Exact Simulation of Fish School Echoes and its Applications

A numerical simulation method was developed to investigate fish school echoes. The simulation incorporates strict expressions for fish target strength model, directivity of a transducer, and echo waveform in order to realize high fidelity. The fish school echoes are constructed by synthesizing single echoes for each ping. Two application examples are shown. One is the confirmation of linearity between the distribution density offish and the simulated volume backscattering strength; the result showed a very good linear relationship. The other example is fish school feature extraction by the wavelet analysis. In the results, no apparent one-to-one correspondence between the given distribution pattern and the results of the wavelet analysis ,but a characteristic wavelet pattern is observed.