Poisonous nature

Is there a crisis in the supply of fish throughout the world?

According to the Food and Agriculture Organisation of the United Nations (UN) "69% of the global fish stocks for which assessments are available are considered either fully exploited, over-fished, depleted or slowly recovering from depletion". Nine of the world's 17 major fisheries are in rapid decline and four are completely "fished out". That is because not enough fish are left in the water to regenerate stocks.

Why are there so few fish left?

Since the 1940s, fishermen have been landing catches of unprecedented sizes - an estimated fivefold increase. Small, close-water fishing boats are being supplanted by massive industrial fleets equipped with sophisticated technology that allows them to track shoals more efficiently. Having found the shoals, they use huge industrial drift nets to pull an amazing amount of fish from the water. Large fishing fleets are also taking "industrial fish", such as capelin, krill and sprat, to make feed for farm animals and farmed fish.

Yet these small fish are of fundamental importance and their absence has an affect on fish such as cod and haddock that are higher up the marine food chain.

What has been done about over-fishing?

Not enough. Most countries regard the sea as an unlimited food source. And, because the boundaries of the problems are so fluid, the nations of the world have had little or no incentive to agree to manage and conserve fishing stocks that lie outside the 200-mile fishing limits of individual countries. Instead, when stocks are scarce, fishermen from different countries fight over the little that is left.

The UN is trying to get agreement for an international treaty to protect migratory fish stocks (such as tuna or salmon) that do not belong to any one nation. The problem would be policing it.

Does this mean that if over-fishing was controlled fish stocks would recover?

No. There is also a threat from pollution. Many fisheries have become a dumping ground for sewage waste and waste from nuclear power stations.

But we wouldn't do that, would we?

Afraid so. The North Sea is turning into something of an unsavoury soup and the UK has been singled out as "the dirtiest man of Europe" for failing to curb agricultural and industrial pollution by the agreed 50%.

What does this mean for the fish?

The status of North Sea mackerel is now officially at "commercial extinction". UK cod and haddock are expected to go the same way. Two Dutch surveys reveal that 40% of common species in the North Sea, such as plaice and sole, show signs of pollution-related diseases.

So if there isn't enough fish in the wild, is farming the solution?

In theory, it could be. And chefs can expect to see more species of farmed fish coming in from all over: turbot and halibut from Norway; sea bass and bream from Greece and France; Arctic char; and Mississippi catfish.

Often these fish are not clearly differentiated from wild. For the vigilant there are ways of recognising farmed fish, such as looking out for fish of a uniform size and a suspiciously steady supply.

Is that good news then?

The reality is that fish farming - aquaculture - has become the intensive factory farming of the sea. The long-established salmon farms have a poor track record for polluting the marine environment with pesticides and delousing treatments, all of which are thought to have caused the diminution of stocks of wild fish such as salmon and sea trout.

Shrimp and prawn farming have developed rapidly all over Asia and tropical Latin America, and appear to be causing havoc there. Half the world's mangrove forests have been cut down, and aquaculture is thought to be the main culprit.

More negative consequences include the killing of other species with the use of chemicals, and discharge of nutrients and chemicals that causes an increase in salinity in surface and ground (drinking) water.

How do farmed fish compare on taste?

Taste tests held by the French Consumers' Association found farmed varieties were generally fattier and flabbier than wild fish (they get a lot less exercise), and didn't taste as good, probably because they are fed industrial fishmeal made from all those over-fished sprat and capelin. The tests also found that although farmed fish appeared more moist to start with, they became dry when cooked. Wild fish initially seemed firmer but remained much moister when cooked.

Most leading chefs prefer wild fish. Objections to the farmed variety include the fact that salmon, for example, are fed artificial colourings in their food and can be routinely treated with antibiotics, either in feed or by vaccination.

Are there any decent farmed fish?

There are some success stories in the shellfish department. "Cultured" or "rope-grown" farmed mussels tend to be cleaner and the shells are in much better condition than those dredged from estuaries.

Most Scottish and Irish oysters of the Pacific variety taste good and can be sold without any further purification because they come from clean waters. Most English farmed oysters require purification before sale.

A few companies are producing more environmentally friendly fish, reared further out to sea where they get more exercise, reducing the chemicals used.

What are the direct consequences of all this marine chaos for chefs?

High fish prices and higher yet to come, even on species previously regarded as staples.

Fish is now the rich, not the poor man's food it used to be. Pound for pound, good wild fish will cost more than the most expensive meat. A plate of good cod and mushy peas may yet out price an Aberdeen Angus entrecôte!