This abstract presents some new results on mesopelagic fish populations from surveys from Crozet to Kerguelen and in the subtropical Indian Ocean. The mesopelagic fauna plays a crucial role in the marine ecosystem trophic web. The study integrates both the subtropical and Southern Ocean species. The surveys from 2017 to 2019 revealed the presence of 141 species, with Myctophids accounting for 61% of the observed abundances. Stomiiformes, including the families Gonostomatidae, Phosichthyidae, Sternoptychidae, and Stomiidae, ranked second in terms of abundance. The distribution patterns of these fish families exhibited variability across the study area. Myctophids exhibited high abundances in the Southern Ocean, with concentrated patches in the subantarctic zone between the Crozet and Kerguelen archipelagos, as well as the eastern part of the Kerguelen Plateau. Stomiiformes, on the other hand, displayed higher dominance in the southern Indian Ocean, with noticeable differences between the western and eastern regions of the study area.
The objective of the research was also to investigate the geographical distribution of mesopelagic fish species and assess their alignment with established biogeographic provinces from 20°W to 160°E and from 30 to 60°S. The results from the 2017-2019 surveys will be combine to international databases for generating an atlas of Myctophid fish. This will form the baseline data for studying in the future the consequences of climate change which is drastic in the subantarctic zone. The global distributions of these species will then be used to establish models of potential habitats and refine the biogeography of the species. Members of the WG EMM are requested to inform us if they have any information on the ecology of Stomiiformes in the South Indian Ocean or the Southern Ocean.