Mowi hails fall in mortalities over August

Mowi Scotland recorded a significant year-on-year drop in salmon mortality during August, which the company said could be down to falling sea temperatures as part of the El Niño cycle.

Mortality at Mowi’s Scottish farms was around one third of that recorded in recent years, when El Niño conditions caused a marine heat wave in the North Atlantic. El Niño is part of the natural climate phenomenon called the El Niño Southern Oscillation (ENSO) and leads to warmer than average sea surface temperatures.

This marine heat wave led to warmer seawater temperatures, Mowi said, causing salmon to suffer gill disease and ultimately led to mortality in 2023 and 2024. This is despite the fact that this period also saw fewer incidents of viral, bacterial and parasitic challenges to farmed salmon.

In August 2024, Mowi Scotland recorded its lowest monthly mortality for more than eight years. The company also achieved record high feeding and growth rates in the cooler coastal waters.

Ben Hadfield, COO of Mowi’s operations in Scotland, Ireland, Faroes and Canada East, explained: “The decline of El Niño conditions, much cooler summer air temperatures and higher rainfall have all benefited our salmon farming operations. We had expected a slightly easier summer due to the declining marine heat wave evident in 2022 and 2023. This weather, combined with our enhanced mitigation measures such as the high capacity to treat salmon with freshwater and the use of bubble curtains to prevent micro jellyfish and algae entering our farming systems, have so far proved effective.

“To see such a big fall in mortality rates is really encouraging because all our focus as salmon farmers is about caring for the fish. Until this year, the warmer seas have presented a big challenge for salmon farmers and the stock we work so hard to rear.”