• Parasites, Hosts and Diseases
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• 제55권3호
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• pp.305-312
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• 2017

The prevalence of Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fish from the water systems of Seomjin-gang (River), the Republic of Korea. Total 1,604 fish from 7 local sites of Seomjin-gang were examined by artificial digestion methods. The metacercariae of C. sinensis were detected in 102 (39.8%) out of 256 fish (14 species) from the upper reaches of Seomjin-gang, i.e., Osucheon (22.3% in 6 fish species) in Imsil-gun, and Seomjin-gang (63.9% in 9 fish species) in Sunchang-gun, Jeollabuk-do. Their average density was 9.0 per infected fish. They were also found in 132 (48.0%) out of 275 fish (12 spp.) from the middle reaches of Seomjin-gang, i.e., Songdaecheon (58.9% in 4 fish species) in Namwon-si, Jeollabuk-do, and Seomjin-gang (45.2% in 10 fish species) in Gokseong-gun, Jeollanam-do. Their average density was 21.0 per infected fish. CsMc were detected in 77 (56.6%) out of 136 fish (11 species) from the lower reaches of Seomjin-gang, i.e., Seomjin-gang (73.3% in 11 fish species) in Gurye-gun, Jeollanam-do, and Namsancheon (8.6% in 1 fish species) in Hadong-gun, Gyeongsangnam-do. Their average density was 64.9 per infected fish. The metacercariae of Metorchis orientalis were also detected in 6 fish species from 4 sites of Seomjin-gang. Conclusively, it has been confirmed that CsMc are more or less prevalent in fish from some water systems of Seomjin-gang in Korea.

• Fisheries and Aquatic Sciences
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• 제6권3호
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• pp.160-163
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• 2003

Mortality of several species of fish and shellfish exposed to Harmful Algal Blooms (HABs) caused by Cochlodinium polykrikoides, Heterosigam akashiwo, Alexandrium tamarense, Eutreptiella gymnastica, Heterocapsa triquetra and Prorocentrum micans was studied. When fish were exposed to a cell density of 8,000 cells $mL^{-1}$ in C. polykrikoides, $35\%$ of flatfish and darkbanded rockfish died within 48 hrs. However, jacopever rockfish had mortality of higher than $85\%$. Rock bream, filefish and red sea bream showed $100\%$ mortality within 10 hrs with an exposure cell density of 8,000 cells $mL^{-1}$. The rest of HABs except for C. polykrikoides showed that there was no fish and shellfish death throughout the 48 hrs even in the maximum cell density of 100,000 cells $mL^{-1}$ These results imply that C. polykrikoides can have a serious impact on fish mortality and it is regarded as an ichthyotoxic dinoflagellate. The fish death may be attributed to anoxia caused by a combination of the production of reactive oxygen species (ROS) and polysaccharide from C. polykrikoides during blooms.

• 수산해양기술연구
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• 제59권3호
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• pp.242-252
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• 2023

In this study, we aimed to determine the seasonal distribution and biomass of fish in Samcheok marine ranching area (MRA) of Republic of Korea using the scientific echosounder. Fish trap and gillnets were used to identify fish species in the survey area, and dB-difference method was used to estimation the spatio-temporal distribution and density of fish. The results showed that the dominant species in Samcheok marine ranching area were Chelidonichthys spinosus, Sebastes inermis, Hexagrammos otakii and Tribolodon hakonensis. The spatio-temporal distribution of fish showed that fish had a relatively higher distribution at night than during the day. In addition, the density of fish by season was highest at night in July at 34.22 g/m² and lowest in April at 0.42 g/m².

• Fisheries and Aquatic Sciences
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• 제27권5호
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• pp.276-282
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• 2024

The present study was conducted to investigate the behavior and distribution characteristics of fishes near an artificial reef close to the waters of Uljin marine ranch. A 200-kHz, dual-beam frequency transducer was attached to the side of a ship for acoustic measurements. The fish formed small groups in the bottom layer near the artificial reef around the afternoon-sunset period; at night, the fish did not form groups and remained individually scattered. During dawn-sunrise and morning, the fish formed groups again and were found near the upper and middle layers of the artificial reef. High density of fish occurred near the middle of the nautical zone during morning, afternoon-sunset, and dawn-sunrise, periods; at nighttime, the distribution was uniform across the entire zone. Moreover, the mean Nautical Area Scattering Coefficients (NASC, m²/nmi²) value was highest during dawn-sunrise at 400.2 m²/nmi², similar during night and morning (100.5 m²/nmi²), and lowest during afternoon-sunset (20.1 m²/nmi²). The present study is expected to provide the background for understanding the behavioral characteristics of fish living near artificial reefs and estimating the density and biomass of fish.

• 환경생물
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• 제37권2호
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• pp.155-163
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• 2019

본 연구에서 바이오플락 환경에서 적정 밀도 구간 산정을 위한 실험을 진행했으며, 본 실험의 결과 밀도 구간 Group 1 (40마리 m^-2)과 Group 2 (60마리 m^-2)에서는 수질 안정을 통해 생리적 변화 없이 13주간 실험이 이루어졌지만, 밀도 구간 Group 3 (80마리 m^-2)과 Group 4 (100마리 m^-2)에서는 아질산염 안정화 실패, 혈액성상 및 혈장성분의 변화를 나타내었다. 물론, 유수를 하지 않는 바이오플락 시스템 특성상 고밀도 구간에 따른 밀도 스트레스뿐만 아니라, 고밀도 구간의 수질불안정에 따른 높은 암모니아 및 아질산 농도에 따른 영향도 복합적으로 고려해야 할 것이다. 본 실험의 결과 밀도 60마리 m^-2까지의 밀도 구간에서 수질안정과 함께 혈액학적 성분의 유의적 변화 없이 100 g 크기의 넙치 사육양성에 적합할 것으로 보인다.

• ALGAE
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• 제30권1호
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• pp.49-58
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• 2015

In September 2007, reports of respiratory irritation and fish kills were received by the Florida Fish and Wildlife Conservation Commission (FWC) from the Jacksonville, Florida area. Water samples collected in this area indicated a bloom of Karenia brevis, the dinoflagellate that produces brevetoxin, which can cause neurotoxic shellfish poisoning. For the next four months, K. brevis was found along approximately 400 km of coastal and Intracoastal waterways from Jacksonville to Jupiter Inlet. This event represents the longest and most extensive red tide the east coast of Florida has experienced and the first time Karenia species other than K. brevis have been reported in this area. This extensive red tide influenced commercial and recreational shellfish harvesting activities along Florida's east coast. Fourteen shellfish harvesting areas (SHAs) were monitored weekly during this event and 10 SHAs were closed for an average of 53 days due to this red tide. The length of SHA closure was dependent on the shellfish species present. Interagency cooperation in monitoring this K. brevis bloom was successful in mitigating any human health impacts. Kernel density estimation was used to create geographic extent maps to help extrapolate discreet sample data points into $5km^2$ radius values for better visualization of the bloom.

• 수산해양기술연구
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• 제50권2호
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• pp.124-130
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• 2014

We aimed to assess the behavior characteristics of fish on an artificial reef using hydroacoustic techniques. The acoustical survey was conducted with a 200 kHz dual beam transducer while fishing on the stone combination reef of Uljin. A school of fish were detected on the artificial reef before sunset and floated on the artificial reef at 30 minutes after sunset. The density (Nautical Area Scattering Coefficient, NASC) of fish that floated on the artificial reef after sunset was about $600m^2/nmi^2$; similar observations (about $50m^2/nmi^2$ or less) were noted after 19:00 hours. Fish caught by fishing on the artificial reef were Sebastes schlegeli, Hexagrammos otakii, Sebastes thompsoni, and Conger myriaster. Resultantly, we demonstrated that hydroacoustic techniques are useful for detecting behavior characteristics of fish in the artificial reef. Such results can be used for basic data to estimate the install effect of the artificial reefs.

• 한국발생생물학회지:발생과생식
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• 제25권4호
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• pp.235-244
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• 2021

Interferon Regulatory Factor 3 (IRF3) is a member of interferon-regulated transcription factor family and is known to play an important role in the innate immune response against viral infections. In this study, the expression of IRF3 in different tissues, developmental stages, and stocking densities of olive flounder was investigated. The expression of IRF3 was observed to gradually increase in early-stage juvenile fish. The highest expression was observed in later-stage juvenile fish when immune tissues were formed. High IRF3 expression was observed in the muscles and the brain tissues. The expression of IRF3 was observed in fish at different stocking densities after viral hemorrhagic septicemia virus (VHSV) infection. It yielded an interesting expression pattern in the muscles and the brain tissues of fish stocked at low density. These observations can be used as basic data for the study of the expression of immune response-related genes against viruses based on stocking density and immune systems in other fish species.

• 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.

• 한국수산과학회지
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• 제48권5호
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• pp.798-804
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• 2015

The distributions of demersal fish along the coast of the South Sea, Korea, were estimated from a hydroacoustic survey and bottom trawl catches in April of 2015. Acoustic data were collected at 38 kHz, and converted into the nautical area scattering coefficient (NASC, m²/n·mile²) for 0.1 n∙mile along eight transects during day and nighttime. Various demersal fish species were collected and the dominant species comprised no more than half of the catch. The estimated acoustic density of demersal fish compared well with the cumulative catch weight from bottom trawl catches in daytime, but showed a low correlation at nighttime. The NASC of pelagic fish determined for anchovy was correlated with water temperature. The combined hydroacoustic and trawl method can be used to understand the spatial/temporal structure and estimate the density of demersal fish in coastal areas.