The focus for this study was to acquire knowledge to scrutinize raw acoustic backscatter, collected during scientific surveys, onboard R/V Dr Fridjof Nansen from June 27 to 9 July 2017, researching small pelagic fish resources within the Mauritanian EEZ. To calculate stock biomass index from survey data and relate species distribution to temperature conditions. Acoustic data were post-processed using the post-processing software Large-Scale Survey System (LSSS) Version 2.0, for data processed after fixing the bottom and surface line, for the surface line we allocate backscatters fish from 10m, then excluding sailing between transects. The acoustic data was preprocessed. Species allocation based on the species proportion in catch, and biomass estimate calculated following FAO guideline.