Some 180,000 salmon of just 250 grams on average had to be slaughtered after a case of infectious salmon anemia (ISA) was confirmed at a farm owned by Firda Sjofarmer in Vatnoy, in the Norwegian western municipality of Gulen.
The outbreak is the first case of ISA to be confirmed so far south in the country in eight years, said the Norwegian Food Safety Authority.
ISA has mainly been a problem in the more northern region of Nordland this year, where five of the six confirmed cases, and the latest suspected case, have occurred so far this year.
In contrast, no case of ISA had been reported south of Stadt, a peninsula on the northwestern part of the Sogn and Fjordane district, for the past eight years, according to NFSA.
Vatnoy is also in Sogn and Fjordane, one of the major salmon farming regions.
Firda has destroyed all the fish at the cage, which numbered 180,000, with an average weight of around 250 grams. The fish had been released to the sea only in August 2013.
Measures to prevent the spread of the disease have been put in place, and nearby sites and wellboats in particular will be monitored.