Acoustic technology is commonly used to estimate the biomass and distribution of fisheries resources in coastal areas and the open ocean. Acoustic surveys were conducted on 24-26 May and 20-21 June, 2005, and 15-18 June and 27-30 July, 2006, near the Tongyoung, Geojae, and Namhae anchovy fishing grounds using a dual beam echo sounder. Information was obtained on the distributions of adult and juvenile anchovy (depth and position). We calculated and compared anchovy biomass using simple summation. In this study, all backscatter was attributed to anchovy. We assumed that the average target strength of anchovy was -70 dB and the average body weight was 3 g in May and June 2005, and that the target strength of anchovy was -65 dB and the average body weight was 5 g for pelagic individuals in July 2006. The anchovy biomass in May 2005 was estimated to be 0.147 million tons using the traditional method, while using the summation method, the estimated anchovy biomass was 0.062 million tons in June 2005, 0.21 million tons in June 2006, and in 0.43 million tons in July 2006.