The target strength (TS) of Japanese horse mackerel was measured by using split-beam echo sounder. The target was kept at the position of dorsal direction incidence and moved across to the beam. Characteristics of TS directivity pattern and measuring precision of position angle by split-beam method were estimated.
As a result, TS pattern in pitch plane shows drastic variation. Beside that, the fluctuations of position angle were increased. I took notice the coherent scattering of fish body structures, also examined the difference of phase in carrier wave. And we discussed the relationship between fish body structures and interference.