Species Identification and Tempo-Spatial Distribution of Anchovy Using Multi-Frequency

Abstract

In this study, we identified the echo signals of anchovies on echograms using the dB-difference method; additionally, the daytime and nighttime distribution characteristics of anchovies were determined. Using the difference in frequency characteristics of 18, 38, 70, 120, and 200 kHz, the dB-difference intervals of −2.1 dB ≤ ΔMVBS18–38 ≤ 4.4 dB, −9.7 dB ≤ ΔMVBS70–38 ≤ 1.3 dB, −10.2 dB ≤ ΔMVBS120–38 ≤ 2.3 dB, and −10.7 dB ≤ ΔMVBS200–38 ≤ 0.3 dB were set to extract the echo signals of anchovies. The results revealed that anchovies showed a relatively higher distribution in the coast than in the open sea. In February, the average density of anchovies was observed to be 3.43 g/m2, whereas in May, it was observed to be 6.02 g/m2. Also, anchovies were found to be mainly distributed at 30-70 m water depths during the day, and at 30–50 m water depths during the night.