Horizon 1 1 10 C-ACTI : Communications avec actes dans un congrès international International conference ICAWA 2017 and 2018 : extended book of abstract : the AWA project : ecosystem approach to the management of fisheries and the marine environment in West African waters ICAWA : International Conference AWA 153 AFRIQUE DE L'OUEST ATLANTIQUE 2019 2018/04/17-20 Dakar (SEN) ; Marseille SRFC/CSRP ; IRD fdi:010078281 ENG https://www.documentation.ird.fr/hor/fdi:010078281 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers20-05/010078281.pdf Horizon (IRD) Diel vertical migration (DVM) of micronekton is a behavioural mechanism driven by a trade-off between predator avoidance and access to prey. This trade-off is controlled by environmental forcing that can lead to changes of DVM pattern under changing environmental conditions. Time series of hydro acoustic surveys between 1995 - 2015 of three large Atlantic ecosystems (Canary Current - CCLME, Guinea Current - GCLME, and Benguela Current - BCLME) were analysed to calculate DVM patterns based on volume backscattering strength (Sv). DVM related descriptors (n=15) were calculated for areas according to bathymetric definitions (shelf = 10 - 150 m bottom depth, slope = 150 - 500 m bottom depth, and plain > 500 m bottom depth). Typical DVM I pattern, with micronekton descending during daytime and ascending during night-time, were observed on the slope and plain in all three ecosystems, but not on the shelf with only negative day-night values in the CCLME and BCLME. Lower daytime Sv values during the day compared to night-time suggest either less dense patches of micronekton leading to negative day-night differences in the CCLME and GCLME or insufficient measurements of certain depth strata (e.g., 0 - 10 m surface). Only a few significant and different DVM descriptors suggest a change in the CCLME and the GCLME in the last 20 years. All other insignificant descriptors assume natural variability in large Atlantic ecosystems. Our results provide insight into inter-annual variability in micronekton DVM patterns. 020 ; 021 ; 036 ; 032