• 수산해양기술연구
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• 제48권4호
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• pp.495-503
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• 2012

An acoustic method for discriminating plankton from fish, in Lake Dom Helvecio of Brazil, is developed. The flow of data from this method is comprised of time varied threshold (TVT), dilation filter, bitmap and mask functions. The TVT can, of itself, precisely explain how to select an appropriate value. The final results of the echogram, which only shows plankton by masking fish signals, is used to examine the acoustic density of plankton by depth and time. The results indicate that the acoustic density of the plankton is at a depth of between 5m to 15m, its density is especially high at 10m to 15m. The results of the acoustic density of plankton by time indicate that May 7 is higher in density than May 8. Future study plans include the use of net samples, environmental datasets to identify the abundance and ecology described by the Chaoborus spp. from other species.

• 수산해양기술연구
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• 제60권1호
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• pp.18-26
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• 2024

In this study, we estimated the distribution density of giant jellyfish in coastal waters of Korea in 2023 and compared the occurrence of giant jellyfish over four years. In May, the giant jellyfish were mainly distributed in the waters of the Yangtze River outflow, and in July, they were highly distributed in the west of Jeju Island and near the south coast of Korea. In addition, when comparing the distribution densities of giant jellyfish in Korea over four years, both acoustic and sighting surveys showed that the highest density of jellyfish occurred in 2021.

• 수산해양기술연구
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• 제51권1호
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• pp.86-93
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• 2015

Anchovy (Engraulis japonicus) is one of the most important species in the South Sea of South Korea. In order to estimate the biomass of anchovy, acoustic surveys, concurrently with trawling, were conducted in April, July, and September of 2013 and February of 2014 off the coast of Tongyeong and Yeosu. However, anchovies were found only during spring (April) and winter (February) surveys. To display only anchovy species confirmed by trawls on empty spaced echograms, virtual echograms were created. Three target strength (TS) values of anchovy were used: TS_z = 20 log L - (20/3) log (1+z/10) - 67.6 (Zhao et al.), TS_y =20 log L - 72.9 (Yoon et al.), TS_f = 20 log L - 71.9 (Foote). For anchovy schools combined with other species e.g., hairtail, squid, and Korean pomfret, their TS values were used to calculate an average TS. As a result, the anchovy biomass in the winter survey was approximately 75,000 tons (TS_z), 90,000 tons (TS_f), 114,000 tons (TS_y), respectively. The biomass in spring was 9,000 tons (TS_z), 9,200 tons (TS_f), 10,000 tons (TS_y). The sampling variance of spring was 70% and of winter was 30%. In order to manage anchovy resource sustainably, larvae and adult anchovy should be separately surveyed, the optimal area, date, and time for acoustic survey should be investigated, and the biomass survey should be done for relatively long and regular base.

• 수산해양기술연구
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• 제50권4호
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• pp.476-486
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• 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
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• 제53권2호
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• pp.132-141
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• 2017

The objective of this study was to provide fundamental information on fish swimming behavioral properties. Acoustic data was collected at nighttime from the $10^{th}$ to $12^{th}$ March, 2016 near Yokji Island in the South Sea of South Korea, and was analyzed using the fish track technique. This technique is to identify groups of single targets, which shows a pattern of systematic movement. As a result, the differences of the behavioral properties such as depth, swimming speed, vertical direction, horizontal direction, tortuosity, and depth change among days were minor; however, statistical results (Welch analysis of variance) showed significant difference between days. Especially, the target strength (TS) of the $11^{th}$ were significantly different from the $10^{th}$ and $12^{th}$. It could be assumed that gizzard shad, which was the dominant species from the catch on the $11^{th}$ March, might have affected this difference. The correlation between TS and other properties was very week. The significant difference seemed even small differences of average values because of the large data volume.

• 수산해양기술연구
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• 제37권3호
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• pp.214-222
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• 2001

연안어장의 해저지형을 조사하기 위한 정밀음향측심시스템은 Public-DGPS 수신기. 싱글빔 음향측심기 및 측량용 소프트웨어로 구성하였으며, 그 유용성을 확인하기 위하여 정치망어장의 해저지형 특성 및 투입된 인공어초의 분포를 조사하였고 그 결과는 다음과 같다. 1. 본 연구에서 사용한 public-DGPS 수신기의 위치측정오차는 DGPS 모드일 때와 GPS 모드일 때 각각 5.47 m, 7.03 m이었다. 2. 실험정치망어장의 수심은 9~10 m이었고 해저는 대체로 평탄하였으며 이 어장으로부터 남쪽으로 120 m 떨어진 곳에 깊이 1~2 m, 폭 10 m내외의 골이 존재하였다. 3. 자란만 부근의 인공어초 수역에는 20개의 사각형 어초 (L3$\times$W3$\times$H3 m)가 수심 15~25 m에 낱개로 투입되어 있었고, 이 인공어초군의 가까이에 높이 5~8 m의 자연초가 있음을 확인할 수 있었다. 4. 본 연구에서 구현한 정밀음향측심시스템은 인공어초사업의 적지선정을 위한 사전조사에 활용할 수 있음을 확인할 수 있었다.

• The Journal of the Acoustical Society of Korea
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• 제25권3E호
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• pp.101-109
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• 2006

Besides dorsal-aspect target strength (TS) of the fish, side-aspect TS information is also acoustically important parameter in fisheries acoustics. In this study, the side-aspect TS of 11 black sea bream (Acanthopagurus schlegeli) were measured using a split beam echosounder of 120, 200, and 420 kHz; total length of the fish ranged from 12.4 to 23.7 cm, and wet weight from 27.5 to 229.8g. For the precise TS measurement with side-aspect angle, we used anesthetized and tethered specimens of known size while being rotated through $360^{\circ}C$ by means of a carousel structure. The side-aspect TS measurements of the fish were conducted by rotating the fish in the horizontal plane at 50 interval. The ping interval was 0.2 second and elapsed time at each angle was 30-60 second. As a result, the measured side-aspect TS data were fitted by sinusoidal function. The relationships between fish length and near full side-aspect TS were as follows: $TS_{120kHz}= 21.46 log (TL)-67.5 (r = 0.70), \;TS_{200 kHz}= 31.03 log (TL)-76.9 (r=0.83),\;TS_{420 kHz}= 30.79 log (TL)-72.2 (r = 0.77)$. For comparison, theoretically estimated side-aspect TS from the Kirchhoff ray mode (KRM) model, which based on swimbladder and body morphology, were compared with the measured TS.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2009년도 학술대회 초록집
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• pp.167-173
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• 2009

2009년 국립해양조사원은 백령도 부근 해역에 대해 바다로 1호에 장착된 Simrad EM3000 다중빔 음향측심기를 이용한 수심측량조사를 실시하였으며 정확한 음속보정을 위해 1일 $7{\sim}10$회 이상의 음속을 관측하였다. 백령도 주변해역은 계절에 따라 여러 질 수괴(쿠로시오 난류, 황해 연안수 등)가 복잡하게 분포하여 여러 형태의 수온 전선이 형성되어 수층 음속 깊이가 최대 10m/s 이상의 차이를 나타냈다. 또한 난수괴 유입으로 인해 수온약층의 깊이가 지역별로 다르게 분포 하였다. 이러한 음속의 국지적 변화는 다중빔을 이용한 수심측량 자료의 정확도를 저하시키는 요인으로 작용한다. 따라서 다중빔을 이용한 수심측량 자료의 정확도를 저하시키는 요인으로 작용한다. 따라서 백령도 주변해역 수심측량 자료의 수평 수직 변화를 음선추적 이론을 이용하여 확인하였다.

• 수산해양기술연구
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• 제51권3호
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• pp.340-347
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• 2015

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.

• 수산해양기술연구
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• 제52권2호
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• pp.111-120
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• 2016

Acoustic surveys using a scientific echosounder and trawl surveys were concurrently carried out in between Geoje and Tongyeong of the South Sea by season. The anchovy schools were identified by trawling in each station and used for frequency response analysis. Frequency responses of anchovy schools by season and species composition ratio were examined using multi-frequencies (18, 38, 70, 120 and 200 kHz). The frequency response r(f), is one of the acoustic characteristics which means the volume back-scattering strength ratio between a reference frequency and other frequencies. In spring, the r(f) of anchovy schools decreased with increased frequency, with the exception of 120kHz. While, in winter, the r(f) continuously decreased inversely proportional to the increase in frequency. Frequency response of anchovy schools presented a distinctive difference between spring and winter, however it did not different in spife of different species composition ratios in schools.