest exporter of shrimp--$3 billion worth in 2001 alone. Through last June, Thailand accounted for 28% of the shrimp imported into the U.S. But this commerce is costly. Long strips of coastline south of Bangkok now look like powdery gray moonscapes. Shrimp farms can raise the salinity of the surrounding soil and water, poisoning the land for agriculture. Some flush their effluent into the sea, killing mangrove trees. Shrimp farming is also practiced in Brazil, India and Ecuador, and in the U.S. in Florida, South Carolina and Texas.