• Journal of fish pathology
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• v.22 no.3
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• pp.193-200
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• 2009

This study was performed to natural infection of Ichthyophthirius multifiliis and mortalities of two fish species were compared at 10${^{\circ}C}$ and 17${^{\circ}C}$ after artificial infection with the parasite. Subsequently compared to motality by the artificial infection with the different parasite orgin of host at 17${^{\circ}C}$ using rainbow trout Oncorhynchus mykiss. The prevalence of Ichthyophthirius multifiliis in cherry salmon was higher than that in rainbow trout during the periods of low temperature but no difference in high temperature season. The parasite was not detectable in culturing water and detritus except May that of density has been high. Susceptibility to the parasite was higher in cherry salmon than in rainbow trout at 10${^{\circ}C}$ of water temperature but no difference between two fish species at 17${^{\circ}C}$. When rainbow trout were infected with Ichthyophthirius multifiliis from rainbow trout and cherry salmon at 17${^{\circ}C}$, there was no difference in death of host. These results suggest that cherry salmon have higher susceptibility to Ichthyophthirius multifiliis than rainbow trout at low temperature.

• Journal of fish pathology
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• v.35 no.2
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• pp.215-223
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• 2022

Disease including parasite, bacteria and virus cause serious mortality to salmonid fish in the aquaculture. In this study, we investigated the current disease status of the rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch) in Yanayang, Pyeongchang, Jeongseon and Yeongwol of Gangwon province in 2021 and performed molecular characterization of those pathogen. For parasites, Ichthyophthirius multifiliis was observed at 2 farms. For bacteria, we identified Aeromonas sobria from kidney of rainbow trout using phylogenetic analysis of gyrB gene. A. salmonicida were isolated from necrosis site of gill cover and fin in coho salmon and necrotic lesion of fin in rainbow trout. Phylogenetic analysis using vap gene indicated that A. salmonicida isolated in this study were clustered with previously reported A. salmonicida subsp. salmonicida isolates. For virus, JRt-Nagano type of infectious haematopoietic necrosis virus was detected in rainbow trout, but infectious pancreatic necrosis virus and Oncorhynchus masou virus were not detected. These results provide useful information for the prevention of disease spread and transmission when cultivating new species such as Atlantic salmon in Korea.

• Korean Journal of Ichthyology
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• v.22 no.4
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• pp.238-248
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• 2010

We performed field investigations at six stations in Buk Stream of Goseong-gun, Gangwon-do, Korea, from May to September 2009 to understand the stream's fish fauna and community structure. In the survey, 31 species belonging to 20 families were collected. Dominant species by number was Zacoo koreanus (30.0%), and subdominant species were Pungitius kaibarae (9.4%) and Rhynchocypris steindachneri (9.3%). In biomass, the dominant species was Tribolodon hakonensis (35.5%), and subdominant species were Z. koreanus (22.5%) and Cobitis pacifica (7.5%). Eight Korean endemic fish species and two endangered species (P. kaibarae and Pungitius sinensis) were collected. In addition, four anadromous fish species (T. hakonensis, Oncorhynchus masou masou, O. keta, Gasterosteus aculeatus) and two amphidromus fish species (Plecoglossus altivelis altivelis and Gymnogobius urotaenia) were observed. Interestingly, we verified the existence of several fish species in Buk Stream where they have not lived before. Those species were previously reported to live only in rivers that run into the western and southern sea of Korea. Five of those species (Zacoo koreanus, Z. platypus, Silurus microdorsalis, Liobagrus andersoni and Coreoperca herzi) were reported in Buk Stream in the 1980s. The other species (Pungtungia herzi, Pseudorasbora parva, Squalidus multimaculatus, Misgurnus mizolepis, Koreocobitis rotundicaudata, Silurus asotus and Odontobutis interrupta) have been introduced since the 1990s.

• Korean Journal of Environment and Ecology
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• v.11 no.1
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• pp.100-110
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• 1997

To clarify the structure and function of ecosystem and establish the method for the conservation of biodiversity and community analysis at Soksacheon and Gyebangcheon, the authors surveyed the aquatic environment and freshwater fish fauna at 13 stations from July, 1995 to June, 1996. Collected 1,908 individuals were belong to 20 Species, 4 Oredr, 1 Suborder, 6 family, 7 Subfamily. The detail results are as follows. 1. It was confirmed that most of the surveyed stations were mountain valley of river type Aa, Ab. River structures were mixed with pebble, sand, rock and water quality of Soksacheon were pH(7.41), [COND.(0.051), TURB.(10.00), DO(8.66), W.T.(15.4)] and Gyebangcheon were pH(7.44), [COND.(0.097), TURB.(21.59), DO(9.35), W.T.(15.4)]. 2. Among them, 18 species were primary freshwater fishes(99.98%) and 2 species of pheripheral freshwater fishes(0.02%). 12 species(60%) of them were endemic species of Korea and they were Moroco kumgangenesis, Microphysogovio longidorsalis, Cobitis rotundicaudata, Misgurnus anguillicaudatus, Coreoleucisus splendidus, Cobitis longicorpus, Oncorhynchus masou ishikawai, Brachymystax lenok, Hemibarbus longirostris, Silurus microdorsalis, Cobitis koreensis koreensis and Hemibarbus mylodon. 3. Dominant species were Moroco kumgangenesis(46.85%) and Zacco temmincki(27.35%).

• Journal of fish pathology
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• v.4 no.2
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• pp.79-85
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• 1991

In Feb., 1990 an epizootic disease to masu salmon fry, Oncorhynchus masou cultured at the hatchery of rainbow trout in Samchok, Kwangwon-do have broken out and induced high mortality over 70%. Externally, the diseased fish showed dark discoloration, abdominal distension with ascites, slight exophthalmus and fecal casts. Internally, the gill and the liver of diseased fish were edematous and pale, and the stomach of moribund fish contained the milkish fluid. Microscopically there was extensive necrosis of the hematopoietic tissue in kidney and spleen, and scattered necrosis of pancreas, liver and lateral muscle. Especially, the necrosis of lamina propria, muscle layer and tela submucosa in the digestive tract known as the typical signs associated with infectious hematopoietic necrosis virus was seen clearly.

• Journal of Korea Water Resources Association
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• v.34 no.4
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• pp.365-379
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• 2001

This paper presents an echo-hydraulic experimental approach to assessment of ascending capacity of migratory fish in a baffled fishway. Sweetfish, Plecoglossus altivelis, trout, Oncorhynchus mykiss, are used in these experiments. Ascending environment of the migratory fish in rivers is analyzed through the results of taco-hydraulic experiments. Important factors affecting the ascending capacity of migratory fish in baffled fishways are the discharge and slope of fishways and the fall height between the fishway entrance and the river bed. In these fishways the migratory capacity of sweetfish for a given fishway discharge is mainly affected by fishway slope, whereas the ascending capacity of trout for a given fishway slope was influenced by the change of fishway discharge. Loss of ascending properties of landlocked salmon, Oncorhynchus masou var ishikawai, was confirmed by these experiments. An ascending hydraulic criteria of the baffled fishway is defined by means of dimensionless factor F$_{f}$ and falling head H$_{f}$. Ascending capacity of migratory fish in existing baffled fishways in river of eastern coastal region is poor because the slope of fishways is verb steep.eep.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.25-25
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• 2003

어류의 번식활동은 뇌-뇌하수체-생식소로 이어지는 내분비기관이 주로 담당하고 있으며, 그 중에서 뇌하수체에서 만들어지는 생식선자극호르몬 (GTH)은 생식소 발달에 매우 중요한 역할을 한다. 한편, GTH는 생식소에서 생성되는 스테로이드호르몬에 의해 유전자의 발현이 조절된다. 본 연구에서는 산천어 (Oncorhynchus masou)의 GTH 유전자발현에 미치는 estradiol-17$\beta$ (E2)의 영향을 생체내에서 먼저 조사하고, 유전자발현조절의 메카니즘을 구명하기 위하여 에스트로젠 수용체 (ER)의 cDNA를 cloning하였다. 또한 내분비교란물질로 알려져 있으며 에스트로젠 수용체와의 유사결합작용이 알려진 노닐페놀 (NP)의 영향도 아울러 조사하였다. 미성숙 산천어를 E2 및 NP (각각 5 mg/kg 및 10 mg/kg 체중)로 처리하면 72 시간째에 뇌하수체내의 $\beta$-actin mRNA에 비해 GTH (FSH$\beta$, LH$\beta$) mRNA가 상대적으로 증가하는 경향을 나타내었다. 뇌하수체에서 분리한 ER의 기본적인 구조는 DNA결합도메인 (Zf-C4), 호르몬결합도메인 (hormone_rec), 기타 전사활성화도메인으로 구성되어 있었으며 (그림 1), 기존에 보고된 에스트로젠 수용체중에서 무지개송어 및 대서양연어의 ER과 각각 98%, 96%의 높은 상동성이 관찰되었다. 향후, 준비된 ER을 재료로 하여 GTH 유전자발현의 호르몬의존성을 조사할 예정이다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.103-109
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• 2000

Complete senuences of the mitochondrial rRNA Benes were determined among six salmonines in Korean Waters (Brachpmystax lenok, Onoorhpchus keta, O. masou mason, O. mason ishikawae, O. mykiss, and albino mutant of O. mykiss). The purposes of this study were to provide the basic information on levels of mtDNA polymorphism among these species for genetic characterization; discuss phylogentic relationships among three Oncorhynchus sepecies; demonstrate the utility of rRNA gene sequence data as a genetic marker for disringuishinf among Korean salmonines. PCR/direct sequencing data indicated the following consistent results; 1) 12S rRNA genes was 945 bases long in Oncorhynchus species, and 946 bases in B. lenot including one insertion. 2) Of sequence variation in mitochondrial rRNA regions, transitional substitutions were superior to transversion. 3) The significant differences were not shown in the intraspecific variation values in these gene regions. The percentage sequence divergence values were ranged from $0.066 to 0.212{\%}$. 4) The interspecific divergences were greater than the intraspecific variation. Nevertheless, ribosomal RMh genes were more conserved among species than the other mitochondrial genes, and they showed potentiality as an intergenic marker for systematics. In addition, phylogenetic trees, constructed from this data, supported that cherry salmon was closer to chum salmon than to rainbow trout, and that lenok was most distantly related species in six salmonid species.

• Journal of fish pathology
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• v.28 no.2
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• pp.113-116
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• 2015

A $0.45-{\mu}m$ membrane filter is generally used to remove bacterial contamination during virus extraction from fish samples. However, the number of fish viruses is drastically reduced after filtration with a $0.45{\mu}m$ filter. In this study, we investigated the effect of filters on virus infectivity titer and the change in virus titer and bacterial number following different centrifugation conditions to determine a suitable procedure for virus extraction from fish samples. $10^{4.05}$ and $10^{5.05}TCID_{50}/ml$ of infectious hematopoietic necrosis virus (IHNV) and $10^{4.05}$ and $10^{4.55}TCID_{50}/ml$ of Oncorhynchus masou virus (OMV) were not detectable after filtration with two types of $0.45-{\mu}m$ filters, except the IHNV titer was reduced by about 10 fold after filter use (company A). No significant difference was found in the virus titer following centrifugation at $880{\times}g$ (30 min) or $3,500{\times}g$ (30 min), whereas IHNV and OMV titers were reduced by about 10 and 10-1000 fold by centrifugation at $14,000{\times}g$ (30 min) and $14,000{\times}g$ (10 and 30 min), respectively. A total of 97.7-99.9% Escherichia coli were eliminated by centrifugation at $880 {\times}g$ (30 min) and $3,500{\times}g$ (30 min). These results show that fish viruses were affected by filtering, even though the effect differed by virus species and filter type. Therefore, centrifugation at $3,500{\times}g$ (30 min) and use of medium with antibiotics may be useful for virus extraction along with a reduction in bacteria.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.1
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• pp.1-6
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• 2008

The changes in osmolality and the gene expression profiles of prolactin (PRL) and growth hormone (GH) with rapid changes in salinity were compared in the eel (Anguilla japonica), crucian carp (Carassius carassius), and masu salmon (Oncorhynchus masou). Fish stocked in freshwater (FW) were abruptly transferred to experimental tanks containing FW, 50% seawater (50% SW), or 100% SW (SW). Blood samples and pituitary glands were collected 2 and 24 hrs after the exposure. No mortality was observed in SW eel (n=6), whereas all of the crucian carp (n=6) and two masu salmon (n=6) exposed to SW died after land 24 hrs, respectively. The PRL mRNA levels of the eel and masu salmon decreased in 50% SW and SW compared to those of the fish kept in FW after 24 hrs, whereas the PRL levels of crucian carp were higher in 50% SW than in FW. Unlike the PRL mRNA levels, the GH mRNA levels of the eel did not differ significantly among three different salinities, while the GH mRNA levels of crucian carp and masu salmon increased significantly in 50% SW and SW after 24 hrs. The serum osmolalities increased marginally in the eel and masu salmon in 50% SW at 24 hrs (19% and 9%, respectively), whereas those of crucian carp increased abruptly in 50% SW (50% increase). These results suggest that the synthesis of PRL and GH is important in relation to the osmoregulatory system with environmental changes in salinity.