Sitting in a busy waterside seafood restaurant on Lamma Island or Cheung Chau, or in Aberdeen or Sai Kung, a diner might be forgiven for wondering what Sadovy and her colleagues are so worried about. It is easy to believe that the delicious seafood on your plate is connected to the fishing boats you can see bobbing at their moorings. And it's natural enough to assume that those exotic live grouper confined in glass tanks at the front of the restaurant have been plucked from local waters by a dedicated fisherman whose family has been harvesting the seas for generations.

In truth, the seafood on your plate is more likely to have been imported or delivered from a fish farm. Although post-trawling ban Hong Kong still has some 4,000 fishing boats, employing 8,800 or so fishermen, the AFCD production estimate of 170 000 tonnes, valued at HK$2.3 billion (2013 figures), is a tiny fraction of our annual seafood orgy.

Government policy is "to conserve the fisheries resources in local waters and promote the sustainable development of the fisheries industry" and Sadovy thinks it could be doing a much better job of doing so.

"The demand for fish is now so high that natural resources simply cannot supply sufficient quantities - that is not a value judgment, that is a fact," says Sadovy, who believes that our insatiable appetite for seafood is still causing enormous damage to the marine environment, not just in local waters but across the South China Sea and Southeast Asia, resulting in shrinking catches, smaller fish and the alarming depletion of the more vulnerable species.

A recent HKU study identified 13 local species that are vulnerable, including two that are "critically endangered" (the croaker, or Chinese bahaba, and the yellow croaker, or crocein croaker). Four were classified as "endangered", including the Hong Kong grouper. Sadovy thinks it astonishing that there is no legislation to protect vulnerable local fish from being caught. Any fisherman lucky enough to catch one is welcome to eat it or sell it to a restaurant - and if nothing changes, will be until the last one is consumed.

Nevertheless, virtually none of the popular fish, such as grouper and coral trout, exhibited live in local seafood restaurants are caught by artisanal fisherfolk casting their nets in local waters. Most of those that are not farmed arrive at Chek Lap Kok inside large oxygenated plastic transport bins as part of a global US$1 billion and largely unregulated trade in live fish.

A recently published report by the ADM Capital Foundation and Ocean Recovery Alliance, called "Mostly Legal but not Sustainable" and sponsored by the Hong Kong International Airport, was co-authored by Sadovy and reveals that, in 2013, live seafood imports to Hong Kong (by air, sea and land) peaked at 15,700 metric tonnes. That's equivalent in weight to about 2,300 large male African elephants.

And according to one industry leader in fish air freight, FishPac, "live fish are normally held in filtered tanks and purged [starved] for 24 to 48 hours prior to packing into bins, to maintain the water quality". That's a polite way of saying that if those fish defecate or vomit in flight, the entire contents of the bin may be dead on arrival. Many of those exotic fish, it seems, are starved, distressed and jet-lagged long before they reach the plate of a Hong Kong diner.

"Not 1 per cent of those sealed containers ever gets checked," claims Doug Woodring, the co-founder of Ocean Recovery Alliance, which published the reef fish report.

He fears that small local fisheries in Southeast Asia are being depleted by aggressive seafood dealers to satisfy consumers in Hong Kong and those whose dinners have passed through the city. It's not just damaging to fish; the trade is hurting traditional fishing communities whose primary source of protein becomes our seafood banquet.

"These guys just rape and pillage fisheries from island to island and then move on when the fish stocks are exhausted," says Woodring.

Conservationists are very concerned about what is called the illegal, unreported and unregulated trade, which occurs at both local and international levels.

"The two biggest things bad that Hong Kong does for the ocean is trade in shark fin and reef fish," says Woodring.

The endangered humphead, or Napoleon, wrasse, which is the only reef fish to be listed by the Convention on International Trade in Endangered Species (Cites), is a prime example. Exports of the humphead wrasse from Malaysia and the Philippines have been banned, there is restricted export quota in Indonesia and tough local laws mean that any trade is subject to a rigorous licensing requirement by the AFCD. Despite these tough measures, high prices mean poaching continues, smuggling is on the up and unpublished reports from WWF and a China market survey conducted in 2012 indicate that about 50,000 of these magnificent endangered fish are sold on the mainland every year, many of them smuggled in through Hong Kong.

"This is a regional problem but Hong Kong is ground zero," says Woodring.

Sadovy points to recent HKU research that shows 80 per cent of all groupers on sale in Hong Kong are juveniles, a state of affairs that has a disastrous effect on a species with a slow reproductive cycle. And if that is not enough to put you off your next seafood blowout, the scientist has more shocking information.

"Almost all Napoleon wrasse seen in Hong Kong restaurants have been caught using cyanide," she says, a "horrible form of fishing". Sadovy describes how fishermen (outside Hong Kong), increasingly desperate to catch rare fish and feed their families, resort to spraying a solution of cyanide over coral reefs that paralyses the gills. They are able to capture the stunned fish and then allow them to recover in tanks of uncontaminated sea water. Tragically though, most other fish in the vicinity, along with thousands of other organisms in the complex reef food chain, are annihilated.

Woodring points to Thai shrimp farms, many of which employ slave labour, he says, and keep their mostly diseased stock alive with a powerful range of antibiotics, to deliver a product that he refers to as the "seafood equivalent of blood diamonds". Woodring believes the solution is to accredit more fish as having come from sustainable sources and, last month, Ocean Recovery Alliance launched the Kin Hong sustainable seafood festival, which committed more than 25 well-known Hong Kong dining establishments to offer seafood accredited by recognised bodies.

However, one successful and environmentally enlightened local seafood restaurant owner is worried that accrediting sustainable sources will never be anything more than a "boutique solution".

You'll not find endangered species such as humphead wrasse on the menu at David Lai's new Fish School, in Sai Ying Pun, which defies local trends by offering locally sourced seafood wherever possible (in about 70 per cent of dishes), to create a link between his diners and the ecosystems of local waters.

As he embarks on a seafood sourcing mission in the Mong Kok wet market, Lai explains that the consumption of live seafood is a Cantonese tradition and it is apparent what his expert eye is seeking as he dismisses one supplier whose grouper are all the same size, indicating they're from a fish farm. He points out a locally line caught fish, identifiable because the hook is still in its mouth, and explains that the stall owners have formed close relationships with the captains of individual boats, who look for specific species depending on the season.

"It's a good thing to get to know the people who catch the fish rather than having something that came from an auction somewhere far away," he says. "These people who derive their living directly from nature have a lot of wisdom."

One of those people of great wisdom is Ho Wah-hei, who has fished out of Cheung Chau since he started working on his father's boat at the age of 10. Ho has seen a significant reduction in the size of the local fishing fleet since those early days but he estimates there are still about 300 small gill netters in Cheung Chau and about 40 larger purse seine fishing boats.

"When I was a boy, there was no government regulation of fishing, so there were many more boats," he says.

Many local fishermen resent the accusation that they are responsible for declining fish stocks and think that it is the city dwellers and their development and disrespect for nature that have caused the damage. Ho is a supporter of the trawling ban "because if all the fish go, there is nothing left for us" and he has an instinctive understanding of the balance between Mother Nature and fishing, like most of his peers. The Tai Po Geoheritage Centre has been engaged in retraining about 100 former fishermen in eco-tourism activities and project manager Eric Keung Siu-lun says, "They understand their environment very well; they need to for their livelihoods."

Ho complains that illegal trawling is still common in local waters, despite his repeated complaints to the authorities, but he reports a noticeable increase in catch since the trawling ban was implemented and says he is now seeing species in local waters that he hasn't seen for decades. Unlike Sadovy and many conservationists, he thinks the government is doing a good job in looking after the marine environment but that it could do better in supporting the fishing industry.

Maintaining a balance between conserving an industry essential to Hong Hong's identity and protecting the fish it needs to catch is a delicate one for Li. The AFCD officer explains that the 2012 trawling ban was just the headline policy in a raft of conservation measures contained in the Fisheries Protection Ordinance.

Other ordinance measures that have since been implemented include: setting up a registration system for local fishing vessels; limiting the number of new entrants; restricting the fishing activities of non-fishing vessels (i.e. you can only use a rod and line on a leisure vessel); and prohibiting non-local vessels from fishing in Hong Kong territorial waters. Li is particularly enthusiastic about the 668 artificial reefs that have been deployed in marine parks, fish culture zones and important spawning and nursery grounds.

"I dived on the artificial reefs last year and I was very happy to see established groups of fish with juveniles, which indicates they are reproducing on the reefs," says Li, a marine biologist with a master's degree in mariculture.

She believes the local fishery is essentially sustain-able now and that the negative impact of trawling has been removed.

"I would say 90 per cent of what we have left are small artisanal vessels (like Ho's) doing gill netting, purse seining, cages or line fishing. I would say with these remaining boats there is no longer a big problem," she says, rejecting Sadovy's demand for legal protection for vulnerable local species on the pragmatic grounds that education is more effective than legal enforcement and that, in practice, it is very complicated and expensive to police the protection of specific species, some of which can be difficult to identify.

Sadovy remains unconvinced by the arguments, though: "I don't see why we can't have legislation to protect individual fish species just as we do for terrestrial animals and the Chinese white dolphin." Like many others, she would also like to see "no-take zones", particularly in marine parks, where fishing is still allowed with a permit, a policy Woodring likens to "allowing hunting in a zoo".

"We are progressing in this way," counters Li, revealing that data is already being collected and analysed and plans being put in place for the establishment of Hong Kong's first fishery protection area (the power to do so having been included in the 2012 legislation), which will incorporate no-take zones or no-take periods and will possibly be located off the northeast New Territories or Sai Kung. And Li is also keen to boost high-quality accredited mariculture; one of the four awards from the HK$500 million Sustainable Fisheries Development Fund, launched in July last year, is for an ambitious mariculture project in Cheung Chau.

The New Tung Fu Loy Aquafarm, set up and operated by former trawler men, aims to raise white flower croaker (a species new to Hong Kong), giant grouper and pompano within enclosure nets that reach from the surface to the sea bed.

Perhaps with more good news from the trawling ban and the implementation of properly enforced fishery protection areas, supplemented by high-quality local mariculture, Hong Kong could one day become a role model for how to manage fisheries in a sustainable way. Locally caught fish might come to be regarded as a premium product, as could properly accredited farmed or imported seafood.

"'Buy local' and the promotion of locally sourced fish is a brilliant concept and it really is possible in Hong Kong - it just needs a vision," says Sadovy.

The next time we order our favourite delicacy at a seafood restaurant, we could play a small part by asking the waiter where our fish has come from, and not just how much it costs.

Fishing methods

Several types of trawling were practised in Hong Kong waters prior to the ban imposed on December 31, 2012, and many of the city's boats still operate in mainland waters, where trawling is now banned in water depths of less than 40 metres and subject to a three-month summer moratorium. Bottom trawlers drag large nets incorporating heavy metal beams or otter boards over the seabed. The apparatus acts like a plough, digging into the seabed, removing everything in its path and creating enormous mud plumes. This method has been likened to towing a giant bulldozer through a rainforest.

Most Hong Kong purse seiners operate at night in northeastern waters and in the shallow bays of the outlying islands. Strong lights and rhythmic banging on the mother vessel attract a shoal of fish while a small sampan assists in a circular manoeuvre of the large net so it encircles the attracted shoal. The bottom is then closed to form a bag with the fish inside. Major catch includes black sea bream, pargo and scads.

Gill netters use a fine monofilament net, often weighted to the seabed and buoyed at the surface to create a vertical wall of mesh in which to trap fish. Discarded or snagged nets can become "ghost nets", those that remain untended on the seafloor entangling fish and marine life and are often seen in rocky or coral areas. Gill netters operate in shallow coastal waters and major catches include horsehead, gold lined sea bream, gold line scad, black sea bream, sweetlip, emperor fish and pargo.

Hong Kong cage fishermen typically use baited traps, into which fish are attracted, entering through tapered openings from which it is difficult to escape. Major catches include rabbitfish, moray eel, cardinal sea bream and crustaceans.

Baited hooks or lures on lines are still popular for fishing in shallow coastal waters. All other types of fishing from a boat require licensing by the AFCD so this remains a popular method.