SALMON farmers across Scotland have breached pollution limits more than 400 times over the past three years, contaminating lochs and endangering wildlife.

Up to 30 companies have exceeded limits imposed by the Scottish Environment Protection Agency (Sepa) on the weight of salmon they can grow. The limits are designed to control the amount of waste food and faeces dumped into the water.

Too many wastes can overwhelm the environment's natural ability to break them down, resulting in damage to the seabed. Nutrients in waste can also contribute to algal blooms.

The revelations come as anti-fishfarming groups prepare to launch new campaigns this month against caged salmon production in Scotland and around the world. They are calling on Sepa to "clamp down" on the companies that are flouting the pollution limits.

"Salmon farmers are being permitted to pollute with impunity and are using Scotland's pristine marine environment as an open sewer for untreated waste discharges, " alleged Don Staniford, the European representative for the Pure Salmon Campaign.

Detailed data released by Sepa under freedom of information legislation reveals every "biomass exceedance" reported by fish-farming companies for 2003, 2004 and 2005. In total, there have been 431 exceedances.

The companies reporting the most breaches are the foreign multinationals that now dominate the Scottish fish farming industry. Marine Harvest, with its headquarters in the Netherlands, recorded 94 breaches, while the Norwegian-owned Pan Fish and its predecessor company, Lighthouse, managed 64.

Two other companies, each with nine breaches in 2005, are now controlled by Marine Harvest and Pan Fish, which are themselves in the process of being merged. The merger is currently under investigation in the UK by the Competition Commission.

Many other salmon-farming companies have reported smaller numbers of exceedances. They range from being a few per cent to more than 50per cent over the limits, with one farm in Shetland reporting a total biomass five times higher than allowed in 2003.

According to Sepa, breaches of its pollution limits could result in salmon farms being sent warning letters, facing legal enforcement action, or being taken to court. In April this year Lakeland Marine Farm was fined GBP1000 at Campbelltown Sheriff Court after pleading guilty to breaching the limit at its site in Loch Shuna, Argyll.

"Major breaches over the biomass limit over a prolonged period can result in the biological breakdown processes in the seabed sediment becoming overwhelmed, " warned Sepa's north area manager, Andy Rosie. "Where this happens, the seabed environment can be significantly damaged and firm enforcement action is required by Sepa."

He pointed out, however, that minor breaches posed little risk, as Sepa's limits were precautionary. Sepa also noted that there was an "improving trend", with reported exceedances declining year on year.

The figures show that there were 206 exceedances in 2003, 135 in 2004 and 90 in 2005. Critics pointed out, however, that overall production dropped due to low salmon prices, which could also help explain the drop in exceedances.

The fish farming industry stressed that most of the breaches were marginal and didn't last long. They were often caused by salmon growing faster than expected, or by bad weather preventing the fish from being harvested.

"Minor, temporary exceedances are very unlikely to result in any significant effects on the environment, " argued John Webster, the technical director of the Scottish Salmon Producers' Organisation.

"It is also encouraging to note that instances of temporary exceedances are becoming fewer year-on-year and the recent introduction of the industry's code of good practice will have a further beneficial influence."

Ben Hadfield, a manager with Marine Harvest (Scotland) Ltd said: "On occasion, because of bad weather, the consent may be breached. Should this happen, the fish are immediately harvested at the first available opportunity."

A spokeswoman for Pan Fish made a similar point, adding that sometimes well-fed fish grew faster than expected.

"This can also cause an inadvertent and temporary small exceedances from time to time, " she said.

NEED TO KNOW

THE FACTS There were 431 breaches of the Scottish Environment Protection Agency's (Sepa) pollution limits by salmon farms between 2003 and 2005.

BACKGROUND According to Sepa's data, 269 fish farms discharged 28,100 tonnes of organic carbon, 8800 tonnes of nitrogen and 1100 tonnes of phosphorus in 2005.

NEED TO KNOW MORE?

www. sepa. org. uk/aquaculture/index.

htm Sepa on fish farming.

www. puresalmon. org The Pure Salmon Campaign.

www. scottishsalmon. co. uk Scottish Salmon Producers' Organisation.