Target strength of tiny roach

Abstract

Seven frozen specimens of surface-adapted roach (Rutilus rutilus), of lengths 32-40 mm and masses 0.20-0.49 g, have been sectioned with a precision microtome. The swimbladder contours have been digitized and the swimbladder volumes determined. For ordinary ultrasonic frequencies the wavelength is much longer than the particular characteristic swimbladder dimensions. However, it is shorter than the wavelength at resonance. The sound scattering is computed according to a resonant swimbladder model.