When my husband in his recent book, "Factory Farming", indicated that a single salmon farm containing 200 tonnes of fish produces more pollution than sewage from a small town, I expected contradiction, if not prosecution.
I had suffered the same paranoia on my own account a few years back, when I wrote in a cookery book, of salmon, "don't be fooled by such optimisms as fresh or Scottish: if it is not labelled 'wild', it is almost certainly farmed". Neither of us met with outright denial, because these criticisms cannot be refuted.
But as with land-based battery farming, environmental consequences of salmon farming are dire and worsening, and markets are saturated with yet another animal protein in excess of what consumers want.
The environmental aspect has come in for most stick, as tourists have realised that scarcely any Scottish sea loch, however remote, is free of ugly square cages, with related onshore blots of discarded gear, feed sacks and sheds. And damage is more than skin deep. Pollution by deoxygenation, caused by waste feedstuffs and faeces, kills all seabed life under the cages, leaving only a deathly white bacterial fur. The seabed can recover when cages are moved, as they usually have to be periodically before the fish succumb to disease build-up or to poisoning gases from their own wastes. But no one knows what the long-term ecological effect of such pollution may be.
This is bad news for sea life, and for shell-fishermen. So is the drug residue which washes out from salmon farms. Then there is "predator control". At best, that means scaring devices and guard-nets round cages; at worst, it involves shooting seals, otters, cormorants, herons.
What of the welfare of the fish themselves? They are deeply stocked in cages about 16m square, at about 12 fish per cubic metre. Like all close-confined stock, they would succumb to diseases and parasites, unless routinely drugged. Wild salmon, from which they are recently descended, have a strong migratory urge, and caged fish swim ceaselessly against the current or round the cages. Most farmed salmon are humanely killed but those from Shetland are bled to death.
The sad thing is that worst-case salmon farming need not exist. Ghillie & Glen foods in Aberdeenshire has found a network of farmers guaranteeing a better system, who produce salmon for smoking under that label. With stocking density about one third the usual, hand-feeding to minimise waste, and careful stockmen looking out for sick fish, the use of preventive drugs and chemicals is eliminated, and growth rate is so good that the tonnage of fish per cubic metre of space at harvest is equal to or better than that expected from up to three times the number.
Of course, it is still questionable how much we need of intensively farmed animal protein. So resist marketing blandishments and use it sparingly: The southern European habit of baking fish with vegetables works well with salmon.
