Salmon deaths down last year – but no-one is cheering

The annual study by the Norwegian Veterinary Institute found that fish mortality in aquaculture last year was 15.4% compared with 16.7% in 2023.

However, the 1.3% decrease is seen as only a modest start rather than something to cheer.

The actual figures remain high with 57.8 million farmed fish deaths recorded in 2024, mainly salmon.

The Institute’s report says the main causes of farmed fish deaths were infectious diseases and injuries during lice treatments.

Ingunn Sommerset, director for fish health and welfare at the Veterinary Institute said: “ In recent years, we have seen that the mortality rate for sea-produced farmed salmon has been steadily increasing. But this is the first time since 2020 that we have seen a decrease.”

The causes of death were:

• infectious diseases at approximately 33%,
• damage to fish at 27% and
• environmental conditions 9%.

The Veterinary Institute also found that sea temperatures, which were very high on the Norwegian coast last year, were also a major problem. It warns that if they continue to rise bacterial issues are likely to increase.

Sommerset said: “We saw an upsurge of a new bacterial disease called pasteurellosis in Western Norway in 2018. Fortunately , it has come under better control . But in 2024, we saw this bacterial disease for the first time in Northern Norway. This indicates that it may have spread.”

She also said that it was unusual to see the bacterial disease piscirickettsiosis so far north.

Piscirickettsiosis can have a major impact on salmon populations, with a mortality rate of up to 90% in some species.