Atlanto Scandian Herring Fisheries Management Plan

Stock Assessment and MSY

Scientific evidence

As set out in Section 3.2 of the JFS, the UK takes an evidence-based approach to fisheries management, making use of the best available scientific evidence. For the purpose of stock management and Total Allowable Catch (TAC) setting, this tends to focus on the use of advice produced by ICES, although other sources of information, including data from the fishing indu.stry, may also be used.

ICES provide annual advice for NSS herring. Different models are used for assessment and advice, depending on availability and quality of data and uncertainty. The type of assessment is categorised from 1 (quantitative/analytical) to 6 (bycatch only data). The advice type is then given based on MSY principles, including data limited approaches (MSY proxy), and/or following a Precautionary Approach. NSS herring is a Category 1 stock which means that it is considered to have full age- and size-structured data on which to base an assessment, and that MSY reference points are available to provide a framework for advice on sustainable management.

Benchmark exercises are a process used by ICES to evaluate existing and new scientific evidence and methods and, where relevant, apply them in the stock assessment process. They are part of the continuous improvement process which ensures that ICES advice is based on the best available scientific evidence. ICES completed an assessment benchmarking process for ASH in 2025. Reference points have been updated; F_MSY has been revised upwards, and MSY B_trigger, B_PA, and B_lim have been reduced.

Assessment of evidence

The following evidence has been collated from the most recent ICES assessment working group report on Widely Distributed Stocks (WGWIDE)^[9].

ASH have a high level of data available overall. On this basis, there is sufficient available scientific evidence for the relevant fisheries policy authorities to make annual MSY assessments of the stocks.and provide advice on sustainable catches using the MSY approach The stock was benchmarked in 2025 with the new assessment model now comprising of data from radio-frequency identification (RFID) tagging, and one new recruitment survey from the Norwegian and Russian Barents Sea ecosystem survey in August−October (BESS).

The SSB on 1 January 2026 is estimated by ICES to be 3.012 million tonnes which is below B_pa (3.177 million t). The spawning stock has been declining since 2009 but increased in 2021 and 2022 followed by a decrease again in 2023 to 2025. The newly benchmarked assessment of NSS leads to a somewhat revised perception of the stock. The estimated SSB in 2024 was 5% lower in this year’s assessment compared to last year; further back in time the difference was larger. In the last 30 years, several large year classes have been produced (1998, 1999, 2002, 2004 and 2016). The year classes 2005-2015 and 2017-2019 are estimated to be average or small. Results from surveys in the Barents Sea the last two years have estimated the size of the 2021 and 2022 year-class above average. Fishing mortality in 2024 is estimated to be 0.156 which is above the management strategy F (0.14) but below F_MSY and F_pa (0.21).

As already noted above, recruitment for ASH is irregular, which means that biomass can fluctuate significantly, with some years of sporadic large recruitment. Therefore, the relative health of the stock also fluctuates

The catch advice for the stock is based on the Long-Term Management Strategy (LTMS) agreed by the European Union, the Faroe Islands, Iceland, Norway, and Russian Federation in 2018, and subsequently by the UK in 2020^[10].