Alastair Robertson: Fishing & Shooting

In spite of suggestions that fish farmer Lighthouse Caledonia was likely to withdraw its application for new salmon cages in Broad Bay near Stornoway, nothing has yet been put in writing to the Comhairle, which is due to consider the application in August. But when the planning committee comes to look at the voluminous sheaf of reports, complaints and planning gobbledegook, it will find among the papers a letter signed by 18 fishery trust biologists, saying "don't do it".

The letter is a response to the comment from planning officers in general that when it comes to fish farms there is often insufficient scientific evidence available to help them assess the risks and come to a balanced conclusion. What the letter says of the Broad Bay application is that while there is no such thing as absolute scientific proof, councillors would be as well to take on trust that if looks like a duck, and walks like a duck, it is, in all probability, a duck, and should be acknowledged as such. In other words, if every time you stick a salmon cage in or near the migratory routes of wild sea trout and salmon and the wild fish stocks then disappear or their numbers decline dramatically, you don't really need a sit down interview with a half dead sea trout covered in lice from caged salmon to work out that there may be a connection.

The letter explains how scientists go about assessing risk and in particular the risk of plonking lice- filled salmon cages within 20km of a river mouth – any river mouth – but particularly the Rivers Gress, Laxdale and Creed that flow into Broad Bay. If the cages are put in Broad Bay, there is every probability that stocks of salmon and sea trout returning to these rivers will decline, say the scientists – all bar one of whom are west coast, fishery trust biologists. Ironically, the health and hugely successful rejuvenation of the Gress in particular has been the work of local anglers, many of whom work for fish farming companies, if not Lighthouse Caledonia itself. If Lighthouse is determined to get its cages in Broad Bay it will of course wheel out its own scientists to argue that ,with improved controls and the moving of cages at regular intervals, everything will be hunky dory.

The question for councillors is whether that is a risk worth taking. Given the fact Lighthouse is building a 5million processing plant at Arnish on a council site and offering another 100 jobs, for the time being at any rate, they might feel it is a risk they are obliged to take for the greater good. But at least they will have had that risk properly explained. And if it all goes pear shaped, they cannot complain they were not warned, as follows: "We must advise that if the Comhairle grant planning permission to Lighthouse Caledonia for the fish farm in Broad Bay, there is a substantial risk that the local fisheries including the rivers Gress, Laxdale and Creed will be adversely affected. This is so even if the fish farmer abides by the aquaculture Code of Good Practice."

• This article was first published in The Scotsman, Saturday June 5, 2010