Global appetite for farmed fish devouring world's wild fish supplies

February 17, 2001

New global study shows the combined impacts of capture fisheries and aquaculture are depleting marine food webs from the top down and the bottom up

Just as the California energy crisis shows what happens when you don't plan ahead for increasing demands on limited resources, we may be headed for a similar crisis in the seas. Today, at the American Association for the Advancement of Science (AAAS) Meeting in San Francisco, an international group of scientists will present new findings on unintended impacts of fish farming that put both oceans and the aquaculture industry at risk. Dr. Daniel Pauly of the University of British Columbia Fisheries Centre will release a new global study, "Farming Up Marine Food Webs" showing that major sectors of the booming aquaculture industry are literally feeding on world fisheries.

Aquaculture, the fastest growing sector of the world food economy, is increasing by 11% a year. Many people expect this growth to relieve pressure on ocean fish stocks, most of which are now fished beyond capacity, and to provide a reliable source of food to a world population that adds 78 million people each year. Paradoxically, Pauly's new study shows that the increasing trend toward farming carnivorous fish means that many types of aquaculture are pushing us towards a worldwide collapse of wild fisheries. Production of a single pound of fish-eating species such as shrimp, salmon, tuna or cod demands 2 to 5 lbs. of wild caught fish that is processed into meal and oil for feeds.

Pauly previously discovered a global pattern of fishing down the food chain, putting more pressure on lower level species as we exhaust the bigger carnivorous fish. (Pauly et al. Feb.6,1998, Science) Conversely, his new analysis demonstrates that the mean trophic level (relative position of organisms within food chains) of farmed fish has been rapidly increasing in almost all regions of the world outside Asia.

The new study discovered that traditional aquaculture --farming fish that eat plants and detritus--is being replaced by modern intensive farming of large, carnivorous fish because overfishing has decimated these fish in the wild. Even in Asia, the ancient home of aquaculture, vegetarian fish like tilapia and carp are now being fed fishmeal and fish oil for faster weight gain and marketability. "The new trend in aquaculture is to drain the seas to feed the farms. Meanwhile capture fisheries now focus on what we once considered bait. These two trends-- farming up and fishing down the food web imply massive impacts on marine ecosystems that are clearly unsustainable," says Pauly.

At the AAAS meetings in San Francisco, a panel of seven international scientists are presenting data showing that aquaculture is necessary to the world's future food security, but warn that the growing demands of the world's food production systems upon a finite quantity of resources means that all aquatic and terrestrial farming systems must become more efficient. Cost-benefit analyses into the viability of certain kinds of aquaculture must incorporate externalities: fisheries decline, aquatic pollution, habitat destruction and impacts on wild stocks. Examples of "good aquaculture" practices include farming vegetarian species and employing polyculture that recycles nutrients and minimizes effluents.

Dr. Jason Clay will also release the findings of a three year study by WWF, the World Bank, FAO and the Network of Aquaculture Centres in Asia Pacific on the best and worst practices of shrimp farming. Shrimp farming now produces half of all internationally traded shrimp. Raising 800,000 metric tonnes yearly world wide, for a total value of US $6 billion, the industry is said to generate benefits for cash strapped countries. Ironically, disease-induced "boom and bust" shrimp farming has resulted in increasing poverty and landlessness, declining food security, and break down of traditional livelihood systems. Impacts have included the destruction of mangroves and wetlands, the large-scale capture of wild larvae and brood-stock, pollution, use of chemicals and antibiotics, intensive fish meal demands and the privatization of public resources.

"Aquaculture is at a critical crossroads," declares Dr. Albert Tacon, head of the Oceanic Institute's Aquatic Feeds and Nutrition Program in Hawaii. "Fish farming could decrease pressure on fisheries and feed the worlds growing population. That's why it is so important to proceed on a sustainable path."

Consumer markets ultimately dictate the type of fish farming that farmers will employ. Consumers should look for vegetarian fish that feed low on the food web including catfish, tilapia, oysters and other shellfish. Aquaculture also needs new policies that will reward the aquaculture industry for engaging in best sustainable practices. " To date, fish farming has been separated from ocean fisheries in regulation, management and mindset," states Stanford economist Dr. Roz Naylor who chairs today's session at AAAS. "It is high time both public and private interests think of these sectors jointly. Without sound ecological practices, the expanding aquaculture industry poses a threat not only to ocean fisheries, but also to itself."


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