Supermarket claims about fish are misleading, Which? says All pre-packed supermarket cod comes from the North East Atlantic, but some waters in this area - such as the North Sea - are over-fished and have restrictions in place. However a number of supermarkets such as Asda, Lidl and Morrisons do not specify where in the North East Atlantic the fish were caught. Marine charities said the findings show that it is impossible for shoppers to know what they are buying. "Without clear information on what seafood is being caught, where it is caught and how it is caught it is impossible for consumers to make the most sustainable choices in the food that they purchase," said Debbie Crockland, fisheries policy officer at the Marine Conservation Society (MCS). Which? also found that salmon sold in Aldi and Lidi is neither organically farmed nor approved by the RSPCA Freedom Food label, which are regarded as the minimum standards in the industry. Tins of tuna sold by John West, Morrisons and Princes do not specify how the tuna was caught. This means that the companies could catch the fish using nets, which campaigners say are controversial as they catch unwanted species. Most retailers favour more fish-friendly "line and pole" catching methods. Richard Lloyd, executive director at Which?, said that supermarkets must start providing "clear and consistent" information to shoppers that is easy to understand "at a glance." "Most fish bought in the UK is purchased from supermarkets so it's disappointing that these stores are not listening to the three-quarters of us who want more sustainable products on the shelves," said Mr Lloyd. Research from the MCS charity last year found that adequate labeling remains a "stumbling block" for supermarkets. Clare Fischer, a spokeswoman for the charity, said that retailers have a long way to go before their labels are sufficiently meaningful. Morrisons told Which? that it is looking at ways to improve its labeling in general, and Lidl said that it is changing its cod packaging to include exactly where the fish was caught. Asda said that it is "committed to ensuring" that the food it sells is "sustainably sourced." Meanwhile Princes, Morrisons and John West said that they will move to 100 per cent "line and pole" tuna in the next few years. Aldi said it strives to provide shoppers with relevant information. Marks & Spencer, Tesco, The Co-op and Sainsbury's were found to sell the most sustainably-caught fish.