SCOTTISH farmed salmon has been dying at twice the normal rate in recent years amid “alarming” infestations of parasites and disease, a conservation charity has claimed.

Mortalities as a percentage of total production have almost doubled in the last four years, Salmon and Trout Conservation Scotland (S&TCS) said.

On the basis of official data, the charity estimates that more than 41 million fish died during 2015 and 2016.

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Andrew Graham-Stewart, director of S&TCS, said: “We fear consumers are in the dark both about the welfare of the farmed salmon, but also the environmental impact of the fish farms producing these fish.

“The alarming incidence of parasites and disease on the fish farms, which causes many of these mortalities, also has major implications for wild fish, particularly the huge numbers of juvenile sea lice released from the farms into the sea lochs where they infest wild salmon and sea trout.”

Salmon farmers have been accused of pumping unsafe quantities of toxic pesticides into lochs amid fears that parasites are becoming increasingly resilient.

The pollution has been condemned as a “toxic timebomb” by environmental campaigners, who have lodged a formal complaint with the European Commission.

But the Scottish Salmon Producers Association has dismissed a sea lice “crisis” insisting that critics of aquaculture “often with their own motivations, publishing data without context, cannot be judged as any kind of independent authority”.

S&TCS claim two-thirds of the deaths in recent years are likely to have occurred on farms accredited by the RSPCA Assured scheme — which requires farmers to take “reasonable steps to minimise the gravid lice population” and “minimise the likelihood of disease outbreaks”.

It has called for RSPCA Assured scheme to be suspended pending an open review.

Mr Graham-Stewart added: “The shocking level of mortalities apparent across the industry, including on RSPCA Assured farms, casts severe doubt on whether RSPCA Assured is much more than a fig leaf, both in terms of the welfare of the farmed fish and the wider environmental performance of the fish farming industry.”

Guy Linley-Adams, solicitor for S&TCS’s aquaculture reform campaign, said: “It should be prompting the Scottish Government to ask serious questions of the industry.”

Scott Landsburgh, SSPO chief executive, said: “Scottish salmon farming companies are doing everything possible to reduce unnecessary mortalities – after all, this product is our livelihood and sustains vast numbers of jobs in remote rural areas of Scotland so it is in our economic interest to get as much of our high quality product to the market as we can.

“The industry will continue to do all we can to minimise unnecessary mortalities in the face of changing environmental circumstances beyond our control, such as the effects of global climate change on the environment where we grow our fish.

“It is the responsibility of the salmon farming industry to meet these challenges head on and ensure we continue to have a sustainable industry in Scotland which protects the environment whilst maximising the economic and social benefits of the sector in the areas where we operate and that is exactly what we are trying to do.”