Nearly half of the seafood we eat today is farmed. And while aquaculture is often equated with pollution, habitat degradation, and health risks, this explosive growth in fish farming may in fact be the most hopeful trend in the world's increasingly troubled food system, according to a new report by Worldwatch Institute.
In Farming Fish for the Future, Senior Researcher Brian Halweil illustrates how, if properly guided, fish farming can not only help feed an expanding global population, but also play a role in healing marine ecosystems battered by overfishing.
"In a world where fresh water and grain supplies are increasingly scarce, raising seafood like oysters, clams, catfish, and tilapia is many times more efficient than factory-farmed chicken or beef," says Halweil. "Farmed fish can be a critical way to add to the global diet to hedge against potential crop losses or shortages in the supply of meat."
"But not all fish farming is created equal," Halweil notes. Carnivorous species like salmon and shrimp, while increasingly popular, consume several times their weight in fish feed-derived from other, typically smaller, fish-as they provide in edible seafood. "It generally requires 20 kilograms of feed to produce just 1 kilogram of tuna," Halweil says. "So even as we depend more on farmed fish, a growing scarcity of fish feed may jeopardize future expansion of the industry."
Poorly run fish farms can generate coastal pollution in the form of excess feed and manure, and escaped fish and disease originating on farms can devastate wild fisheries. For example, a fish farm with 200,000 salmon releases nutrients and fecal matter roughly equivalent to the raw sewage generated by 20,000 to 60,000 people. Scotland's salmon aquaculture industry is estimated to produce the same amount of nitrogen waste as the untreated sewage of 3.2 million people-just over half the country's population.
Cramped facilities can also create ill health for fish, costing producers millions of dollars in disease prevention and foregone revenues. In recent years, shrimp farmers in China have lost $120 million to bacterial fish diseases and $420 million to shrimp diseases.
Fish farming has expanded to meet the soaring global demand for seafood. On average, each person on the planet is eating four times as much seafood as was consumed in 1950. The average per-capita consumption of farmed seafood has increased nearly 1,000 percent since 1970, in contrast to per-capita meat consumption, which grew just 60 percent.
In 2006, fish farmers raised nearly 70 million tons of seafood worth more than $80 billion-nearly double the volume of a decade earlier. Experts predict that farmed seafood will grow an additional 70 percent by 2030.
How can fish farming be made more sustainable? Innovative industry practices are key, but a shift toward sustainable fish farming will also require a fundamental change in public attitudes. This includes a willingness to prioritize fish that are lower on the food chain, such as shellfish and tilapia. But can consumers today be mobilized to shift the aquaculture industry in the same way they pressured tuna fleets to adopt more dolphin-friendly practices in the 1980s?
The need for more sustainable fish farming is critical, according to the report. Farmed seafood provides 42 percent of the world's seafood supply, and is on target to exceed half in the next decade, yet there are no widely accepted standards for what constitutes "good" fish farming. By comparison, the organic food industry has strong international and national standards, even though it constitutes just 3 to 5 percent of the world's food supply.
This points to a greater role for aquaculture certification and standards in the coming years, Halweil says. Efforts currently under way seek to model the effective labeling systems that exist in other areas of agriculture, such as for wild-caught fish, heritage breeds of livestock, and organic and local foods.
"The last wild ingredient in our diet is no longer completely wild," says Halweil. "This doesn't have to be a permanent situation, since wild fish stocks can recover. But as more coastal ecosystems are transformed into sites for fish pens, cages, and cultured seaweeds, fish farmers and the food industry will need to make ecological restoration as much a goal as meeting the growing demand for seafood."
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