Consumers are not being given enough information on labels to allow them to make the choice to buy sustainable fish, according to conservationists.
The Marine Conservation Society (MCS) said it is still “virtually impossible to tell precisely where most fish and fish products have been caught”.
But the British Retail Consortium said retailers do “give consumers as much information as possible”.
The MCS’s views come amid the launch of its new website aimed at consumers.
Where labelling by retailers is concerned, the MCS said information that is more detailed than the species, the ocean it comes from and the fishing method is needed to help people discriminate between sustainable and unsustainable seafood.
The MCS has published comprehensive updated advice on buying fish caught from sustainably managed stocks.
The latest advice issued by the conservationists shows improvements in the management and status of stocks in some fisheries, including cod from the eastern and western Baltic and the north-east Arctic, and anchovies from the Bay of Biscay.
However, the situation has worsened where other fish are concerned.
Dover sole caught by the destructive method of beam trawling in the western English Channel, the Irish Sea and south-west and west Ireland has been listed as a fish to avoid.
And consumers have also been urged to avoid yellowfin tuna caught using purse seine nets or long lines in the Indian Ocean.
But eating skipjack tuna caught using poles and lines in the Western Atlantic has the green light thanks to improvements in data on the stocks.
Dr Peter Duncan, of the MCS, said: “If supermarkets could get their produce from well-managed fisheries and label it as such, it opens up new opportunities for the public and fishermen. It’s a win-win.”
He added: “The use of a traffic light system to indicate the nutritional value of supermarket produce is now well-established. However the labelling of fish and fish products sold in supermarkets has not kept up.
Sustainable fish ‘importance’
“It is still virtually impossible to tell precisely where most fish and fish products have been caught.”
But Andrew Opie, the British Retail Consortium’s food director, said retailers know the importance of sustainable fish to their customers.
“They’re doing everything they can to source sustainable produce and give consumers as much information as possible,” he said.
“Supermarket customers are already told the species of fish they’re buying, how it was caught and the region it came from – much more information than is provided by most of the catering industry, for example.
Mr Opie also scrutinised the term “sustainable”.
He said: “What is meant by ‘sustainable’ fish changes all the time, depending on stocks, the environment, and which pressure group you listen to.
“A raft of different interpretations among environmentalists lies behind much of the confusion, not the labelling provided by supermarkets.”
The conservation group is also urging people to vary the type of fish they buy, as the majority of sales focus on just five species – tuna, cod, salmon, prawns and haddock.
The MCS said fish such as pollack, gurnard, coley, dab, sprats were all tasty alternatives.
And consumers are being urged to avoid some fish altogether, such as eels and bluefin tuna.
The conservation group has launched a Good Fish Guide website to make it easier for people to shop for sustainable seafood in supermarkets and restaurants.
The more comprehensive Fish Online website used by the public, chefs and industry, has also been updated.