Acoustical backscattering strength characteristics and density estimates of Japanese common squid distributed in Yellow Sea

), which was distributed in East Sea, was recently caught in Yellow Sea during asummer season from 2006. The fishery resources density research was carried out in Korea-ChinaProvisional Water Zone using trawl fishing gear and acoustics in National Fisheries Research &Development Institute in Korea. This paper showed the analysis on the acoustical backscattering strength bytwo frequencies(38kHz, 120kHz) for Japanese common squid by acoustical scattering theoretical modelbased on size distribution for survey period, and estimate the density distribution for squids integrated layerwhich was extracted from any scatterers distributed in water column using two frequency difference methodwhich has been used to distinguish fish shoals or specific target scatterers from sound scattering layer whichis composed of various zooplankton. Furthermore, the entire range of their density estimation was suggestedusing by Monte Carlo simulation under considering each uncertainty such as size distributions or swimmingangle and so on in survey area.Key words : Japanese common squid, Todarodes pacificus, Acoustical scattering theoretical model, DWBA,Density estimates