The company's business support manager, Steve Bracken, said around 125,000 salmon with an average weight of 5kg had died following the outbreak of bacterial infection Pasteurella skyensis on the North Shore West and North Shore East sites, which are close together.
MH Scotland still has around 2,000 tonnes of biomass on the sites and is hoping many of the remaining fish will be unaffected. "The whole site is not infected," said Bracken. "Hopefully it (the disease) will die off. We are definitely through the worst of it."
Harmless to humans
Bracken pointed out that Pasteurella skyensis only affects fish and is completely harmless to humans.
"Strains of the Pasteurella bacteria are present in many species of fish and outbreaks of infection occur from time to time. In the salmon farming industry we are experiencing ongoing changes in the sea conditions, due to factors such as climate change and global warming, which mean we have to monitor our fish even more carefully and be ready to respond accordingly.
“The salmon are responding well to treatment from our team of vets and we hope that we are close to resolving the problem.
“So far 500 tonnes or approximately 125,000 fish have died. The dead fish are handled by a specialist waste management company who take them away by lorry to the mainland where they are treated by anaerobic digestion. The biogas produced is sold to the National Grid and the end product is used for fertiliser.”
Smell of decay
The company has apologised to local people concerned about the smell of decay in the area and the sight of lorries carrying away dead fish.
Bracken said the pathogen was first identified at one of the company's farms on Skye in 2002. It was also seen there in the late 1990s but at the time the company was not sure what it was.
"In its worst case it kills fish but it does respond to treatment and that is what we are carrying out at Loch Erisort at the moment," Mr Bracken said. "We use antibiotics to control the infection and it has taken time but we are seeing that the antibiotics are working."
He said the company had managed to stop the disease from reaching another Marine Harvest fish farm in Loch Erisort, just one mile away at Tavay.