• 수산해양기술연구
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• 제28권4호
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• pp.347-359
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• 1992

The movements of three striped jack (Caranx delicatissimus, 24cm of body length) were tracked by ultrasonic telemetry in the Nunoura Bay in August 1990. A school of the striped jack has been released near by the fish farming rafts by Goto branch of the Fisheries Agency and Japan Sea-Farming Association. To investigate the staying area and the swimming pattern of the fish, small size pinger($\Phi$8.5$\times$L35mm, 140dB re 1$\mu$Pa at 1m, 69kHz) was tagged on the dorsal fin without any anesthesia. The movements of three tagged fish are monitored at the same time with four omni-directional hydrophones. The locations of the fish are calculated by the hyperbolic method and tracked by a technique so called time division scheme which uses both the pulse interval and the phase. Three pingers used have the pulse interval of 1.7, 1.8 and 1.9sec, respectively, and the common pulse duration of 15ms. In results it was capable to estimate behavior right after the release, swimming speeds and approximate moving area of the fish. The movements were tracked for a week continuously, and it was found out that the staying area of the fish was around or under the farming rafts. Sometimes they swam together but most of the time they move separately. The average swimming speed of those fish was about two times of the body length.

• 한국어병학회지
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• 제19권1호
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• pp.55-64
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• 2006

2003~2004년 봄, 대량 폐사한 가물치 자어 (부화 후 15~30일령)에서 랩도바이러스 유사 병원체를 분리하였다. 분리 바이러스주는 EPC cell과 SSN-1 cell에서 잘 증식하는 반면 FHM cell에는 감수성이 없었고 감염된 EPC cell에서 전형적인 랩도바이러스 모양의 탄환형 바이러스 입자 (45×100 nm)를 다수 관찰할 수 있었다. 분리 바이러스주의 증식 적온은 20~25℃이었고, 15℃이하에서는 증식할 수 없었으며, 30℃ 이상에서는 증식하지는 않았으나 초기 감염가를 유지하였다. 분리 바이러스는 15일령 및 40일령의 가물치 자치어에서는 침지 감염에서 병원성이 높은 반면, 90일령 이상의 중간 육성어에서는 폐사를 나타내지는 않았다.

• Fisheries and Aquatic Sciences
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• 제11권2호
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• pp.113-123
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• 2008

We modeled fish school movements as a capture process in relation to the purse seine method using the three steps of the stimulus-response process (i.e., input stimuli, central decision-making and output reaction). Input stimuli of the model were categorized as either physical stimuli such as visual stimulus, sound stimulus, water flow, and weather or as biological stimuli such as species and size, swimming performance, sensual sensitivity, and presence of prey or predators. The output process determining the spatial orientation of the fish school for 3-D movements was based on swimming speed and angular change in the fish response, and these movements were animated as the relative geometry between the fish school and the purse seine. Simulations were carried out for skipjack tuna (Katsuwonus pelamis) schools reacting to a pelagic purse seine in the southwest Pacific Ocean. Simulation results showed that escape ratios varied from 20 to 70% by the relevant ranges in the stimulus-response thresholds, swimming speeds, and angular changes of fish schools were similar to those observed in the field. Therefore, with knowledge of relevant parameters, this model can be used to predict capture and escape probabilities of purse seine operations for different fish species or conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권12호
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• pp.4866-4888
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• 2020

One major and time-consuming task in fish production is obtaining an accurate estimate of the number of fish produced. In most Nigerian farms, fish counting is performed manually. Digital image processing (DIP) is an inexpensive solution, but its accuracy is affected by noise, overlapping fish, and interfering objects. This study developed a catfish recognition and counting algorithm that introduces detection before counting and consists of six steps: image acquisition, pre-processing, segmentation, feature extraction, recognition, and counting. Images were acquired and pre-processed. The segmentation was performed by applying three methods: image binarization using Otsu thresholding, morphological operations using fill hole, dilation, and opening operations, and boundary segmentation using edge detection. The boundary features were extracted using a chain code algorithm and Fourier descriptors (CH-FD), which were used to train an artificial neural network (ANN) to perform the recognition. The new counting approach, based on the geometry of the fish, was applied to determine the number of fish and was found to be suitable for counting fish of any size and handling overlap. The accuracies of the segmentation algorithm, boundary pixel and Fourier descriptors (BD-FD), and the proposed CH-FD method were 90.34%, 96.6%, and 100% respectively. The proposed counting algorithm demonstrated 100% accuracy.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제3권1호
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• pp.47-53
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• 2022

The escape behavior of prey fish to predator attack is directly linked to the survival of the fish. In this study, I explored the escape behavior of Medaka fish to bird attacks. To simulate the attack, I designed a model triangular-shaped bird to slide along a fishing line connected between rods at both ends of the tank. The triangular shape was set to 10×15 (S=1), 15×20 (S=2), and 20×25 cm (S=3) with base×height. The slope (θ) of the fishing line, which determines the attack speed of the model bird, was set to values of 15° (θ=1), 30° (θ=2), and 45° (θ=3). The escape behavior was characterized using five variables: escape speed (ν), escape acceleration (α), responsiveness (γ), branch length similarity entropy (ε), and alignment (ϕ). The experimental results showed when (S, θ)=(fixed, varied), the change in values of the five variables were not significant. Thus, the fish respond more sensitively to S than to θ In contrast, when (S, θ)=(varied, fixed), ν, α, and γ showed increasing trends but ε and ϕ did not change much. This indicates the nature of fish escape behavior irrespective of the threat is inherent in ε and ϕ. I found that fish escape behavior can be divided into two types for the five physical quantities. In particular, the analysis showed that the type was mainly determined by the size of the model bird.

• 한국수산과학회지
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• 제41권1호
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• pp.26-31
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• 2008

The feeding habits of chub mackerel (Scomber japonicus) were studied based on an examination of the stomach contents of 512 specimens collected between November 2005 and October 2006 in the South Sea of Korea. The specimens ranged in fork length (FL) from 23.4-37.5 cm. Chub mackerel is a piscivore and consumes mainly Teleosts such as Engraulis japonicus. Its diet also includes amphipods, crabs, Euphausia, chaetognaths and shrimp. Smaller individuals (<26 cm FL) consume mainly crabs. The proportion of these prey items decreases with increasing fish size, and this decrease paralleles the increased consumption of fish. The prey size increases with S. japonicus size.

• Fisheries and Aquatic Sciences
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• 제7권1호
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• pp.46-50
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• 2004

Feeding habits of Rudarius ercodes collected from a Zostera marina bed in Jindong Bay, Korea were studied. R. ercodes was a omnivore which consumed mainly gammarid amphipods, polychaetes and eelgrass (z. marina). Its diets also included a small amount of copepods, urochordates and caprellid amphipods. R. ercodes showed ontogenetic changes in feeding habits. Small individuals less than 2cm SL fed mainly on copepods, however, gammarid amphipods and polychaetes were heavily selected with increasing fish size. The consumption of eelgrass by R. ercodes was $10-20\%$ all size classes. The dietary breadth of R. ercodes were varied with fish size

• 한국식품영양과학회지
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• 제37권8호
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• pp.1058-1068
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• 2008

초등학교 학교급식 조리사를 대상으로 초등학생들에게 적합한 품목별 식재료의 크기에 대한 설문조사를 실시한 결과, 응답자의 대부분이 일반 성인식으로 제공되는 크기보다 3/4(0.75배) 또는 2/4 정도 작게 제공하는 것이 적당하다고 응답하였다. 식재료 규격을 설정하고 실제로 현장에 적용하는 실험은 사진자료를 이용한 조사, 실제섭취량 조사 등 2가지 방법으로 초등학교에 6개교에서 학령별로 실시하였으며 전체적으로 크기에 따라 학생들의 실제 섭취량과 선호도가 달라지는 것으로 나타났다. 이들 결과에 따라 식단별 식재료 규격을 3종류로 구분하고 크기가 표시된 흰색 아크릴판(가로${\times}$세로, $290{\times}210\;mm$)을 이용하여 식단별 연령별로 적합한 식재료크기를 설정하였으며 실제크기와 대조하여 사진자료로 작성하였다. 이들 자료를 다시 식단별로 분류하여 식재료 품목별 커팅 크기와 코드를 설정하였으며 설정된 식재료는 품목별로 나물 12종, 야채 15종, 김치 9종, 젓갈 2종, 튀김 8종, 육류 5종, 어류 19종, 건어물 5종로 최종결과는 책자로 제작이 가능하도록 편집전문가를 통한 수정작업으로 완성시켰다.

• 생태와환경
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• 제41권4호
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• pp.431-440
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• 2008

Turbid water or suspended sediment is associated with negative effects on aquatic organisms; fish, aquatic invertebrate, and periphyton. Effects of turbid water on fish differ depending on their developmental stage and a level of turbidity. Low turbid water may cause feeding and predation rates, reaction distance, and avoidance in fish, and it could make fish to die under high turbidity and long period. Therefore, it is very important to find out how turbid water or suspended sediment can affect fish in domestic watersheds. The objectives of this study were 1) to introduce international case studies and their standards to deal with suspended sediment, 2) to determine acute toxicity in 4 major freshwater fishes, and 3) to determine in relation to adverse effect of macroinvertebrates and fish. Impacts of turbid water on fish can be categorized into direct and indirect effects, and some factors such as duration and frequency of exposure, toxicity, temperature, life stage of fish, size of particle, time of occurrence, availability of and access to refugia, etc, play important role to decide magnitude of effect. A review of turbidity standard in USA, Canada, and Europe indicated that each standard varied with natural condition, and Alaska allowed liberal increase of turbidity over natural conditions in streams. Even though acute toxicity with four different species did not show any fatal effect, it should be considered to conduct a chronic test (long-term) for more detailed assessment. Compared to the control, dominance index of macroinvertebrates was greater in the turbid site, whereas biotic index, species diversity index, species richness index, and ecological score were smaller in the turbid site. According to histopathological analysis with gills of macroinvertebrate and fishes, morphological and physiological modification of gills due to suspended sediments can cause disturbance of respiration, excretion and secretion. In conclusion, in order to maintain good and healthy aquatic ecosystem, it is the best to minimize or prevent impact by occurrence of turbid water in stream and reservoir. We must make every effort to maintain and manage healthy aquatic ecosystem with additional investigation using various assessment tools and periodic biomonitoring of fish.

• Journal of Ecology and Environment
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• 제44권1호
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• pp.54-61
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• 2020

Background: Most fish undergo prey switch from juvenile to adult. It is thought that slightly different feeding habits occur among adult fishes due to growth, spawning, habitat change, and so on. Therefore, the diet of the John Dory Zeus faber (≥ 24 cm TL) was studied in the coastal waters of Korea by analysis of stomach contents, with comparison by season and size class of diet composition and prey diversity. Monthly samples were taken from February 2017 to January 2018. Results: The results showed that the John Dory was a piscivorous predator, and pisces had occupied 82.3% of IRI%. Trichiurus lepturus and Trachurus japonicus were important preys in all size classes and seasons. Diet composition differed among the size classes and seasons (Chi-square test, P < 0.05). As body size of Z. faber increased, the occurrence of benthic fish (Glyptocephalus stelleri) tended to increase. The seasonal prey composition also changed depending on the abundant species of each season. Conclusions: Z. faber is a piscivorous predator. The consumption habits of Z. faber appear to different results by their size and seasons. This study suggests that Z. faber could be considered an opportunistic predator.