Here we present fish observation data obtained during the first EGIM deployment at the OBSEA observatory, which led to the development of a methodology for correlating fish activity and biologically relevant oceanographic variables. In addition to salinity, temperature, sound speed, water depth and dissolved oxygen data measured by the EGIM, two underwater digital cameras were deployed to provide ecological observations: a CAM1 camera rotating 360° and five metres apart, and a fixed CAM2 camera pointed at an artificial reef where fish activity is observed. For the analysis, the two close cameras were considered as one. For each image, the total number of fish was counted. All visible individuals were taxonomically classified as detailed as possible, using the latest scientific nomenclature from FISHBase.