• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.624-629
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• 2017

A rainbow trout Onchorhynchus mykiss farm located in Gangwon province, South Korea, experienced approximately 10% mortality in June 2017. Most diseased fish had a markedly distended, gas-filled stomach, and exhibited abnormal behavior at the water surface. In this study, we attempted to identify the cause of stomach distension syndrome in those rainbow trout. The stomach of most of the affected fish were full of unidentified gases and some exudate, and yeast was isolated from the stomach mucosa. Pure cultures of yeast were identified using a multilocus sequence typing scheme based on 18S rRNA, internal transcribed spacers, large subunit rRNA, and the gene encoding the largest subunit of RNA polymerase II (RPB1). The RPB1 gene sequences were compared with those of related species available in a database. The yeast was identified as Scheffersomyces coipomoensis (Candida coipomoensis) based on sequence analyses. This is the first study to reveal that Sch. coipomoensis is a potential causative agent of stomach distension syndrome in farmed rainbow trout. Our results will be helpful for future related studies, and indicate that farmers and stakeholders should observe this emerging disease closely.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.6
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• pp.910-916
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• 2022

The purpose of this study is to evaluate the effect of underwater non-thermal dielectric barrier discharge plasma (DBD plasma) on the sterilization of three types of pathogenic bacteria that cause diseases in freshwater fish and the reduction of a tetracycline antibiotics. This experiment was conducted in the DBD plasma generator, and the voltages used to generate plasma were 11.6 kV and 23.1 kV. The measurement intervals were 0, 1, 5, 10 and 15 min. As a result of DBD plasma treatment, Aeromonas hydrophila, Edwardsiella tarda and Pseudomonas fluorescens were removed 93-99% after 5 min at 23.1 kV, and the tetracycline antibiotics were reduced 70-95% after 15 min at 23.1 kV. In this study, as a result of treating the effluent with DBD plasma at a fish farm where the medicinal bath was conducted with oxytetracycline-HCl (OTC-HCl) products, OTC-HCl decreased by 62% after 10 min at 23.1 kV.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.716-720
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• 2023

This study was designed to analyze the effects of reducing water turnover in olive flounder Paralichthys olivaceus farms, focusing on olive flounder growth, decreasing electricity costs, and developing measures to ensure business stability. Daily water turnover was set at 18 in the control group and six in the experimental group. Juvenile fish were reared for 12 months. No significant differences in mean weight were observed between groups until five months. After five months, the mean weight of the control group grew significantly faster than that of the experimental group. Maintaining water turnovers leverl at six turnovers for the first five months after stocking juvenile fish and then increasing water turnover resulted in a 34.4% reduction in electricity costs compared to the control group. This approach presents a potential method to enhance the profitability of olive flounder farms and ensure stable productivity and profitability without sacrificing olive flounder growth.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.369-376
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• 2021

In Korea, fish is a major food source, and sustainable production of fish is critical for the aquaculture industry. Recently, infectious diseases have become an unavoidable problem in aquaculture and have caused serious economic losses. Therefore, there is an urgent need to overcome this challenge to increase productivity in aquaculture. Vaccination is the most effective and long-term measure for improving the management of a fish farm. Sales of fish vaccines in Korea have been steadily increasing, with a confirmed increase from 600 million won in 2007 to 3.4 billion won in 2018. As of 2021, 30 licensed fish vaccines, including both single and combination vaccines containing more than two inactivated pathogens, have been approved in Korea for 10 fish pathogens. Twenty-eight of these are used in olive flounder Paralichthys olivaceus; however, only two vaccines are used in starry flounder Platichthys stellatus, red seabream Ragrus major and rock bream Oplegnathus fasciatus. Therefore, vaccine development is required not only for the olive flounder but also for other cultured fish species. The development of effective vaccines and vaccination programs for fish is a continuous requirement for a sustainable aquaculture industry.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.6
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• pp.379-384
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• 2005

A high-performance liquid chromatography assay method for oxolinic acid in fish products was developed, evaluated and validated through the monitoring of oxolinic acid based on farming and distribution. The recovery rate of the developed method was $102.3-106.7\%$ as compared to conventional methods. The stock solution was stable for 3 weeks under refrigerated condition at $4^{\circ}C$ The performance limit was evaluated as 0.01ppm of oxolinic acid in fish muscle. 478 fish samples such as olive flounder, genuine porgy, common sea bass and black rock fish collected from fish farms in the coastal area from September 2001 to October 2004 were analyzed to evaluate overall efficiency of the modified method and to monitor the actual condition of oxolinic acid usage in fish farm. According to the monitoring results, the modified method was suitable for analysis of oxolinic acid in fish muscle and oxolinic acid might be used in a small portion of fish farms. The suggested analysis method of oxolinic acid was registered in the Korean Official Methods of Food Analysis and is being utilized for fishery products by the Korea Food and Drug Adminstration and the National Fisheries Products Quality Inspection Service.

• Journal of fish pathology
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• v.23 no.2
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• pp.165-176
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• 2010

In May 2007, mass mortality of Israeli carp, Cyprinus carpio L., was occured on a pond farm located in Jeollabukdo Province, Korea. The mortality rates reached up to 2% of the total fish in the farm per day. Typical clinical signs were abdominal distension, reddish foci on the skin, enteritis, liver congestion and enlarged spleen and kidney. On the basis of biochemical characteristics and 16S rDNA sequence, the causative bacteria isolated from affected carp were identified as Aeromonas veronii. Histologically, degeneration of hepatocytes and congestion in sinusoids were observed in the liver. Spleen showed hemorrhage and the destruction of the sheathed tissues. In kidney, necrotized renal tubules and glomerular destructions were observed. Intestinal tissues revealed necrotized and severe hemorrhage. Mass hemorrhage was observed in muscles. This is the first report that A. veronii caused mortality in cultured Israeli carp in Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.6
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• pp.604-608
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• 2009

This study was conducted to evaluate extruded pellet (EP) diet compared with a raw fish moist pellet (MP) diet for flounder, Paralichthys olivaceus on field feeding experiments in Jeju area. The experimental EP diet (juvenile, growing and adult) was prepared based on the former studies on nutrient requirements and feed ingredient of flounder. Fish were distributed randomly to each aquarium as a group of 102,300 fish (initial mean weight 97 g) in field experiment I and reared randomly to each aquarium as a group of 40,000 fish (initial mean weight 120 g) in field experiment II. In field feeding experiment I conducted in commercial flounder farm, survival, wt. gain (94-1,090 g), feed efficiency and condition factor of fish fed experimental EP were comparable to those of fish fed MP, but considerably higher protein efficiency ratio were observed in fish fed experimental EP. In field feeding experiment II, no significant difference was observed in final mean weight of fish fed the experimental EP (1,234 g) and MP (1,286 g), and any noticeable problem caused by feeding the experimental EP was not found during the whole period of feeding trial. Survival of fish fed the experimental EP was lower than that of MP, and there was no significant difference in feed efficiency between the fish fed experimental EP and MP. Therefore, these results strongly suggest that diet EP could be developed to replace MP diet for the marketable size (1.3 kg) of production for flounder without adverse effects on growth performance. In particular, abdominal dropsy and reduction of condition factor, which are frequently occurred in commercial EP feeding farms, were not observed in flounder fed experimental EP.

• Journal of Life Science
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• v.9 no.3
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• pp.241-247
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• 1999

Antibiotics have been routinely used to control the disease of farm-raised animals in the aquaculture facilities without any criterion based on a pharmacokinetic study. This lack of information on the effective usage of antibiotics would have brought the farmers to use excessive and/or less dosages, causing the advent of drug-resistant bacteria as well as economic loss and possible contamination of the local farming area. Until recently, few studies on a detailed manual for the antibiotic usage including chemotherapy procedure, dosage, and treatment schedule of the aquatic antibiotics have been conducted throughout the world. To the worse, there is no available criterion for optimal usage of aquatic antibiotics to control diseases in aquatic farms in this country because every country has its own aquacultural system. Therefore, based on the previous studies on the usage of the various antibiotics, our studies are to focus on the development of optimal method for the detection of various antibiotics on the fate of antibiotics applied to the fish, including absorption, circulation, and secretion physiology. Pharmacokinetic study were to sep up the optimal detective condition against residual antibiotics of fish by HPLC. The grinding pefloxacin for 15 min is most effective in dissolution test and pharmacokinetic parameters. Pharmacokinetic parameters were satisfactory for 15 min-grinding products and they can be explained as one-compartment model.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.5
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• pp.324-329
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• 2008

Vibrio parahaemolyticus species, which cause acute gastroenteritis in humans, were isolated from farmed fish and seawater and their antimicrobial-resistance pattern and factor were investigated. They exhibited the highest resistance to ampicillin (88.9%), followed by trimethoprim (51.9%) and rifampin (22.2%). The relatively high resistance to trimethoprim was unexpected because trimethoprim was not commonly used in fish farming in Korea. R plasmid related resistance was identified by the treatment of novobiocin (7 ug/mL) and it was named as pVPBW1. A putative trimethoprim resistance gene in 2.0 kb fragment of pVPBW1 was also confirmed.

• Journal of fish pathology
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• v.36 no.2
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• pp.251-261
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• 2023

Photobacterium sp. YW2207 was isolated from rainbow trout raised in a fish farm located in Yeongwol-gun, Gangwon Province, South Korea. Based on 16S rRNA sequence analysis and phylogenetic analysis, it was confirmed that Photobacterium sp. YW2207 showed 100% similarity with Photobacterium piscicola and Photobacterium phosphoreum, and 94.6% similarity with P. damselae subsp. damselae. Biochemical analysis revealed that Photobacterium sp. YW2207 is a Gram-negative, motile bacterium with a cell size of 1.5~3×3~5 ㎛. The bacteria were cultured on nutrient agar, brain heart infusion agar, Muller-Hinton agar, tryptic soy agar, and thiosulfate citrate bile sucrose agar with NaCl concentrations ranging from 0 to 2.5%. The API50CHE and API20E tests indicated lower utilization capabilities compared to the P. damselae strains provided in the API database. Furthermore, unlike most Photobacterium species, Photobacterium sp. YW2207 presented negative for catalase test. Results from the flow cytometric measurement indicated that Photobacterium sp. YW2207 exhibited a more diverse distribution of cell sizes and had larger cell sizes compared with P. damselae subsp. damselae. Minimum inhibitory concentration tests showed that Photobacterium sp. YW2207 had low susceptibility to β-Lactam and aminoglycoside antibiotics, while having high susceptibility to tetracycline, doxycycline, and quinolone antibiotics. Pathogenicity on rainbow trout revealed that an immersion of 1×10⁵ CFU/ml did not cause mortality or clinical symptoms.