Mediterranean and Black Sea fisheries feature a great variety of target species, vessels and fishing gears and play an important socioeconomic role in the whole region. The mandate of the General Fisheries Commission for the Mediterranean (GFCM) is to ensure the sustainability of fisheries activities through the adoption of adequate management measures. The assessment of the size and state of the stocks exploited by fisheries is one of the pillars of modern management. The GFCM as the responsible Regional Fisheries Management Organisations (RFMO) of the Mediterranean and Black Sea has established permanent working groups on dermersal and small pelagic fish species where fisheries scientists perform their analysis and provide the best scientific advice to better manage fisheries and fish stocks. The groups, in cooperation with regional programs under the Regional Sea Conventions, set standards and guidelines for the collection, transmission and analysis of these data.