Application of backscattering models for Target Strength measurement of Trachurus mediterraneus and Scomber colias in the Mediterranean Sea

In this study, X-Ray and Computer Tomography scans were performed on 82 individual fish collected during the Mediterranean International Acoustic Survey (MEDIAS) 2020 and 2021 carried out in the Adriatic Sea (Mediterranean) [8] for the application of backscattering models. The DICOM files were processed with Image J - 3D slicer and 3D Doctor software to get accurate morphometric characteristic measurements of swimbladder and fish body from 2D and 3D digital images, which were settled as input data for Kirchhoff ray mode model (KRM) and Finite Element Method (FEM) (Figure 1). KRM model accounts for resonant and geometric backscatter using a low mode solution and Kirchhoff-Ray approximation to sum the energy of consecutive gas-filled and fluid-filled cylinders of 1 mm thick [9]. KRM is an analytical model that approximates the shape of the body and swimbladder, hence does not require extensive computation [10].