Pelagic fish distribution and ontogenetic vertical migration in common mesopelagic species off Lutzow-Holm Bay (Indian Ocean sector, Southern Ocean) during austral summer

The horizontal and vertical distributions of fish were examined off Lutzow-Holm Bay in the Indian Ocean sector of the Southern Ocean during midnight sun in January 2005. Fish were sampled from six discrete depth layers (0-2,000 m). The most abundant fish in layers from the surface to 200 m were larval stages of Electrona antarctica and Notolepis coatsi. In layers from 200 to 2,000 m, fish assemblages were relatively uniform among all stations and were dominated by E. antarctica (juvenile-subadult), Cyclothone microdon, and Bathylagus antarcticus. Cluster analysis revealed three epipelagic communities related to water temperature and salinity. An ontogenetic habitat shift to deeper layers was apparent for E. antarctica, N. coatsi, and B. antarcticus. Preferences for warm waters were observed in E. antarctica (larvae) and N. coatsi (preflexion to flexion larvae), although they were distributed across a broad range of temperature and salinity in epipelagic zones.