Verification of the Backscattering Strength Based on the Swimming Behavior of Antarctic Krill

Abstract

This study provides an estimate of the SDWBA-modelled mean target strength for given sets of krill length and swimming orientation. The range of the dB identification window for krill length was between 28 mm and 67 mm and the distribution of swimming orientation N[11.0°, 4.0°] was estimated to be between 0.06–10.97 dB, while the range estimated using N[53.1°, 21.4°], i.e., the distribution of orientation obtained under the brightest illuminance level, was 5.21–9.82 dB. The range of the dB window calculated using N[45.2°, 23.0°], obtained under the second brightest illuminance level, was 3.83–11.76 dB, and the range calculated with N[48.1°, 23.0°], obtained under the third illuminance level, was 3.83–11.76 dB. The range of the dB window calculated by N[45.9°, 23.0°] was 3.41–11.75 dB, and the range of the dB window for krill length ranging from 28 mm to 67 mm was 4.05–11.34 dB. In all the swimming orientations, the smaller the krill size was the lower the averaged target strength value was; likewise, the larger the krill size was the higher the averaged target strength value was. The result indicated that swimming orientation impacted greatly on the range of frequency differences of Antarctic krill.