Nations gather this week to decide how many Atlantic bluefin tuna they can extract from the sea without destroying the multi-billion dollar business that keeps Japan supplied in gourmet sushi and sashimi.
The highly charged debate pits dug-in economic interests against mounting concern that the gleaming, fatty fish is teetering close to the edge of viability.
Industrial-scale fishing in the Mediterranean and eastern Atlantic over the last four decades has depleted stocks by 85 percent, scientists say.
The reason is not hard to find: a single specimen of Thunnus thynnus, which can grow to two metres (six feet) and weigh 400 kilos (900 pounds), can fetch over 100,000 euros (137,00 dollars) in Japanese wholesale markets.
|Fishermen haul out tuna after a catch.|
Conservationists warn that stocks will collapse unless the International Commission for the Conservation of Atlantic Tunas (ICCAT), meeting in Paris for ten days from Wednesday, suspends or sharply reduces catches long enough for the species to recover.
They also say the 48-nation body is riddled with fraud, a claim bolstered by recent investigative reports and France's admission in 2007 that its catch for that year was more than double the authorized limit.
"There is so much illegal fishing going on that the only responsible thing to do is to suspend the fishery, get it sorted out, and then open it slowly so the species can recover," said Sue Lieberman, policy director for the US-based Pew Environment Group.
Industry representatives, backed by their governments, say ICCAT has cracked down on renegade fishing in the last three years by adding independent on-board inspectors and an improved ship-to-market tracking system.
ICCAT scientists, they point out, recently concluded that a 13,500-tonne annual quota for the period 2011-2013 "will likely allow the stock to increase during that period".
And that would put the species on track for a 60-percent chance of achieving a so-called "maximum sustainable yield" by 2022, they argue.
"That's still a 40-percent chance of failure," countered Chantal Juoanno, French junior minister for ecology.
"If that happens, there are no more tuna, and no more fisheries," she told AFP last week.
Even so, French fisheries minister, Bruno Le Maire, announced later the same day that France favoured rolling over the 2010 quota at least one more year "to guarantee a good balance between resources ... and the interests of fishermen."
The European Union is also beset by the same policy tug-of-war.
Last month EU Fisheries Commissioner Maria Damanaki proposed to cut the 2011 quota by more than half to 6,000 tonnes, a level consistent with a 97-percent change of sustainability by 2022.
The next day, however, she backtracked after fierce opposition from some member states, calling instead for "a substantial reduction."
The EU has yet to adopt a common position ahead of this week's meeting.
Privately, most green groups are not optimistic that ICCAT will halve next year's catch, much less suspend it entirely.
But other critical conservation measures, they say, may stand a better chance of being adopted.
One is the creation of sanctuaries in the two known spawning grounds for Atlantic bluefin tuna, in the Mediterranean and the Gulf of Mexico.
They also expect ICCAT to tighten data reporting and compliance in order to curtail "illegal, unreported and unregulated" fishing.
"This meeting is a critical test for ICCAT's credibility," commented Michael Hirshfield, chief scientist for the US-based advocacy group Oceana.
Led by Japan -- which consumes 80 percent of the Atlantic bluefin catch -- many ICCAT nations lobbied fiercely earlier this year to reject a ban on international trade under the UN, arguing that ICCAT could manage stocks.
"Now it is up to them to show that they meant it, by actually supporting conservation decisions," Hirshfield said.
Pressure is also building to set catch limits for several species of sharks, some of which have been listed as globally "endangered" and "vulnerable" by the International Union for the Conservation of Nature (IUCN).
Tens of millions of sharks including the mako and the oceanic white tip, are killed every year. They are prized by Chinese gourmets for their fins.