• Journal of Marine Life Science
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• v.1 no.2
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• pp.117-120
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• 2016

The success or failure of aquaculture heavily depends on how effectively to manage aquatic animal diseases. The paper is to estimate the direct effects of economic benefits on aquatic animal disease prevention program using economic surplus analysis. The economic benefits include changes in consumer and producer surplus owing to a reduction effect of aquatic animal mortality and the consumption recovery effect. The annual changes in producer surplus for flounder, rockfish and others cultured is estimated as 2.33 billion won totally (0.87 billion won, 1.01 billion won and 0.45 billion won respectively) and the annual changes in consumer surplus 10.15 billion won totally (6.36 billion won, 1.85 billion won and 1.94 billion won respectively). Therefore, total annual economic benefit is 12.5 billion won.

• Journal of fish pathology
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• v.33 no.1
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• pp.55-62
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• 2020

In order to search candidates for the treatment of myxosporean emaciation disease of olive flounder, Paralichthys olivaceus, in vitro and in vivo experiments were conducted using products such as Coxi-stop, Coxiclin, and BLEAN80. In the case of Coxi-stop, whose major component is toltrazuril, in vitro experiment using BF-2 cells showed a tendency of reducing the activity of myxosporea and did not exhibit cytotoxicity such as cell lysis. In the in vivo activity measurements, the experimental group immersed with Coxi-stop showed a lower cumulative mortality rate than the control group, this result is similar to the previous report that toltrazuril has a therapeutic effect on parasitic fish disease. This study suggests that toltrazuril is a potential candidate for the treatment of emaciation disease of olive flounder.

• Journal of fish pathology
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• v.8 no.2
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• pp.99-109
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• 1995

The diseased larvae of the flounder, Paralichthys olivaceus, were sampled several times from a fish hatchery located in Cheju Island between December, 1991 and April, 1992. They turned out to be infected with Vibrio sp. and diagnosed as intestinal necrosis of flounder larvae(INFL) based on morphological, biological, and biochemical examinations. INFL was known to be caused by the live food organism infected with Vibrio sp. The optimal growth conditions of the isolates for temperature, pH, and NaCl concentration were $20\sim30^{\circ}C$, 6~8, and 2~4%, respectively. In the drug sensitivity test, the isolates were sensitive to oxytetracycline, nalidixic acid, kanamycin, and novobiocin, but resistant to ampicillin, erythromycin, spiramycin and sulfa-drug.

• Journal of fish pathology
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• v.34 no.1
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• pp.31-38
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• 2021

The objective of this study was to determine comparative biochemical characteristics and RAPD (random amplified polymorphic DNA) profiles of 18 strains of Edwardsiella tarda isolated from cultured olive flounder (Paralichthys olivaceus) and eel (Anguilla spp) that showed diseases between 1996 and 2010 in Korea. In terms of biochemical properties, they showed four patterns with differences in citrate degradation and production of H₂S and indole. All strains were identified as E. tarda. Characteristics of isolates were not classified according to their host. As a result of PCR with E. tarda-specific primer, EDtT, the same band of about 270 bp was detected in all 18 isolates. However, no specific band was detected in type strains of E. tarda or Edwardsiella ictaluri. As a result of RAPD PCR performed with primer No. 5 and No. 6 of a Ready-To-Go-RAPD kit, the band profile showed clear differences among isolates of olive flounder, isolates of eel, and E. tarda and E. ictaluri type strains. It was possible to organize their characteristics according to the origin of host with possibility to develop tools for pathogen monitoring.

• Journal of fish pathology
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• v.33 no.1
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• pp.7-14
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• 2020

A disease that manifested severe anemia of the gills occurred in the olive flounder (Paralichthys olivaceus), which was cultured for 5-6 months with a recirculation water system in the laboratory. Microscopic observations showed immature parasite in the gills and mature adults in the oral cavity. The matured parasite was 5.60-9.32 (7.42) mm in total length, with 4 pairs of clamps on the pedunculated haptor, which was separated from the body proper by a long isthmus. From the morphological observations of the larvae, it was identified as Neoheterobothirum hirame belonging to the monogenea. The average hematocrite of infected fish was 10.3 ± 2.8%, significantly lower than that of normal flounder 31.4 ± 4.2%. Histopathologically, fish infected with N. hirame exhibited reduced numbers of erythrocytes in blood vessels of the gill filament and lamellae, reduced red pulp area of the spleen, and hepatocyte atrophy. From the above results, the cause of severe anemia in olive flounder was identified as N. hirame infection. This study shows an example where the growth of pathogens can be a problem in the recirculation system due to low water exchange rate.

• Korean Journal of Ichthyology
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• v.18 no.4
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• pp.283-292
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• 2006

Expressed sequence tag (EST) analysis was conducted using a complementary DNA (cDNA) library made from the kidney mRNA of olive flounder (Paralichthys olivaceus). In the survey of 390 ESTs chosen from the kidney cDNA library, 250 ESTs showed significant homology to previously described genes while 140 ESTs were unidentified or novel. Comparative analysis of the 250 identified ESTs showed that 14 (5.6%) clones were representing 11 unique genes identified as homologous to the previously reported olive flounder ESTs, 198 (79.2%) clones representing 160 unique genes were identified as orthologs of known genes from other organisms, and orthologs were established for 38 (15.2%) clones representing 37 genes of known sequences with unknown functions. We also identified several kinds of immune associated proteins, indicating EST as a powerful method for identifying immunerelated genes of fish as well as identifying novel genes. Further studies using cDNA microarrays are needed to identify the differentially expressed transcripts after disease infection.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.2
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• pp.236-243
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• 2004

Antimicrobial effect of chitosan and its oligosaccharides was examined on Vibrios sp., Edwardsiella tarda and Streptococcus sp., which are major pathogenic bacteria inducing bacterial diseases of acquacultured flounder. Chitosan oligosaccharides (COS ) were produced by enzymatic hydrolysis of chitosan in an ultrafiltration mombrane bioreactor system which was established with three membranes with different molecular weight cut-off (MWCO) 1,000, 5,000 and 10,000, and fractionated into three kinds of COS, based on their molecular weight sizes. The three kinds of COS were as follows : relatively high molecular weight COS [HMW-COS, molecular weight distribution of 7,000 to 24,000 Da〕, medium molecular weight COS 〔MMW-COS, 1,500 to 6,000 Da〕, and low molecular weight COS 〔LMW-COS, 1,000 to 1,500 Da). Chitosan and HMW-COS effectively inhibited the growths of Vibrio sp. and Streptococcus sp. and their antimicrobial activities were superior to the others with smaller molecular weights. This result suggested that antimicrobial effect of chitosan preparations extremely depend on their molecular weight sizes. Antimicrobial effect of chitosan and HMW-COS on E. tarda was improved by longer inoculation times. Scanning electron microscopy in morphological change of E. tarda treated with chitosan preparations showed that chitosan and HMW-COS bound to the cells and suppressed the growth of the cells. This observation appears to prove the fact that positive charged amines of chitosan electrostatically bind to negative charged compounds of cell walls.

• Journal of fish pathology
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• v.22 no.3
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• pp.275-282
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• 2009

In this study, effect of mating group, mating dam and mating sire was analyzed using olive flounder Paralichthys olivaceus challenged with Edwardsiella tarda. A challenge test was conducted using 1,708 olive flounder fingerlings obtained through $4{\times}4$ factorial cross from parents selected based on resistant degree. Regarding the means of resistant index, survival rate and days of survival by each mating group, the group(RR) produced by mating among resistant parents were 17.98, 13.77%, and 18.36 days, respectively; the group(SS) produced by mating among susceptible parents were 12.46, 2.71%, and 12.40 days, respectively. This study gives an indication that challenge test results may be successfully used as selection criteria for disease resistance to E. tarda in olive flounder, P. olivaceus.

• Journal of fish pathology
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• v.22 no.1
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• pp.53-65
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• 2009

Tenacibaculum maritimum (formerly Flexibacter maritimus) is the aetiological agent of an ulcerative and necrotic disease commonly called tenacibaculosis in marine fish. Tenacibaculosis is an economically important disease in a great variety species in Jeju Island cultured fish and leading to this pathogen initially affected by skin, mouth, fins, tail causing severe necrotic and ulcerative lesions on the body surface. In the present study, A-7 strain was isolated from Paralichthys olivaceus showing symptoms of tenacibaculosis and identified as T. maritimum by morphological, biochemical and molecular biological analysis. T. maritimum A-7 is experimentally infected through immersion route in Paralichthys olivaceus which the disease outbreaks in land-based fish tanks of Jeju Island. Up to data a number of treatments proposed for the tenacibaculosis outbreaks are based on the immersion administration of drugs in tank. Oxytetracycline is the most widely used disinfectants in fish farms. However, most of fish farms manager and consumers have expressed concern as bioaccumulation in tissue and its environmental. In addition, this antimicrobial compounds is expensive in fish farmers. The overcome of this problem is desired the application of natural plant derived products. To obtain as 70% EtOH extract antimicrobial compounds against tenacibaculosis from 35 species of Jeju Island native plants were screened for antimicrobial activity against T. maritimum. In the present study were identified most of the plant extracts were better antimicrobial activity against T. maritimum.

• Journal of fish pathology
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• v.20 no.1
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• pp.61-70
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• 2007

The epidemiological study was performed to survey the prevalence of bacterial disease of cultured olive flounder, Paralichthys olivaceus from October, 2004 to August, 2006 in Korea. A total of 1,271 of fish samples were collected at random includes fish exhibiting clinical signs of the disease in question. The total 331 samples among 738 cases of infectious diseases were infected with 366 bacteria isolates including Vibrio spp. (42.1%), Streptococcus spp. (16.9%), Edwardsiella tarda (12.3%), Photobacterium damselae subsp. damselae (8.2%), Pseudomonas spp. (2.2%) or others (18.3%). Vibrio spp. and P. damselae subsp. damselae were continually isolated through all seasons but Streptococcus spp. and E. tarda were mainly isolated from May to November. The 206 cases were showed mixed infection with other bacteria (3.6%), parasites (31.4%) or virus (41.7%); Vibrio spp. (n=21), Streptococcus spp. (n=13), Trichodina (n=76), Scutica (n=31), VNNV (n=112), VHSV (n=46).