Distribution and diel vertical migration of mesopelagic fishes in the Southern Sargasso Sea — observations through hydroacoustics and stratified catches

Abstract Vertical distribution patterns and relative abundance of mesopelagic fish species other major taxonomic groups were investigated through vertically stratified trawl sampling hydroacoustic analyses along the subtropical convergence zone from 52° W to 70° in oligotrophic Sargasso Sea. Persistent stationary layers several migrating components different scattering characteristics detected. The results reveal varying vertical migration patterns, including times onset diel depths a migrant pathway emerging daily lower deep layer (DSL) at dusk upper DSL without affecting its composition. Fish identification was made based on morphological confirmed by genetic barcoding subsamples. In total, 5022 specimens 27 families, 62 genera 70 caught. terms (A) biomass (M), catches dominated families Myctophidae (A=59.1%, M=47.4% total catch) Melamphaidae (A=22.5%, M=17.1%). Stomiidae most species-rich with 31 12 species, respectively. Catches two easternmost stations Scopelogadus mizolepis Nannobrachium cuprarium, while Bolinichthys photothorax Ceratoscopelus warmingii abundant westernmost stations. This study provides insights into behaviour Sea adds our understanding community this large oceanic area.