2026 Mackerel Survey: Improvement, Not Recovery

Publisert den 30.08.2026 av Per Arne Fagervoll Meek

2026 Atlantic Mackerel Series - Part 5

The survey indicates higher biomass, substantially more individual fish and a stronger recruitment signal. These are important findings after the weak results reported in 2025 and the subsequent advice for a sharp reduction in catches.

They do not, however, demonstrate that the mature stock has recovered. Before drawing conclusions, the survey results must be integrated with catch data, age composition and the other inputs used in the ICES stock assessment.

A clear improvement from 2025

The International Ecosystem Summer Survey in the Nordic Seas, known as IESSNS, is carried out jointly by several coastal states. Participating research vessels cover large parts of the Nordic Seas and adjoining waters to measure the distribution, abundance, size and age composition of pelagic species.

Within the area used for the established year-to-year comparison, the preliminary 2026 results show a mackerel biomass index of approximately 1.8 million tonnes and an abundance index of approximately 5.18 billion individuals. This represents a 10% increase in biomass and a 36% increase in the number of fish compared with 2025. The uncertainty around the biomass estimate was also lower than last year.

When the Danish North Sea survey is included, the combined index reaches approximately 3.3 million tonnes and 10.75 billion individuals.

A stronger signal from younger fish

One of the most encouraging findings concerns recruitment. The 2024 year class, now observed as two-year-old fish, was the largest year class in the survey.

The combined recruitment index was approximately 3.17 billion two-year-olds. This was the third-highest result recorded since 2018 and above the average for the period from 2018 to 2026. The North Sea was particularly important, accounting for approximately 63% of the age-two index.

This suggests that more young mackerel may be entering the stock than recent results indicated. If this year class survives and recruits successfully into the mature population, it could contribute positively to the spawning stock over the coming years.

That remains a conditional conclusion. Young fish do not yet contribute fully to spawning-stock biomass, while older mackerel remain comparatively weakly represented. A stronger recruitment index is positive, but it does not demonstrate that the mature stock has already recovered.

Why the 2025 results mattered

The corresponding survey in 2025 formed part of a much weaker overall stock picture. ICES subsequently advised that catches in 2026 should not exceed 174,357 tonnes, representing a 70% reduction from the previous advice level.

The recommendation reflected more than one survey result. ICES combines survey indices with commercial catch data, age composition, estimated fishing mortality, recruitment and other biological information in an integrated stock assessment.

The concern was not simply that fewer mackerel had been observed during one summer. The assessment indicated that the spawning stock had declined and that there was a substantial probability of it falling below the biological limit reference point, known as Blim.

Advice, reference TAC and national quotas

It is essential to distinguish between the scientific advice, the four-party reference TAC and the combined national quotas.

Norway, the United Kingdom, Iceland and the Faroe Islands adopted an arrangement using 299,010 tonnes as the reference TAC. This represented a reduction of approximately 48% from the 2025 level, but remained 72% above the ICES advice.

The 299,010-tonne figure appeared as an alternative catch scenario in the ICES calculations, but it was not the recommended catch level. ICES estimated a higher probability of the spawning stock falling below Blim under this scenario than under the advice scenario.

The reference TAC should not be confused with the combined national quotas established for the fishery. Once allocations made outside the four-party arrangement are included, the combined national quotas amount to close to 390,000 tonnes, subject to transfers, adjustments and differences in how individual quota components are reported.

This is approximately 30% above the four-party reference TAC and more than twice the catch advised by ICES. The biological effect of the 2026 fishery must ultimately be assessed against realised total catches from the stock - not only the reference TAC selected by the four parties.

Positive findings do not retrospectively validate the quotas

It would be premature to interpret the survey improvement as evidence that the higher catch levels established for 2026 were correct.

The survey provides an observation of distribution and relative abundance during a defined period. ICES must now combine these results with:

• Commercial catch and sampling data
• Updated age composition and recruitment estimates
• Fishing mortality
• Other surveys and biological information
• Assumptions concerning natural mortality and stock development

Only after this information has been integrated into the assessment will it become possible to determine whether the stock was larger, or developed more favourably, than previously estimated.

The appropriate first comparison is therefore not between the survey index and the political quota decision. It is between the new observations and the stock development assumed in the previous ICES assessment.

If the updated model confirms stronger recruitment, a larger stock or lower risk than previously calculated, the outlook may improve. That would still not automatically demonstrate that combined national quotas close to 390,000 tonnes were sustainable.

Encouraging, but not yet a recovery

The preliminary report provides legitimate reasons for greater optimism than a year ago. More fish were observed, the biomass index increased, survey precision improved and the 2024 year class provides a potentially important recruitment signal.

At the same time, the mature component of the stock remains the central concern. Older fish are still comparatively weakly represented, and a large share of the positive recruitment signal originates from fish that have not yet entered the spawning stock fully.

The next milestone

The preliminary survey results will now form part of the scientific process leading to the next ICES advice. That assessment should show whether the stronger survey and recruitment indices materially change the estimated spawning-stock biomass, fishing mortality and short-term biological risk.

Until then, two conclusions can be held at the same time:

For the market, the survey provides an early indication that recruitment may be improving. For fisheries management, it raises a more demanding question: whether that improvement is sufficiently strong - and sufficiently established - to withstand the fishing pressure authorised for 2026.

Sources: Preliminary 2026 IESSNS survey report; Institute of Marine Research; ICES advice for Northeast Atlantic mackerel; 2026 coastal-state mackerel arrangements and published national quota decisions.

Some illustrations made with AI.