Salmon regulators have been in denial about the environmental catastrophe that salmon aquaculture has visited on West Highland lochs and rivers. Not before time, the Scottish government is considering banning farms from some sensitive coastal areas and forcing farmers to publish information about lice levels on specific farms.

Why the tentative rethink when, traditionally, Scottish politicians and civil servants have been bullish in defence of this dirty industry? The circumstantial evidence that lice and chemicals from salmon farms have decimated wild stocks is hard to ignore. Even SEPA, the environmental ‘watchdog’ that has in the past adopted a laid-back attitude to the pollution and disease caused by salmon farms, appears to be waking up.

It’s no coincidence that stocks of wild fish are quite healthy on Scotland’s east coast, where there are no salmon farms, and in a parlous state on the west coast, where all the salmon farms are located. The Scottish government is doubtless influenced by Norway - the pioneer of salmon aquaculture - where regulators have restricted the spread of fish farms amid mounting concern over the depletion of wild fish stocks.

The head of Norway’s Directorate for Nature Management recently called for a 50% cut in salmon production there because, for the second year running, the lice problem is so severe. Even then he said such a cut might not be enough to save Norway’s fragile wild salmon stocks because “the problem is very big and not under control”. Scottish farmed salmon is widely seen by switched-on consumers as the marine equivalent of the factory-farmed battery hen or broiler chicken.

The only thing going for it is that it’s cheap. The Marine Conservation Society and Greenpeace both give it the thumbs down and advocate instead sustainable wild Alaskan salmon with MSC certification.

Alex Salmond wants Scotland to be seen as having a clean, green natural environment. Tackling the unholy mess created by salmon farms would show he was serious. Instead, he has signed a trade deal with China that will see Scotland double salmon production to satisfy Chinese demand. He can’t have it both ways.

It is wilfully irresponsible to do deals on farmed salmon without first confronting the grave problems caused by current production levels.