Blue whiting stocks in the North Atlantic have surged sharply even after repeated storms disrupted research vessels and forced changes to survey plans, according to the latest international spawning stock survey. The 2026 estimate puts total stock biomass at 3.0 million tonnes — a 32% increase from 2025 — while total fish numbers rose 34%.
The result comes from the International Blue Whiting Spawning Stock Survey (IBWSS) 2026, carried out by vessels from the Faroe Islands, Ireland, the Netherlands, Norway and Spain during March and April. Researchers completed the survey within the planned 21-day window despite poor weather, which caused multiple interruptions at sea.
The survey estimated a total of 32.4 billion blue whiting. Of these, the spawning stock alone accounted for 2.9 million tonnes, up 31% year on year. Researchers described the estimate as robust despite difficult conditions.
Young fish now dominate the stock
The age profile of the stock shifted in 2026.
Blue whiting aged two to five years now dominate the population and make up 83% of the stock combined. Five-year-old fish from the 2021 year class were the strongest single group and represented 30% of total abundance, followed by four-year-old fish from the 2022 year class at 20%.
Researchers also found that more than 92% of two-year-old fish were already mature and contributing to spawning biomass. In contrast, immature fish represented only a small share of the stock.
Core fishing grounds grew stronger
The biggest concentration of blue whiting remained close to the continental shelf edge.
Most fish were recorded between 55°N and 59°N, especially in the northern section of the Rockall Trough, which remained the core distribution area. That zone alone accounted for more than three quarters of total biomass and increased 26% in biomass compared with 2025.
One of the strongest regional gains came in the Faroe/Shetland Channel, where biomass rose 138% and abundance jumped 179% year on year. Researchers linked this partly to a high share of immature fish.
By contrast, biomass around Porcupine Bank fell sharply. Researchers said this likely reflected northward migration during the survey period rather than a collapse in stock size.
Storms disrupted vessels — but survey held together
The survey covered 5,311 nautical miles across six main survey areas and achieved a geographical coverage similar to that in 2025. Several vessels had to suspend operations more than once because of severe weather. Survey effort was redirected into core areas to protect data quality.
Researchers also tested how rough seas affect acoustic measurements. A comparison of survey runs showed that weather-related noise could reduce acoustic signals by around 3.6% under poor conditions, reinforcing the need for weather-aware survey design and data processing.
Overall, the group concluded that the 2026 estimate remains representative and supports a picture of a stronger blue whiting stock entering the next management cycle.