Can we feed the world with farmed fish?

For years, scientists and activists have sounded the alarm that humans' appetite for seafood is outpacing what fishermen can sustainably catch. But new research suggests there is space on the open ocean for farming essentially all the seafood humans can eat. A team of scientists led by Rebecca Gentry, of the University of California, Santa Barbara, found that widescale aquaculture utilizing much of the ocean's coastal waters could outproduce the global demand for seafood by a staggering 100 times.Their paper, published Monday in the journal Nature Ecology & Evolution, could have significant implications for a planet whose human population is projected to reach 10 billion by 2050. Nearly every coastal country has the potential to meet its own domestic demand for seafood, "typically using only a minute fraction of its ocean territory," write the authors.In their research, the scientists analyzed the potential of virtually every square mile of the ocean's surface for producing 120 different species of fish and 60 species of bivalves – that is, mussels, clams, oysters and scallops. They immediately eliminated ocean waters deeper than about 650 feet, since ocean aquaculture generally requires anchoring floating pens and cages to the seafloor. They sought out areas rich in dissolved oxygen and phytoplankton – essential for bivalves, which filter microscopic food from the water. The researchers also excluded marine protected areas and regions where floating pens and cages might block shipping lanes and port entries or interfere with oil extraction.They calculated that marine aquaculture could produce 16.5 billion tons of fish per year, or about 4,000 pounds per person."And we were being very, very conservative in our calculations," says co-author Halley Froehlich, a postdoctoral researcher at UC Santa Barbara.