Are Fish Farms Sustainable?
Fish farms produce about 25 percent of the seafood people eat worldwide. That percentage is likely to increase because most wild fish stocks are overexploited. Traditional fish farming as practiced in parts of China and India has been sustainable and has provided people with an important source of protein. These fish — tilapia, carp, catfish — eat microscopic plants and animals. Salmon on the other hand are high level predators that eat fish in the wild. Three pounds of wild-caught fish need to be processed into feed to produce one pound of farmed salmon.
About one third of the world’s total fish harvest is now coverted to fish meal and fish oils to make livestock feed, primarily for chickens, but also pigs, cattle and farmed fish. This places an additional burden on the world’s already overtaxed fisheries. In addition, some forms of aquaculture are highly destructive, especially in Latin America and Asia where wholesale conversion of shorelines to shrimp farms has wiped out mangrove forests and displaced local fishermen.
We spoke with Rebecca Goldburg one of the authors of a recent Science article about the environmental costs and benefits of aquaculture.