Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK)

The main terms of reference for the ICES Working Group for the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) were to update, quality check, and report relevant data for the working group, to update and audit the assessment and forecasts of the stocks, to produce a first draft of the advice on the fish stocks, and to prepare planning for benchmarks in future years. Ecosystem changes have been analytically considered in the assessments for cod, haddock, and whiting in the form of varying natural mortalities estimated by the ICES Working Group on Multispecies Assessment Methods (WGSAM). Conservation status advice was considered but WGNSSK did not identify any conservation aspects for its stocks. From this year the Nephrops stocks have been removed from WGNSSK and will be assessed by a new working group WGNEPH. 

Recent benchmarks 

A benchmark that involved WGNSSK stocks was organized in 2024–2025. The WKBNSCS benchmark for North Sea turbot (tur.27.4) and for eastern English Channel plaice (ple.27.7d) evaluated the appropriateness of data and methods to determine stock status.  

State of the stocks 

The main impression in recent years is that fishing pressure has been reduced substantially for many North Sea stocks of roundfish and flatfish compared to the beginning of the century. Five stocks with agreed reference points (category 1 stocks) have SSB higher than MSY B_trigger (haddock in 4, 6.a and 20, plaice in 4 and 20, turbot in 4, whiting in 4 and 7.d and witch in 3.a, 4 and 7.d). The SSB of saithe in 3.a, 4 and 6 is just above B_lim. The SSB of sole in 7.d and plaice in 7.d is below B_lim. Several North Sea stocks are exploited at or below F_MSY levels (haddock in 4, 6.a and 20, plaice in 4 and 20, sole in 7.d, turbot in 4, whiting in 4 and 7.d, and witch in 3.a, 4 and 7.d); however, plaice in 7.d, and saithe in 3.a, 4 and 6 are fished above F_MSY. An important feature is that recruitment remains poor compared to historical average levels for most gadoids, although there have been signs of strong recruitment for whiting in most recent years. However, recruitment in 2024 appears to be still low for the gadoids and lower than previous years for flatfish stocks, with the exception of plaice in 4 and 20, turbot in 4, and whiting in 4 and 7d.  

WGNSSK is also responsible for the assessment of several data-limited stocks (category 2+ stocks) that are mainly bycatch in demersal fisheries; brill in 3.a, 4 and 7.d–e, lemon sole in 3.a, 4 and 7.d, dab in 3.a and 4, flounder in 3.a and 4, turbot in 3.a, whiting in 3.a, grey gurnard in 3.a, 4 and 7.d, striped red mullet in 3.a, 4, 7.d, pollack in 3.a and 4 and saithe in 7-10. Annual advice is required for brill in 3.a, 4 and 7.d–e, turbot in 3.a, and lemon sole in 3.a, 4 and 7.d. Biennial advice is required for striped red mullet in 3.a, 4 and 7.d, flounder in 3.a and 4, grey gurnard in 3.a, 4 and 7.d (due in 2026), and whiting in 3.a (due in 2026). Triennial advice is now required for dab in 3.a and 4, saithe in 7-10, and pollack in 3.a and 4 (due in 2027).  

Category 2–6 fish stocks: In 2025, new advice has been produced for bll.27.3a47de (category 2), for dab.27.3a4, fle.27.3a4, lem.27.3a47d, mur.27.3a47d (category 3), and pok.27.7-10 (category 5). Advice was produced following the WKLIFE X rules. Advice was not provided for gug.27.3a47d, whg.27.3a (category 3), and pol.27.3a4 (category 5).  

Advice for cod.27.46a7d20, sol.27.4 and tur.27.3a was postponed to the autumn. 

The summary of stock status is as follows:  

Category 1 stocks 

• Cod (cod.27.46a7d20): advice in autumn.
• Haddock (had.27.46a20): Spawning-stock biomass has increased sharply since 2019 and is now well above MSY B_trigger. Fishing pressure has declined since the beginning of the 2000s, but it has been above F_MSY for most of the time-series. Since 2021, fishing pressure has been below F_MSY. Recruitment (age 0) since 2000 has been low with occasional larger year classes. Three recent year classes (2019, 2020, and 2022) have all been above the recent mean. Recruitment in 2024 is estimated to be low.
• Norway pout (nop.27.3a4): advice in autumn.
• Plaice (ple.27.420): The spawning-stock biomass is well above MSY B_trigger and has markedly increased since 2008, following a substantial reduction in fishing pressure since 1999. Currently, fishing pressure on the stock is below F_MSY. Recruitment (age 1) in 2022 is the second highest in the time-series, while recruitment in 2024 is the third highest.
• Plaice (ple.27.7d): The spawning-stock biomass has increased rapidly from 2010 following a period of higher recruitment between 2009 and 2019. However, since 2016, SSB has gradually declined and is now at a level just below B_lim. Higher fishing pressure from 2015 onwards and lower recruitment from 2021 onwards contributed to this decrease in SSB. Fishing pressure on the stock is currently situated above F_MSY. Recruitment (age 1) 2024 appears to be low. 
• Saithe (pok.27.3a46): Spawning-stock biomass has mostly decreased since the early 2000s and is currently just above B_lim. Fishing pressure has decreased and stabilized above F_MSY since 2000. Currently, fishing pressure on the stock is above F_MSY. Recruitment (age 3) has shown an overall decreasing trend over time but slightly increasing in 2022. Recruitment in 2024 is low. 
• Sole (sol.27.4): advice in autumn. 
• Sole (sol.27.7d): The spawning-stock biomass has decreased since 2014 and is estimated to be fluctuating around B_lim since 2017. Currently, SSB is estimated to be below B_lim. Fishing pressure has decreased since 2007, stabilised around F_MSY from 2019 onwards and is currently estimated below F_MSY. Recruitment (age 1) is estimated to be on a relatively low level since 2012 and the 2024 recruitment is slightly increasing compared to the preceding two years. 
• Turbot (tur.27.4): The spawning-stock biomass has increased since 2004 and has been above MSY B_trigger since 2007. Currently, spawning stock size is above MSY B_trigger. Fishing pressure has been above F_MSY from 2018-2021, but decreased after to levels below F_MSY. Recruitment (age 1) is variable without a trend. In 2024, it is estimated to be higher than the preceding 4 years. 
• Whiting (whg.27.47d): Spawning-stock biomass has increased substantially in recent years and is now well above MSY B_trigger. Fishing pressure has been below F_MSY since the early 1990s. Currently, fishing pressure on the stock is well below F_MSY. Recruitment (age 0) has been fluctuating without trend, but the 2019 and 2020 year classes are estimated to be the largest since 2002. Recruitment in 2024 is estimated above average.  
• Witch (wit.27.3a47d): Spawning-stock biomass has decreased and has been below MSY B_trigger since the end of the 1990s but is above MSY B_trigger in 2025. Fishing pressure has been above F_MSY since the beginning of the time-series. Currently, fishing pressure on the stock is at F_MSY. Recruitment (age 1) has decreased since 2019 and is at lower levels in 2024. 

Category 2 stocks 

• Brill (bll.27.3a47de): Catches declined sharply in recent years. The relative exploitable biomass (B/B_MSY) has been above the reference point since the beginning of the time-series. Relative fishing pressure (F/F_MSY) has decreased since 2000 and is currently below F_MSY. 
• Turbot (tur.27.3a): advice in autumn.  

Category 3 stocks  

• Dab (dab.27.3a4): The stock size indicator has decreased since 2016 but is still above I_trigger. Currently, fishing pressure on the stock is below the F_{MSY proxy}. 
• Flounder (fle.27.3a4): The stock size indicator has gradually decreased since 2008 and is below I_trigger in 2025. Currently, fishing pressure on the stock is below the F_{MSY proxy}.  
• Grey gurnard (gug.27.3a47d): rollover advice.  
• Lemon sole (lem.27.3a47d): The stock size indicator has decreased since 2016 and is below I_trigger in 2024. Currently, fishing pressure on the stock is below the F_{MSY proxy}.  
• Striped red mullet (mur.27.3a47d): The stock size indicator has fluctuated above I_trigger in the most recent years and is above I_trigger in 2024. Currently, fishing pressure on the stock is above the F_{MSY proxy}.  
• Whiting (whg.27.3a): rollover advice.  

Category 5 stocks 

• Saithe (pok.27.7-10): Catches have decreased steadily since 2013. Catches in 2024 are the lowest of the time-series. 
• Pollack (pol.27.3a4): rollover advice.  

Summary of retrospective analysis (WKFORBIAS decision tree) 

To quantify retrospective patterns in the assessments of category 1 and 2 stocks, estimates of five-year retrospective peels are produced for fishing pressure, SSB and recruitment, and plotted with confidence bounds of the current assessment. The retrospective statistics (Mohn’s rho) are reported as a measure of quality. The decision tree formulated by WKFORBIAS (ICES, 2020) was considered to ensure more consistency in how advice is provided.