The paper provided an overview of some of the basic information available relevant to the identification and listing of Operational Units in the Adriatic Sea (Geographical Management Units 17 and 18). Preliminary figures and composition of the Adriatic fishing fleet as a total and by country, fishing gear and vessel size were given together with the base ports. The sardine fishery in the Northern and Central Adriatic was used as an example of the application of Operational Units. Within this Sub-area (17) the sardine stock is considered to be shared by the fishing fleets of the coastal states and it is believed to be a single stock. Therefore, the paper proposed to consider only one Operational Unit for this resource and some of its specific, or elementary, components such as base ports, fleet segments and fishing seasonality were indicated as an example of the complementary and desirable information.