Area backscattering strength (Samean, dB) for all fish schools obtained from each echo sounder and the number of Japanese anchovies (N) in the study area calculated using Samean and the TSs.

TS is shown in previous studies [46,47], and N here is the fish density n calculated in Eq 7 multiplied by the area of the fish school.声靶强度（Target Strength，TS）已在既往研究[46,47]中被阐明；此处的N为按公式7计算得到的鱼群密度n与鱼群面积的乘积。