PELMED is an acoustic and a trawl identification survey which covers the continental shelf (20-200m deep) of the Gulf of Lion and the PACA region. The acoustic survey is carried out according to parallel transects separated by 12 nautical miles and perpendicular to the coast (9 transects in the Gulf of Lion). The sampling design includes also an inter-transects (path between two transects) which makes it possible to prospect on a constant depth and thus to refine the spatial coverage. The primary goal of PELMED is the spatio-temporal assessment of small pelagic biomass, in particular anchovy and sardine biomasses. In the north-western Mediterranean, the majority of anchovy breeding populations are located on the continental shelf of the Gulf of Lion and in northern Catalonia in July, hence the choice of this period for the implementation of the survey. Furthermore, carrying out the survey in July allows also to obtain an estimate of the recruitment of the sardine (which reproduces in winter). The indicators resulting from this survey (stock assessment) as well as the research outcomes are based on the history of the PELMED survey, it is therefore necessary for the sake of continuity and comparison between years to continue observations at the same time each year (July).

The PELMED survey seeks also to accumulate as much data as possible on the various compartments of the pelagic ecosystem, ranging from physical parameters (temperature, salinity, etc) to higher predators (marine mammals, birds), through the different lower trophic levels (phyto- and zooplankton, small pelagic fish). Thus, after each trawl or at each end of transect, a hydrological station is carried out with hydrological measurements along the water column thanks to a bathysonde, the sampling of seawater for phytoplankton analysis using a Niskin bottle and zooplankton net vertical tows (WP2). Finally, throughout the survey an observer is embarked to identify and enumerate birds and marine mammals.