KUSHIMOTO, Japan — Tokihiko Okada was on his boat one recent morning when his cellphone rang with an urgent order from a Tokyo department store. Its gourmet food section was running low on sashimi. Could he rustle up an extra tuna right away?
Mr. Okada, a researcher at Osaka’s Kinki University, was only too happy to oblige—and he didn’t need a fishing pole or a net. Instead, he relayed the message to a diver who plunged into a round pen with an electric harpoon and stunned an 88-pound Pacific bluefin tuna, raised from birth in captivity. It was pulled out and slaughtered immediately on the boat.
Not long ago, full farming of tuna was considered impossible. Now the business is beginning to take off, as part of a broader revolution in aquaculture that is radically changing the world’s food supply.
“We get so many orders these days that we have been catching them before we can give them enough time to grow,” said Mr. Okada, a tanned 57-year-old who is both academic and entrepreneur. “One more year in the water, and this fish would have been much fatter,” as much as 130 pounds, he added.
With a decadeslong global consumption boom depleting natural fish populations of all kinds, demand is increasingly being met by farm-grown seafood. In 2012, farmed fish accounted for a record 42.2% of global output, compared with 13.4% in 1990 and 25.7% in 2000. A full 56% of global shrimp consumption now comes from farms, mostly in Southeast Asia and China. Oysters are started in hatcheries and then seeded in ocean beds. Atlantic salmon farming, which only started in earnest in the mid-1980s, now accounts for 99% of world-wide production—so much so that it has drawn criticism for polluting local water systems and spreading diseases to wild fish.