Icelandic salmon farmer Arctic Fish was not responsible for the biological incident earlier this year which cost the company almost £6m (ISK 1bn), an official investigation has found.
The Dýrafjörður based business in the Westfjords region, part of Norway Royal Salmon, lost 2,500 tonnes of fish – a quarter of all the salmon in the fjord – due to weather and health related problems.
It became evident something was wrong in mid-January with the incident reaching a peak the following month.
The slaughter ship Norwegian Gannet was brought over a month later to help cut losses by harvesting the affected fish. It finished its task on 4 March.
Now the Icelandic veterinary authority Mast has published a report saying the company was not at fault.
The report says the episode was due to a number of external, but related factors, largely triggered by poor weather conditions.
Mast said there was a sharp drop in sea temperatures in January with fish suffering physiological problems and wounds taking longer to heal.
The report continues: “Tissue samples were taken for research. The results showed a rather poor condition of the gills and tissue changes in the heart and blood transfusions to other organs indicated that the fish had heart and muscle inflammation (HSMI) caused by the virus Piscine Reo.
“This virus is widespread in both fish farming and in the natural environment but it is not considered notifiable.
“This was followed by a period with many stormy days that made the situation worse and losses began to increase in both the breeding areas at Haukadalsbót and Eyrarhlíð II. “
The affected fish were also moved between pens during the summer and treated for lice in December which made them vulnerable.
“Mast is of the opinion that these reductions did not occur due to the conduct of the operator, but that various external and related factors caused these reductions,” the report concludes.