NEW YORK: More than 20 million people employed in the fishing industry may need to be retrained for other work over the next 40 years if the final collapse of fish stocks in the world's oceans is to be avoided, the United Nations has warned.

The UN's environment branch, UNEP, gave a preview on Monday of its green economy report to be published in October.

It said if the world remained on its path of overfishing, fish stocks could become uneconomic to exploit, or extinct, by 2050.

Pavan Sukhdev, head of the initiative, said: ''Already 30 per cent of the ocean fisheries have collapsed and are producing less than 10 per cent of their original ability.''

At the heart of the analysis is the $27 billion ($31 billion) in subsidies the UN estimates is being injected into fishing every year, mainly by developing countries.