In Australia, a tankful of southern bluefin tuna — regal, predatory fish prized for their buttery sashimi meat — began to spawn, and they didn't stop for more than a month. "People said, 'It can't be done, it can't be done,' " said Hagen Stehr, founder of Clean Seas, the Australian company that operates the breeding facility. "Now we've done it." Scientists believe that the breeding population of the highly migratory southern bluefin has probably plummeted more than 90% since the 1950s. Others have gotten Pacific bluefin to spawn and grow in ocean cages, but by coaxing the notoriously fussy southern bluefin to breed in landlocked tanks, Clean Seas may finally have given the future of bluefin aquaculture legs.