Buying sustainably sourced fish should be straightforward given the amount of focus on over-fishing in recent years. But a Which? investigation has found that this is not the case. Despite three quarters of people telling us that they want to know if the fish they buy is sustainable, we found labels were still inconsistent, and sometimes meaningless.

We looked at cod, salmon and tuna from the main supermarkets, including the main brands. We included fresh, frozen and canned fillets and steaks. When we last looked two years ago, sustainable sourcing of fish was becoming a competitive issue, with many supermarkets looking to stock only fish from sustainable sources. Fish labelling has also been on the EU’s agenda, so we expected things to have improved.

In the case of cod, we found there was a huge variety in the way it was labelled. Asda and Young’s labelled where the cod was caught (North East Atlantic), but gave no information about method of catch or a specific stock area. Aldi, Lidl and Morrisons provided method of catch, but not a specific stock area.

Marks & Spencer, Tesco and Waitrose provided the full information, but The Co-operative and Sainsbury’s were the only ones to sell fish labelled as Marine Stewardship Council-certified. Morrisons told us most of its cod is also MSC-certified and is looking at improving its labelling, as is Young’s. Lidl has said it will start labelling the stock area.

” Labels were still inconsistent and sometimes meaningless”

In terms of farmed salmon, all the products, with the exception of Aldi and Lidl, were labelled as either organically farmed or RSPCA Freedom Food. The wild salmon we found on sale was all MSC-certified. Tinned wild salmon was also MSC-certified or labelled as being from sustainable stocks.

A number of supermarkets (Asda, The Co-op, M&S, Sainsbury’s, Tesco and Waitrose) stated that their tuna was all pole-and-line-caught. Tuna can also be caught by purse seiner, where a large net encircles the fish and increases the risk of catching unwanted or young fish. Aldi, Lidl, Morrisons, John West and Princes stock tuna caught this way, but John West, Morrisons and Princes didn’t specify method of catch on the label. They told us that they are aiming for 100% pole-and-line-caught tuna in the next few years.

Overall our latest research shows there’s still a long way to go. Consumers have to look at labels carefully and know a lot about specific catch areas and methods to make more sustainable choices.

Which? wants to see all brands and supermarkets label products simply, clearly and consistently. Surely it shouldn’t have to be so difficult?