Spectrum Analysis of Variations in Dorsal Scattering Patterns of an Individual Fish

Abstract

We tried to analyze the spectrum of echo scattering patterns from individual fish, in order to clarify the cause of periodic changes in dorsal aspect scattering patterns. Targets of individual fish of three species were measured in three states, whole, without bladder, and skeleton. The power spectrum was calculated from scattering patterns which transformed to distanceamplitude co-ordinates from incidence angle-amplitude co-ordinates. The elemental patterns and power proportion of each frequency band were calculated by using convolution integration of the power spectrum and filter-fuction in the frequency region. Analysis shows that a relationship was observed between fish species, or fish figure, and the characteristics of the changing period.