Sixty-three countries have agreed to ban the killing of sharks for their fins in the Atlantic Ocean, a move that conservationists said could help bolster the predators' declining population.

The Bush administration pushed for the binding measure, which was adopted unanimously by the International Commission for the Conservation of Atlantic Tunas, an international coalition that manages tuna and swordfish fisheries in the Atlantic. Sharks are often caught by accident along with tuna and swordfish, and fishermen cut off their fins to sell them in Asia for shark fin soup, which can sell for $100 a bowl.

Fishermen often cut off the fins and throw the carcasses overboard because it leaves more room for other catches.

Despite sharks' feared reputation, they are a coveted commercial and recreational commodity, and there are no international catch limits on a species that has declined precipitously in the past few decades. Canadian authorities declared North Atlantic porbeagle sharks an endangered species in May after surveys showed their numbers had declined by 90 percent since the 1960s.

National Marine Fisheries Service Director William Hogarth, who led the U.S. delegation to the commission's New Orleans meeting, said the agreement "is what we needed to ensure the survival of Atlantic sharks."

The United States prohibited shark "finning" in the Atlantic more than a decade ago, but other countries have been slower to follow.

South Korea initially resisted the ban, and any country can still opt out in the next six months before the restrictions take effect. The ban does not apply to other oceans, and environmentalists plan to lobby for a finning ban in the Pacific.

Tens of millions of sharks are killed each year, but it is hard to pin down an exact number because countries do not have to track how many sharks are caught and where they are captured; the commission also agreed to monitor shark catch worldwide and identify where the creatures nurse.