To chip away at this culture, campaigners have targeted different aspects of the issue, not only on the part of consumers but also those who transport the fins, and sell shark's fin dishes.

Airlines have been responding to a campaign spearheaded by Hong Kong marine conservation charity MyOcean, and supported by other conservation groups such as the WWF and Hong Kong Shark Foundation.

They issued a letter to about 60 airlines, asking them to stop transporting shark's fin and other shark products. Airfreight only brings in about 10 per cent of Hong Kong's shark's fin, so Alex Hofford, executive director of MyOcean, hopes to pressure shipping companies next. He anticipates it will be harder because "shipping companies are less susceptible to public pressure".

Still, Jerry McLean, director of the Hong Kong Shark Foundation, says: "If we can make it harder to ship, then the cost both in time and profits to the traders and restaurants goes up, and it becomes less economical to offer as a product."

Aside from the supply chain, McLean says, "The central issue is about dealing with demand. It's about giving consumers the right information to make an informed choice and get it off the dinner table."

The government has been omitting shark's fin from its official banquets, but that is a matter of budget rather than principle, says Tracy Tsang Chui-chi, senior programme officer for WWF Hong Kong's shark fin initiatives. "The Hong Kong government has no policy regarding shark's fin at official functions," she says.

That's why environmental groups are seeking a formal stance from the government, to set an example.

But Hofford argues there can be no lobbying of legislators until there is increased public awareness.

"The shark's fin trade in Hong Kong is very strong - the fishing lobbies are very well financed. Shark's fin is almost worth as much as gold, so they've got a lot of money to go around."

WWF Hong Kong has made some progress with three anti-shark-fin campaigns: "No Shark Fin Pledge" for corporations as well as individuals, and "Alternative Shark-free Menu" for food and beverage operators. The corporate pledge is for companies to commit to not buying or selling shark's fin, or serving it at corporate functions.

Participating restaurants and caterers offer set menus that allow diners not to choose shark's fin. To date, there are 115 such outlets. That's a tiny fraction of the roughly 4,700 Chinese restaurants in Hong Kong, but Tsang is hopeful: "Some of these restaurants are part of large chains and a lot of people eat in those restaurants."

Maxim's Group, one of Hong Kong's largest operators of Chinese restaurants, and part of WWF's Alternative Shark-free Menu programme, says that "although shark's fin is seen as a traditional food item in Chinese banquets, there is a gradual change of customers choosing a no shark's fin menu".

"We have been to wedding expos as mystery shoppers, approaching wedding banquet providers, and many will offer us 'eco' menus without us prompting them," says Tsang. "When we ask what 'eco' means, they all explain that it has no shark's fin."

The success of anti-shark's-fin campaigns on consumers can be hard to measure as "there's no real metric," says Hofford. Evidence of responses to them are largely "anecdotal".

In an attempt to gauge public sentiment and consumption patterns, the Island Junior Chamber, part of the Junior Chamber International Hong Kong, a non-governmental leadership development organisation, conducted a survey of more than 1,000 participants in May and June.

It found that 95 per cent of people surveyed recall seeing anti-shark's-fin campaigns. That is a dramatic increase from the 59 per cent found in a similar study undertaken by the University of Hong Kong in 2011. Also, 93 per cent of respondents said they would be willing to substitute shark's fin with something else.

Tse Wing-lam, a twenty-something media industry worker, says: "For our own small family dinners, I ask her family not to order shark's fin and replace it instead with fish maw," another luxurious dried seafood ingredient.

But changes in attitudes will be "more visible", she suggests, "when the younger generations, who are more exposed to the social media … come to organise their own weddings".

She thinks wedding hosts still feel obliged to serve shark's fin at banquets because of the Chinese tradition of guests having to bring a monetary gift, in essence, paying for their meal.

Tse has been trying to convince a friend who is about to get married to take shark's fin off the banquet menu, but her friend is hesitant.

"They don't want to upset their relatives and guests, although not serving shark's fin isn't a concern for the couple. She told me that some wedding guests complain about their hosts being stingy, that their big wedding gift didn't even buy them shark's fin."

McLean says successful campaigns are those that enable people, or companies, to take action. With their shark pledge campaign, they approach companies to start a discussion. This gives business operators a chance to show leadership in the community, which benefits the cause. It's a win-win situation.

"If a company implements a well-thought-out no shark product policy, then that's a result and we'll champion them," he says. "This is fairly black and white for us."

Although the issue of shark protection stems from "a rational argument that shark take-out rates are far exceeding shark reproduction rates", he says, culture and a lack of environmental awareness prevent the public from changing their habits.

Hofford says: "There's certainly a disconnect with Hong Kong people and nature."

Still, there has been a shift in public opinion since photographs were released in January of the masses of shark's fin drying on Kennedy Town rooftops.

"It went viral," Hofford says. "NGOs can publish 20-page reports, but it just leaves people cold until they see it in an image. The power of images really changes hearts and minds."

Hofford believes that the media, and, in particular, social media, are vital to the cause. "Older people are less susceptible to social pressures," he says. "But young people are done with eating shark's fin."

In the meantime, many older Hongkongers still expect shark's fin dishes at banquets. "They think it's a grand thing to eat for occasions like Lunar New Year," Tse says. "To them, other foods don't carry the same weight as shark's fin."