A UN wildlife conference placed one shark species on a protective list but blocked efforts to do the same for other types hunted to meet mounting Asian demand for shark fin soup.
Conservationists welcomed the new protection for porbeagle sharks, which are about 2.5 metres long and hit by overfishing in the Atlantic and Mediterranean.
But they criticised delegates at the 175-nation Convention on International Trade in Endangered Species (Cites) for failing to restrict trade in several other sharks.
"Politics and economics have trumped science, especially on marine conservation issues," said Matt Rand, director of global shark conservation at Pew Group.
The global shark product trade was worth $310 million in 2005, according to Traffic, a wildlife trade monitoring group. Shark populations are dwindling as a result of overfishing.
The conference rejected greater trade protection for the oceanic whitetip, scalloped hammerhead, great, smooth and dusky hammerhead, sandbar and spiny dogfish sharks.
The March 13-25 conference in Doha, Qatar, previously denied bluefin tuna and red and pink coral more protective listings. A protective listing requires a two-thirds majority.
"Once again Cites has failed to listen to the scientists.
"The decision not to list these sharks today is a conservation catastrophe for these species," said Glenn Sant, global marine programme coordinator for Traffic.
One of the world's most expensive food products, a bowl of shark fin soup can cost $100, with a single fin worth more than $1,300.
Up to 10 million kilos of shark fin are exported annually to Hong Kong by nearly 87 countries, according to Oceana, a marine conservation group.
Demand for the soup has exploded in Asia, where an expanding middle class can now more easily afford a delicacy once reserved for the wealthy. Japan, Indonesia, Malaysia, Taiwan, Thailand and China are big shark fin consumers.
The porbeagle proposal was made by the European Union and Palau. Voting was by secret ballot but South American, European and North American nations are believed to have been in favour, with many Asian nations against.
Nations exporting porbeagle meat and fins will have to ensure trade is legal and sustainable.
"Some of the biggest players are supporting a protective listing because in the end, it's not advantageous for them to oppose measures that will help preserve the species," said Anne Schroeer, an economist at Oceana.
Some of the votes, including for scalloped hammerhead sharks, came close to mustering the two-thirds majority needed for protection.
Supporters of a ban might try to have a repeat vote on the conference's final day, allowed under Cites rules.
Up to 73 million sharks are killed each year, primarily for their fins, according to environmental organisation Greenpeace.
Sharks are especially vulnerable to over-fishing because they are late to mature, long-lived and produce few young.