The discovery of high quantities of cancer-causing chemicals in farmed salmon from Scotland is catastrophic news for fish farming in Britain, as well as for the already hard-pressed fishing fleets.
The loss in sales that will follow will affect them both - because the chemicals found in farmed salmon do not come from the water they swim in but from the food they eat. This food is manufactured from fish caught on the bottom of the seas round Britain, predominantly in the North Sea.
Salmon, like all animals at the top of the food chain, accumulate toxins in their fat and flesh from their food. In nature they eat smaller prey in the sea. In fish farms this is substituted with pellets containing oil and fish meal manufactured from wild fish.
Wild salmon contain relatively low toxins and are safe to eat in any quantity, providing all the benefits of oily fish. But UK farmed fish are often fed from wild fish that have eaten even smaller prey living in the mud at the bottom of the North Sea, where some of the nastiest chemicals from the industrial and farming revolution have washed and settled.
If salmon farms are to survive they will need to demonstrate that their fish is safe to eat, and will have to find alternative "clean" sources of food. This will mean boycotting fish food derived from catches around British coasts.
To try to save the rising costs of fish oil, some are already experimenting with vegetable oils with similar properties. So far, however, this is proving difficult. The nutrients salmon thrive on are currently only available in wild fish, so to cut out chemicals farmers will have to snub the British fish ing industry and buy fish meal and oil from cleaner parts of the world.
Salmon farming is now a worldwide industry, and the consumption of the fish, once one of the world's luxury foods, has increased 40 times in the past 20 years.
The annual growth rate is 14% in the EU and even higher in the US.
At the same time prices have plummeted, putting salmon alongside herring as the cheapest fresh fish on the counter. It is now cheaper than cod, which was once the poor man's staple.
Profit margins for fish farms are tiny, with competition from places such as Chile, which has no native salmon, making life for European fish farmers extremely difficult. The biggest selling point for Scottish salmon has been its branding as a quality local product. But now scientists are suggesting the label should be used as a health warning to potential consumers, which would be akin to marking it with a skull and crossbones.
With international stocks seriously depleted, farming fish has been seen as a way to provide healthy high protein food at relatively low prices.
But, as environmental groups have pointed out, most farmed fish are fed on wild fish, adding to the stock depletion problem. One tonne of farmed salmon requires four tonnes of wild fish.
With heavy restrictions on fishing for larger wild fish such as cod and haddock, fishing fleets are increasingly turning their attention to smaller varieties to sell to the manufacturers of food for the fish farming business.
This business of "fishing down the food chain", as it is called, has further depleted the world's stocks because many of the small fish caught are immature specimens that would have provided tomorrow's wild fish stocks.
For the Scottish fish farmers, this means finding unconta-minated pellets for food will be increasingly difficult and expensive, which is bound to drive up costs and make it even harder to compete.
Devastating blow to industry reeling from financial downturn
The report comes as a body blow for Scotland's salmon farmers after a difficult year. Prices have slumped in the past year and there have been a series of studies condemning the industry for the quality of its product and its impact on wild fish.
"What can you say?" said one salmon farmer, who asked not to be named, yesterday. "There isn't a week goes by when there isn't negative press. Everybody is totally depressed. Why do we need this?"
Scotland has the world's third-largest salmon farming industry. There are 328 farms producing some 150,000 tonnes of fish each year. The industry is worth about £500m annually, more than the Highland beef and lamb industries put together and accounts for half of all food exports. More than 6,500 people are employed by the trade and ancillary industries, mostly in remote parts where work is hard to come by. But the boom in business has been matched by criticism.
Last June, a study by Southampton University found traces of radioactive waste in salmon on sale in major supermarkets. Two months later figures showed that 1m farmed fish had escaped from their cages in the past six years.
Conservationists say they have devastated wild fish stocks through interbreeding and sea lice infestations. Julie Edgar of Scottish Quality Salmon, the industry watchdog, said the report's authors had "disregarded the fact that the Food Standards Agency in the UK, the EU and the food and drug administration in the US are satisfied that the level of these things found in salmon are fine and levels are dropping all the time."
But Friends of the Earth Scotland said the study confirmed growing concerns about the quality of farmed fish.
