The total biomass of farmed Atlantic salmon at sea is trending slightly lower than in November 2024, declining by 0.2% (Figure 1), according to the Norwegian Directorate of Fisheries. However, the live biomass increased by 0.7% month-on-month (m-o-m). The accumulated harvest until November grew by 12.3% year-to-date (YTD), despite a slowdown in salmon removals since October. In November, the harvest dropped by 14.5% m-o-m and by 2.1% year-on-year (y-o-y) (Figure 1).
Figure 1: Harvested weight in round weight equivalent (WFE), measured in metric tons (mt), and total biomass at the end of each month in mt, with monthly data from 2023 to the most recent period for farmed Atlantic salmon. Source: Norwegian Directorate of Fisheries.
After an unusually warm year, sea surface temperatures (SST) in the salmon farming region of Norway have begun to fall. For most of 2025, the monthly average SST was higher than normal, a condition that can increase the risk of health issues such as sea lice infestations and gill problems. In December 2025 the average SST registered 8.0 °C, up from 7.3 °C in December 2024 and above the historical December average of 7.0 °C. Industry participants report that the expected decline in temperatures over the winter could reduce stress on fish and lower the prevalence and severity of temperature-related diseases. Lower SSTs may also ease treatment challenges and reduce mortality risk, although the extent of improvement will depend on the rate of cooling, local farm management practices, and other environmental factors.
Figure 2: Monthly average of sea surface temperatures (SSTs) in degrees Celsius across the coast of Norway. Source: UK Met Office — GHRSST Level 4 OSTIA Global Foundation Sea Surface Temperature Analysis.
Lower temperatures are likely to lead to a decrease in growth rates. This matches the historical pattern of slower harvest levels in January and February, during which biomass usually declines. Under these conditions, a more moderate supply of Norwegian salmon is projected.
Written by Boris Ampuero
