Modelling of sandeel (Ammodytes marinus) target strenght. Underwater Acoustic Measurements: Technologies & Results

Acoustic target strength of sandeel (Ammodytes marinus) was computed using a finite element approach. Target strength was found as a function of fish tilt-angle and acoustic frequency, and was computed from three-dimensional reconstructions of the fish form. Sandeels lack swimbladder and are small perch-like fish that bury in the bottom substrate.

The morphometric data were derived from digitized cross-sections of sandeel as well as high-resolution magnetic resonance images. The finite element method is a versatile tool to estimate fish target strength. It can be used over a great frequency range and with no constrictions on fish tilt angle. It can also in theory handle scattering from all parts of the fish like its swimbladder, flesh, and bone. The disadvantage is the considerable computational cost, especially at high frequencies, resulting in a practical high-frequency limit. Results from the finite element computations were also compared with results from other scattering models and in situ measurements.

 

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