The following is an extract from a statement submitted by Global Aquaculture Alliance President George W. Chamberlain and International Fishmeal and Oil Manufacturers Association Director General Stuart M. Barlow to the journal Nature, in response to the publication's June 29 article entitled "Effect of aquaculture on world fish supplies. The Australian Prawn Farmer’s Association is an Associate Member of the Global Aquaculture Alliance.

The authors linked the facts that some fishery stocks are overfished, that the top capture species are used for fishmeal production, and that the growth of aquaculture relies on fishmeal to draw the conclusion that aquaculture is causing overfishing. This is incorrect. The U.N. Food & Agriculture Organization classified 16% of fishery stocks as overfished and 6% as depleted, but these are high-value demersal species exploited for human consumption. The principal stocks used for fishmeal production are small, bony pelagic species, generally unsuitable for human consumption, such as anchoveta, Chilean jack mackerel, and menhaden. These are classified by FAO as fully fished, which is indeed the goal of fisheries development.

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The statement by Naylor et al. that "growth [of aquaculture] helps to explain current patterns of ocean fish capture" is contrary to the data. Aquaculture production has grown steadily, while annual worldwide fishmeal production has remained stable at 6-7 million metric tons, except for a decline during the 1998 El Niño period (Figure 1). As aquaculture has grown, it has diverted a growing portion of the fishmeal supply from its traditional use in feeds for land animals, because fishmeal is a higher-value ingredient for aquaculture feeds than for poultry, swine or cattle. If fishmeal were completely eliminated from aquaculture feeds, it would continue to be produced for land animals.

Aquaculture currently uses 35% of the world fishmeal supply. By the year 2010, it is expected to increase its share to 56%. The mechanism of aquaculture displacing traditional fishmeal users was illustrated during the 1998 El Niño, when fishmeal supply fell by 20%, fishmeal prices rose, and the share of fishmeal consumed by aquaculture increased from 33% to 40% at the expense of land animal feeds. Anchovy stocks were not overfished during that period, and they have since returned to normal levels as confirmed by recent data from IMARPE, the research unit for the Peruvian government, as well as current catch statistics.

Concerns expressed by Naylor et al. about habitat destruction and disease transmission are exaggerated. In the early years of milkfish and shrimp farming, governments condoned and even encouraged the conversion of mangrove areas. However, that practice has been reversed by regulatory, technological and economic forces. The aquaculture industry supports conservation of mangroves, and replanting efforts have been initiated in many areas. The economic impact of infectious disease on aquaculture businesses has led to rapid improvements in health management through vaccines and improved husbandry techniques.

A balanced assessment of the effect of aquaculture on world fish supplies must take into account the sustainable use of fishmeal and recent advances in culture practices, which have greatly reduced environmental impact. Aquaculture is a young endeavor and a work in progress, but it relieves stress on the environment by supplying one fourth of the world's seafood, at a time when many stocks are being fished at or beyond their limits.