A sonar responding acoustic tag (SRAT) was developed. The SRAT responds to the signal transmitted from a sonar and transmits the pulse signal to the sonar. The SRATs response signals are appeared on the sonar display. The prototype of SRAT responded to the sonar signal between 20 to 90 kHz. The frequency of the transmitting signal was 31.25kHz or 62.50kHz. The size of SRAT was φ25×150mm, 100g in air and 70g in water. The multilayer piezoelectric element was used as the transducer. The battery life was about one month. Experiments to examine the response range were performed using 68 kHz sonar whose source level was 210dB re 1μPa at 1m. The SRAT signals could be observed around 200m distance on the sonar display. Experiments were performed using a tuna purse seine. The sonar frequency of the fishing vessel was 28kHz and the source level was 220dB re 1μPa at 1m. The SRAT was attached to the purse seiner for measuring shape of net. As the result of this experiment, the maximum response distance of the SRAT was confirmed as 400m. The SRAT is useful for actual fishing such as the observation of purse seine shapes.
