Sir: You are right to blow the whistle on salmon farming ("Fish farm waste suspected in poisoning of Scottish waters", 2 August) and to call for a move away from cage salmon farming and towards organic farming ("The way to save the salmon", 30 July).
The problem is that salmon farming takes place in cages where contaminated wastes are discharged directly into the open sea and its feed contains medicines, antibiotics, colourings and even GM soya. As yet, there are no organic salmon farms in the UK.
However, Deborah Orr is wrong to state that "there has been absolutely no research into the impact that intensive salmon farming may have on the environment". Indeed, the figure of 50,000 tonnes of chemical wastes discharged by Scottish salmon farms every year is derived directly from a report produced last year by the Scottish Environment Protection Agency (SEPA). The exact amount of other wastes such as uneaten feed, faeces and nitrogen is simply not known but it is alarming.
Research has estimated that salmon farms in Scotland discharge 9,000 tonnes of ammonia alone, which is equivalent to waste from 7 million people. Considering Scotland's population is only 5 million the scale of the problem is only too clear.
Unfortunately, what little research that has been carried out is not widely known and when funded by industry the "private and confidential" results seldom reach the public domain. So much for transparency.
The Government's latest pounds 1m study assessing the environmental impact of salmon farming is a case in point. Not only is it co-funded by the Scottish Salmon Growers Association but its results will not be known for five years. In a classic example of the antithesis of the precautionary principle, the study is called "Post-authorisation assessment of the environmental impact of sea-lice treatments used in farmed salmon". The results will only be known after the chemicals have been used for five years.
SEPA admitted this year that "caged fish farming is an activity where treatment of discharges to the aquatic environment is difficult to provide" and urged the new Scottish Parliament "to make the control of cage fish farming more efficient and effective".
In the continuing absence of any waste treatment strategies or organic salmon farming we have to assume that the Government is content to permit salmon farming the free use of the Scottish environment as an open sewer.
Friends of the Earth Scotland