Toxic Tiger Prawns

Is your prawn cocktail toxic?  Read this and you may never want to eat one again

By Alex Renton
Last updated at 10:12 PM on 03rd October 2008

Southern Vietnam is hot and sticky at any time, but the humid air inside the Huong family’s hut, perched on a prawn-pond dyke in the Mekong Delta, is almost unbearable.

The single room is rank with chemicals: we cough and sneeze when we enter.

There’s an acrid dust all over the mud floor, which makes you worry for little Huong Thi Mai, a seven-year-old girl who is sitting on the bed near the door watching her parents work.

King prawns

Asian farmers are using an array of banned drugs to produce prawns for British consumption

I glance at her bare shins for signs of the skin infections that are common among prawn farm workers, but she looks OK. At least for now.

Mr Huong is proud: ‘This is a very modern prawn-farming business,’ he says. And, with luck and four months’ hard labour, it is going to make him and his family quite rich.

After they’ve paid their debts, the Huongs hope to buy a moped and their first fridge. Thi Mai might go to a new school. ‘We can have a better life,’ says Mrs Huong.

But until the tiger prawns are ready for harvest, and shipped off to Britain, Europe or America, the family must live here, keeping a 24-hour watch beside the sour-smelling pond.

They’ve borrowed £4,000, a huge sum for this family, to invest in prawn larvae, feed and medicines – and they need to keep alert in case anyone tries to steal the growing prawns.

Modernity, for Mr Huong, appears to be chiefly measured in chemicals. I count 13 different pots, jars and sacks of these in the hut, and he eagerly talks me through them.

He’s particularly keen on a compound called ‘Super Star’ – the Vietnamese print on the label says it ‘intensifies the metabolism to help prawns grow fat’. He learnt about this additive on a course run by the Vietnamese government at a local fishery training centre.

‘We’re not allowed to use much  –  only ten bottles per crop,’ he says.

There are other glossy labels  –  most of them for products made in Thailand, the centre of the world’s prawn-farming industry. Mr Huong mixes up feed in a basin while we talk. The basic feed, he says, is soya, broken rice and fish, and prawn parts. But in it goes a large dose of something called ‘Amino-Pro’. ‘It helps the prawns taste better,’ he says.

The label has familiar words from stock-cube packets: aspartic acid, glutamic acid and taurine, which is the key element of the energy drink Red Bull. Then there is Vitamix, ‘to make prawns grow faster’, Calphorax ‘to help the shell thicken and give better colour’ and Vin Superclear ‘to kill pests, viruses and smells’. On top of all this is a seasoning of antibiotics.

Prawn farming is an ancient activity in tropical countries. Coastal peoples in Indonesia and Vietnam have trapped young marine prawns in brackish ponds for at least 500 years, feeding them up with fish scraps and household waste to eat or sell. The prawns, properly farmed, are sweet and juicy: it’s a lucrative business.

But the trade has changed drastically since black tiger prawns became a popular luxury in wealthy parts of the world during the Nineties. The cottage industry was swiftly industrialised. From Ecuador to Indonesia, coastal farmers punched holes in sea defences to let salt water into their paddy fields.

As with salmon, coffee and a host of other once rare and expensive foods, the demand from rich countries brought more and more producers into the market.

Tiger or ‘king’ prawns and their siblings have become a staple of Britain’s supermarkets. The result? Ever-falling prices, but increasing use of chemicals and dropping quality.

The chemicals used in these production systems  –  which pack 20 prawns into one square metre of foul, endlessly recycled water  –  have been shown again and again to harm the workers involved, the environment and very possibly the consumers.

Yet shoppers are more in love with tiger prawns than ever. Tropical farmed prawns are now Britain’s fifth most popular seafood. Sales were up 14 per cent last year  –  and we now spend £169 million a year on them, four times as much as we spend on frozen burgers.

At Marks & Spencer, which has seen a 20 per cent increase in king prawn sales, a spokesman told me tropical prawns are ‘so fashionable’ because they are ‘a light and healthy option’.

Prawn cocktail

Rising demand for prawns has led to falling prices but an increase in the use of chemicals

Enthusiastic endorsement from celebrity chefs has helped the boom – Gordon Ramsay recently salivated over king prawn and wonton soup on The F Word, while Jamie Oliver suggested a recipe for them on skewers.

Light and healthy? I think about this as we follow Mr Huong past a litter of prawn-feed bags to the pond, which measures 400 square metres – about the size of two tennis courts.

It was once the family’s ancestral rice paddy, and at this time of year the growing seedlings should be turning the landscape a brilliant yellow-green. But the pond – like all the others nearby  –  is now a viscous grey, like old washing-up water.

Mr Huong paddles off in a small boat, scattering the feed he mixed earlier. A system of paddle wheels, driven by a diesel engine, lies ready to stir up the water and bring oxygen to the shellfish packed beneath. There are 80,000 of them below the surface.

Back on the dyke, he dips a net into the opaque water, and pulls up a few of the animals to weigh them and inspect them for deformities. They are two months old, and about the size of my index finger.

The Huongs – again, like all their neighbours – opened the dykes and turned to prawn farming because of the fantastic profits available.

A field that would have provided enough rice for the family to eat, plus a little extra to sell for essentials, has become a life-changing asset. If this crop is successful, the Huongs will sell the prawns for £8,000  –  if prices hold up  –  after only four months.

This is an enormous amount in a country where many rural people still survive on less than £1 a day. As a result, rice farmers have now become chemists, experts in the complex biology of intensively farmed prawns.

Across the dykes, we see men and women in conical hats dipping testtubes in the water, checking acidity levels and examining prawns in test nets for the dreaded signals of disease: reddening shells, mis-shapen bodies, white spots on their legs.

The prawns, packed into the ponds, are terribly prone to illness. Mr Huong’s last batch of prawn larvae all died after a month  –  he doesn’t know why. Indeed, white-spot virus almost killed off the entire industry in Vietnam two years ago.

Having gambled everything on prawns, people will do anything to protect their investment. That includes using any chemicals that may seem to help.

‘Often we get consignments of antibiotics for human use that are past the date they can be used by,’ a villager told me.

On the main road out of town, near Mr Huong’s farm, there is a government sign. Under a vivid picture of jars, bottles and dead prawns, it lists all the chemicals that prawn farmers must not use – 51 of them.

They include many human antibiotics, penicillins, and some names I recognise from the bad days of the European fish-farming industry – nitrofuran, chloramphenicol and organophosphate pesticides.

This poster shows the efforts the Vietnamese government has been taking to educate farmers. But when everything hinges on a successful crop, it is inevitable that some are willing to take risks.

Back in Britain, I ran the long list of chemicals we had found in use at Mr Huong’s prawn farm past Peter Bridson, who is in charge of aquaculture at the Soil Association. Nothing we had found surprised him.

‘You see this repeatedly in industrial aquaculture. There’s a get-rich-quick attitude. Everyone follows the boom, but one false step and it crashes. And disease is usually the problem.’

Most of the chemicals we photographed in Mr Huong’s shed are pesticides, feed enhancers and growth stimulants.

‘These types of products are commonly used in Asia,’ says Bridson. ‘The farmers experiment. Someone chucks something in his tanks and gets good results. He tells his mates and the product becomes mainstream in the area – whether it actually does anything or not.’

Mr Huong’s Super Star contains a chemical commonly used as a ‘ nutritional enhancer’. It is marketed by the company Bayer in Europe as ‘Butaphosphan’.

On Bayer’s website all I can find is a recommendation that it be used for injecting into sheep, dogs and cats suffering from ‘stress, over-exertion or exhaustion’ and as a tonic in cases of weakness or anaemia in animals. (Note that Bayer does not supply the chemical in Vietnam nor market it as a ‘nutritional enhancer’.)

Some chemicals may do more harm than good  –  and not just to the image of the tropical prawn. Super Star also contains methyl hydroxybenzoate, an anti-fungal preservative which is banned in France and Australia. It has been linked to cancer in some beauty treatments.

The most dubious thing we found in the Huong’s arsenal of chemicals was in a pot named ‘N300’ – a ‘medicine for digestion and liver function’, made by a Vietnamese company called Cong Ty TNHH.


To ensure good-quality prawns, customers are being urged to be prepared to pay more

It contained beta glucan, a harmless component of many human nutrition supplements, but also norfloxacin, an antibiotic usually used to treat gonorrhea and urinary tract infections in humans. It is ‘under watch’ by the U.S. Federal Drug Administration because of increased reports of nasty side effects, including damage to tendons.

Norfloxacin and its siblings, the fluoroquinolones, are banned for use in animals for human consumption in the U.S., and subject to EU controls on imports. Misuse of the fluoroquinolones is increasingly blamed for the rise in resistance to anti-bacterial medicines, and five floxacins are listed on the poster of banned chemicals we saw at the entrance to the village.

Since 2005, Vietnam’s fishery ministry has banned the use of fluoroquinolones in fish destined for the North American market, but not, apparently, for European countries. From the pile of empty N300 jars we saw, there is a lot of fluoroquinolone in the feed for Mr Huong’s prawns.

Numerous surveys have been done on the effects of the antibiotics that are used in prawn farming across the world (31 different ones were identified in Vietnam in a 2006 study, among a total of 155 different drugs).

They conclude that, although the antibiotics may rise to detectable levels in the bodies of prawns, even greater damage is being done to the environment in which they’re farmed.

It’s Mr Huong’s daughter Thi Mai who may have problems when doctors try to treat her for skin complaints, diarrhoea, respiratory problems or other bacterial infections, including malaria. They may find she is resistant to certain antibiotics.

But the effects could be felt further away. Scientists have speculated that outbreaks of salmonella poisoning in Europe and the U.S. may have been started by antibiotic-resistant salmonella in farmed fish from Asia.

And the leaking of antibiotics and pesticides into the delicate ecosystem in the coastal shallows of prawn-farming countries will have effects no one yet fully understands.

Peter Bridson worries the chemicals will intensify, because the water system is closed, with water being re-used from one farm to another, leading to an even greater build-up of chemicals in the prawn ponds.

So how worried should we prawn lovers be? Well, Food & Water Watch, an American lobby group that has studied prawn farming for ten years, issued a warning in its latest report.

It said: ‘The negative effects of eating industrially-produced tiger prawns may include neurological damage from ingesting chemicals such as endosulfans, an allergic response to penicillin residues, or infection by an antibiotic-resistant pathogen such as E-coli.’

That is a judicious ‘may’.

What is certain is that banned or controlled chemicals are coming into Europe with farmed prawns, despite the promises of governments and retailers to stop this happening.

Last year, the EU rejected shipments of farmed prawn from six major exporters in India because they contained chloramphenicol and nitrofurans – two once-common antibiotics which are now known to be carcinogenic. One causes leukaemia.

The EU claims this shows its regulations work, but the fact remains that the EU is thought to test only 1 per cent of such shipments. The real scale of the problem could be far wider. In Louisiana, a prawn-producing region which conducts its own tests on imports, chloramphenicol was found in 9 per cent of all foreign prawn shipments in 2007.

I’m grateful to Taras Grescoe for that last piece of information. His new book, Bottomfeeder, describes the scary practices of the fishing industry in nauseating detail. Grescoe thinks farmed prawns are the most disgusting of all the industrially farmed foods – even worse than battery chickens. And he doesn’t eat them.

But boycotting farmed prawns won’t hurt the real villains in all this. As in any tale of shipping foods of the poor world to the rich in bulk, it is big corporations, processors and retailers which make the bulk of profits, and they should therefore take responsibility. Unlike small-scale producers like Mr Huong, they would survive a collapse of the prawn market.

No, to make a difference across the tropics, we customers must demand better prawns, raised in a way that’s good for them and the people who farm them. And that means we have to be prepared to pay more for them.

On my desk I have two 212g boxes from my local Tesco of uncooked peeled king prawns from Vietnam, which I found on sale at two for £5. That means the 60 or so prawns cost me just over 8p each.

Once the costs of shelling, freezing, packing and shipping have been factored in – not to mention the supermarket’s own profit margin  –  the producer would have been obliged to sell his prawns for a few pennies each. That is simply not enough to ensure decent standards of welfare and production.

Bad prawn farming is caused by the same things as bad chicken farming – the relentless pressure on prices forced on producers by supermarkets.

The result is a prawn cocktail that only a chemist could love.