Exploratory Study for Acoustical Species Identification of Anchovies in the South Sea of South Korea

Abstract

We conducted a hydroacoustic-trawl survey from April 16–19, 2013, for acoustical identification of anchovies in the South Sea of South Korea. Three types of fish schools were defined on the basis of the trawl results: L7 (schools mixed with 57 % hairtail and 37 % anchovy), L8 (schools with 95 % anchovy), and L1 (schools with unknown species). According to the results, the bathymetric characteristics (school depth, water depth, and altitude) of L1 were similar to those of L7; however, the morphometric characteristics (length, height, area, and image compactness) of L1 were similar to those of L8. To confirm whether L1 was more similar to L8 or L7, we used the ΔMVBS method [where ΔMVBS is difference of mean volume backscattering strength (MVBS) at 38 and 120 kHz] with three cell sizes, 0.1 nmi × 2 m, 0.25 nmi × 4 m, and 0.5 nmi × 5 m; the ΔMVBS pattern of L1 seemed similar to that of L8, but not that of L7. By using one-way analysis of variance, we noted significant differences of frequency characteristics between L7 and L8 and L7 and L1, supporting the results of the ΔMVBS method. Moreover, only 0.1 nmi × 2 m and 0.25 nmi × 4 m were the appropriate cell sizes for anchovy species identification. This exploratory study may form the basis for other species identification.