• Applied Microscopy
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• v.41 no.3
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• pp.205-213
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• 2011

Numerous anisakids were parasitic near the digestive tract of the black rockfish, Sebastes schlegeli and some anisakids observed on the liver of the host. Anisakids in the host were identified three species (Hysterothylacium sp., Anisakis simplex, A. pegreffii) and Hysterothylacium sp. was the high occurrence of anisakid worms in the host. Hysterothylacium sp. was shorter and thinner than A. simplex. Both of anisakids observed lip, mouth, nerve ring, excretory pore and excretory duct in the anterior portion. In the mid portion, anisakids had esophagus, ventriculus and intestine and especially, Hysterothylacium sp. had intestinal ceacum and ventricular appendage. There was conical nodulose apex at the end of the posterior portion in Hysterothylacium sp. and spine in A. simplex. SEM examination revealed that there was three lip near the mouth of Hysterothylacium sp. Dorsal lip was approximately 65 ${\mu}m$ and paried lateroventral lip were approximately 60 ${\mu}m$ in the width. All lips were found double papilla (approximately 8 ${\mu}m$ in the width). The body width of the Hysterothylacium sp. and A. simplex was approximately 480 ${\mu}m$ and 900 ${\mu}m$ respectively. The hight of the lateral alae was about 7 ${\mu}m$ and width of papilla on the cornical nodulose apex was about 3.3 ${\mu}m$ in Hysterothylacium sp. The hight of spine was approximately 20 ${\mu}m$ in A. simplex. There was mainly Hysterothylacium sp. in the intestinal lumen of the host. The nematod worms were parasitic near the mucosal fold and in the submucosal. In the mucosal epidermal layer, it was increased mucous cells by the infection of the parasites.

• Journal of fish pathology
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• v.25 no.3
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• pp.263-270
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• 2012

This study surveyed for the prevalence of parasites, bacteria and viruses in four fish species, olive flounder (Paralichthys olivaceus), red sea bream (Pagrus major), black sea bream (Acathopagrus schlegeli) and black rockfish (Sebastes schlegeli) in 2010. The survey was aimed to compare the pathogens detected from wild and cultured fish for an epidemiological study. Anisakis sp. was predominantly detected from wild olive flounder and red sea bream (58.6% and 41.7% respectively), but not from the cultured fishes, suggesting anisakid infection is rare in cultured fish. The wild fish get in contact with the anisakids through their prey such as small fishes or crustaceans which carry the anisakids; whereas the cultured fish are fed with formulated feed, free of anisakids. Bacterial detection rates from the wild fishes examined in the study were lower than those of cultured fishes. Vibrio sp. dominated among detected bacterial population in cultured olive flounder (18%). Since vibriosis is known as a secondary infection caused by other stressful factors such as parasitic infections, handling and chemical treatment, it seems that cultured olive flounder are exposed to stressful environment. Viruses diagnosed in the study showed difference in distribution between wild and cultured fishes; hirame rhabdovirus (HRV) (0.1%) and lymphocystis disease virus (LCDV) (3.9%) were detected in the cultured olive flounder, but not in the wild fish, and marine birnavirus (MBV) (1.7%) and red sea bream iridovirus (RSIV) (3.2%) were detected from the wild and cultured red sea bream, respectively. From the survey conducted, it can be concluded that even though some pathogens (Trichodina sp., Microcotyle sp., etc.) are detected from both the wild and cultured fish, pathogens such as Anisakis sp., Vibrio sp. and LCDV showed difference in distribution in the wild and cultured host of same fish species and this can be attributed to their environmental condition and feeding.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.137-142
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• 2000

Cultured juvenile black rockfish, Sebastes schiegeli as a seed for sen ranching project were compared with the similar size of wild fish. Wild fish were analyzed and compared with cultured fish in body indices, and moisture, crude protein, lipid, ash, many kinds of amino acids and various minerals in the whole-body of juvenile rockfish from three different populations. There were significant (P<0.05) differences in the moisture, crude lipid, and ash in the whole-body of fish among three different populations; the moisture content of wild fish was higher than that of both cultured fish. The lipid content in wild and tank cultured fish was lowest and highest, respectively; The lipid content of fish cultured in embanked system was intermediate values. The condition factor (CE), hepatosomatic index (HSI), and intraperitoneal fat (IPE) of fish cultured in tank system and embanked system were significantly (P<0.05) higher than those of wild fish. But fish cultured in tank system produced similar intestinosomatic index (ISI) and muscle ratio (MR) values as the wild fish. There were significant differences in asparatic acid, glutamic acid, isoleucine, leucine, lysine, phenylalanine, threonine, valine of whole-body fish cultured by different methods; the wild fish was highest in these amino acids, followed by fish cultured in embanked system and then fish cultured in tank system. There were also significant differences in Ca, P, Mg, Mn, Zn of whole-body fish cultured by different methods: wild fish and fish cultured in tank system produced highest in Ca, P, Mg, Zn and lowest in Mn, respectively. There were significant differences in moisture, crude lipid, ash, many kinds of amino acids, several minerals, CE, HSI, UE, and ISI among the three juvenile populations; whole-body of wild fish showed higher in moisture, ash, asparatic acid, glutamic acid, isoleucine, leucine, Iysine, phenylalanine, threonine, valine, Ca, P, Mg, and Zn than fish cultured in embanked system, while they showed lower in the rest of the nutritious parameters studied.

• Journal of Food Hygiene and Safety
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• v.17 no.4
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• pp.193-200
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• 2002

Three species of fish such as yellow tail (Seriola quinqueradiata), bastard halibut (Paralichthys olivaceus) and black rockfish (Sebastes schlegeli) were exposed to the dinoflagellate, Cochlodinium polykrikoides, and quality changes of fish after death were investigated during the extended storage. The volatile basic nitrogen (VBN) and aerobic plate counts (APC) were determined in the muscles of fish, arid organoleptic change was evaluated in the kills, skins and muscles. APC in all the fish species did not change in 6 hours of storage, but increased gradually thereafter. VBN contents in the muscles continuously increased throughout the storage of fish. Slightly higher levels of APC and VBN were observed in the tested fish than control fish, which had been exposed to air until died and stored in seawater without treating C. polykrikoides. After 12 hours of storage, APC and VBN contents in the muscles did not exceed the initial spoilage limit, 10$^{5}$ CFU/g fur APC and 30 mg/100 g for VBN, in all of the fish including control fish. Organoleptic change in fish treated with C. polykrikoides did not greatly differ from the control fish. After 8 hours of storage, distinctive deterioration of muscle was detected organoleptically in the treated fish and the control fish. The compiled result indicated that moribund fish exposed to C. polykrikoides bloom should be handled properly in 6 hours of storage after death of fish.

• Journal of fish pathology
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• v.19 no.3
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• pp.207-214
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• 2006

Diagnostic monitoring in fish farms with land-based tanks and net cases was conducted in eastern, western, southern and Jeju island of Korea for the summer period from 2000 to 2006. Total 3,518-fish samples of marine and freshwater fishes in 25 fish species were tested for pathogens. Fish species tested were olive flounder (Paralichthys olivaceus), fleshy prawn (Fenneropenaeus chinensis Osbeck), black rockfish (Sebastes schlegeli), rock bream (Oplegnathus fasciatus), red sea bream (Pagrus major), black seabream (Acanthopagrus schlegeli), sea bass (Lateolabrax japinicus), gray mullet (Mugil cephalus), rainbow trout (Onchorhynchus mykiss) and others. The infection rates by bacterial pathogens in the years of 2000, 2001, 2002, 2003, 2004, 2005 and 2006 were 22.4%, 34.5%, 14.1%, 15.3%, 17.7%, 13.5% and 5%, respectively. The infection rates by parasitic pathogens were 20%, 33.8%, 12.4%, 14.1%, 9.2%, 10.5% and 10.7%, respectively. The infection rates by viral pathogens were 22.4%, 13.5%, 10.3%, 5.4%, 9.7%, 10.2% and 15.8%, respectively. The infection rates by mixed pathogens were 10.3%, 0%, 44.9%, 50.9%, 31.9%, 38.4% and 39.6%, respectively. The rates of mixed infections were very low until 2001. The rates were higher than those of singer infections from 2002 to 2006. During the diagnostic monitoring from 2000 to 2006, the main bacterial pathogens were Vibrio (41.2%) and Streptococcus (28.8%). The infection rate by protozoa (85.7%) mainly including Scuticociliates and Trichodina was highest. The infection rate by viral necrosis virus (VNNV, 42.2%) was the highest of the viral pathogens.

• Journal of fish pathology
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• v.20 no.3
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• pp.237-247
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• 2007

In 1999, Vibrio harveyi infection occurred among cultured marine finfishes including olive flounder (Paralichthys olivaceus), black rockfish (Sebastes schlegeli), and turbot (Scophtalmus maximus) in the province of Gyeongsang, Korea. We examined the various microbiological characteristics of this V. harveyi strains. V. harveyi was grown well in the 3% NaCl at 30℃. The swarming activity appeared to be an one of the characteristic properties of the V. harveyi was the highest in the 2% NaCl concentration at TSA medium. These cells were elongated and had the several lateral flagella which is not waved and shorter than polar flagella. It was not luminescent in the all isolated strains. Whole cell of the V. harveyi had a major protein of 50 kDa and presented various band around of 40 kDa in strains.

• Fisheries and Aquatic Sciences
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• v.7 no.2
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• pp.58-63
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• 2004

Five urease-positive Vibrio parahaemolyticus strains were isolated from Kamak Bay in Yeosu in 2002 and 2003. V. parahaemolyticus YKB4 and YKB14 were isolated from seawater, YFB20 from black rockfish (Sebastes schlegeli), and YFO2l and YFO22 from olive flounder (Paralichthys olivaceus). The five urease-positive strains (YKB4, YKB14, YFB20, YFO21, and YFO22) did not show hemolysin and protease activity, while they did alter in color (to red) as the bacteria grew in the urea broth medium. All samples showed identical biochemical characteristics as a reference strain, V. parahaemolyticus KCTC2471, except in urease production. The five urease-positive strains showed urease activities at a mid stationary phase, and their activity was maximal in the late stationary phase of their culture supernatant. The addition of urea to the Luria-Bertani (LB) broth medium significantly affected the initial production of urease of V. parahaemolyticus isolates. Mortality by urease-positive V. parahaemolyticus YKB4, YKB14, YFO2l, and YFO22 was significantly high, being$60-80\%$, while YFB20 only reflected a rate of $20\%$. Protease-positive V. parahaemolyticus FM39 and FM50 showed a $40\%$ and $60\%$ mortality rate, respectively. However, hemolysin-positive V. parahaemolyticus had no mortality, like the non-pathogenic V. parahaemolyticus KCTC2471, while V. vulnificus resulted in a $40\%$ mortality rate. Injection with urease-positive V. parahaemolyticus strains showed mortality within 12 hrs in mice, and the strains could be isolated from the dead mice.

• Journal of Aquaculture
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• v.8 no.2
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• pp.117-131
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• 1995

In order to improve the present running seawater system for seedling production of marine fishes, rearing experiments with the juveniles of black seabream (Acanthopagrus schlegeli) and oblong rockfish (Sebastes oblongus) were conducted. The recirculating seawater system (F) equipped with the rotating biological contactors and the running seawater system (R) were used. Environmental factors, growth, survival rate and rearing density of the fish were compared between two systems during the experimental period. In the rearing experiment of black seabream, water temperature in F was fluctuated with surrounding air temperature and was higher than that in R. Specific gravity of the rearing seawater in F was relatively stable in the range of 1.0252 to 1.0266, while that in R was greatly fluctuated. pH in F turned out to be 7.51, but pH in R was similar to that in the natural seawater. Dissolved nitrite and nitrate in F were higher than those in R. While no significant differences in the growth of black seabream juveniles were recognized between two systems, survival rates of fishes in F were higher than those of fishes in R. In the rearing experiment of oblong rockfish, water temperature in F was higher than that in R. Specific gravity in F was slightly higher than that in R which showed relatively less fluctuation in the range of 1.0253 to 1.0270. pH in F turned out to be 7.96, but pH in R was similar to that in the natural seawater. Dissolved nitrite and nitrate in F were higher than those in R, but ammonia was lower in F. The juveniles of oblong rockfish reared in F grew significantly faster in their total length and body weight than those in R (P<0.05). However, survival rates of fishes between two systems showed no significant differences.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.4
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• pp.181-195
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• 2005

To study the effects of aquaculture activity of marine cage fish farms on marine environment, field researches including hydrography, sediment, benthos and trap experiment at the marine cage fish farms(Site A) around estuaries of Tongyeong city were carried out during June $26\~27$, 2003. A simulation using numerical model-DEPOMOD was conducted to predict the solid deposition from fish cage and to assess the probable solid deposition, and the efficiency of environmental management of marine cage fish farms was studied. The marine cage fish farms cultured mainly common sea bass (Lateolabrax japonicus), red seabream (Pagrus major), striped breakperch (Oplegnathus fasciatus) and black rockfish(Sebastes schlegeli), and total amount of cultured fish of the Site A were 23.1MT. The amount of husbandry fish by unit area(and volume) of the fish cage was $43.0kg\;m^{-2}(6.1kg\;m^{-3})$. The daily mean amounts of food fed by unit biomass and cage area were $30.8g\;kg^{-1}day^{-1},\;1.32kg\;m^{-2}day^{-1},$ respectively, at the Site A. The concentration of ORP of the sediment below the center at the Site A was -334.6 mV and the concentrations of AVS, COD, Carbon and Nitrogen were $0.43mg\;g^{-1}dry,\;17.75mg\;g^{-1}dry,\;10.19mg\;g^{-1}dry\;and\;3.49mg\;g^{-1}dry$, respectively. Capitella capitata was dominant benthic species which occupied $57.8\%$ of total species, and the Infaunal Trophical Index(ITI) was marked below 20 within 20 m distance from the edge of the Site A. The result of trap experiment, the solid deposition from the Site A was $34,485g\;m^{-2}yr^{-1}$ at 0 m from the center of the cage and $18,915g\;m^{-2}yr^{-1}$ at 42 m. From a model simulation, it was estimated that using a model simulation, the proportion of unfed food was $40\%$ at the Site A and the annual total amount of solid deposition was 63,401 accounting for $24.4\%$ of the annual total food fed at the Site A. The area solid deposition settled was estimated to be $8,450m^2$, which was about 16 times of the total area of fish cage at the Site A. And concerning ITI and abundance of benthos, the model predicted that sustainable solid flux at the Site A was below $10,000gm^{-2}yr^{-1}$. The percentage of food wasted was main element of solid deposition at the marine cage fish farms, and for minimizing solid deposition it is necessary to increase the efficiency of the food uptake. Based on the result of the model simulation, if the percentage of food wasted decreases to $10\%$ from the current $40\%$, then the solid deposition could decrease to a half. In addition, it was predicted that if farmers use EP pellets as food fed instead of MP and fish trash, solid deposition could decrease by $57\%$. Also this study proposes that the cage facility ratio of the licensed area be decreased to less than $5\%$ to minimize the sediment pollution.