Basketball superstar Yao Ming and British entrepreneur Richard Branson joined forces on Thursday to get shark fin soup off the menu and save some of the species from extinction.

The soup, considered a delicacy, is widely served at top-class restaurants on the mainland, Hong Kong and Taiwan. To cater for demand about 1.5 million sharks are slaughtered every week for their fins, a move that endangers some species.

"Few people know the importance of sharks in maintaining the ecological balance," recently retired NBA star Yao said in Shanghai during an event, sponsored by conservation group WildAid, to launch the campaign against the shark fin trade.

"Nor do they realize the cruelty of the finning process," Yao said.

After the fins are sliced off, sharks are discarded back to the ocean where they are condemned to a slow, agonizing death due to diminished speed and maneuverability.

"There is no reasonable explanation for the cruelty," Yao said.

Despite growing calls to ban the trade and consumption of shark products, demand in China has been growing rapidly as the economy booms.

"Those who eat shark fin soup told me they don't particularly like it," Branson, president of Virgin Atlantic Airlines, said.

"It was just the tradition. That means it's possible to get people to switch to other food, and make the soup unfashionable."

Yu Zhengming, a middle-aged businessman from Wenzhou, Zhejiang province, said delicacies, such as shark fin, abalone and bird's nest, are "staples for a luxurious banquet".

It is common practice in wealthy circles to give money in red envelopes as wedding gifts and the new couples, in return, try to provide a banquet worth the value of the large amount of money they received. They do this by serving expensive cuisine, Yu said.

Wu Qi, a 25-year-old white-collar worker in Shanghai, is planning her wedding for later this year. "We booked the 5,888 yuan (US$922) per table banquet, and shark fin soup is listed on all three potential menus."

Wu and her fiance finally convinced their parents to serve sea cucumber instead. They said that their friends would be concerned about the environmental effect, especially as one of them works for Greenpeace.

Some restaurants and hotels, such as URBN Hotel Shanghai where the campaign launch was held, have taken action.

The Dragon Hotel, a five-star hotel in Hangzhou, Zhejiang province, announced it had stopped providing shark fin dishes from Sept 19.

Bao Rongjun, the hotel's communication manager, said more than 30 shark fin dishes were removed from the menu.

"Our business will suffer. The hotel will see its revenue drop by 6 million yuan (US$940,000) a year," she said.

Jin Ding Xuan, a Cantonese seafood restaurant chain in Beijing, has gone a step further by stopping all sales of live seafood.

"We stopped selling live seafood last October," Sui Tongping, manager at the Ditan branch in Beijing, said.

"People like shark fin for its rarity. It doesn't have any special nutritional element," he added.