A joint MesoBED/MEDIAS survey just took place in Korinthiakos gulf, Greece. Korinthiakos gulf is an enclosed basin with bottom depths exceeding 900 m and Deep Scattering Layers present at different depth strata. In this first MesoBED research cruise, mesopelagic fish samples were collected during day and night from the water column up to 650 m depth, along with plankton samples and oceanographic parameters. At least 8 mesopelagic fish species belonging to the families Myctophidae, Sternoptychidae and Stomiidae were identified and their diel vertical migration was recorded with scientific echosounders. Samples will be transferred to lab for detailed identification and further measurements, while acoustic data are awaiting for echo integration and statistical analysis. More research cruises are scheduled in selected areas of the Aegean Sea.