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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.
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.
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.
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.
남서대서양 한국 원양 저연승 어선의 조업 분포 및 비막치어(Dissostichus eleginoides) CPUE 변화
박겸준 ( Kyum Joon Park ),최석관 ( Seok-gwan Choi ),안두해 ( Doo-hae An ) 한국수산과학회(구 한국수산학회) 2021 한국수산과학회지 Vol.54 No.1
This study used the commercial fishing data of Korean high sea bottom longline vessels in the South West Atlantic Ocean from 2013 to 2019 to identify the distribution of fishing grounds of Korean longline vessels. We estimated the CPUE of the Patagonian toothfish Dissostichus eleginoides and the changes in its stock status. The fishing grounds of Korean longline vessels were observed to concentrate on the exclusive economic zone (EEZ) boundary between Argentina, Uruguay, and Falkland owing to the high seas of 41-55 °S in the south and 49-60 °W in the west. A high intensity of fishing was seen in the middle area, which was horizontal from the 3.1 subarea. In all the three subareas, CPUEs have had the tendency to decline since 2013. Although the CPUEs in the 3.2.1-2 subareas were the highest in each subarea, there was no significant difference in each subarea (P>0.05). It is believed that the establishment of a regional fisheries organization or the strengthening of the management of FAO is necessary for the management of Southwest Atlantic fisheries and sustainable fishing, because the portion and scope of Korean longline vessels are very low in the Southwest Atlantic; however, the CPUE is estimated to have declined.
조업선에서 수집한 음향자료에 대한 잡음 제거 기법에 관한 연구
이형빈 ( Hyungbeen Lee ),최석관 ( Seok Gwan Choi ),이경훈 ( Kyounghoon Lee ),이재봉 ( Jae Bong Lee ),이종희 ( Jong Hee Lee ),최정화 ( Jung Hwa Choi ) 한국수산해양기술학회 2015 수산해양기술연구 Vol.51 No.3
The Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) is utilized to manage krill resources using acoustic data collection and a scientific observer program operating on the fishing boats. However, the acoustic data were contained seriously noise, example of background, spike, and intermittent noise, due to purpose of fish boats. In this study, the noise removal techniques were confirmed the potential of the acoustic data analysis. Acoustic system and frequency used in the survey were commercial echosounder (ES70, SIMRAD) and 200 kHz split beam transducer. Acoustic data were analyzed using Echoview software (Myriax), and general data analysis and new noise removal method was used. Although a variety of noise, most of the noises have been removed using the noise removal processing. We confirmed the possibility of analyzing the acoustic data obtained from fish boats. The results will be useful for analysis of the acoustic data acquired from krill fishing boats.
서해 남부와 남해 서부의 한 정점에서 수온 및 염분과 멸치 어군의 특징의 관련성 시각화
강명희 ( Myoung Hee Kang ),최석관 ( Seok Gwan Choi ),황보규 ( Bo Kyu Hwang ) 한국어업기술학회 2014 수산해양기술연구 Vol.50 No.1
Morphological and positional characteristics of anchovy aggregations, confirmed by trawling, were examined in two locations of the southern part of the West Sea (T1) and the western side of South Sea (T11) of South Korea. Morphological characteristics(mean length, height and area) of the anchovy aggregations at T1 were smaller than those at T11, however the positional characteristics(distributional depth and bottom depth) of the aggregations at T1 were larger than those at T11. Diverse dataset such as the ship``s cruise track, the cruse map, and interpolated three-dimensional-like water temperature were visualized in multiple dimensions. For a comprehensive understanding of the anchovy aggregations within their surrounding circumstances, the interpolated water temperature transferred to the location of anchovy aggregations at both stations were visualized based on geospatial information. Using quantitative investigation, the overall range of change in water temperature and salinity of anchovy aggregation sat stations was considerably small. However, the water temperature and salinity of anchovy aggregations at T11 were somewhat higher than those at T1.
남서대서양 아르헨티나 짧은지느러미오징어(Illex argentinus)의 어획변동
구정은 ( Jeong Eun Ku ),최석관 ( Seok-gwan Choi ),안두해 ( Doo-hae An ),김은정 ( Eunjung Kim ) 한국수산과학회(구 한국수산학회) 2020 한국수산과학회지 Vol.53 No.6
The spatial and temporal catch variations of Argentine shortfin squid Illex argentinus in the Southwest Atlantic Ocean (SWA) were analyzed using Korean squid-jigging fishery data collected through electronic reporting system (ERS) from 2016 to 2020. The ERS linked with GPS has been implemented for collecting fishing data from all Korean fishing vessels operating in international waters since November 2015. The fishing period of the Korean squid-jigging fishery in the SWA runs from early summer to autumn (December to June) in the Southern Hemisphere. The fishing ground was extended from 42°S to 48°S along the Patagonian continental shelf and slope, and the main fishing ground was formed around the Falkland Islands. The yearly catch per unit effort (CPUE) of I. argentinus fluctuated between 1.69 and 7.53 tons/day. In this study, during the fishing season, a south and westward shift on the fishing ground was observed indicating the feeding migration of the south Patagonian stock. The shift in monthly fishing centroids differed according to fishing season. The gradual southward shifts of fishing centroids were observed in the catch years (2017 and 2018), whereas unapparent shifts in fishing centroids were observed in the low catch years (2016 and 2019).