By Richard Black
Environment correspondent, BBC News website, Barcelona
Japan's taste for bluefin tuna drives much of the fishing
Major tuna-fishing nations have backed calls for temporary closure of the Mediterranean tuna fishery, branded a "disgrace" by a recent expert report.
The World Conservation Congress passed a motion calling for closure of the bluefin fishery until scientifically sound recovery plans are in place.
Catches are estimated to be about four times higher than scientists recommend.
Spain, which has the biggest quota for Mediterranean tuna, and Japan, the biggest consumer, voted in favour.
The organisation responsible for managing the fishery, the International Commission for the Conservation of Atlantic Tunas (Iccat), was pilloried in a recent independent report which it had been obliged to commission.
Experts from Australia, Japan and Canada noted that the body's performance was "widely regarded as an international disgrace", and that the international community in whose interests Iccat operates "deserves better performance than it has received to date".
The report put the blame firmly on the shoulders of Iccat's member nations which, it said, did not stamp down on illegal fishing, did not provide accurate catch data, and failed to implement proper monitoring arrangements for its fleets.
It concluded there were far too many boats chasing too few fish.
The report recommended an interim ban on fishing in the Mediterranean and eastern Atlantic, a measure that the US has previously backed.
In 2006, Iccat scientists recommended catches be limited to about 15,000 tonnes per year.
But the government appointees that make the decisions chose to allow quotas twice as big, and it is estimated that a further 20,000 tonnes are landed illegally each year.
As a result, the number of fish has fallen to about one-third of its level in the 1970s.
Spain's support for its own fleet has been viewed as one of the principal reasons why catches have not been brought down to sustainable levels.
But here in Barcelona, the Spanish delegation announced that "with satisfaction and responsibility, Spain has participated in building up consensus to get a compromise that will allow us to reverse the critical situation in the bluefin tuna population in the eastern Atlantic and the Mediterranean."
The motion they backed calls for Iccat to shorten the fishing season especially during the spawning months of May and June, establish protection zones around spawning sites and suspend fishing completely until member nations have begun to reduce the size of their fleets.
"We hope it's the end of the degradation of the management of the bluefin tuna fishery," said Sergi Tudela, head of the fisheries programme with environment group WWF.
"Today, it's a turning point - for the first time, important countries like Spain and Japan have supported bold and explicit action to avoid collapse of the stock, and we hope the spirit of this meeting will be continued next month in the crucial Iccat meeting in Marrakesh."
That meeting could decide on a closure, or on other conservation measures.
Japan's demand for bluefin for the lucrative sashimi business is widely cited as the trade's main driver.
But it appears that Japan will back calls for a moratorium.
Fisheries agency official Hideki Moronuki told BBC News: "Urgent and effective action has to be taken for the conservation and sustainable use of this particular species.
"We believe that with this particular motion we can do something for the conservation of bluefin tuna, so that in future it can become a sustainable fishery."