Ifremer, the French research institute for the exploitation of the sea, contributes, through its work and expertise, to the knowledge of the oceans and their resources, the monitoring of the marine and coastal environments and the sustainable development of maritime activities. Ifremer’s around 1400 permanent staff are located in five centers and 20 stations located around the European French coast and overseas. Ifremer has joined the SUMMER project to collect data and gain knowledge on the diversity and role of mesopelagic organisms in the oceans. Ifremer’s focus is on the Bay of Biscay, which is the scientific playing ground of the participating research unit. In collaboration with the University of La Rochelle, Ifremer is supervising a PhD thesis aiming to provide a first quantitative description of the composition of small mesopelagic fish communities, both in terms of taxonomic diversity, functional diversity and trophic structure, as well as its importance in the transfer of matter and energy to top predators. Ifremer’s scientists are thrilled about the opportunity SUMMER offers to learn more about the mesopelagic ecosystem.