Major changes to rules on shark finning are needed to preserve the health of the world's shark populations, conservationists say.
Campaign group Oceana says confusing regulations and poor enforcement mean rule-breaking is common.
Actor and activist Ted Danson told BBC News that proper management could rescue species in decline.
More than a half of ocean-going sharks, and about a third of European species, are threatened with extinction.
"The basic problem is it's a fishery that's not even considered a fishery in most areas," said Mr Danson.
"You go out and you fish for swordfish and you catch 20 sharks, [and you say] 'it's a shark, who cares, we don't count them - doesn't matter'.
"So you have a fishery that's not managed and not controlled."
Of the estimated 100 million sharks caught each year, about half are taken accidentally by fishermen looking for such species as tuna, marlin or swordfish.
The remainder are targeted principally for their fins, which are used in shark fin soup, a delicacy in parts of East Asia.
The EU and US both have rules governing this catch. But Oceana believes - as do other environmental groups - that the differences between Brussels and Washington are a boon to would-be rule breakers.
"What they do is allow fishermen to cut fins off sharks and then land sharks and fins in specified ratios," said Mike Hirschfield, the organisation's chief scientist.
"And you can imagine all of the opportunities for mischief that result."
About 50 million sharks a year are caught accidentally
The EU dictates that the weight of fins landed must amount to no more than 5% of the weight of shark carcasses landed.
US scientists believe that figure is too high, allowing fishermen to land two or even three fins for every carcass, with the remains of the rest of the sharks dumped overboard.
US rules for the Pacific limit fin landings to 5% of dressed weight - the weight after all the inedible parts such as bones and gut have been removed.
In the Atlantic and Gulf of Mexico, regulations have recently been tightened to say that sharks must be landed with fins attached. This may extend to the Pacific soon, and Oceana would like to see as a global standard.
"Requiring that sharks be landed with their fins attached is by far the most reliable means of enforcing a ban on shark finning," commented Sonja Fordham, policy director of the Shark Alliance.
"It also improves the ability to collect species-specific catch information that is important for population assessment."
Had its chips
The UK is the fourth largest shark-fishing nation in Europe.
Britons partaking of fish and chips will sometimes be eating shark - though you might not always know it.
Properly called the spiny dogfish or spurdog (Squalus acanthias), the chippy's favoured shark is more usually labelled as rock salmon.
Populations in the northeast Atlantic are categorised as Critically Endangered by IUCN, the global conservation organisation that compiles the annual Red List of Threatened Species.
But in a global sense, UK fish and chip shops are a minor player in the decline of sharks.
Seafood industry body Seafish says sales of spiny dogfish are so marginal as not to feature on retail datasheets.
"The UK has historically been a voice for sustainable fishing," said Dr Hirschfield.
"But many policies governing sharks are set in Brussels, and it's ministers of the different countries that ultimately have the final say in Brussels - so the UK needs to continue to be a voice for sustainable fishing."
But Ms Fordham argued the UK could tighten up its own act.
"The UK is one of only five EU member states that issue special permits to allow the removal of fins at sea under the EU finning ban," she said.
"The UK could lead the way toward a solid EU finning ban by discontinuing these problematic permits, thereby ensuring that shark fins remain attached through to the point of landing."
Much of the time and attention of environment officials in Brussels and London - and in other capitals - is now taken up with climate change.
Some conservationists fear other important issues are being sidelined - a position which Ted Danson regrets.
"Let's say - cross our fingers - that we solve the problem with global warming; by the time we do that, it's quite conceivable that we've fished out our oceans," he said.
"I don't think you can compartmentalise any more, you need to handle all these problems simultaneously."
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