Sixteen out of 21 oceanic shark and ray species, which are caught for their valuable fins and meat, face the threat of extinction, the IUCN Shark Specialist Group (SSG) said on Friday.

The SSG cited a study conducted by 15 scientists from 13 research institutes around the world.

Thresher sharks, silky sharks, short-fin mako, and the great white shark are under particular threat as they take a long time to mature and reproduce. Scientists have warned that the current trend could upset the overall balance of the marine environment.

Growing demand for shark fin soup has been driven by rapid growth among Asian economies, the scientists said. Catches are unregulated and unsustainable, as no international catch limits for oceanic sharks have been issued.

"The current rate of biodiversity loss is ten to a hundred times greater than historic extinction rates, and as humans make increasing use of ocean resources it is possible that many more aquatic species, particularly sharks, are coming under threat," says Dulvy, now based at Simon Fraser University, Vancouver.

The results of the study were published in Aquatic Conservation: Marine and Freshwater Ecosystems. The group has urged governments to protect sharks.