• 수산해양기술연구
• /
• 제50권4호
• /
• pp.476-486
• /
• 2014

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 $13^{\circ}C$ 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.

• 수산해양기술연구
• /
• 제32권1호
• /
• pp.16-23
• /
• 1996

Spatial distribution characteristics, volume backscattering strength and species composition of midwater trawling catch was analyzed biological and acoustical characteristics of anchovy shoal, using a high resolution echo - sounder at the south region of East sea of Korea. 1) In the survey site A of Lat.35$^{\circ}$55'N, Long.129$^{\circ}$45'E, the anchovy shoal of small to middle size with the horizontal range of 10~25m and large size with the horizontal range of 40~50m were distributed together. However in the survey site B of Lat.35$^{\circ}$38'N, Long.129$^{\circ}$40'E, the anchovy shoal was observed to be mainly small size which about 78% of the detected shoal. Another was that the anchovy shoal with the vertical range of 2~8m occupied about 68.6% in the survey site A and that of 6~12m occupied about 42.5% in the survey site B. The mainly the site A and B were found to be 10~50m super (2), 64.5% and 20~80m super (2), 66%, respectively. 2) The volume backscattering strength in the site A and B were observed to be -44.0~ -28.0dB, respectively. In the site A, the backscattering strength of -40.0~ -30.0dB was analyzed about 41.4%. 3) Most of total anchovy shoal was concentrated in the water layer of 50~100m in depth with 15.3~18.5$^{\circ}C$, 34.0~34.3$\textperthousand$ in the survey site A and 14.2~16.4$^{\circ}C$, 34.1~34.2$\textperthousand$ in the survey site B. 4) Mean total length(TL) and body weight(BW) of anchovy in the survey site A were 9.9cm and 4.4g respectively, with TL-BW relationship of BW=0.0007T$L^3.65$super (3.85). In site B, mean total length(TL) and body weight(BW) were 11.2cm and 8.7g, with TL-BW relationship of BW=0.0023T$L^3.36$.

• 수산해양기술연구
• /
• 제52권4호
• /
• pp.318-324
• /
• 2016

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 < $S_{V\;120\;kHz-38\;kHz}$ < 12 dB (i.e. a common $S_{V\;120\;kHz-38\;kHz}$ 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.

• 수산해양기술연구
• /
• 제50권4호
• /
• pp.551-555
• /
• 2014

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.

• 수산해양기술연구
• /
• 제27권1호
• /
• pp.13-20
• /
• 1991

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 $\rho(마리/m$ 상(3))와 평균체적산란강도 (dB)와의 사이에는 다음의 관계식이 성립하였다. =-41.9+11.0 $Log(\rho),$ r=0.97 이 식에 회귀직선의 기울기 11은 이론적인 값 10에 거의 근사하였다.

• 한국음향학회지
• /
• 제15권4호
• /
• pp.18-23
• /
• 1996

산란강도의 변동에 따른 통계적 특성은 능동소나의 성능에 영향을 미칠 뿐만 아니라, 주요 산란과정을 이해하는 측면에서 매우 중요하다. 본 논문에서는 천해에서 측정한 해저면 후방산란 신호의 통계적 특성 분석에 대한 내용을 기술하였다. 천천히 움직이는 30kHz의 실험용 소나로 해저면에 대한 자료를 수집하였다. 신호의 진폭변화에 대한 시${\cdot}$공간 상관함수를 계산하였다. 또한, 넓은 빔과 좁은 빔 신호의 포락선에대한 분포함수와 오경보 확률을 계산하고, 이론 모델과 비교를 시도하였다. 분석 결과에서 이동음원에 의한 해저면 후방산란 변동의 통계적 특성은 고정된 음원의 경우와 다른 특징을 나타냈다.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1992년도 학술논문발표회 논문집 제11권 1호
• /
• pp.127-130
• /
• 1992

한국 근해에서 능동소나 (active sonar) 사용시 사용되는 environmental parameters 가운데 하나인 volume reverberation(REv)을 산출하기 위하여 플랑크톤에 의한 후방산란 강도(backscattering strength)에 대한 연구를 하였다. 이를 위하여 수산진흥원 자료(80-89년)중 부유생물조사표에서 후방산란 강도가 다른 종에 비하여 큰 copepoda의 개체수를 평균한 후, 수심별 개체수를 계산하여 수심별, 주파수별(10, 50kHz), 계절별(2월, 8월) 후방산란 강도와 multipath eigenray model을 이용하여 REv를 산출하였다. 예로 사용한 동남해역(zone:S3), 서해중부해역(zone:W3)에서 주파수별 REv는 일반적인 형태인 포기에는 고주파가 높고, 1.5초 이후에는 저주파가 높게 나타났다. 그러나 여름이 겨울보다 플랑크톤 개체수가 많아 후방산란 강도가 크지만(2-5dB), REv는 겨울이 더 크게 나타났다. 이러한 이유는 SVP profile에 의한 pressure 계산결과, 여름에는 ray가 down-ward이고 겨울에는 duct를 형성하여 ray가 거의 direct로 진행하므로 transmission loss가 여름이 크기 때문이다. 또한 ray tracing결과 여름철에는 ray crossing이 많아 겨울에 비하여 fluctuation이 심하게 나타나는 현상을 보이고 있다. 두 지역 이외에도 한국근해의 정확한 REv을 예측하기 위해서는 플랑크톤의 정확한 측정과, 이론적인 수치와 비교할 수 있는 실측치를 얻는 것이 필요하다고 볼 수 있다.

• 수산해양기술연구
• /
• 제26권2호
• /
• pp.143-150
• /
• 1990

동지나해의 어업자원량을 정량적으로 평가하기 위한 시도로서, 부산수산대학교와 일본 북해도대학이 공동으로 실시한 제1차 동지나해의 저서어족자원조사중에서 계량어군탐지기를 이용하여 수집한 각종의 기초자료를 분석, 검토한 결과를 요약하면 다음과 같다. 1. 동지나해의 24회 조사 Line에서 저층 Trawl에 의해 어획된 어종수는 총 96어종이고, 1시간 예망당 평균어획량은 58.8kg/hour이었다. 2. 저층 Trawl을 행한 수탐층(약 4.5m)에 분포하는 어군의 평균체적산란강도는 25KHz와 100KHz에서 각각 -63.9dB, -67.3dB로서 저주파수의 경우가 고주파수보다 약 3.4dB 더 높았다. 3. 전수탐층(송수파기과 해저간)에 분포하는 어군의 평균체적산란강도는 25KHz와 100KHz에서 각각 -61.9dB, -67.0dB로서 역시 저주파수의 경우가 고주파수보다 약 1.5dB 더 높았다. 4. 저층 Trawl을 행한 수탐층에 분포하는 어군의 평균체적산란강도(SV, dB)와 이 때 어획된 전위제적당의 평균어획량(kg)으로부터 추정한 kg당의 평균반사강도는 25KHz와 100KHz에서 각각 -23.6dB/kg, -26.3dB/kg로서 저주파수의 경우가 고주파수보다 약 2.7dB/kg 더 컸다.

• The Journal of the Acoustical Society of Korea
• /
• 제15권2E호
• /
• pp.45-49
• /
• 1996

From the reverberation signals received in the shallower water, the surface scattered signals are identified by using the multipath eigneray model that provides launch angles, grazing angles and transmission loss from the high frequency directional source to and from the rough surface. For small scale surface waves, the perturbation method is used to compute the backscattering strength for various grazing angles and wind speeds. A scheme to inversely estimate the wind speed, by which the observed surface reverberation levels are produced, has been tested. In result, for low grazing angles the perturbation method can be used to predict the backscattering stregth, thereby the surface wind can be indirectly estimated.

• 수산해양기술연구
• /
• 제32권3호
• /
• pp.266-272
• /
• 1996

The distribution and abundance of fish in the Cheju southeastern area was studied by the combined hydroacoustic and bottom trawl surveys in April 1994 and in July 1995, respectively. The main purpose of these investigations was to provide the basic data for this management and the biomass estimation of commercially important demersal fish stocks in this area. The hydroacoustic surveys were performed by using a 50 kHz scientific echo sounder system with a microcomputer-based echo integrator. Acoustical measurements of fish abundance and distribution were conducted along the cruise tracks of research vessel and during all trawl hauls by continuous echo sounding. The average weight-normalized target strength for demersal fish aggregations was derived from the relationship between the mean volume backscattering strength for the depth strata of trawl hauls and the weight per cubic meter of trawl catches. The geographical distribution of fish stocks in the 1994 survey area was investigated in relation to oceanographic conditions. The results obtained can be summarized as follows: 1. From the 1994 and 1995 survey data, the relationship between the mean volume backscattering strength (, dB) for the depth strata of trawl hauls and the weight (W, kg/$m^3$) per cubic meter of trawl catches was expressed by the following equation = - 32.8+ lOlog(W) The average weighted-target strength value at 50 kHz derived from this equation was .. 32.8 dB/kg. 2. In 1994 and 1995, both surveys showed a trend of decreasing fish abundance toward the southern area of the Cheju Island with high densities offish along the west coast ofth.e Tsushima Island. The highest demersal concentrations in the southern area of the CheJu Island appeared in bottom waters colder than $12^{\circ}C.$. . 3. From the results of combined bottom trawl and hydroacoustic surveys, the estunated fish densities in the southeastern area of the Cheju Island were 1.5488 x $10^-4$kg/$m^3$ in the 1994 surveyand 1.9498 x $10^-4$kg/$m^3$ in the 1995 survey, respectively.