Measurement of Target Strength of Euphausia pacifica Using a High-Frequency Broadband Signal

Abstract

The target strength (TS) spectrum of a marine organism is a key factor in the target discrimination of that organism. In this study, the side-aspect TS spectrum of Euphausia pacifica was measured as a function of the incident angle of the ensonified wave in a seawater tank using a broadband transducer with a bandwidth of 300–700 kHz. The measurements were compared with the theoretical predictions by the distorted-wave Born approximation-based deformed-cylinder model (DWBA model). The TS pattern measurements were in good agreement with the DWBA model predictions for the main lobe but not with those for the side lobe. The measurements of the relationship between the normalized mean TS spectrum and the total length divided by wavelength ratio were in good agreement with model predictions.