To the Chinese, status is vital not just at meetings of the in-laws, of course, but also in business and diplomacy, and there have been signs of social change here as well. A campaign by WWF-Hong Kong has persuaded more than 150 corporations, including HSBC and Alibaba, to eliminate shark fin soup at their functions. Shangri-La Hotels and Resorts stopped serving shark fin at its 116 properties, half of which are in China. Last summer, the Chinese government announced that it would stop serving the dish at official state banquets. The media have also jumped on the anti-shark-fin bandwagon: recent investigative reports by CCTV, China’s largest television network, reported that much of the shark fin served at top restaurants was fake and that actual shark fin was full of mercury and devoid of nutritional value.

Of course, it’s important to consider other reasons for the drop in reported trade. Nearly all the Hong Kong customs codes for imports changed for 2012, and a large portion of the shark trade may have been reclassified. Shelley Clarke, a fisheries scientist who published the first systematic study of the shark fin trade in 2006, believes that China’s recent austerity drive and a rumored internal crackdown on smuggling have had a powerful complementary effect. But Ms. Clarke agrees that increased awareness is part of the picture.

“It’s a fantastic awakening that the Chinese public has had,” says Sonja Fordham, who is president of Shark Advocates International and led the first efforts to establish American and international bans on shark finning. Mr. Knights told me that traders had been cutting their prices by 40 percent, and multiple sources — from fishermen in Indonesia to undercover agents in China — reported a 50 to 70 percent sales decline in 2012. New data from the Census and Statistics Department show fin imports in the first quarter of 2013 down another 40 percent from the first quarter of 2012, using the new coding categories. While it’s unclear how much reducing Chinese demand will stem the global harvest of sharks, these are encouraging signs, and not just of local import.

The potential to change the consumption patterns of the Chinese middle class has powerful implications for every conceivable commodity, from beef and cars to electricity and water. The government’s apparent embrace of the campaign against shark fin consumption is also crucial. Any long-term solution to overfishing — or climate change or air pollution — will require progressive policies as well as progressive consumers.

When Chinese brides say no to shark fin soup, we should all take notice. The future preferences of consumers in China and India add up to far more than just local custom. Declining shark fin consumption may be a lesson that there is an accounting for taste after all.