• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.1
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• pp.54-63
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• 2005

Detection ranges of acoustic instruments mainly used for fisheries and their research are derived as the range bordered by a certain signal-to-noise ration (SNR) thershold. The SNR is depicted by several factors on transmitting and receiving, sound propagation, scattering by objects, and mainly self-ship noise. The detection ranges are shown for several fisheries instrument, such as echo sounder, quantiative echo sounder, and bio-telemetry system. The results can be used for designing the instruments, examining the capability of user's own instruments, and interpreting obtained data or echograms. Increasing transmitting power is not as effective for high frequencies as for low frequencies to increase the detection range. Comparison of volume backscattering strengths obtained by the quantitative echo sounder at several frequencies should be done within the same detection range. By applying the concept of the detection range for the bio-telemetry receiver beams, the number of the beams and the beamwidths can be determined.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.197-201
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• 2002

The object of this study was to find out the probability of the abundance estimation by geographical parameters of fish school during the acoustic survey using scanning sonar. The acoustic survey was carried out in Funka Bay, off southern Hokkaido, Japan in December 1998. The 180-degree scanning sonar and the echo sounder were used simultaneously. The relationship was examined between geographical parameters (fish school area and volume) measured by sonar and area back scattering coefficient by the echo sounder. The obtained result showed positive correlation. Therefore, the use of geographical parameters of fish school is a useful method in estimating fish school abundance in the acoustic survey using sonar.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.29-30
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• 2000

최근, 전자 및 컴퓨터 기술이 눈부신 발달과 더불어 개발된 과학어군탐지기는 해양생물자원을 신속하고도 정확히 평가하는 수단으로서 인정받아 실용화 단계에 있다. 그러나, 계량어군탐지기를 이용한 자원량 추정기술을 보다 더 정도 높고, 효율적인 방법으로서 정착하기 위해서는 선결해야 할 문제점이 몇 가지 있다. 먼저 대상생물의 식별로서 조사하고자 하는 생물과 다른 해양생물과를 식별하는 것이며, 나아가 같은 생물에 있어서도 분포수심, 유영 자세 등에 의해서도 자원의 추정정도가 다르므로 이에 대한 연구가 필요 불가결하다. (중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2002.10a
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• pp.17-20
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• 2002

수산자원의 현존량을 추정함에 있어, 계량어군탐지기(이하, 계량어탐 이라 한다)를 이용한 음향자원량 조사는 넓은 수역을 단시간에 조사 가능한 효율적인 방법으로서 확립되어 있다. 한편, 최근에 멸치, 꽁치 등의 표층어종의 자원량조사의 필요성이 높아지고 있지만, 계량어탐은 수직 빔을 이용하므로, 표층의 탐지범위가 좁고, 어군의 선체도피행동이나 표층 데드죤이 존재한다. 그 때문에, 표층을 광범위하게 탐지 가능한 소너를 이용한 자원량 추정법의 개발이 요구되고 있다. (중략)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.4
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• pp.372-377
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• 1998

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.45-46
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• 2000

음향학적 방법은 컴퓨터 기술의 발달과 더불어 급속으로 발전하여, 짧은 시간에 넓은 해역을 대상으로 거의 실시간으로 해양생물 분포상태를 파악하고, 또한 수심층을 대상으로 다양한 자료를 수집할 수 있다. 황해의 어족자원을 효과적으로 관리하기 위해서는 어족자원의 분포에 대한 정확한 정보가 필요한 실정이다. 이를 위하여 황해광역생태계(Large Marine Ecosystem, LME) 연구의 하나로 어족 자원 조사가 수행되었으며, 본 연구는 두 번째 결과이다. (중략)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.202-209
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• 2000

In order to estimate demersal fishes using acoustic echo sounders and echo integrators, we consider several problems that are accurate bottom detection, optimum bottom offset and dead zone. The dead zone where no fish detection are summed distance resolution by the half pulse length of transmitted pulse and beam angle above the seabed. This paper has considered the dead-zone correction method to be technically correct for survey of demersal fishes. A comparison between near-bottom SV profiles acquired in Funka Bay, Hokkaido, of Japan, the East China Sea and the Yellow Sea, of Korea, with before and after the bottom correction, shows that the SV obtained with after the bottom correction is 2∼3dB higher than before the bottom correction in Funka Bay, and 17dB higher in East China Sea, too.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.55-56
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• 2003

현재, 국립수산과학원은 매년 한반도 주변수역, 인도양, 북태평양 및 기타 해역에 대한 어업자원조사를 실시하고 있는 데, 이 조사에서는 split beam 방식 계량어군탐지기에 의한 음향학적 조사와 중층트롤에 의한 시험조업 등이 병행되고 있다. 그러나, 대상 어류의 체장 추정을 위한 연구는 아직까지 수행되고 있지 않고 있는 바, TAC제도를 시행하고 있는 우리나라로서는 한반도 주변 수역에 서식하는 어종별, 체장별, 사용 주파수별 어류의 체장추정에 필요한 음향반사강도의 data bank를 구축하는 것이 시급한 선결과제가 되고 있다. (중략)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.1
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• pp.1-12
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• 1991

An experiment has been carefully designed and performed to verify the theory for the echointergration technique of estimating the density of fish school by the use of steel spheres in a laboratory tank. The spheres used to simulate a fish school were randomly distributed throughout the insonified volume to produce the acoustic echoes similar to those scattered from real fish schools. The backscattered echoes were measured as a function of target density at tow frequencies of 50kHz and 200kHz. Data acquisition, processing and analysis were performed by means of the microcomputer-based sonar-echo processor including a FFT analyzer. Acoustic scattering characteristics of a 36cm mackerel was investigated by measuring fish echoes with frequencies ranging from 47.8kHz to 52.0kHz. The fluctuation of bottom echoes caused by the effects of fish-school attenuation and multiple scattering which occurred in dense aggregations of fishes was also examined by analyzing the echograms of sardine schools obtained by a 50kHz telesounder in the set-net's bagnet, and the echograms obtained by a scientific echo sounder of 50kHz in the East China Sea, respectively. The results obtained can be summarized as follows: 1. The measured and the calculated echo shapes on the steel sphere used to simulate a fish school were in close agreement. 2. The waveform and amplitude of echo signals by a mackerel without swimbladder fluctuated irregularly with the measuring frequency. 3. When a collection of 30 targets/m super(3) lied the shadow region behind another collection of 5 targets/m super(3), the mean losses in echo energy for the 30 targets/m super(3) were about -0.4dB at 50kHz and about -0.2dB at 200kHz, respectively. 4. In the echograms obtained in the East China Sea, the bottom echoes fluctuated remarkably when the dense aggregations of fish appeared between transducer and seabed. Especially, in the case of the echograms of sardine school obtained in a set-net's bagnet, the disappearance of bottom echoes and the lengthening of the echo trace by fish aggregations were observed. Then the mean density of the sardine school was estimated as 36 fish/m super(3). It suggests that when the distribution density of fishes in oceans is greater than this density, the effects of fish-school attenuation and multiple scattering must be taken into account as a possible source of error in fish abundance estimates. 5. The relationship between mean backscattering strength (, dB) and target density ($\rho$, No./m super(3)) were expressed by the equations: =-46.2+13.7 Log($\rho$) at 50kHz and =-43.9+13.4 Log($\rho$) at 200kHz. 6. The difference between the experimentally derived number and the actual number of targets gradually decreased with an increase in the target density and was within 20% when the density was 30 targets/m super(3). From these results, we concluded that when the number of targets in the insonified volume is large, the validity of the echo-integration technique of estimating the density of fish schools could be expected.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.195-201
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• 2000

This paper discusses methods for the stable bottom detection and the optimum bottom offset which enable to separate the fish echoes from the bottom echoes with echo integration of demersal fish. In preprocessing of the echo signal, the bottom detection has to be done stably against the fluctuation of echo level and the bottom offset has to be set to a minimum height such that near bottom fish echoes are included Two methods of bottom detection, namely echo level threshold method and maximum echo slope method were compared and analyzed. The echo level method works well if the ideal threshold level was given but it sometimes misses the bottom because of the fluctuation of the echo. Another method to detect the bottom which uses maximum echo slope indicates the simple and stable bottom detection. In addition, the bottom offset has to be set near to the bottom but not to include the bottom echo. Optimum bottom offset should be set a few samples before the detected bottom echo which relates the beginning of pulse shape and acoustic beam pattern to the bottom feature.