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EXECUTIVE SUMMARY

The Ad hoc Working Group on European hake (WGHKE) was organized following the recognition by the forty-seventh session of the General Fisheries Commission for the Mediterranean (GFCM) of the continued overexploitation of European hake stocks in the Mediterranean, particularly in the western subregion. The WGHKE was held on 11–13 March 2025 at GFCM headquarters in Rome, Italy, and in hybrid modality, involving 72 experts from research institutes across the Mediterranean, the European Commission (DG MARE), and the GFCM Secretariat. In this context the meeting aimed to review a Mediterranean basin- and subregional basis data and stock assessment model assumptions to develop good practice guidelines for assessing this species and to draft a roadmap for future work. The WGHKE undertook: i) a comparative analyses and synthesis of biological assumptions and selectivity estimates in current European hake assessments within the GFCM area competence, including a Shiny Applications support tool; ii) a scoping exercise of data availability with focus on the Western Mediterranean stocks; and iii) evaluated assessment challenges and sources of bias in statistical catch at age models (a4a) and surplus production models (SPiCT). Comprehensive recommendations were given towards developing good practice guidelines for commonly used assessment approaches, and capacity building and advancing on data-limited and data-moderate integrated assessment tools was recommended. A short-term roadmap was drafted that involved a proposal for new benchmark assessments for European hake stocks in the Western Mediterranean subregion (including in GSA 3, GSA 4, GSAs 1-5-6-7 and GSAs 8-9-11) that should prioritise the use of candidate models that can adequately account for the complexity of the biology by sex and the multi-fleet nature of the fisheries and associated selectivity patterns, pending a prioritisation exercise and a re-evaluation of connectivity and stock structuring across GSAs. A medium-term roadmap involved a proposal towards strategic approaches of developing spatially explicit stock assessment models for European hake in the Mediterranean Sea.