Commercial split beam echosounder (ES70) installed on a krill fishing vessel was calibrated in order to utilize it in estimating biomass of Antarctic krill (Euphausia superba). The method of calibration was to analyze the difference between the bottom backscattering strength of the commercial split beam echosounder (i.e. ES70) and the scientific echosounder (i.e. EK60) at one of transects near South Shetland Islands designated by CCAMLR. 38 kHz and 120 kHz were used for the calibration, and krill swarm signal levels obtained from multi frequencies, was examined to verify the calibration result. The analysis result indicated possibility of calibration by bottom backscattering strength, since the proportion of krill swarm signals within 2 dB < SV 120 kHz-38 kHz < 12 dB (i.e. a common SV 120 kHz-38 kHz range of 38 kHz and 120 kHz to be an indicator of Antarctic krill) over the total acoustic signals were 26.95% and 92.04%, respectively before and after the calibration.

ADCPs have been widely used to estimate the dynamic characteristics and biomass of sound scattering layers (SSLs), and swimming speed of fish schools for analyzing SSLs spatial distribution and/or various behavior patterns. This result showed that the verification of the mean volume backscattering strength (MVBS or averaged SV, dB) acquired by the ADCP would be necessary for a quantitative analysis on the spatial distribution and the biomass estimation of the SSLs or fish school when ADCP is used for estimating their biomass. In addition, the calibrated sphere method was used to verify values of each MVBS obtained from 4 beams of ADCP (153.6 kHz) on the base of 3 frequencies (38, 120, 200 kHz) of Scientific echo sounder's split beam system. Then, the measured SV values were compared and analyzed in its Target Strength (TS, dB) values estimated by a theoretical acoustic scattering model.

This study is aimed to understand the vertical distribution of fish in the daytime and nighttime using an acoustic survey in Yondam reservoir of Jeollabuk-do, and an acoustical backscattering strength of dominant species, bass (Micropterus salmoides) and a bluegill (Lepomis macrochirus), which are classified as the ecosystem disturbing species. The results showed that the fish school was distributed in the shallow areas of less than 10 m depth during the period of Aug. and Oct. where it had a strong thermocline, otherwise, it was distributed over 10-times density under stable water temperatures as 13°C in Nov. There was no vertical patchiness difference between daytime and nighttime unlike the typical marine ecosystem. The dominant species were crucian carp, bluegill, bass. The hydroacoustic method can provide the spatial distribution and effective removal ways of the ecosystem disturbing species in inland fisheries.

Due to change of various marine environments according to seawater temperature rising, Japanese common squid(Todarodes pacificus), which was distributed in East Sea, was recently caught in Yellow Sea during a summer season from 2006. The fishery resources density research was carried out in Korea-China Provisional 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 by two frequencies(38kHz, 120kHz) for Japanese common squid by acoustical scattering theoretical model based on size distribution for survey period, and estimate the density distribution for squid s integrated layer which was extracted from any scatterers distributed in water column using two frequency difference method which has been used to distinguish fish shoals or specific target scatterers from sound scattering layer which is composed of various zooplankton. Furthermore, the entire range of their density estimation was suggested using by Monte Carlo simulation under considering each uncertainty such as size distributions or swimming angle and so on in survey area.

어군의 분포밀도와 초음파산란강도의 관계를 검토하기 위하여, 50kHz의 주파수에서 net cage (농망)에 분포밀도가 기지인 어군을 수용하고, 어군밀도의 변화에 기인하는 echo energy의 변동을 고찰하고, 또 cage 실험에 의해 추정한 어체의 평균적인 반사강도와 개개의 어체를 대상으로 구한 평균반사강도를 상호 비교, 검토한 결과를 요약하면 다음과 같다. 1. cage 실험에 의한 붕어의 평균반사강도는 -41.9dB로서, 이 값은 현장에서 개개의 붕어(마취어, 평균체장 19.1cm)를 대상으로 측정한 평균반사강도 -42.6dB보다 0.7dB 더 컸다. 2. cage내에 수용한 어군의 분포밀도가 증가함에 따라, 어군에 의한 평균체적산란강도는 직선적으로 증가하는 경향을 나타내었다. 즉, 어군밀도가 7, 13, 20, 26, 39, 52, 66 마리/m 상(3)였을 때, 각각의 어군에 의한 평균체적산란강도는 -33.0, -28.9, -27.6, -24.3, -25.1, -23.6, -22.1dB이었다. 3. 어군밀도 σ(마리/m 상(3))와 평균체적산란강도 (dB)와의 사이에는 다음의 관계식이 성립하였다. =-41.9+11.0 Log(σ), r=0.97 이 식에 회귀직선의 기울기 11은 이론적인 값 10에 거의 근사하였다.