수중음향을 이용한 해초 서식처(Seagrass Habitats)의 공간 및 수직 분포 추정

강돈혁,나형술,김종만,나정열,명정구,조성호 한국해양과학기술원 2006 Ocean and Polar Research Vol.28 No.3

Seagrass meadows are considered as critical habitats for a wide variety of marine organisms in coastal and estuarine ecosystems. In many cases, studies on the spatial/temporal distribution of seagrass have depended on direct observations using SCUBA diving. As an alternative method for studying seagrass distribution, an application of hydroacoustic technique has been assessed for mapping seagrass distribution in Dongdae Bay, on the south coast of Korea, in September 2005. Data were collected using high frequency transducer (420 kHz split-beam), which was installed with towed body system. The system was linked to DGPS to make geo-referenced data. Additionally, in situ seagrass distribution has been observed using underwater cameras and SCUBA diving at four stations in order to compare with acoustic data. Acoustic survey was conducted along 23 transects with 3-4 knot ship speed. Seagrass beds were vertically limited to depths less than 3.5 m and seagrass height ranged between 55 and 90 cm at the study sites. Dense seagrass beds were mainly found at the entrance of the bay and at a flat area around the center of the bay. Although the study area was a relatively small, the vertical and spatial distributions of the seagrass were highly variable with bathymetry and region. Considering dominant species, Zostera marina L., preliminary estimation of seagrass biomass with acoustic and direct sampling data was approximately 56.55 g/m2, and total biomass of 104 tones (coefficient variation: 25.77%) was estimated at the study area. Hydroacoustic method provided valuable information to understand distribution pattern and to estimate seagrass biomass.

학술발표회 : 6 ) 자원분야 : 구두발표 ; 남극 남쉐틀란드 군도 주변 해역의 크릴 분포 및 자원량

강돈혁,이윤호,신형철,나정열 한국국제경제학회 2001 춘계 수산관련학회 공동학술대회발표 요지집 Vol.0 No.-

동해 남서해역에서 ADCP 자료에 의한 후방산란 강도와 수온구조와의 비교

강돈혁 부산수산대학 해양과학연구소 1994 연구논문집-부산수산대학교 해양과학공동연구소 Vol.26 No.-

남해 연안에 분포하는 해파리(Aurelia aurita, Cyanea nozakii)의 복수 개체에 의한 음향 표적강도 특성

강돈혁,김정훈,임선호 한국해양과학기술원 2010 Ocean and Polar Research Vol.32 No.2

Understanding the abundance and distribution of massive jellyfish is necessary to forecast where or when their blooms will happen. The acoustic technique is one of the most useful methods of obtaining information if the acoustic characteristics of the targets are known. This study was conducted to determine the acoustic target strength (TS, dB) of two jellyfish species, Aurelia aurita and Cyanea nozakii, in the southern coast of Korea. For the ex situ measurements, 120, 200, and 420 kHz split beam transducers were used, and jellyfish with various bell lengths were arranged to prepare multiple jellyfish. Under 2 vertical individuals, the mean TS for multiple A. aurita at 120, 200, and 420 kHz was −72.7, −71.7, and −68.2 dB,respectively. In the case of 5 vertical individuals, the mean TS of the species was −71.3, −68.2, and −62.0dB. Finally, the mean TS of C. nozakii at 120, 200, and 200 kHz was −62.0, −60.3, and −58.2 dB under 2individuals and −58.1, −57.4, and −54.0 dB under 4 individuals, respectively. For both species, higher numbers of jellyfish resulted in a higher TS. In addition, higher frequencies were associated with a higher TS for the same jellyfish. These TS results for two species can be used as essential data for the acoustic detection of jellyfish in an open ocean or coastal area.

수산 음향 기법을 이용한 연안 저서 어군의 시.공간 분포 및 안정성 조사

강돈혁,이창원,조성호,명정구 한국해양과학기술원 2008 Ocean and Polar Research Vol.30 No.1

Hydroacoustic technique was used to analyze spatiotemporal stability and distribution of demersal fish aggregations in the coastal region to overcome some limitations of the existing methods such as net and diving. The survey was carried out in the Baekeum Bay on the south coast of Korea in January 2007. The bottom depth in the study site ranges from 7 to 25 m. In order to outline aggregations of demersal fish initial scanning using 200 kHz split-beam transducer was randomly conducted over the large area. Having detected fish aggregation in the specific region, intensive acoustic survey of irregular star pattern was carried out along 14 transects across the area in question. The results of the acoustic survey show that all demersal fish aggregations are concentrated about 5 m from sea bottom having a slight slope and remain steady with no spatial or temporal variations during acoustic survey. The hydroacoustic method used in this study offers a new approach to understand vertical and horizontal distribution, spatiotemporal stability, and biomass estimate of demersal fish aggregations in coastal regions. Additionally, the number of individual fish estimated from in situ acoustic target strength data can be used to understand the standing stock of demersal fish aggregation.

음향 조사에 의한 2002/2003 하계 시기의 남극 남쉐틀랜드 군도와 남오크니섬 사이의 크릴 밀도

강돈혁,김수암,신형철,이윤호,김영신 한국해양과학기술원 2005 Ocean and Polar Research Vol.27 No.1

Acoustic survey for density and biomass estimate of Antarctic krill, Euphausia superba, was conducted in the large area between South Shetland Islands and South Orkney Islands, during November 30-December 30, 2002. Considering oceanographic and geographic properties, the study area was divided into six sub-regions. Acoustic system and frequency used in the survey were quantitative echo sounder (Simrad EK500) and 38, 120-kHz split beam transducers. In order to discriminate krill aggregations in all acoustic signal, difference of mean volume backscattering strength (DMVBS) method of the two frequencies was introduced. Averaged krill density for the overall surveyed area was 23.5 g/m2, and spatially averaged estimates of krill density were 44.9 g /m2 (north of the South Shetland Islands), 30.3 g/m2 (Bransfield Strait), 11.3 g/m2 (near the Elephant Island), 13.6 g/m2 (north of the Elephant Island), 18.1 g/m2 (between Elephant Island and South Orkney Islands) and 21.7 g/m2 (northwest of the South Orkney Islands) at each sub-area. In the two sub-regions with surveyed area, estimated krill biomass in the north of the Elephant Island was 0.315 million tones with a CV of 18.35% (6,766 mile2), and between Elephant Island and South Orkney Islands was 1.26 million tones with a CV of 9.45% (20,299 mile2). As a whole, the krill density in the early summer season was low level, comparing with that of January-February. This suggested that major krill swarms in the around South Shetland Islands were reached in the mid-summer seasons from western part of the Antarctic Peninsula, and the low krill density also affects the density variation of the krill between Elephant Island and South Orkney Islands.

초음파를 이용한 유해적조의 실시간 음향탐지 시스템 개발 및 평가

강돈혁,임선호,이형빈,도재원,이윤호,최지웅 한국해양과학기술원 2013 Ocean and Polar Research Vol.35 No.1

The toxic, Harmful Algal Blooms (HABs) caused by the Cochlodinium polykrikoides have a serious impact on the coastal waters of Korea. In this study, the acoustic detection system was developed for rapid HABs detection, based on the acoustic backscattering properties of the C. polykrikoides. The developed system was mainly composed of a pulser-receiver board, a signal processor board, a control board, a network board, a power board, ultrasonic sensors (3.5 and 5.0 MHz), an environmental sensor, GPS, and a land-based control unit. To evaluate the performance of the system, a trail was done at a laboratory, and two in situ trials were conducted: (1) when there was no red tide, and (2) when there was red tide. In the laboratory evaluation, the system performed well in accordance with the number of C. polykrikoides in the received level. Second, under the condition when there was no red tide in the field, there was a good correlation between the acoustic data and sampling data. Finally, under the condition when there was red tide in the field, the system successfully worked at various densities in accordance with the number of C. polykrikoides, and the results corresponded with the sampling data and monitoring result of NFRDI (National Fisheries Research & Development Institute). From the laboratory and field evaluations, the developed acoustic detection system for early detecting HABs has demonstrated that it could be a significant system to monitor the occurrence of HABs in coastal regions.

제주도 서쪽 연안에서 음향자원 조사를 이용한 저층 어군의 시.공간 분포

강돈혁,유준택,명정구,임양재,이창원 한국해양과학기술원 2008 Ocean and Polar Research Vol.30 No.2

This study aims at assessment of spatio-temporal distribution of demersal fish aggregations near the west coast of Jeju Island using hydroacoustic survey. A 200 kHz split beam transducer attached to a small to wed body was used for all acoustic investigations. The received acoustic data were in situ acoustic target strength (TS, dB) for all pings and nautical area scattering coefficient (NASC, m2/mile2) for 0.1 mile along 12 acoustic transects. Demersal fish aggregations are distributed around the coastal slope having 20 to 30 m depth throughout all seasons. The concentration is higher during the summer season. With regard spatial distribution, higher demersal fish aggregations have been detected near the West coast of Shinchang and especially near Chagwi-do. Pelagic fish aggregations were higher to the south of Chagwi-do during the spring season. Additionally, standing stock of demersal fish aggregations from the NASC data, TS function, and length-weight function of dominant species was estimated as follows: 3.2 ton (CV 21.8%) in December 2006, 17.9 ton (CV 21.6%) in April 2007, 30.8 ton (CV 17.8%) in June 2007, and 22.5 ton (CV 24.2%) in October 2007. The application of hydroacoustic methods offers a new approach to understanding spatio-temporal structure and estimate the biomass of demersal fish aggregations in the coastal area. And the results can be made up limitations of qualitative analysis through net and diving for fisheries resources survey in coastal area.

부레를 가진 어류의 음향산란 강도에 관한 연구: 참돔의 길이 및 행동에 따른 산란강도

강돈혁,황두진,나정열,김수암 한국음향학회 2001 韓國音響學會誌 Vol.20 No.5

The backscattered sound energy by fish depends on size and physical structure and, most important, on the presence or absence of a swimbladder. Target strength experiments of red seabream (Pagrus major) were conducted by using 38 (split-beam), 120 (split-beam) and 200 kHz (dual-beam) frequencies with live fishes confined in a net-cage and free swimming in tank without the cage, respectively. For 38, 120, and 200 kHz frequencies, target strength equations are expressed as a function of fish length:TS/sub 38kHz/=20 log/sub 1o(l)/-66.41, TS/sub 120kHz/=20 log/sub 1o(1)/-71.80, and TS/sub 200kHz/=20 log/sub 1o(1)/-73.94. To test the acoustic models by using Helmholtz-Kirchhoff ray approximation, predictions of target strength based on swimbladder morphometries are compared with target strength measurements. The target strength of whole fish depends on variations in swimbladder morphology than fish body morphology. In the mean time, when the fish is confined in the net cage, scattering length by the backscattered signal matched with the Gaussian PDF, while under the free-swimming condition, scattering length is close to the Rayleigh PDF. 부레를 가진 어류의 산란 강도를 조사하기 위하여 길이가 다른 참돔 (red seabream, pagrus major)을 이용한 음향 실험을 실시하였다. 대상 어류를 살아 있는 상태로 - (1) 망 내에 각각 넣은 후, (2) 자유 유영 상태로 놓은후 - 3개의 음향센서 (38, 120, 200kHz)를 이용하여 길이에 따른 산란강도를 측정하였다. 실험 결과 길이에 따른 참돔의 산란 강도는 각 주파수별로 TS/sub 38㎑/=20 log/sub 10(l)/ -66.41, TS/sub 120㎑/=20 log/sub lo(1)/ -71.80, TS/sub 200㎑/=20 log/sub 10(1)/ -73.94로 나타났다. 실험 결과와 이론 모델을 비교하기 위하여 어류의 형태를 근거로 한 Helmholtz-Kirchhoff 음선 근사법을 사용한 결과, 산란강도는 어류 몸체보다는 부레에 의한 효과가 95%이상으로 나타났다. 한편, 수신된 산란강도 자료를 이용한 확률밀도 함수로부터 어류의 행태에 따른 산란강도 변위는 망 내의 산란체에서는 가우스 확률밀도함수 (Gaussian PDF)로, 자유 유영 상태에서는 레일리 확률밀도함수 (Rayleigh PDF) 특성을 나타냈다.

수중음향 모델을 위한 보름달물해파리(Aurelia aurita s.l.)의 체내 음속비 및 밀도비

강돈혁,이창원,이형빈,김미라 한국해양과학기술원 2012 Ocean and Polar Research Vol.34 No.1

Physical properties such as sound speed contrast (h) and density contrast (g) of the interested target are key parameters to understand acoustic characteristics by using theoretical scattering models. The density and sound speed of moon jellyfish (common jellyfish, Aurelia aurita s.l.) were measured. Sound speed contrast (h) was measured from travel time difference (time-of-flight method) of an acoustic signal in a water tank for APOP studies (Acoustic Properties Of zooplankton). Density contrast (g) was measured by the displacement volume and wet weight (dual-density method). The sound speed remained almost constant as the moon jellyfish increased in bell length. The mean values±standard deviation of h and g were 1.0005±0.0012 and 0.9808±0.0195), respectively. These results will provide important input for use in theoretical scattering models for estimating the acoustic target strength of jellyfish.