Two applications for a dual-beam transducer in hydroacoustic fish assessment systems

This paper describes the advantages of using a narrow- and a wide-beam acoustic transducer in systems for estimating fish abundance. In the technique considered, the acoustic pulse is transmitted with a narrow beam and the echo is received on both the narrow and wide beams. The signals received at the two transducers can be used to determine the acoustic scattering cross section of the fish. The mean value of the acoustic scattering cross section can be used to evaluate the scale factor needed by echo integrators to obtain an absolute abundance estimate. The outputs of the two transducers can also be used to control the sampling volume in an echo counting system.