Understanding patterns of fish backscatter, size and density around petroleum platforms of the U.S. Gulf of Mexico using hydroacoustic data

•Hydroacoustic indices of fish (density, backscatter, size) were examined at U.S. Gulf of Mexico platforms.•Fish density and mean backscatter were higher at coastal platforms in comparison to the deeper sites.•Density and backscatter were higher in close proximity to the platforms.•Salinity and temperature both had significant effects on all hydroacoustic indices.•Vertical compression of fishes occurred in the water column in the presence of hypoxia.