Countries involved in bluefin tuna fishing have decided to do more to protect a species of shark against collateral killing, environmental groups said

(AP) -- Delegates at an international conservation meeting agreed Saturday on a measure mandating that silky sharks accidentally caught in fishing gear be released back into the sea alive, marine advocacy groups said.

The 48-member International Commission for the Conservation of Atlantic Tunas (ICCAT), however - ending a weeklong meeting in Istanbul - failed to reach consensus on other threatened shark species, the groups said.

Conservationists also said more could have been done to save swordfish from decline in the Mediterranean while the World Wildlife Fund said steps adopted to preserve bluefin tuna remained insufficient.

While establishing protections for the silky sharks, ICCAT - which manages tuna in the Atlantic and Mediterranean as well as species, like sharks, that have traditionally been accidental catches for tuna fishermen - made an exception for coastal developing countries, where the predators can continue to be caught for local consumption of their meat and not for the trade of their fins.

The sharks, named after the silk-like smooth texture of their skins, are among shark species most vulnerable to decline, threatened by the international trade in shark fins due to an increasing demand mainly in Asia for shark fin soup.

Marine advocacy groups, including Oceana and The Pew Environment Group, welcomed the measure saying it would help overturn the silky sharks' decline, though they also said they had hoped for more.

"Cutting the nets to free sharks when they are caught, will give a large number of them a real chance to survive," Susan Lieberman, director of international Policy at the Pew Environment Group, told The Associated Press by telephone. "The measure is an important step."

The group estimates that up to 1.5 million silky sharks are traded annually for their fins, and that up to 40 percent can survive if they are returned to the sea alive.

"It is a very good step forward in protecting one the most vulnerable species," said Elizabeth Griffin Wilson, senior manager of marine wildlife at Oceana.

The advocacy groups however, expressed disappointment that no measure had been taken to protect porbeagle sharks, or to establish catch limits for blue and shortfin mako sharks.

"It's another year that they could not reach a decision for the porbeagle shark," Lieberman said of the species which continue to be fished in Canadian waters.

Other measures adopted by ICCAT in Istanbul include a requirement for members to submit data on the species they catch or risk losing their right to catch those species in the following year. Oceana has said failure to report on catches were preventing conservationists from adequately assessing the impact of fisheries on threatened species.

On swordfish, ICCAT agreed on a set measures, including setting a minimum size for catch, but Oceana said "more should be done."

The conservation body also agreed on a system to electronically track data on bluefin tuna to better control fraudulent practices and help keep fishing closer to the legal quotas. A Pew report has found that in 2010, the amount of Mediterranean bluefin tuna traded surpassed the ICCAT quota by 141 percent.

The WWF said, however, the measure did not include data on fish transfers to tuna fattening farms in the Mediterranean arguing that this allowed for the "laundering of illegal, unregulated and unreported catches." The group called for a more "reliable" data assessment or for the total ban of tuna farming in the Mediterranean.

In a move to fight illegal fishing, ICCAT members also decided that vessels measuring 12 meters or more - instead of the previous 20 meters or more - would be inspected on arrival to port, Pew said.

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