Fish farm breakthrough that could save the bluefin

The highly-prized bluefin tuna is now endangered as a result of over-fishing (ALAMY)

The prospect of farming the endangered bluefin tuna from eggs to fully mature adults has come a step closer with the first natural mass spawning of the species in captivity.

A brood stock of bluefin tuna, used in highly-prized sashimi, have produced millions of eggs that have hatched into larvae at a research facility on Croatia's Adriatic coast operated by a US fish-farming company.

Umami Sustainable Seafood of San Diego said it was the first time that bluefin tuna in captivity had reproduced naturally without being treated artificially with hormones. It may soon be possible to rear bluefin tuna entirely on fish farms without taking them from the wild, the company said.

Umami already "farms" bluefin tuna by capturing young fish in the wild and raising them to adults in pens.

"Although we still have a lot of work left to do in achieving our ultimate goal of developing economically viable processes of raising fish from fry, these results prove that our experience, and our understanding of the species, is paying off," said Oli Valur Steindorsson, Umami's chief executive.