A world body of fishing and shipping nations approved a catch quota Monday to protect the overharvested Mediterranean swordfish, its population slashed by more than two-thirds in 30 years.

The limit was set at 10,500 tonnes for 2017 at a meeting of the 51-member International Commission for the Conservation of Atlantic Tunas (ICCAT) in Vilamoura, Portugal.

It will be further tightened by three percent per year between 2018 and 2022 as part of a larger 15-year plan to rebuild Mediterranean swordfish stocks by 2031.

"It's done. Finally, ICCAT on its 50th anniversary moved a step forward on this too long-neglected stock," Ilaria Vielmini of conservation group Oceana told AFP in the coastal town where the commission held its annual meeting.

According to Oceana, stocks of the fish are "practically exhausted" after three decades of heavy overfishing of the pricey gourmet favourite.

The European Union, which takes about 80 percent of Mediterranean swordfish catches and proposed a quota, said this was a decisive step towards the conservation of the stock.

"The European Union holds a special responsibility to saving swordfish. We owe it to our fishermen, especially the small-scale ones," EU environment and fisheries commissioner Karmenu Vella said in a statement.

"Thousands of jobs would be on the line had we not agreed this important step today."

The swordfish quota will be reexamined following a scientific stock recount scheduled for 2019.

While the swordfish species as a whole is not threatened, its Mediterranean sub-group is "overfished", according to the International Union for the Conservation of Nature, which keeps a "Red List" of species that are endangered or at risk of becoming so.

The Mediterranean stock has plummeted 70 percent since 1985 and over two-thirds percent of total catches were of immature fish that had not yet had a chance to reproduce.

- 'First step -

Italy is the main taker of Mediterranean swordfish, followed by Morocco, Spain, Greece and Tunisia.

"The agreement also improves technical and control measures," said the EU.

"This includes the increase of the minimum size to protect juveniles, the control of... sport and recreational fishery, the recording and reporting of the catches, the introduction of a scheme of international inspections and the deployment of scientific observers."

Green groups welcomed the first-ever swordfish quota, but with disappointment that it was not stricter.

The limit for 2017 is higher than the catch taken in each of the last four years -- about 10,000 tonnes.

"This was the compromise (needed) to reach the consensus," said Alessandro Buzzi of conservation group WWF.

The three-percent annual reduction was "very weak", he said, but any quota was better than none.

"It is a first step towards recovery," added Vielmini. "I hope it is a turning point."

The ICCAT is comprised of 50 countries as well as the EU bloc.

It is responsible for conservation of tunas and related species in the Atlantic Ocean and adjacent seas, as well as creatures which get tangled up as bycatch in tuna fishing.

Importantly, the commission oversees fishing of Atlantic bluefin tuna.

With the help of quotas, the spawning stock rebounded to 585,000 tonnes by 2013, nearly double the levels of the 1950s, according to ICCAT figures.

Two years ago, the commission's members decided on a 20-percent annual increase over three years in bluefin tuna quotas in the Mediterranean and East Atlantic, despite objections that evidence of stock recovery was sketchy.

The limit for 2015 was 16,142 tonnes, rising to 19,296 this year, and 23,155 in 2017, when a new stock and quota assessment is due.

Prior to the meeting in Portugal, some countries had called for a relaxation of quotas to be discussed -- but the issue never came up, observers told AFP.