WASHINGTON - By the end of this year, the world is projected to reach an unheralded but historic milestone: Half of the fish and shellfish we consume will be raised by humans, rather than caught in the wild.
Reaching this tipping point is reshaping everything from our oceans to the livelihoods and diets of people across the globe. It has also prompted a new round of scientific and political scrutiny, as researchers and public officials examine how aquaculture is affecting the world's environment and seafood supply.
"Hunting and gathering has reached its maximum," said Ronald Hardy, who directs the University of Idaho's Aquaculture Research Institute and co-authored a study on the subject in the Proceedings of the National Academy of Sciences. "We've got to grow more."
The drive to bring fish "from egg to plate," as Hardy puts it, has the potential to answer a growing demand for seafood worldwide, as well as reduce some of the imports that compose more than 80 percent of the fish and shellfish Americans eat each year. But without technological advances to improve efficiency, it could threaten to wipe out the forage fish that lie at the bottom of the ocean's food chain and potentially contaminate parts of the sea.
And consumers will have to accept that they are eating a different kind of fish than the ones that swim wild: ones that might have eaten unused poultry trimmings, been vaccinated, consumed antibiotics or been selected for certain genetic traits.
Although there is still debate about farming's share of the world fish supply - the United Nations' Food and Agriculture Organization estimates it stood at 44.3 percent in 2007, whereas the PNAS study says it will reach over half in a matter of months - no one questions that aquaculture has grown exponentially as the world's wild catch has flattened out. In 1970, farmed fish accounted for 6.3 percent of global seafood supply.
This trend reflects global urbanization - studies show that as more people move to cities, they are consuming more seafood - but it is changing the world's seascape as well. Vessels now venture to the Antarctic Ocean to catch the tiny krill that have sustained penguins and seals there for millennia, and slender poles strung with farmed oysters and seaweed jut out of Japan's once-pristine Matsushima Bay.
Chinese freshwater fish farms are replacing traditional agricultural plots there, according to Karen Seto of the Yale School of Forestry and Environmental Studies, and Nature Conservancy senior scientist Mike Beck said some Chinese bays are so crammed with net pens that they are no longer navigable.
Moreover, fishermen such as Shannon Moore, who catches salmon in Washington state's Puget Sound, worries about how farmed fish's parasites are affecting wild stocks. "These young wild critters are pretty small, and they can ill afford to have these hitchhikers on them," Moore said, referring to parasites that plague juveniles migrating near Canadian fish farms.
But aquaculture's proponents suggest that farming represents the best chance of giving people a chance to make a living off the sea. Sebastian Belle, executive director of the Maine Aquaculture Association, noted that three-quarters of his group's members are either current or former commercial fishermen, and although the average age of Mainers with a fishing lease permit is 57, the average for those with a fish-farm permit is 33. "It's really the next generation of watermen," Belle said.
Jane Lubchenco, who used to write about aquaculture's environmental impacts as an academic before taking the helm of the National Oceanic and Atmospheric Administration, announced this month her agency will come up with a national policy to address fish farming. "It's important that aquaculture be done in a way that's sustainable," she said in an interview.
Farms are expanding in traditional U.S. fishing strongholds, such as New England, the Gulf of Mexico and the Pacific Northwest, and freshwater fish farms continue to operate in states such as Alabama, Arkansas and Mississippi. Freshwater species such as catfish, trout and tilapia still dominate the nation's farmed fish production, but such niche products as oysters with regional appellations and sustainably raised shrimp and caviar now fetch a premium in the United States.
Michael Rubino, who directs NOAA's aquaculture program, said he envisions a future in which the country is "producing seafood from a range of technologies, with wild catch on one side, aquaculture on another, and a whole range in-between."
One-fourth to one-third of the world's fish catch is landed just to produce the fish oil and fish meal that fish, poultry and pig-farming operations demand, depleting stocks of forage fish such as anchovies, sardines and menhaden. Aquaculture has become more efficient" In 1995, it took an average of 1.04 kilograms of wild fish to produce 1 kilogram of farmed fish, according to the PNAS study, and in 2007 it took 0.63 kilograms to achieve the same result. The sector's share of global fish-oil and fish- meal supplies has doubled in the last decade, as the industry has boomed.