Major sectors of the global aquaculture industry are contributing to the collapse of world fisheries, a recent study notes. The most significant move toward the farming of carnivorous fish species is taking place in non-Asian countries, the study notes. Asian aquaculture remains, on balance, a net producer of fish while non-Asian aquaculture has increasingly tended to become a net fish consumer. A previous study by Pauly found that commercial fisheries are catching fewer top members of the food chain. The study demonstrated for the first time that large, long-lived fish from the top of the food web such as tuna, are being replaced by smaller, fish with shorter life spans at the bottom of the food chain.
Many scientists expect aquaculture to relieve pressure on the ocean's fish stocks.
Yet the farming of carnivorous species such as salmon can intensify pressure on wild fisheries because they can require up to five pounds of wild fish per each pound of salmon produced. Conservationists cite a number of other environmental concerns involving farmed salmon, from water pollution to bycatch of marine birds and mammals to disease, escapement and algal blooms. Aquaculture has become the fastest-growing sector of the world food economy, with an 11 percent rate of increase each year. Expanding from 13 million tons of fish produced in 1990 to 31 million tons in 1998, aquaculture is expected to surpass cattle ranching as a source of the world's protein in the next 10 years. Requiring less energy than livestock production, fish farming has been touted as a solution to feeding a world population that adds 78 million people each year.