Abstract: Evaluation of the relative contribution of the living objects with different sizes to sound scattering at sea is presented. The relative contribution to the total scattering depends on two factors: size spectrum of oceanic biomass and individual scattering properties of organisms. Various coefficients in the power function describing dependence of biomass concentration on individual size are tested and compared. Simple high-pass model of scattering is used. Flesh and swimbladder contributions are considered separately.