Fishing nations agree to drop their quota for catching Atlantic bluefin tuna by 600 tonnes next year.
Western scientists say tuna stocks have plunged more than 80 per cent since the 1970s.
On Saturday fishing nations meeting in Paris backed a new quota of 12, 900 tonnes of Atlantic bluefin for 2011, just 600 tonnes down on this year.
Environment campaign groups says the system is toothless.
SOUNDBITE: Susan Lieberman, deputy director, PEW environmental group, saying (English):
"They've adopted some compliance and enforcement measures. That's nice but there's no consequences. If countries don't comply they still get a quota. We're very disappointed and it really calls into question the whole system of managing our fisheries on the high seas, in particular tuna."
The new level has been set by the International Commission for the Conservation of Atlantic Tuna.
France, Spain and Italy catch most of the Atlantic bluefin consumed worldwide.
All but a fifth of it goes to Japan.
The fish can weigh up to 650 kilogrammes and can fetch up to 100, 000 dollars.
Saturday's gathering of fishing nations also agreed to several new measures to protect some shark species but rejected moves to strengthen a ban on shark finning by outlawing the removal of fins at sea.