"Customer awareness about over-fishing is quite low, especially when compared to the public's knowledge of organic farming. But when we tell people about our fish policy they're always really interested," says Ms Boulton.

While cod does get a look-in at The Pelican - if it can be sourced from certain grounds off Norway and Iceland - the fish policy has seen British catches such as John Dory, pollock and witch go on the menu.

"Lots of diners have never had them before and need to ask what they taste like. It's good to encourage diversification and our chefs enjoy cooking whatever fish has come in."

A sustainable fish supper does, of course, bump up your bill, but Essex-based supplier Ben Woodcraft says the market is growing.

Saving fishermen

"I began selling these fish because they're what the public seems to want. More people are becoming conscious of what they eat. It is more expensive, but you get what you pay for."

Much of what Mr Woodcraft sells to businesses such as The Pelican comes from small day boats which operate just a few miles from the coast.

A fisherman himself for 20 years, Mr Woodcraft says it's not only endangered fish that stand to gain from ethical consumers. The small fishing communities from which he buys and their skills will also be preserved.

"Big firms with their factory ships and trawlers want to make as much money as possible. When the fish run out they'll invest in another business. For communities where sons, fathers and grandfathers have been fishermen, it's a way of life they want for the next generation."

Day fishermen are the "last of the hunters" and are as concerned about the state of the seas as any environmentalist, Mr Woodcraft says. If consumers want to aid them and safeguard fish stocks, "they'll have to vote with their feet".

Name that tuna

That's often easier said than done, according to Bernadette Clarke of the Marine Conservation Society. Labelling in restaurants or at the fish counter is either non-existent or woefully inadequate, she says.

"European Union regulations will soon see the area of capture and common name displayed on all fish packaging - but that's still too vague."

Knowing that a fish comes from the Mediterranean, for instance, will not help the ethnical shopper. And since one man's endangered Patagonian toothfish is another man's Chilean sea bass, using so-called common names is open to abuse.

It may involve a bit of research and perhaps the foregoing of your favourite supper, but exercising the same care when buying fish as many do when hunting out free-range eggs may help repair the damage done to our seas, says Ms Clarke.

"It's sad that we've managed to muck up such a bountiful resource through greed and bad management."