Farming the sea to feed the world

USC (US)—On a coastal flat in the Pacific Northwest, marine biologists from the University of Southern California are pinning their hopes on the quest for bigger and faster-growing oysters as a way to examine the pressing nutritional needs of an increasingly crowded planet.

Oysters pack huge amounts of protein, along with an alphabet soup of vitamins, lots of omega-3 fatty acids, and hefty doses of minerals—all in one low-calorie package. For marine biologists who wonder where humanity will find the next great meal, the oyster ranks high on the list of prospects.

“It’s not going to be krill,” says Donal Manahan, director of USC’s Wrigley Institute for Environmental Studies.

Not only more flavorful than krill, oysters exhibit a remarkable property known as hybrid vigor—possibly unique in the animal world. And oysters are only the start, says Manahan. He calls for a Blue Revolution in all kinds of seafood to follow the Green one that boosted crop yields over the last century.

“We’re going to have to make future decisions as a society regarding how to provide enough food for a growing population,” he says. United Nations experts estimate that humans will number almost 9 billion by 2050.

“If you look globally, the untapped potential of producing more food from the oceans is enormous,” adds Hauke Kite-Powell, a research specialist at the Woods Hole Oceanographic Institution who sits with Manahan on a National Academies committee studying the issue.

Aquaculture, or mariculture, is still a sliver of the world’s farming output, and a dirty word to those who like their fish wild. In a few years, says Manahan, the world catch of farmed fish will surpass the wild-caught total for the first time in history. The most recent statistics show that in 2007, aquaculture supplied 42 percent of fish consumed worldwide. In the next year or two, that should hit 50 percent.

Prices bear out the trend. Even high-end farmed species such as oysters have come down since 1997 when compared to lowly wild Arctic fish like haddock and Pollock—once staples of cheap cafeteria food, and still major ingredients in fish sticks and fast-food sandwiches.

Experiments performed by David Hutchins, another USC marine biologist, predict that ocean warming will shift the food web in the Arctic toward smaller organisms, reducing the food supply for the major commercial fish.

“It doesn’t look good up there,” Hutchins says. “It looks like the food chain is changing in a way that is not supporting these top predators, of which of course we’re the biggest top predator. There is some question as to how much of that is due to over-fishing and how much of that is due to climate shifts; probably they’re both involved.”

Farming the supersized oyster
Unlike any farmed animal, oysters exhibit hybrid vigor. It’s a somewhat mysterious process that, along with expanded use of nitrogen fertilizer, boosted crop yields during the 20th century, increasing the average yield of corn per acre across the United States sevenfold.

If different strains of corn are inbred—forced to cross with themselves—the offspring look predictably small and withered. But cross two different inbred strains, and their offspring sometimes explode in size, outgrowing not just their inbred parents, but also their vigorous grandparents.

By trying thousands of different crosses, seed companies have developed healthy varieties that dwarf the corn farmed during the early part of the last century. And every year, new and slightly bigger or faster-growing varieties come to market.

The process has an obvious limit: No amount of hybridization can extract more than the soil’s available energy. As crop improvements approach the land’s maximum yield, the world’s population continues to grow exponentially.

USC professor Dennis Hedgecock is sure that oysters have hybrid vigor. He has bred some to grow twice as fast as their wild ancestors. In a 2007 paper in the National Proceedings of the National Academy of Sciences, he and Manahan, along with scientists at biotech giant Solexa, identified 350 genes involved in oyster growth.

Yet even now, Hedgecock knows of no other lab working on hybrid vigor in oysters. He attributes this scientific incuriosity to the challenge of actually demonstrating hybrid vigor. To do so, a researcher must be able to breed hundreds of millions of baby oysters, and then find a commercial farm willing to grow them outside the lab.

Hedgecock has done both. His lab’s research caught the eye of Joth Davis, head of research and development at Taylor Shellfish Farms, located on the bays and inlets of Washington’s Puget Sound.

At a December 2007 meeting with Hedgecock and Davis, owner Paul Taylor agreed to commit time and space for growing Hedgecock’s hybrids. Currently the operation is testing three varieties and focusing on one.

“This particular hybrid cross is great,” Davis says. Having watched the lab specimens grow bigger faster, he expects the harvest, due in 2011, to fulfill its promise.

Taylor plans to sell the 5 to 8 million mature oysters that result from the project, keep 90 percent of the seed for in-house breeding, and offer the rest to other growers.

“Almost any time we make an inbred line and we cross them, their offspring are better than their inbred parents . . . and often they’re better than wild,” Hedgecock says.

Oysters even pack an attractive bonus for those worried about toxic algal blooms. Research on algae points to nutrient runoff from urban areas—mostly sewage and lawn fertilizer—as a possible cause. It turns out oysters are especially good at recycling such nutrients, says Kite-Powell, Manahan’s colleague on the National Academies mariculture committee.

“This is a natural filtration process that is reasonably well understood,” he says, adding that “it’s a piece of the answer; it’s not by any means a silver bullet.”

But in some cases, it seems that oyster farming “is actually an activity that pays for itself while performing this ecosystem service.”

Is aquaculture inevitable?
The committee that Manahan and Kite-Powell serve on is studying, among other things, a conflict between oyster farmers, park visitors and residents in Northern California’s Marin County. Similar conflicts might occur among residents of Malibu if sea pens were proposed for the waters off their beachfront homes.

Manahan is not unsympathetic, but says, “We can’t just sit here and do nothing. What’s going on now is an infinitesimal drop in the ocean of what will happen if there’s a climate shift. You think the cost of food is expensive now? Wait until rainfall patterns in the Midwest change.”

Manahan, who became director of the USC Wrigley Institute in 2008, plans to focus to a large degree on food, energy and water.

“And don’t think they’re not linked,” he warns.

He believes the generation growing up today will hear politicians talk about food the way they now talk about oil. “We need to grow our own” may replace slogans about drilling for oil, he says. “Because when it comes to aquatic foods, we have no policy.”

Read more about USC’s aquaculture research: “The Case for Fish and Oyster Farming”

More USC news: http://uscnews.usc.edu/