Between 63 million and 273 million sharks are killed every year, mainly for their fins and other parts and the proposal places dozens of species of requiem shark and hammerhead shark families on Appendix II of global CITES accord.
Delegates at a global summit on trade in endangered species have postponed until Friday a vote on whether to approve a proposal to protect sharks, a move that could drastically reduce the lucrative and often cruel shark fin trade.
The proposal would place dozens of species of the requiem shark and the hammerhead shark families on Appendix II of the Convention on International Trade in Endangered Species (CITES).
The appendix lists species that may not yet be threatened with extinction but may become so unless trade in them is closely controlled.
If the plenary meeting gives the green light, "it would be a historic decision," Panamanian delegate Shirley Binder, who presided over the meeting, told the AFP news agency.
"For the first time CITES would be handling a very large number of shark species, which would be approximately 90 percent of the market," she said.
Although a vote had been expected on Thursday, Binder suspended the session late in the afternoon and pushed it to Friday, as debate over the hippo trade between the European Union and African countries dragged on.
Insatiable appetite in Asia for shark fins, which make their way onto dinner tables in Hong Kong, Taiwan and Japan, has spurred their trade.
Despite being described as almost tasteless and gelatinous, shark fin soup is viewed as a delicacy and is enjoyed by the very wealthy, often at weddings and expensive banquets.
Shark fins, representing a market of about $500 million per year, can sell for about $1,000 a kilogramme.
From villain to darling
Sharks have long been seen as the villain of the seas they have occupied for more than 400 million years, drawing horror with their depiction in films such as "Jaws," and occasional attacks on humans.
However, these ancient predators have undergone an image makeover in recent years as conservationists have highlighted the crucial role they play in regulating the ocean ecosystem.
According to the Pew Environment Group, between 63 million and 273 million sharks are killed every year, mainly for their fins and other parts.
With many shark species taking more than 10 years to reach sexual maturity, and having a low fertility rate, the constant hunting of the species has decimated their numbers.
In many parts of the world, fisherman lop the shark's fins off at sea, tossing the shark back into the ocean for a cruel death by suffocation or blood loss.
The efforts by conservationists led to a turning point in 2013, when CITES imposed the first trade restrictions on some shark species.
"We are in the middle of a very large shark extinction crisis," Luke Warwick, director of shark protection for the NGO Wildlife Conservation Society (WCS), told AFP at the beginning of the summit.
During hours-long fierce debate on Thursday, Japan and Peru sought to reduce the number of shark species that would be protected.
Japan had proposed that the trade restriction be reduced to 19 species of requiem sharks, and Peru called for the blue shark to be removed from the list.
However, both suggestions were rejected.
"We hope that nothing extraordinary happens and that these entire families of sharks are ratified for inclusion in Annex II," Chilean delegate Ricardo Saez told AFP.
Several delegations, including hosts Panama, displayed stuffed toy sharks on their tables during the earlier Committee I debate.
The plenary will also vote Friday on ratifying a proposal to protect guitarfish, a species of ray.
The shark initiative was one of the most discussed at this year's CITES summit in Panama, with the proposal co-sponsored by the European Union and 15 countries.
Participants at the summit considered 52 proposals to change species' protection levels.
All are up for ratification.
CITES, which came into force in 1975, has set international trade rules for more than 36,000 wild species.
Its signatories include 183 countries and the European Union.