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The ICES Working Group on Ecosystem Assessment of Western European Shelf Seas (WGEA-WESS) aims to provide high quality science in support to holistic, adaptive, evidence-based man-agement in the Celtic seas, Bay of Biscay and Iberian coast regions. The group works towards developing integrated ecosystem assessments for both the (i) Celtic Seas and (ii) Bay of Biscay and Iberian Coast which are summarized in the Ecosystem Overviews (EOs) advice products that were recently updated. Integrated Trend Analysis (ITA) were performed for multiple sub-ecoregions and used to develop an understanding of ecosystem responses to pressures at varying spatial scales. Ecosystem models (primarily Ecopath with Ecosim; EwE) were developed and identified for fisheries and spatial management advice. The updated Celtic Seas EO represents a large step forward for EOs, with the inclusion of novel sections on climate change, foodweb and productivity, the first application of the new guidelines for building the conceptual diagram, inclusion of socio-economic indicators, and progress made toward complying with the Transparent Assessment Framework (TAF). We highlight ongoing issues relevant to the development and communication of EO conceptual diagrams. A common methodology using dynamic factor analysis (DFA) was used to perform ITA in a comparable way for seven subregions. This was supported by the design and compilation of the first standardized cross-regional dataset. A comparison of the main trends evidenced among subregions over the period 1993–2020 was conducted and will be published soon. A list of available and developing EWE models for the region was also generated. Here, we re-port on the advances in temporal and spatial ecosystem modelling, such as their capacity to model the impacts of sector activities (e.g. renewables and fisheries) and quantify foodweb indi-cators. We also reflect on model quality assessment with the key run of the Irish sea EwE model. The group highlighted the hurdles and gaps in current models in support of EBM, such as the choice of a relevant functional, spatial, and temporal scales and the impacts of model structure on our capacity to draw comparisons from models of different regions. The group aims to ad-dress these issues in coming years and identify routes for ecosystem model derived information into ICES advice. info:eu-repo/semantics/publishedVersion

The Working Group on Multispecies Assessment Methods (WGSAM) aims at enabling research on predator-prey interactions for developing advice on the ecosystem approach to fisheries management.This report details results related to WGSAM term of reference B: “Update of key-runs (standardized model runs updated with recent data) of multispecies and ecosystem models for different ICES regions”. Multispecies model key-runs are used in ICES advice processes, and WGSAM provides critical expert review of these key-runs to recommend appropriate use of results.Although key-run reviews have been conducted in the past, requests for reviews are increasing. Therefore, WGSAM first formalized a consistent set of review criteria to conduct key-run reviews. These are outlined in section 2 of this report and are posted online (https://iceseg.github.io/wg_WGSAM/ReviewCriteria.html). WGSAM then applied these review criteria to one key-run for the North Sea ecosystem. The review is detailed in section 3 of this report. As the review criteria were applied, WGSAM also noted any difficulties with the review process in order to further refine the review criteria and to make future key-run reviews more efficient and effective.WGSAM recommends the use of natural mortality estimates from the North Sea SMS key-run for use in single species stock assessment models of North Sea cod, haddock, herring, Norway pout, southern North Sea sandeel, northern North Sea sandeel, sprat, and whiting.

The Working Group on Multispecies Assessment Methods (WGSAM) aims to advance the operational use of knowledge on predator-prey interactions for advice on fisheries and ecosystem management. This report summarises the achievements of a 3-year cycle during which the group consolidated criteria to evaluate key-runs and more in general the skills assessment of multispecies models, released key-runs for the Baltic Sea, North Sea and Irish Sea all evaluated with those criteria, progressed in the areas of multiple models comparison, ensemble modelling and on the estimation of biological reference points in the context of multispecies interactions. The updated keyruns for the North Sea and the Baltic Sea provided the best available estimates of predation mortality for a number of key commercial stocks in these two ecoregions which have been already integrated into the stock assessments throughout benchmarks and inter-benchmarks. Analyses accumulate showing that ignoring strong trophic interactions may lead to bias in the perception of stocks status and in the calculation of reference points. Evaluations show advantages of using multi-model ensembles to capture the dynamics of the main stocks and the system overall. Results accumulated so far suggest that the benefits of ensemble modelling exist for both simple models, i.e. multispecies production models, as well as more complex ecosystem models. Various approaches are available to the practice of ensemble modelling, including a fully Bayesian ensemble framework suitable also for multi-model forecasts. The report includes also progresses with software developments to enhance accessibility of some complex routines, including ensemble modelling beyond “just a simple average approach” and computation of multispecies reference points, to a broader group of modellers and users. The group sees these developments as a great opportunity to work more towards cross-platform comparisons and further on multispecies skill assessment which will remain important themes for continuation of the work. To further progress the use of multispecies and ecosystem models, collection of ecosystem data remains highly relevant, with priority on stomach data and other information on processes affecting trophic interactions and trophodynamics of ecosystems (i.e., predator-prey overlap, temperature-dependent consumption, availability of other food).