Ocean Deoxygenation Conference | Kiel 2018

In 2015, 5 stations each were sampled in the tropical Atlantic and the West-Sahara OMZ for mesopelagic fauna. Community analysis revealed a close relationship between OMZ and tropical region, although some species increased in abundance in the OMZ (e.g. Nannobrachium isaacsi, Myctophidae; Malacosteus niger, Malacosteidae). Length composition and size ranges revealed a smaller maximum size for OMZ specimens (except for Myctophum affine, Myctophidae) and a significant difference in size structure for 11 out 14 tested species. A tenfold higher abundance of specimens in the size range 30-60 mm standard length appeared in the OMZ. It is concluded that observed differences in length structure are due to environmental changes and local productivity.