Target strength measurement of Selar boops (Oxeye scad) using 38 kHz and 120 kHz

Furuno FQ-80 Scientific Echo Sounder can be performed on dual-frequency capabilities, 38 kHz and 120 kHz, as an individually or simultaneously. Measurement of target strength (TS) for Selar boops (Oxeye scad) had been deployed using FQ-80 on 228 dB and 236 dB of source level (SL) at low and high frequency, respectively. The fish were sited in the net cage at the bottom of the vessel. TS value, depth, and position (x-y-z) of single fish which detected at every ping at low and high frequency has been observed from recorded echogram using FQ-80 Analyzer. Fish TS detected at low and high frequency are ranging from -47.40 to -38.33 dB with the average of -44.49 dB and -45.19 to -42.76 dB with the average of -43.96 dB. Thus, fish TS detected at higher frequency is stronger than at lower frequency.