Fish Farms Not Sustainable, Experts Warn

MONITOR Wire Services

Aquaculture, the fastest growing sector of the world food economy, is increasing by 11 percent a year. Many people expect this growth to relieve pressure on ocean fish stocks, most of which are now fished beyond capacity. One out of every four fish consumed worldwide was raised on a farm. But the irony is that fish farming often comes at a surprising cost to wild fish populations.

The problem, points out Rosamond Naylor, an economist at the Stanford Institute for International Studies, is that farmed salmon, shrimp and other carnivorous species often take more out of the oceans than they keep in. That's because certain farmed fish are given processed feed made from wild catches of herring, mackerel, sardine and other ocean varieties. 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.

"People should be aware that they are not doing the environment a favor at all by eating farmed salmon," she says.

On balance, aquaculture still adds to the world's supply of seafood, she says. Yet fish farming influences wild populations -- displacing natural breeding habitats, spreading disease and polluting the oceans in many ways that haven't been measured.

Commercial fish farms are expanding rapidly, especially in Asia, taking up thousands of square miles of coastal land. Even in Asia, vegetarian fish like tilapia and carp are now being fed fishmeal and fish oil for faster weight gain and marketability.

Shrimp farming now produces half of all internationally traded shrimp. Raising 800,000 metric tons yearly world wide, for a total value of $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, pollution, use of chemicals and antibiotics, and the privatization of public resources.

"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 Dr. Daniel Pauly of the University of British Columbia.

Farming more vegetarian fish and shellfish -- such as carp and mussels -- is one way to produce needed fish protein for people without depleting ocean populations, Naylor contends.

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. Shellfish farming, in fact, purifies the water by filtering out algae and waste, adds Naylor.

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," Naylor says. "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."