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Mackerel tuna ( Euthynnus affinis ) is a pelagic fish from Scombridae family and one of the commercially important species. The fish is mostly found in the water column from the surface down to about 50 m. Mackerel tuna spread widely in the tropical and subtropical waters, including the Indian Ocean, Pacific, Mediterranean Sea, and Black Sea. Since the level of exploitation of this fish resource is relatively high, it is critical to have an accurate assessment on the status of the stock. In this paper we report and discuss the measurement results of the acoustic target strength (TS) of Mackerel tuna using acoustic broadband technique. A broadband technique was used to better characterized the basic TS-Frequency relationship of the target, and hence less bias in biomass estimation. Target Strength measurement was performed using SIMRAD EK-80 scientific acoustic instrument with frequency bandwidth 160-240 kHz and sound pulse was transmitted to the target with 1 CW pulse and 8 FM pulse. The fish was tethered and positioned directly below the acoustic transducer. The results of the measurements are presented in terms of TS-Frequency. It is found that the TS-F relationship fluctuates, where the highest TS value -54.64 ± 4.64 dB is in 190-200 kHz frequency interval.

Measurement and analysis of TS-Frequency relationship on mackerel tuna (Euthynnus affinis) using bandwidth frequency