At least 1.3 million sharks, many of which are listed as endangered, were harvested from the Atlantic in 2008 by industrial-scale fisheries as unhampered by-catch or size limits, according to a tally released on Monday.
The actual figure may be seven times larger due to under-reporting, said the study, released by advocacy group Oceana on the sidelines of a meeting of the International Commission for the Conservation of Atlantic Tunas (ICCAT).
Convening in Paris on 27 November, the 48-member ICCAT is charged with ensuring that commercial fisheries are sustainable. It has the authority to set catch quotas and restrictions.
While the global spotlight has highlighted the plight of the Atlantic bluefin tuna, many species of high-value sharks are in even more trouble, say marine biologists.
“Sharks are virtually unmanaged at international level,” said Elizabeth Griffin Wilson of Oceana. “ICCAT has a responsibility to protect our oceans' top predators.”
Under the UN Convention on the Law of the Sea, “highly migratory” sharks must be managed by international bodies.
Of the 21 species found in the Atlantic, three-quarters are classified as threatened with extinction.
North Atlantic populations of the oceanic white tip, for example, have declined by 70 per cent, and hammerheads by more than 99 percent, according to the International Union for the Conservation of Nature (IUCN).
Other species - including the porbeagle, common thresher and shortfin mako - have also been overexploited, and may be teetering on the brink of viability.
Many are fished for their fins - prized as a delicacy in Chinese cuisine - and then tossed, dead or dying, back into the sea once the choice morsels have been sliced off.
The practice is prohibited, but loopholes in the regulation have allowed the ban to be widely ignored.
Oceana and several conservation groups, backed by some governments, have called upon ICCAT to set catch quotas and other protective measures for these and other vulnerable sharks.
The United States has proposed requiring that all sharks be brought back to shore whole, which would boost enforcement of the finning ban and help scientists measure population levels.
Japan -- which quashed a drive earlier this year to protect four threatened shark species under the UN Convention on International Trade in Endangered Species (CITES) -- is now urging ICCAT to prohibit fishing one of them, the oceanic white tip.
The initiative “is an example showing our commitment for conservation of shark resources,” the head of the Japanese delegation said in an opening statement.
Sharks have reigned at the top of the ocean food chain for hundreds of millions of years.
But the consummate predators are especially vulnerable to industrial-scale overfishing because they mature slowly and produce few offspring.