Mowi Scotland's H1 was best in five years for fish health
The best fish health for the first six months of this year has been recorded across Mowi Scotland’s farms, compared to the same time period for the last five years, the salmon producer has reported.
In its monthly staff newsletter, The Scoop, Mowi states that improvements have been made across a number of areas including:
- Reduction in overall mortality
- Improved management of plankton blooms
- Improvement in treatment of gill infections
- Reduction in bacterial infections
- Sea lice levels at the lowest since 2017
- Feed conversion ratio
- Increase in average weight – the best year since 2017
- Post-smolts having a highly impactful effect on production
- Excellent performance across freshwater sites
Mowi Scotland’s health, welfare, and biology director Herve Migaud, told The Scoop: “All the investment in wellboats, vaccines, post-smolt and feeding operations, together with adapting our strategies, is paying off. So far this year, we have witnessed the best fish health and welfare for five years. Interestingly, this year has also been warmer than 2024 and, so far, our farming teams are proving that they can adapt to a changing climate.
More to do
“There is no room for complacency as we demand the very highest standards of fish health and welfare. There are still areas where we would like to see improvements, such as cardiomyopathies and saprolegnia control in freshwater, but we are confident that our new selective breeding programme, launched last year, will start to make an impact in these areas as the programme is fully up and running later this year.”
There are still areas where we would like to see improvements, such as cardiomyopathies and saprolegnia control in freshwater, but we are confident that our new selective breeding programme will start to make an impact in these areas
Herve Migaud
H1 2025 saw a 20% reduction in overall mortality expressed as biomass and 45% when expressed as a number compared to H1 2024. This continues a positive trajectory, with significant improvements already noted in 2024, compared to 2022 and 2023, reported Mowi.
Analysis of mortality on a monthly basis also shows promising results with a monthly average mortality of 0.77% versus 1.14% in 2024 for salmon farmed at sea.
Algal blooms
Mowi has experienced both a reduced prevalence and an improved management of plankton blooms, especially harmful toxic species. It says this shows that daily sampling and analysis, as well as staff training on managing plankton blooms, is making a positive impact.
The first half of 2025 also saw a significant reduction in gill infection-related mortality, averaging 0.1% per month in salmon farmed at sea. This is down from a monthly average of 0.28% and is a validation, says Mowi, of its strategy on amoebic gill disease (AGD) and investment in state-of-the-art wellboats as a treatment.
Mowi has also recorded a 79% reduction in the number of farmed salmon mortalities at sea due to bacterial infections during the first half of 2025 compared to 2024.
“This proves that our preventive health strategy, including the use of new vaccines, as well as enhanced biosecurity measures, is making a positive impact and resulting in less antimicrobials being used year on year,” the company stated. During H1, Mowi Scotland launched a new large scale research programme with the University of Edinburgh’s Roslin Institute to develop more robustness in its stocks and to continue to improve health and welfare of farmed salmon.
Feed conversion
Excellent feed conversion ratio has been achieved in farms that have harvested in the first six months of the year, most notably at Gorsten where a feed ratio of 1.002 was recorded. In addition to the quality of the feed produced at Mowi’s feed plants, this can also be attributed to Mowi’s significant investment in a new Remote Operations Centre in Fort William where feed is managed for up to 16 farms on the west coast.
Mowi’s post smolt strategy has played an important role in the overall improvement of fish health this year with the first ever crop harvested within 11 to 14 months at sea.
The company also enjoyed excellent performance at freshwater farms, including a record high number of smolts being transferred to sea in the first six months of 2025.
