There's something fishy going on: How mislabelled cod is slipping through the net

It's hard to pinpoint the moment that most of us first came into contact with a fish. Maybe it was as we stared into a pond as a toddler or happened to wander past a pet shop. Perhaps one or two of us had a whole fish served up on a plate as a bizarre form of edible education by our parents.

The vast majority of the British public only come face to face with a fish when shopping. We buy it by the trawler load, spending more than £2.85bn on supermarket seafood in 2010 alone.

With this has come increased awareness of the huge environmental problems facing fish stocks around the globe. According to a survey from the Consumers Association, 80 per cent of fish buyers believe supermarkets should only sell sustainable fish. The vast majority also seek to buy responsibly sourced fish whenever possible,

The major UK supermarkets have strived to catch this eco-wave; all of the big retailers now promote responsibly sourced fish in the hope of drawing ethically minded customers towards their aisles. Tour the supermarkets and you will see up to seven eco-labels appearing on the fish stands as a badge of honour for their origins.

"Seafood traceability is an essential business requirement," explains James Simpson of the Marine Stewardship Council. "Particularly when you are making claims about sustainability."

Yet it may not all be quite as it seems. Researchers working for Channel 4's Dispatches series have recently toured the UK buying fish from Asda, Tesco and Sainsbury's. Working under the direction of DNA expert Dr Stefano Mariani at University College Dublin, the team focused exclusively on cod for the simple reason that it has been studied by biologists for more than a century. "If we talk about cod, we can be dead certain that we won't make mistakes," explains Dr Mariani.

After carefully drawing samples from the centre of the fish, the supermarket produce was put through a strenuous DNA barcoding process to see if the claims made on the packets matched the produce inside.

The samples from Asda were fine, and Sainsbury's was only blemished by a mix-up at a store in Balham, London, where a staff member accidentally served the researchers haddock instead of cod. But the results for Tesco were alarming. Four of the 21 samples taken from Tesco were mislabelled.

Given that Dispatches made totally random purchases, the implication is that the UK's largest fish retailer may not be quite as eco-friendly as it claims.

"We can never condone mislabelling," says Philip MacMullen, the head of environmental responsibility at Seafish, the seafood trade body. "It is simply bad practice."

The Dispatches claims relate to one particular cod product brought from Tesco stores in Perth, Stevenage, Cardiff and London labelled as 'breaded cod fillets, caught in the Pacific Ocean/China'. The packets also bore the phrase "responsibly sourced".

Rather than being caught in the Far East, Dr Mariani's results show the fish to be Atlantic cod – an entirely different species to the well-stocked Pacific variety, and one that is known to be suffering from severe overfishing in a number of locations.

While it is impossible to know if the Tesco cod came from any of these depleted areas, the DNA results conclusively show there are problems in the supermarket's supply chain auditing, undermining any claims it makes to being environmentally aware.

"If the label is incorrect, in terms of where the fish was caught, then that cannot be argued as responsibly sourced," argues marine biologist Melissa Pritchard from the environmental law organisation ClientEarth.

In response, a Tesco spokesperson has admitted the firm's error and apologised, saying "Tesco prides itself on the clarity and accuracy of the information it gives to customers. Unfortunately, on this occasion, we were provided with incorrect information by our supplier. This has now been rectified and we are sorry for the error.

"We source cod from the Atlantic and Pacific across our range and are absolutely confident that both always come from responsibly managed fisheries. All our fish is fully traceable, so the labelling error does not affect our sustainability commitment."

This may or may not be the case, but by making such a fundamental error the supermarket has poked a big hole in the crucial element underpinning any voluntary labelling scheme: trust.

Ultimately, Tesco also has to take full responsibility for the claims made on its produce – regardless of whether the faulty information stems from an error made on a trawler, at a market or production plant.

"When you are getting fish from a boat here and a boat there and a large supplier, it can be difficult to keep them in the different consignment streams," adds MacMullen. "But having said that, consumers should always know where their fish is coming from."

Luckily, the solution may lie just around the corner thanks to a number of developments in DNA testing that will make it possible for scientists to more accurately pinpoint the exact location a fish originates from, offering all manner of benefits for ocean conservationists and fish regulators alike. This, and the International Barcode of Life initiative and the EU-funded FishPopTrace survey at Bangor University, will make it increasingly unlikely that a supermarket can get its labelling wrong, and therefore improve consumers' confidence in their claims.

"The tools we are hoping to develop will be used throughout the supply chain – at sea, right through to when they are dunked in batter and put on a plate," explains Professor Gary Carvalho, who heads the Bangor team.

"To do this you have to focus on very small bits of DNA that are incredibly robust. Even boiling, freezing and thawing doesn't prevent us using a DNA fingerprinting test.

"Our aim is to produce a kit that can be used by the industry where there will be random sampling to test against the huge amount of paper certification that's already in place."

Yet this is all in the future. As things stand a UK consumer looking for ethically sourced fish is faced with a barrage of logos and unproven claims that the Dispatches investigation clearly shows can't always be trusted.

So the solution would seem to lie in simplifying the labelling system to the point that there is one easily recognised and completely trusted icon stamped on a box.

"What consumers need is reassurance, not a flurry of confusing labels," adds Pritchard. "They want to be able to walk into the retailer and trust it and know that if it says it is responsibly sourced then that is the case.

"We liken it closely to organic food, where you cannot use that term unless you can prove it is organic and it is regulated and the consumer trusts it. Can you imagine if you bought something organic and it turned out to have been sprayed with all manner of chemicals? There would be uproar!"

Dispatches: Fish Unwrapped airs on Channel 4, 15 January, 7.05pm

Fresh or foul?

While it's easy to think that the pristine, ice-wrapped fish on a supermarket wet counter has literally just been plucked from the ocean, Dispatches has discovered the vast majority is actually just frozen fish that's been carefully thawed out.

Yet the supermarkets are not doing anything wrong: under law they simply have to inform their customers that a fish has been frozen, and each of the big three retailers are doing this with their labelling.

The problem is that Dispatches discovered Asda and Tesco generally placing the words "previously frozen" in tiny print at the bottom of the labels beside conspicuously large signs advertising 'fresh fish'.

"When people go to the fresh fish counter in the supermarket they're actually thinking 'right, okay, I'm going to buy something that isn't frozen'," says Jenny Driscoll from Which?.

"You've got to be really clear about what you're selling them, and be upfront with it."

When asked about this, Asda admitted their signs are "not ideal" and are in the process of removing them to replace them with something else.

Asda added that the "overwhelming majority" of the fish they sell is fresh and they offer previously frozen fish, clearly labelled at the point of sale, because customers like to be able to buy certain species all year round.

Tesco struck a slightly more unrepentant tone, saying that if the fish has been previously frozen it is made clear on the individual labels.

While neither supermarket has broken the law, it can clearly be argued that they are hoodwinking the public to a certain extent.

It is also something that the fishing trade body Seafish deplores.

"If a fish is frozen at sea within a few hours of being caught it retains many of its intrinsic qualities. So you will often find frozen fish is better quality," explains Philip MacMullen.

"But it should be clear. We couldn't condone making the writing so small that people don't know what they are buying," he insists.