HONG KONG — Few things epitomize the burgeoning affluence and consumerism of the swelling middle class in mainland China as well as the soaring sales of luxury handbags, cars, and shark fin soup. Yes, shark fin soup.

Once a delicacy confined to the upper echelons of Chinese society, the pricey soup is considered a must-serve at the lavish banquets that mark big occasions like weddings or corporate celebrations. And thanks to the galloping economic growth China has achieved since the 1990s, the soup is within the financial reach of millions of newly prosperous people.

The result has been severe overfishing. Scientists estimate that many millions of sharks are killed every year, primarily for their valuable fins.

Add to that the fact that these creatures reproduce slowly, and you get a sharp decline in global shark populations, to the extent that some scientists say about 30 percent of all shark species are in danger of extinction. And because sharks are at the top of the food chain, their declines have a profound effect on the balance of marine ecosystems.