The Marine Conservation Society (MCS) wants restaurateurs and customers to think before they order.

The UK pressure group, dedicated to protecting the marine environment and its wildlife, has produced the first detailed guide to eating eco-friendly fish: The Good Fish Guide.

No fewer than 20 species, including staples such as European hake, haddock and halibut as well as skate, monkfish and swordfish, should be off the menu from now on in order to conserve stocks. According to the United Nations' Food and Agriculture Organisation, more than 70 per cent of stocks are over-fished.

Martha Holmes, BBC TV producer for the Blue Planet series, who wrote the introduction to the guide said: 'Many people are aware of the over-fishing problem, but would like to learn about the bigger picture and know how they can make a difference as consumers.'

The Good Fish Guide recommends buying from fisheries certified by the Marine Stewardship Council. A hand-line mackerel fishery, for example, has about 300 boats working with an annual quota of just under 2,000 tonnes; the equivalent to what an industrial type boat with a purse-seine net will take in a week.

Restaurant chain Loch Fyne is backing the guide and has agreed to take skate, monkfish and swordfish off the menu. MCS will be advising fish suppliers, supermarkets and restaurant chains to provide more information on how and where their stocks are fished, and to avoid selling the 'top 20' species which are listed on www.mcsuk.org

The Good Fish Guide is available for £9.50 (inc p&p) direct from the Marine Conservation Society; tel: 01989 566017 or online at www.mcsuk.org