The SES_GR2_Mesozooplankton dataset is based on samples taken during August-September 2008 in Ionian Sea, Libyan Sea, Southern Aegean Sea and Northern Aegean Sea. Sampling volume was estimated by the net mouth surface and the towing distance for WP-2. The sample was split on board in two halves by using the beaker approach. The first sub-sample was immediately fixed and preserved in a seawater formalin solution containing about 4% buffered formaldehyde to allow the determination of species composition abundance. Pipette for the subsamples used in the taxonomic analysis of zooplankton under binocular microscope.