BRUSSELS, June 6 (Reuters) - The European Union agreed on Thursday to tighten an existing ban on "shark finning", or slicing fins off sharks often while they are still alive, which environmental campaigners say is cruel and threatens the survival of some species.
Once the change comes into effect, the ban will forbid shark finning by all vessels in EU waters and by all EU-registered vessels anywhere in the world, a move its supporters believe will put pressure on countries where the practice is common.
"Shark finning is one of the main threats to the shark population," said Sandrine Polti, policy adviser to the Shark Alliance. "We're now in a much better position to push for a global shark-finning ban."
A surge in demand for shark fins, mostly for soup and traditional medicine in Asia, and in particular China, means they can fetch up to 1,000 euros ($1,300) each.
The proposed new law, approved by EU ministers and expected to come into effect later this year, closes a loophole in EU rules by which fishermen with special permits are still allowed to remove fins from shark carcasses at sea.
Under the tighter rules, fishermen will have to land all sharks with their fins attached, although they will be allowed to slice partly through each fin and fold it against the carcass for ease of storage and handling.
Portugal, worried about the impact of the changes on fishing revenues, voted against the law, ministers said in a statement, but it was not able to veto the agreement.
Animal rights groups say finning is cruel because the shark is often still alive when the fin is removed and drowns when it is thrown back into the water.
The practice also poses a threat to several species that play a vital role in maintaining the balance of marine ecosystems, environmental groups add.
About one-third of all shark species are threatened with extinction, according to the International Union for Conservation of Nature.
Sharks are particularly vulnerable to over-fishing because of their slow growth rate and small number of young.
The EU supplies around a third of all shark fins to the Hong Kong market, the global centre of the shark fin trade. ($1 = 0.7642 euros) (Reporting by Barbara Lewis; editing by Rex Merrifield and Mike Collett-White)