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That's not an easy question to answer, because the rapid growth of aquaculture has been accompanied by environmental costs. In the past, the dense salmon farms of Canada and northern Europe helped spread disease among wild fish while releasing waste into coastal waters. Mangrove forests, which provide a valuable habitat for coastal life, have been razed to make way for Thailand's shrimp farms. Especially troubling, many of the most popular farmed species are carnivores, meaning they need to be fed at least partly with other fish. By one count, about 2 lb. of wild fish ground up to make fish meal is needed on average to produce 1 lb. of farmed fish, which leaves the ocean at a net loss. "Aquaculture's reliance on fish meal and fish oil is a major concern for marine conservation," says Sebastian Troeng, a marine expert with Conservation International.
But unless you can convince 1.3 billion Chinese not to mention everyone else in a growing world that they don't deserve the occasional sushi roll, aquaculture will keep growing. As it does, it will need to become more efficient and less polluting. The good news is that the industry is improving. More farmable but less familiar species like the barramundi which yields more protein than it takes in as feed may have to supplement popular fish like cod that haven't taken as well to aquaculture. We may even need to genetically engineer popular species to make them grow faster and bigger. And perhaps most of all, we need to accept that on a planet with a population of nearly 7 billion and climbing, we may no longer be able to indulge our taste for the last wild food. We've farmed the land. Now we have little choice but to farm the sea as well.
Aquaculture and Its Discontents
To the average shopper, farmed fish is barely distinguishable from its wild cousin except, often, in price. Without the growth in aquaculture, many of our favorite kinds of seafood would likely be much more expensive than they are now. And chances are, you get what you paid for: farmed seafood can be inferior to wild fish in taste and may not always have the same nutritional value. Salmon raised in an aquaculture environment, for instance, often have lower levels of cardiovascular-friendly omega-3s than wild fish, and farmed fillets would actually be gray without a pink chemical dye. And if you're eating farmed seafood, you're almost certainly getting it from overseas: U.S. aquaculture accounts for just 5% of Americans' seafood consumption. The Monterey Bay Aquarium's Seafood Watch program mostly discourages consumers from choosing farmed fish, both for health reasons and because of worries over the environmental impact of aquaculture. "There's a real difference in the regulation you might see in other countries compared with the U.S.," says Peter Bridson, Monterey's aquaculture-research manager.
At the same time, it's important to look at the big picture. For health reasons, most of us should be eating more fish. For its new dietary guidelines, the U.S. government just upped the recommended consumption of seafood to 8 oz. or more a week which is more than twice what the average American eats and 12 oz. for pregnant women. In a report this month, the U.N. said global food production would need to increase by as much as 100% by 2050 to meet growing demand and seafood, as a vital protein source, will have to be part of that. Farming is unavoidable. "There may be a price split between expensive wild fish and cheaper farmed fish," says Don Perkins, head of the Gulf of Maine Research Institute. "But seafood consumption will spread because we need it for health reasons."
To understand global aquaculture its potential and its problems it helps to look at the industry's track record in China, a country responsible for 61% of the world's aquaculture. China has begun exporting industrially produced catfish, shrimp and tilapia in recent years. As production pressures have ramped up, Chinese manufacturers have packed their ponds more tightly, leading to disease and pollution from fish waste. That waste can overload coastal waters with nutrients, causing dead zones that can strangle sea life. To fight the diseases worsened by crowding, Chinese fish farmers have liberally used antibiotics and other drugs, including malachite green, an antifungal agent and potential carcinogen that was banned by Beijing in 2002 but shows up periodically in exports. "It is still a problem," says Wong Ming Hung, a biology professor at Hong Kong Baptist University.
While China remains a laggard on safety though experts say its fish-farming industry is improving as it matures there's no denying that aquaculture can be messy. A badly run near-shore farm of 200,000 salmon can flush nitrogen and phosphorus into the water at levels equal to the sewage from a town of 20,000 people. But for all that, fish farming's bad reputation isn't entirely deserved, especially if it's compared with farming on land.