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주파수차법을 이용한 남극크릴(Euphausia superba)의 종 식별에 관한 연구
최석관,한인우,황두진,김태호,안두해,이경훈 한국수산과학회 2017 한국수산과학회지 Vol.50 No.6
Antarctic krill Euphausia superba are important components of the Antarctic marine ecosystem both economicallyand ecologically; to manage this species effectively, their distribution and abundance must be understood. Using theKwang Ja-Ho (3,012 tonnage), a commercial fishing vessel, we conducted acoustic surveys during April 13-24, 2016,to estimate the distribution and population size of krill around the South Shetland Islands of the Antarctic Continent,We used acoustic techniques based on the dB-difference, a method used mainly to classify of marine species. Wefound that Antarctic krill were present in numbers over 99% at six survey stations, with the exception of Station 3,where we only found Electrona carlsbergi. There was no difference in cell size due to frequency differences, but echosignals differed between species: 4.7-12.0 dB for Antarctic krill, and -4.1~0 dB for Electrona carlsbergi.
계량어탐 및 트롤조사에 의한 봄철 한국 남해 멸치(Engraulis japonicus) 자원의 현존량 추정
최석관,김진영,김순송,최영민,최광호 한국수산자원학회 2001 한국수산자원학회지 Vol.4 No.-
봄철 한국 남해안에 서식하는 멸치의 분포특성과 현존 자원량을 추정하기 위하여 2000년 4-5월 및 2001년 3월에 실시한 계량어탐과 트롤조사 및 해양환경조사 자료를 이용하였다. 그 결과, 멸치는 남해동부해역의 여수에서 부산에 이르는 연안해역을 중심으로 띠 모양을 이루며 고밀도로 분포하였고, 남해서부해역에서는 제주도 서쪽해역에서 낮은 밀도로 분포하였다. 멸치가 고밀도로 분포한 해역의 표층수온과 염분은 12-15℃, 33.6-34.5의 범위로 각각 나타났다. 계량어탐과 트롤조사에 의하여 분석된 멸치의 현존 자원량은 2000년에는 198,970톤, 2001년에는 117,740톤으로 추정되어 봄철의 한국 남해안은 월동장에서 북상하는 멸치의 주요서식처로 확인되었다. Spatial distribution characteristics and biomass of Pacific anchovy, Engraulis japonicus, in the southern Korean waters during spring season were estimated by the hydroacoustic, trawl and oceanographic surveys in April-May 2000 and March 2001. Pacific anchovy appeared high-density schools in the coastal waters with the range of 12-15℃ sea surface temperature and 33.6-34.5 sea surface salinity from Busan to Yeosu and low-density in the western part of Jeju Island during spring season, 2000 and 2001. Biomass of Pacific anchovy by echo integration and trawl survey was estimated to be 198,970 tons in 2000 and 117,740 tons in 2001. The fact that Pacific anchovy distributed with high density in coastal waters of southern part of Korea during spring season identified this region as main habitat of Pacific anchovy stock migrating northward from over wintering ground.
최석관,윤은아,안두해,정상덕,이재봉,이경훈 한국해양과학기술원 2018 Ocean science journal Vol.53 No.4
In this study, the dB difference and characteristics of krill swarms inhabiting Subarea 48.1, which includes the west and south of the South Shetland Island and the Elephant Island peripheries, were estimated to distinguish Antarctic krill, using acoustics. From April 13 to 24, 2016, acoustic data were collected along 24 survey lines using the frequencies 38 and 120 kHz, and middle trawling was performed at 7 stations. Using the difference between the dB values of two volume backscattering strength (Sv) frequencies (38 and 120 kHz), a clear acoustic distinction could be made between Antarctic krill (4.9 to 12.0 dB) and fish (?4.0 to ?0.2 dB). The distributions and mean Sv of krill swarms in the Elephant Island peripheries and south of South Shetland Island were higher than those in the west of South Shetland Island. The mean length/ height ratio of krill swarms in the west of the South Shetland Island (64.5) was higher than that in the south (35.9) and the Elephant Island peripheries (33.8), with the length of the aggregations exceeding their height. Most krill swarms were distributed between the surface layer (less than 10 m below sea level) and within 200 m of water depth. These results are expected to serve as baseline data for evaluating krill density and biomass by distinguishing them from fish, using acoustics.
최석관 ( Seok-gwan Choi ),오택윤 ( Taeg Yun Oh ) 한국수산과학회 2013 한국수산과학회지 Vol.46 No.2
The characteristics of the oceanographic environment in the Aleutian Basin of the Bering Sea during spring in 1996, 1997, and 1999 were clarified. An investigation of the water properties revealed five basic layers in the Bering Sea during spring: (1) a surface layer of warm and low-salinity water induced by solar heating, (2) a subsurface layer of cold and low-salinity water propagated slowly by heat from the surface layer, (3) a thermo cline layer where salinity was constant but temperature sharply decreased. (4) a temperature inversion layer, and (5) a deep layer with a gradual decrease in temperature and increase in salinity toward the bottom. The ranges of water temperature and salinity were l.8-5.5t and 31.81-34.08 in 1996, 1.5-7.2t and 31.9-34.06 in 1997, and 0.5-5.6°C and 32.0-34.11 in 1999, respectively. The water temperature of the surface layer was approximately I .6°C higher in 1997 than in 1996 and 1999. The lowest temperature at a depth of 100-150 m was about I t lower in 1999 than in 1996 and 1997. Nutrient levels (nitrate, phosphate. and silicate) contributing to the control of the growth of phytoplankton were higher in the Aleutian Basin than in the eastern continental shelf and Bogoslof Island area. This was closely associated with the phytoplankton distribution. Nutrient concentrations were lowest at a depth of 25 m. The high primary production at that depth was confirmed from the vertical distribution of chlorophyll a. Chlorophyll a levels were above 4.0 uL-1 in some areas in 1996 and 1999. but below 2.0 uL-1 in most areas in 1997. Zooplankton density was about three times higher in 1999 than in 1997.
최석관 ( Seok-gwan Choi ),윤은아 ( Eun-a Yoon ),한인우 ( Inwoo Han ),오우석 ( Wooseok Oh ) 한국수산과학회(구 한국수산학회) 2016 한국수산과학회지 Vol.49 No.6
This study compared the density of fish determined using three different echogram methods: the frequency-differ-ence, time variable, and threshold modification methods. An acoustic survey was conducted off the coast of Jeju Island after sunset. Data at 38 and 120 kHz frequencies were collected using a commercial fishing vessel. As a refer-ence point, the value of ΔMVBS<sub>120-38kHz </sub> that distinguished fish from zooplankton using the 38 and 120 kHz frequen-cies was set at < 2 dB. The estimated density of fish along the survey line was 0.1-30.4, 0.1-64.3, and 0.1-51.7 m<sup>2</sup>/ nmi<sup>2</sup> using the frequency difference, time variable threshold, and threshold modification methods, respectively. The results of this study constitute basic research for estimating fish densities.
상업어선의 어군탐지기를 이용한 남극크릴(Euphausia superba) 자원량 추정
최석관 ( Seok-gwan Choi ),한인우 ( Inwoo Han ),안두해 ( Doo-hae An ),정상덕 ( Sang-deok Chung ),윤은아 ( Eun-a Yoon ),이경훈 ( Kyounghoon Lee ) 한국수산과학회(구 한국수산학회) 2018 한국수산과학회지 Vol.51 No.4
The Antarctic krill Euphausia superba is important commercially and ecologically as a basic component of the Antarctic Ocean ecosystem. To manage this resource, it is important to determine the distribution and standing of krill in the water layer. Acoustic methods can capture information about the entire water layer quickly. Acoustic surveys were conducted from March 3 to March 14, 2017, using the commercial fishing boat Sejong (7,765 tons). Acoustic systems with a frequency of 38 kHz and a 200 kHz commercial echo sounder (ES70, Simrad, Norway) were used and the acquired data were processed using post processing software. The density and standing of Antarctic krill were determined using the two-frequency difference method, using the characteristics of two frequencies. To compare the frequency difference of krill, the method using the frequency difference according to the krill length, recommended by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the values extracted according to the krill length at survey stations where only krill were collected during the study period, were compared. The frequency difference ranges were 3.96-5.91 dB and -3.0~13.8 dB, respectively.
남극 남쉐틀랜드 군도 주변 해저면 음향신호를 이용한 상업용 어군탐지기 보정 연구
최석관 ( Seok-gwan Choi ),이형빈 ( Hyungbeen Lee ),이경훈 ( Kyounghoon Lee ),이재봉 ( Jaebong Lee ) 한국어업기술학회 2016 수산해양기술연구 Vol.52 No.4
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<sub>V 120 kHz-38 kHz</sub> < 12 dB (i.e. a common S<sub>V 120 kHz-38 kHz</sub> 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.