The finest fish are wriggling out of reach of local restaurateurs and wholesalers as fishermen sell their hauls at sea, writes Charley Lanyon

Fresh seafood features prominently in Cantonese cuisine and Hong Kong certainly loves its fish, especially live reef fish such as grouper and humphead wrasse. Chefs at high-end seafood restaurants routinely pay top dollar for the best specimens.

Japan is perhaps the only place in the world better known for its fondness for seafood.

However, the size and quality of catches being sold in Hong Kong has declined markedly in the past decade. Much of that stems from severe overfishing in surrounding waters, but another major cause is that the supply is being siphoned off. Mainland buyers often meet Hong Kong fishing boats while they are at sea, then snap up the best of the catch before the locals even get a look at the haul.

The practice of selling catches to the highest bidders at sea is an open secret to people in related businesses, and one that chefs and seafood sellers in Hong Kong are powerless to do anything about.

"In Hong Kong, people negotiate hard for a better price, but mainland and Japanese boats just say, 'Hey, here's the money'," explains a seafood importer who does not want to be named.

Local fishermen welcome this offshore trade because "there's more money and less hassle", he says. Mainland and Japanese buyers are able to offer far higher prices than their counterparts in Hong Kong, which helps make up for the smaller catches they are getting. "You shouldn't be shocked. It's pure business."

The effects of this off-the-books business are easy to see in the restaurants and markets of Hong Kong.

"It's been common knowledge for the past few years, but you never actually see what's missing - due to mainland consumption," says chef David Lai, who runs the On Lot 10 and Bistronomique restaurants. "The most tangible signs may be the steady rise in prices."

To the seafood importer, however, the most noticeable changes are at the table: "At lavish banquets, the centrepiece is often an enormous grouper or locally caught lobster. But in recent decades those centrepieces have shrunk considerably. You now have to settle for more portions of smaller fish."

This can be tough for some Hong Kong diners to swallow; as the importer points out: "In [Chinese] banquets, it's all about size."

Lai and other chefs of Western restaurants have also felt the pinch. "Certain species such as the yellow croaker, which is in high demand due to its popularity in traditional Shanghainese recipes, command stratospheric prices that normal Hong Kong people can't afford," he says.

Getting his hands on a large specimen can be almost impossible. "Anything above one catty, or 600 grams, is considered big, and the largest ones can be worth many thousands of dollars. These fish are rare, and they automatically go to the mainland." Even well-known restaurateurs such as Lai can be at a disadvantage when securing the finest morsels:

"Once in a while my fish people will call me in the morning to ask whether I want to buy some rare fish they caught or found. Basically, I have three seconds to say 'yes' or else they end up going north," he says. "We get first right of refusal because we are loyal customers and we always pay cash and don't waste time bargaining."

It's is a huge change from when fishermen such as Cheng Hing plied the seas during the 1970s. While Hong Kong was taking off, China was still a centralised economy with relatively poor living standards. Mainland fishermen were required to sell what they caught to the state at set prices, but it wasn't long before more daring souls were quietly selling choice picks from their catch to Hong Kong boats.

"It was a total reversal [of the current situation]," says Cheng, whose family has been fishing for generations.

In the past, Hongkongers were able to pay more. Nowadays, "it's the Chinese boats that approach Hong Kong fishermen [out at sea] and try to buy their catch right there for a higher price," he says.

Cheng, who became a wholesaler after his fishing days, says sales of frozen and chilled seafood are regulated by the Fish Marketing Organisation, but the trade of live fish falls into a grey area.

"So, from a business perspective, Hong Kong fishermen are happy because they don't have to use expensive fuel to return to Hong Kong and waste time on government procedures to sell their fish."

It's much more convenient for the fishermen, who can continue trawling instead of coming ashore to offload their haul before going out to sea again, he says.

Convenience aside, most Hongkongers simply don't have the spending power to compete with wealthy mainland consumers. "Hong Kong people have to accept it because they're poor these days compared with the Chinese," says the importer.

Lai agrees: "We live in a capitalist society driven by supply and demand, and we can't pretend to have it both ways ... In the '60s and '70s Hong Kong was the land of opportunity, and people did so well that there was a saying to describe it - 'eating shark fin with rice'. Who are we to judge?"

Of course, it's not only mainlanders who are snatching up the best seafood, including hand-picked diver scallops. "There are huge diver scallops caught by Hong Kong fishing boats all the time, but Hong Kong only ever gets the second-largest ones because Japanese fishing boats buy all the big ones first," the importer says.

In any case, he points out that the notion of provenance for seafood is flawed and mainly used as a marketing gimmick. If a fish is described as Japanese, that just means it was brought to market on a Japanese boat, not caught in Japanese waters.

Trading fish at sea is common among many nations, though local barrister Lawrence Lau suggests the practice treads risky legal waters in Hong Kong.

"Buying marine livestock in Hong Kong waters for seamen's personal supply and consumption is not an issue," Lau says. "However, if the vessel is buying such livestock for reselling for profit, then it has to acquire a business permit from the Immigration Department, as these Chinese seamen are doing business in Hong Kong, not just in transit. Not to mention the vessel or the enterprise needs a business registration here for taxation purposes."

Even if fishermen sell their catch outside Hong Kong waters, they could still find themselves in legal trouble.

"The act of conveying marine livestock acquired in Hong Kong out of Hong Kong waters is an act of exporting. You need to file a manifest with Customs and Excise. Also, the [seafood] may require hygiene clearance before leaving the port."

However, Chinese President Xi Jinping's high-profile drive against excessive spending by officials is starting to hit fine-dining habits on the mainland. Just as Xi's anti-corruption crackdowns have dented sales of luxury goods in Hong Kong, so too have they curbed mainland appetites for expensive, status foods such as wagyu beef, shark fin and abalone.

Initial reports suggest this has benefited local seafood stalls. "Hell, yes, I've noticed a change," says the importer. "You see a lot nicer seafood. Right now everything is back on the market."

Lai wouldn't go that far, but he concedes that the central government's recent austerity drive is denting luxury consumption significantly.

But declining fish populations as a result of overfishing around the world may soon make any gripes over lack of access to choice morsels a non-issue.

"Prosperous societies in the developed world ought to look in the mirror for a reality check," Lai says. "We have consumed more than anyone in the history of the world, and in the process damaged the environment and exhausted natural resources."

According to the Food and Agricultural Organisation, Hong Kong consumed 500,403 tonnes of seafood in 2009. This worked out to 71.6kg of seafood per person - about 3.9 times more than the global average of 18.4kg per capita and twice the per capita consumption on the mainland.

"It is an absurd notion that any resources are ours and that we need to be protected," the chef contends. "The environment needs to be protected everywhere. If anything, we should lead the effort in conservation rather than consumption."