Simultaneous identification of multiple signals from phase modulation-coded transmitters for acoustic biotelemetry of fish school

Multiple signals must be identified from different fish simultaneously to observe group behavior using acoustic biotelemetry. We demonstrated simultaneous identification of multiple signals using a new phase modulation-coded telemetry system. We deployed eight transmitters with a 1.28-s signal transmitting interval at the same location, and two receivers that were 18.5 m and 38.0 m away from the transmitters. The detection rates of the two receivers during 15 min of recording were 77.0% and 73.0%. These results show that multiple signals from several transmitters were detected simultaneously by the receivers and were discriminated at high resolution (<2 s). This new telemetry system will be useful in studies on fish schooling behavior, aggregation, and predator-prey interactions.