Acoustic backscattering by Atlantic mackerel as being representative of fish that lack a swimbladder. Backscattering by individual fish

Abstract

Abstract Developing acoustic methods for the identification of fish remains a long-term objective of fisheries acoustics. The accuracy of abundance estimation may be increased when the acoustic-scattering characteristics of the fish are known, including their expected variability and uncertainty. The modelling approach is valuable during the process of interpreting multi-frequency echograms. This paper attempts to improve the understanding of sound backscattering of fish without a swimbladder, here represented by Atlantic mackerel (Scomber scombrus). Our approach includes results from modelling as well as comparisons with field data. There will be two papers. The first is a study of the non-averaged backscattering characteristics. This initial analysis is important for the understanding of the averaged backscattering cross-section, which will be considered in the second paper. In that paper the relative importance of bones in acoustic backscattering at higher frequencies will be verified.