SPECTRUM ANALYSIS OF VARIATIONS IN DORSAL SCATTERING PATTERNS OF AN INDIVIDUAL FISH

We tried to analyze the spectrum of echo scattering patterns from indi vidual fish, in order to clarify the cause of periodic changes in dors al aspect scattering patterns. Targets of individual fish of three spe cies were measured in three states, whole, without bladder, and skelet on. The power spectrum was calculated from scattering patterns which t ransformed to distance-amplitude co-ordinates from incidence angle-amp litude co-ordinates. The elemental patterns and power proportion of ea ch frequency band were calculated by using convolution integration of the power spectrum and filter-fuction in the frequency region. Analysi s shows that a relationship was observed between fish species, or fish figure, and the characteristics of the changing period.