You've got to get up early to catch Hagen Stehr.

Dozens of pallets of frozen herring line the deck of the “King Fish,” one of the burly 68-year-old's many fishing boats.

It's heading out to huge cages six nautical miles off the South Australian coast. Each contains about 3000 hungry tuna.

“It's time for breakfast. This is the first feeding of the day,” Stehr says. The cages are the fisherman's fortune. And perhaps wild tuna's last best hope.

Numbers of southern bluefin tuna have diminished drastically in recent decades. The International Union for the Conservation of Nature (IUCN) lists the species, prized for sushi, as critically endangered. It estimates that we've lost at least 85 percent of breeding-age tuna since 1960.

Tighter fishing quotas in the 1990s turned Stehr from a hunter of the seas to a farmer. He skirted limits on take-sizes by herding the smaller fish he caught into cages, where they were fattened and sold for greater profit later.

A multi-million-euro business

Aquaculture costs a lot of money. Especially for tuna. The predators' insatiable appetite requires about 25 kilograms of prey-fish to produce one kilo of tuna.

Stehr feeds his tuna 30 to 40 tons of herring and sardines a day.

“It's as if you were to throw $30,000 to $40,000 into the ocean. And then you just pray to God that it pays off,” he says.

After six months, most of the tuna are frozen, shipped to Japan, and land on plates as sushi.

Japan's huge demand drives the global tuna business. Most of the catch lands in the fish markets there. In Tokyo's auction halls, a full-grown 200 kilogram tuna can sell for more than 100,000 euros.

From sailor to millionaire

Stehr's business acumen, and a growing international appetite for tuna, have made the German-born Australian a multi-millionaire.

At the age of 12, Stehr ran away from his home in the northern German city of Salzgitter to join seaman's school near Bremen.

He slaved away on a freighter and fought with the French Foreign Legion. After turning 18, he found himself in Port Lincoln, South Australia, where he has worked himself up to becoming one of the country's 200 wealthiest people. 

Fishing licenses he once purchased for $15 Australian are now worth millions.

Along with a handful of competitors, he helped turn Port Lincoln into a fishing capital with the country's highest per capita density of millionaires.

The next challenge

Yet for all their fattening in pens, tuna have proved remarkably difficult to breed in captivity. Supplying the demand for sushi continues to depend on catching wild tuna. 

“Tuna fish are much more sensitive than other fish." says Morton Deichmann, a marine biologist. 

"When they're stressed, they stop eating and die. It's difficult to contain them without hurting them. We still have to figure out how this works.”

Deichmann works for Clean Seas Tuna, a company Stehr helped found with the ambition of breeding tuna.

Its first breakthrough still brings a tear to his eye.

A virtual migration

The problem is that southern bluefin tuna love their freedom. They don't spawn until they have covered a journey of hundreds of kilometers.

They migrate from Australia's southern coast, via the west coast, to waters around Papua New Guinea, then back. The journey takes five months.

Stehr's response was to fool them.

In 2006, Clean Seas began an experiment. Using helicopters, it flew female tuna, weighing over 100 kilograms, to a 40-meter research pool on land.  

The tuna were exposed to changing currents, salinity and water temperatures appropriate to their migration route. A computer even controlled a light installation to mimic star patterns and phases of the moon.

A long road

Success came on March 12, 2009: The fish bred for the first time outside the ocean.

It was a historic moment for Stehr, but not the end of the road. Challenges remain. Not least, finding a substitute for the tuna's prey fish, which themselves face overexploitation.

This year Stehr wants to introduce 10-centimer long tuna into feeding pens. The farm-bred fish are expected to come onto the market by 2015.

As lucrative as his idea may be, Stehr says it is also a milestone for the conservation of a species he once helped plunder.

“The worldwide tuna population is becoming more and more endangered," Deichmann says.

"We have found the right way to deal with this problem if we still want to eat fish in the future.”

Author: Norbert Lübbers/kms
Editor: Nathan Witkop