Comparison of the volume backscattering strength measured by EK60 and EK80

Abstract

Walleye pollack (Gadus chalcogrammus) resources are abundant around Hokkaido in Japan. The acoustic survey of the walleye pollack using the quantitative echo-sounder has been performed around Hokkaido since 1995. The quantitative echo-sounder that is mainly used for this survey is the EK60 system consisting of GPT + ER60 software made by Simrad. On the other hand, EK80 system using the WBT has been released in 2015, and the acoustic survey will be conducted by EK80 system from now. Therefore, it is necessary to examine whether the acoustic data measured by the EK60 and EK80 systems are identical. In this study, in the area where sound scattering layer was seen, these two systems were used alternately on the same track line to examine whether there are differences in the acoustic data to be measured. Systems used in this study were GPT in frequency 38, 120, and 200 kHz, controlled by ER60 (Ver.2.4.3) and WBT in CW mode at 120, 200 kHz controlled by EK80 (Ver.1.8.3). The acoustic data of the same transect were collected by both systems. The difference of SV between both systems will be discussed.