On average, Hong Kongers eat twice as much fish as the rest of the world. But most of it doesn’t come from the sea – it’s farmed. Joyee Chan rolls up her trousers and checks out four ways that fish are raised in Hong Kong and examines the environmental challenges the industry now faces. Photography by Calvin Sit
Lo Hoi-gan shows off a fish from one of his polyculture ponds
By 2030, the World Bank predicts that two in every three fish consumed on Earth will come from a fish farm. In Hong Kong, we eat twice as much fish per person as the global average. So, if we’re going to meet this huge demand, we need to practice local fish farming in an environmentally responsible manner. And we need to do it soon. While capture fisheries located in the sea around the world have long been under fire for overexploiting and damaging the oceans, aquaculture is not as flawless as it may at first seem.
In fact, all captive fisheries are linked to environmental damage in the ocean, regardless of their location. Hatcheries, for example, where young fish are bred, are constantly in want of new genes to prevent inbreeding. This in turn drives a demand for hunting of large, fecund fishes in the seas. Young wild fish – often called ‘trash fish’ due to their low market value – are also sought and hunted as food for aquaculture’s valuable ‘cash crops’, like groupers. The uneaten feed and waste from inshore fish farms can also easily trigger algal blooms, or red tides, which cause widespread havoc on ecosystems.
There are four main types of aquaculture, also known as fish farming, currently carried out in HK. Polyculture features multiple species in a single space; indoor mariculture uses seawater in tanks under cover; inshore mariculture sees farms located directly into the ocean and aquaponics is a complete system which combines aquaculture with hydrophonics (plants) in a symbiotic environment. Join us as we explore how these four practices work and what challenges they face...
Polyculture
A polyculture pond in Yuen Long
More than a thousand years ago, during the Tang Dynasty, Chinese fish farmers developed an intricate polyculture in which different species of carp were raised in the same pond to form a complementary food web. The idea was to get maximum productivity with minimal maintenance.
This practice is still used today in about a thousand hectares of ponds in the northwestern New Territories. Lo Hoi-gan, affectionately known as Uncle Root, has been running 13 ponds next to rows of houses at Fairview Park in Yuen Long since 1973. He keeps seven species of fish in each pool but he feeds mainly the grey mullet – one of the city’s four most famous freshwater fish, well-loved for its sweet flesh when steamed with lemons.
Other species are stocked for various purposes: surface feeders, bighead carp, silver carp and tilapia keep algal levels in check. Grass carp, true to its name, is good at grazing weeds along pond banks. Bottom dwelling common and mud carp vacuum up organic waste that gathers on the muddy pond bed, stirring up buried nutrients as they go, which in turn benefits the other species.
“It’s important to determine the golden ratio of fish species, otherwise you end up with murky waters,” says Lo. “My ponds host mostly grey mullets and mud carps.” Lo used to feed his fish with peanut meal – but not any more due to soaring costs. Now he sources unsold bread, biscuits and peanut butter from local factories. “Customers say my grey mullets don’t taste as aromatic – but what can I do when I can’t afford peanut meal?” asks Lo.
In the heyday of freshwater aquaculture in the 1990s, Yuen Long churned out 6,130 tonnes of freshwater fish per year. Now the production has dropped by two-thirds. Many fish farmers have retired or left the industry for easier jobs.
Lo’s business is one of the few that has survived into a third generation. His 53-year-old son and 30-year-old grandson – who has an engineering degree – hope to keep the tradition alive.
Indoor mariculture
Inside Aquaculture Technologies Asia
Tucked into the oyster-farming district of Lau Fau Shan, the city’s first large-scale indoor fish farm, Aquaculture Technologies Asia, raises about 20,000 giant groupers destined for dining tables in homes, hotels and restaurants.
One of the masterminds behind the venture is Mark Kwok Chi-yat, executive director of department store Wing On. He and his business partners, having tried their hand at traditional mariculture and live fish import in the 90s, were disappointed at the local water quality and realised flown-in fish taste poorer because they are easily stressed.
Their solution was to bring mariculture indoors and ‘make the unpredictable predictable’ in 2003. The water in which their groupers swim in is salted tap water, recycled and purified by bio-filtration and UV-filtration. The environment is dim and warm year-round like the groupers’ natural habitat in the coral reefs. “Traditional mariculture considers a survival rate of 50 percent acceptable – ours is above 90 percent,” says Kwok.
The model benefits the environment too. Firstly, it contains waste on land. “Excess feed given to fish in sea cages will ruin the sea bed, create bacteria growth and lead to outbreaks of red tide,” says Kwok. Secondly, by sourcing grouper fingerlings from Taiwanese hatcheries, wild populations won’t be harmed. “In theory, we can eat 50,000 fish this season and expect to have another 50,000 next season,” adds Kwok.
The downside is that the operation inevitably demands significant amounts of energy, Kwok admits. To reduce its carbon footprint, the firm has partnered with CLP Power to install solar panels to power the farm’s lights and ventilation.
The company’s green philosophy has impressed WWF Hong Kong and has earned its fish a place on the NGO’s sustainable seafood guide. Kwok believes there is potential for indoor mariculture in landlocked areas. “But,” he says, “it won’t make sense in places where the real estate cost is high.”
Inshore mariculture
Inshore mariculture on Lamma Island
Within an unpopulated bay in northern Lamma Island in 1982, Law Bak-fuk built his first fish-cultivating sea cages with wooden planks and blue plastic buckets. Today, his floating farm, boasting 500 cages, is one of Hong Kong’s largest. Green grouper, sabah grouper – a hybrid of two groupers – sea chub, snapper and pompano are among the various species he stocks. His choice is entirely practical because groupers are highly pollution tolerant and fast-growing – and they attract a premium.
Law’s stocks used to feed on the trash fish that are harvested by trawlers. Since the trawling ban came into force in 2013, though, the price of his regular feed rose – because fishermen have to work further offshore – and Law reluctantly replaced part of their diet with food pellets, although these may contain grinded trash fish. He still believes trash fish provides better nutrition.
The sea is Law’s best friend. The currents take away his stock’s waste for free. But it can easily turn into his worst enemy. Red tide, an algal bloom that can be toxic to both fish and humans, is a sporadic visitor at his farm. The most serious red tide to hit the waters around the SAR, which arrived in 1998, devastated the industry, wiping out 80 percent of the stock and leaving many farmers bankrupt. In many places the industry is still recovering.
Law Bak-fuk ‘in his office’
Now the government places artificial reefs near fish farms to attract marine organisms to break down the waste gathered in the sea bed. It also warns the industry of any bad omen on the horizon. If the plague is non-toxic, Law pumps extra oxygen into the water, which sorts out the problem. If it’s much worse, he either immediately isolates his stocks, sends them to the market or hoists anchor and takes his farm to safer waters.
Inshore mariculture on Lamma Island
Another problem the industry faces is an ageing workforce. Most mariculture operations are family-run and most workers are over 40 years old. Law hopes to attract new blood because he believes, despite the risks, mariculture is still lucrative and it requires less maintenance now that there is pellet feed. He’s also replaced part of the wooden platforms with plastic. Every little helps.
Aquaponics
Augustine To Yat-man with an e-farm fish
Augustine To Yat-man longed to name his acre-large aquaponics facility in Fanling ‘Eco-Farm’. For now, with his grand green vision half-complete, it’s just ‘E-Farm’. Since 2013, his team has been working hard to convert the organic vegetable farm into a mini self-sustaining ecosystem by adding a fish pond and worm cultivating station. His goal is to recycle food waste collected from restaurant chains like Café De Coral into feed for black soldier fly larvae, which becomes food for tilapia and jade perch, whose excretions then fertilise his greens.
The system was inspired by permaculture, which promotes environmentally, economically and socially sustainable agriculture. “After taking a permaculture course in Australia, I decided to harness the wetland and stream on our premises, and find a way to replace imported fertiliser and fish feed, which carries a high carbon footprint,” says To. He adds that aquaponics not only harnesses every ounce of nutrient from the system and does the environment good, it also cuts the overall operational cost.
But his system is far from perfect. The farm hasn’t weaned off fertiliser and pellet feed because it lacks the manpower and funds to build a mechanic waste water recycling system and a proper larvae-cultivating facility. “The current larvae-cultivating room is pretty makeshift,” says To. “We have just received financial aid from the government to build a greenhouse – since worms favour warm conditions – to handle more food waste and generate enough fish food year round.”
Always looking to improve his system, To has teamed up with researchers at Chinese University to find out how to maximise the productivity of larvae-cultivating. But aquaponics facilities like To’s are a rare breed. Although he has conducted several workshops to promote the idea, he says none of his students have implemented it on a commercial scale – most just attend for fun.
The way forward
The world – and, by proxy, Hong Kong – needs to manage both capture fisheries and aquaculture properly to meet our seafood needs, says Professor Yvonne Sadovy, an expert in fisheries at the University of Hong Kong. “Mariculture needs to be more efficient and productive, less wasteful and polluting and less harmful to wild populations than it is now,” she tells us.
The first step, she suggests, is to move away from carnivorous fishes. “The reason is their feed contains fish oil and fish meal that come from trash fish and forage fish – like sardines and anchovies off South America – that are important to the food chain. Overexploitation could lead to ecosystem collapse,” says Sadovy. She adds that ‘there is quite a movement for humans to directly consume those fish [used for fish feed] and not wastefully feed them to other fish [in terms of energy conversion]’.
Another problem is that although hatcheries supply aquaculture with large amounts of fingerlings, wild genes need to be injected and some aquacultures still source their young fish directly from the wild. “Scientists have found yellow croakers, after several generations in captivity, experience too much inbreeding. That’s a practical side of mariculture that hasn’t been solved.” Sadovy stresses that ‘none of these are net gains’. “They have implications,” she says. “There’s a lot of experimentation to find out how we are going to do this better.”
The right way to go is polyculture and ecosystem-based mariculture approaches, says Sadovy. “Polyculture is sort of like creating a mini ecosystem,” she tells us, “where the waste of one species generates food for another. So you get lots of reusing and recycling of energy in that system.”
Hong Kong fish farming statistics
.jpg)
100kg
The amount of worms that can be produced by a ton of food waste. This will feed and produce 70kg of fish at E-farm
10kg-15kg
of ‘trash fish’ yields 1kg of groupers in mariculture. In contrast, 2kg of pellet feed is only needed for same results
$315 million
Mariculture in HK suffered a loss of this much during the 1998 red tide outbreak
6%
Aquaculture generated this much of the total revenue of local fisheries production last year