Description: This file contains data on numerical abundance of early stages of fishes collected in April 2015 across the tropical and equatorial Atlantic. Eleven stations were sampled both day and night, from the oligotrophic region close to the Brazilian coast to the more productive region off the western African coast. Samples were obtained by means of a Multiple Opening/Closing Net and Environmental Sensing System (Wiebe et al., 1985), MOCNESS-1 m2 net, from 800 m to the surface, discriminating 8 layers of the water column. Samples were fixed on board and stored in 5% buffered formalin and seawater for later sorting and identification in the laboratory. These data were obtained within the project: "Migrants and Active Flux In the Atlantic Ocean, financed by the Spanish Ministerio de Ciencia e Innovación CTM2012-39587-C04.

Description: This file contains data on numerical abundance of mesopelagic fishes collected in April 2015 across the tropical and equatorial Atlantic. Twelve stations were visited day and night, from the oligotrophic region close to the Brazilian coast to the more productive region off the western African coast. Hauls were performed with a scientific midwater trawl, the Mesopelagos (designed by Meillat, 2012), which works with a single traction cable. The gear consists of graded-mesh netting starting with 30 mm and ending with 4 mm. At the end of the net, a multi-sampler (designed for the present investigation by one of the co-authors, A. Castellón-CSIC) was installed to obtain samples from 5 different depth layers of the water column. For some stations, where lots of gelatinous organisms, or Sargassum weed occurred, the system could not work and the data presented integrates the water column from 800 m to the surface. The depth of the net was controlled by a SCANMAR system. Samples were identified on board or frozen for a later identification in the laboratory. These data were obtained within the project: "Migrants and Active Flux In the Atlantic Ocean, financed by the Spanish Ministerio de Ciencia e Innovación CTM2012-39587-C04.

Description: The vertical distributions of early developmental stages of oceanic fishes were investigated across the tropical and equatorial Atlantic, from oligotrophic waters close to the Brazilian coast to more productive waters close to the Mauritanian Upwelling Region. Stratification of the water column was observed throughout the study region. Fishes were caught with a MOCNESS-1 net with mouth area of 1 m2 at 11 stations. Each station was sampled both during the day and at night within a single 24-h period. The investigation covered both larvae and transforming stages from the surface to 800 m depth. Distribution patterns were analysed, and weighted mean depths for the larvae and transforming stages of each species were calculated for day and night conditions. Forty-seven different species were found. The highest number of species occurred in the three stations south of Cape Verde Islands, characterized by a mixture of South Atlantic Central Water (SACW) and Eastern North Atlantic Central Water (ENACW). There was a marked drop in species richness in the three stations closer to the African upwelling, dominated by ENACW. The highest abundances occurred in the families Myctophidae, Sternoptychidae, Gonostomatidae and Phosichthyidae. Day and night vertical distributions of larvae and transforming stages showed contrasting patterns, both in the depths of the main concentration layers in the water column, and in the diel migration patterns (where these were observed). Larvae generally showed a preference for the upper mixed layer (ca. 0–50 m) and upper thermocline (ca. 50–100 m), except for sternoptychids, which were also abundant in the lower thermocline layer (100–200 m) and even extended into the mesopelagic zone (down to 500 m). Transforming stages showed a more widespread distribution, with main concentrations in the mesopelagic zone (200–800 m). Larvae showed peak concentrations in the more illuminated and zooplankton-rich upper mixed layers during the day and a wider distribution through the upper 100 m during the night. For most species, transforming stages were concentrated in the mesopelagic layers both day and night, although in some species (Diaphus cf. vanhoeffeni and Vinciguerria nimbaria), the transforming stages displayed vertical migration into the upper 100 m at night, in a manner similar to their adult stages.