A new ultrasonic pinger system using synchronising method for tracking fish [using Caranx delicatissimus]

We have developed a new fish tracking system using a synchronising method. The system consists of an ultrasonic pinger, four hydrophones, a four channel receiver, an 8-bit single board computer with ADC, a personal computer, an electronic magnetic compass and a DGPS receiving system. In this system, the bearings of the pinger are calculated using the short base line by measuring the receiving time differences of a pulse between channels. The distance from the hydrophone to the pinger is calculated by using an original method, in which the receiver and the pinger are syn-chronised to measure the interval between received pulses. A Synchronising drift error which accumulates with time is corrected by using the distance calculated from the transmission loss. This method gives a more accurate measurement of distance. Using this system, we successfully tracked three striped jack Caranx delicatissimus for five days.