Several decades ago, diners in search of a nice piece of cod would most likely head for the local chip shop.

Today, the white-fleshed fish is a regular feature on the menus of the most fashionable restaurants.

Cod: No longer destined for the chippie

How did cod become the dish of the day? It is a simple case of supply and demand - stocks are dwindling, so prices are rising.

Thus invested with the cach� only rarity and expense provide, cod is in demand.

Even the humble cod 'n' chips supper has more than doubled in price in the last 10 years.

This week, the scientists advising the European Commission and EU member states warned that many North Sea cod stocks were so depleted that fishing could be banned.

Cod is likely to become even more of a rarity.

"Once there's a demand for something, it becomes vulnerable to overfishing," a Marine Conservation Society spokeswoman says.

"This has a considerable impact on the environment, particularly on marine diversity."

Fashion pack

As with fashions in clothes and music, society's taste in fish is cyclical.

Once oysters were considered to be the culinary equivalent of hamburgers, and were a standard addition to steak and kidney pies. No longer.

Mushy peas with your salmon, sir?

Some 200 years ago, apprentices in London went on strike to protest against being fed salmon more than five times a week.

Yet thanks to improved curing techniques introduced in the past century, salmon too became a luxury item.

Since the early 1990s, consumption has doubled and salmon - the vast majority of it farmed - has become ubiquitous once again.

A Midlands chippie even offers battered salmon as a cheaper alternative to cod. The king of fish has truly lost its crown.

Although wild salmon remains popular with foodies, stocks are in serious decline. Some Scottish rivers limit catches to one fish per rod a week.

A further threat is the 395,000 farmed salmon estimated to have escaped their cages this year.

Through interbreeding with their wild cousins, these fish can pass on lice and diseases - and can play havoc with the gene pool.

Fish at risk

As British palettes grow more adventurous, consumption of so-called exotic varieties is on the increase.

Tuna: More than just a sandwich-filler

"Although cod is still a favourite, particularly in England, there's been an increase in consumption of swordfish and tuna," says Mandy Queen of Sea Fish, the industry authority responsible for promoting all types of fish.

Yet swordfish is on the World Conservation Union's list of endangered species.

In the United States, environmentalists staged a two-year campaign to discourage chefs and shoppers from buying the fish. New regulations to protect Atlantic stocks have since been passed.

And tuna - popular at the top and bottom ends of the market - is also at risk. World catches have doubled in the past decade.

Not only does tinned tuna outsell any other type of canned fish or meat, fresh tuna is in demand at swanky eateries.

Treasures of the deep

Earlier this year, a large frozen tuna fetched �55,000 wholesale in a Japanese fish market. A decade earlier, it would probably have been destined for the catfood factory.

Such prices make illegal fishing worth the risk for "pirate" fleets. According the UN, unregulated fishing has doubled in the past decade.

An albatross drowned on a toothfish line (Greenpeace photo)

The ships are typically registered in countries such as Panama, Honduras and Cyprus to avoid fishing regulations, but are owned by companies in Europe, the US and Japan.

As well as tuna, the hooks are baited for the Patagonian toothfish, also known as the Chilean or Antarctic sea bream - or "white gold" to those in the illegal fishing business.

As a deep-sea dweller which takes 10 years to reach maturity, the toothfish is unlikely to be farmed.

Thus it seems destined to remain on the haute cuisine must-have list - limited stocks available, no end-of-line sales.