Great sharks are disappearing from the world’s oceans, the American Association for the Advancement of Science conference in Boston heard on Sunday. Unregulated fishing has led to catastrophic declines – and nine shark species will be added this year to the official Red List of animals at heightened risk of extinction.

Julia Baum of the Scripps Institution of Oceanography in California said there was particular concern about the scalloped hammerhead shark, “which will be listed as globally ‘endangered’ [by the International Union for the Conservation of Nature] due to overfishing and high demand for its valuable fins in the shark fin trade”.

To highlight the recently recognised threat to sharks, Ms Baum, who is on the IUCN’s specialist shark group, obtained permission to preview this year’s Red List, which will be released in October.

“Our oceans are being emptied of sharks, and the scale of the problem is global,” she said. “We are looking at a high risk of extinction for some of these species over the next few years.” The loss of “top predators” such as sharks can seriously damage whole marine ecosystems.

Research over the past five years at Dalhousie University in Canada shows that all shark species have declined by more than 50 per cent since the early 1970s in the north-west Atlantic. Many large coastal sharks had much greater falls in population: tiger, scalloped hammerhead, bull and dusky sharks are down by more than 95 per cent.

The United Nations General Assembly passed a resolution last December calling for immediate shark catch limits as well as a ban on shark finning, the practice of removing only a shark’s fins and dumping the still live but now helpless fish into the ocean to die. But there are no agencies ready to put these proposals into practice, Ms Baum said.

Between 23m and 76m sharks pass through the Hong Kong fin market every year, according to Ms Baum. Each fin fetches between $100 and $300. Millions also die because they are caught accidentally by boats catching tuna and swordfish.