Indian environmentalists have called on the government to curb trading in the whale shark, the world's largest fish.

The fish, which can be up to eighteen meters long and weigh up to twelve tonnes, sell for more than two-thousand dollars each.

Conservationists say they are concerned about over-fishing of the species, with an estimated six-hundred caught off the western state of Gujarat over a fifteen-month period.

They say most whale sharks are caught for export markets such as Taiwan. Although several countries have banned the trade in whale sharks, the fish has no legal protection in India outside marine parks.

From the newsroom of the BBC World Service