Detection range of acoustic instruments for fisheries

Abstract

Detection ranges of acoustic instruments mainly used for fisheries and their research are derived as the range bordered by a certain signal-to-noise ratio (SNR) threshold. The SNR is depicted by several factors on transmitting and receiving, sound propagation, scattering by objects, and mainly self-ship noise. The detection ranges are shown for several fisheries instruments: fisheries echo sounder, quantitative echo sounder, and bio-telemetry system. The results can be used for designing the instruments, examining the capability of user’s own instruments, and interpreting obtained data or echograms. Some examples of the results follow. Increasing transmitting power is not as effective for high frequencies as for low frequencies to increase the detection range. Comparison of volume backscattering strengths obtained by the quantitative echo sounder at several frequencies for the purpose of rough species’ identification should be done within the same detection range. By applying the concept of the detection range for the bio-telemetry receiver beams, the number of the beams and the beamwidths can be determined.