A NEW ULTRASONIC PINGER SYSTEM USING SYNC HRONIZING METHOD FOR TRACKING FISH

We have developed a new fish tracking system using a synchronising met hod. The system consists of an ultrasonic pinger, four hydrophones, a four channel receiver, an 8-bit single board computer with ADC, a pers onal computer, an electronic magnetic compass and a DGPS receiving sys tem. In this system, the bearings of the pinger are calculated using t he short base line by measuring the receiving time differences of a pu lse between channels. The distance from the hydrophone to the pinger i s calculated by using an original method, in which the receiver and th e pinger are synchronised to measure the interval between received pul ses. A Synchronising drift error which accumulates with time is correc ted by using the distance calculated from the transmission loss. This method gives a more accurate measurement of distance. Using this syste m, we successfully tracked three striped jack Caranx delicatissimus fo r five days.