The hydroacoustic characteristics of scattering layers measured during a cruise of the R/V Professor Siedlecki in 1984 during the months July and September, are presented in the form of vertical and horizontal distributions of column scattering strength and volume backscattering strength. These distributions are compared with the results of physical and biological sampling. Acoustical measurements were carried out using a 38-kHz echo sounder and an analog integration system connected with a computer. Biological sampling was conducted by using a Bongo net and a large pelagic trawl with a small mesh inset, of the type used for commercial krill catches. This paper presents parameters of diel migrations of scattering layers, investigated between latitudes 37°–46° N and longitudes 12°–30° W for a 24-h period. The relative stability of the value of column scattering strength during the 24-h period and its relationship to catch results indicate that acoustical measurements are a promising tool for a quick, large-scale description of scattering layers. The results presented are also useful as a guide for future surveys having the same objective.