• Journal of fish pathology
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• v.20 no.2
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• pp.161-167
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• 2007

Acute toxicity of formalin (37% formaldehyde) was conducted to determine the median lethal concentration (LC50) on eel (avarage weight 96 ± 3.6 g, average total length 43 cm), Anguilla japonica at concentrations ranging from 0 to 500 ppm. In particular, this study was designed to estimate the safety concentrations of formalin in testing eels to eradicate Pseudodactylogyrus. All fish died after 10 hours and 24 hours at 500 ppm and 400 ppm, respectively. After 24 hours, cumulative mortality was 96.6% and 13.3% at 300 ppm and 200 ppm formalin, respectively. However, all experimental fish were alive after 24 hours at 100 ppm. The lethal concentration values were computed by using non-linear least square method. At the start of the test, water temperature, pH and dissolved oxygen level were 27～28℃, 7.4 and 5.55 ppm, respectively. The 24 hr-LC50 were 269 ppm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.115-118
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• 2000

The production of cultured coho salmon (Oncorhpchus kisutoh) in Korea has being increased year after year. Smolt being reared in freshwater suffer transferring into seawater and are farmed in cages for fattening. This handling processes including transportation, confinement into cages are unavoidable stress to fish in salmon farming and often end up to mass mortality, This study aimed to investigate the impact of handling process on the stress responses of coho salmon. The indicator of stress was measured by cortisol to be a first response, and for the second response test, glucose, triBlyceride, cholesterol, lactate and electrolyte of $K^+, Na^+, Cl^-$ in serum and the activities of alanine aminotrtnferase (ALT), aspartate aminotransferase(AST) and lactate dehydrogenase (LDH) were analyzed. As a result, the concentration of cortisol, glucose as well as LDH activity were significantly increased, whereas others showed no difference comparing with control group. It obviously demonstrated that handling process made fish stressful.

• Journal of Aquaculture
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• v.11 no.2
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• pp.167-172
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• 1998

Rhynchocypris oxycephalus was incised through the midlateral line between the dorsal and pectoral fins and the wounds were closed with absorbable synthetic suture, and here we describe histological details on the nature of second-intention wound healing, rate of healing, and the nature of granulation tissue contraction. Postoperative survivals were 95% and 99%, compared to 100% for counterpart control fish, among fish at just and 7 days after surgery, respectively. By 14~42 days after surgery, fish had no mortality. The granulation tissue was epithelialized from day 7 through day 22 postsurgery. By 28 days postsurgery, the granulation tissue had contracted the wound margins into apposition. By 35~42 days postsurgery, the granulatin tissue contained collagen fiber and the epidermis contained well-differentiated alarm substance cells ; thus, the epidermis over the wound site was histologically normal in most fish, showed that wound healing was essentially complete within 35 days of surgery.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.582-588
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• 2013

The impact of global warming on aquatic systems has been a priority research area in the past decade. However, the possibility that increased temperatures will cause shifts in viral disease outbreaks has not been well addressed. In the present study, with increasing water temperature (WT) in the coastal area of Korea, we estimated the possibility of changes in fish viral diseases. From the present time, WT may rise between 0.62 and $1.7^{\circ}C$ by 2050, and the effect on aquaculture could be more adverse than benefitial. Red seabream iridovirus disease (RSIVD) and viral nervous necrosis (VNN) cause high mortality above 22 and $24^{\circ}C$, respectively, and outbreaks could commence earlier and persist for prolonged periods. Nevertheless, the period of occurrence of viral hemorrhagic septicemia (VHS), which outbreaks at a lower WT (< $18^{\circ}C$), could be shorter than the current infectious period. Thermal stress in fish causes reductions in growth and immunocompetence; thus, increases in summer WT can lead to the development of new viral diseases. WT has a strong influence on fish population dynamics; therefore, entry of new viruses and changes in the prevalence of infection can be expected if carrier fishes are introduced or migrate to Korean waters.

• Journal of fish pathology
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• v.26 no.1
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• pp.1-9
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• 2013

The acute toxicity and sublethal effects of nitrite on the dark-banded rockfish, Sebastes inermis (mean body weight: $83.3{\pm}7.2$ g), were studied under static conditions for a period of 96 h. The acute toxicity of nitrite was at the 50% lethal concentration ($LC_{50}$) of 700 mg/L. The sublethal effects on selected hematological parameters of the dark-banded rockfish, such as its osmolality, hematocrit, cortisol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), were measured after 0, 6, 12, 24, 48, 72, and 96 h of exposure to 0, 50, 100, 200, 400, or 700 mg/L nitrite. Sublethal nitrite caused a progressive reduction in the hematocrit of the fish, depending on the nitrite concentration and the exposure period. Exposure to 100-700 mg/L nitrite for 96 h caused a reduction in the hematocrit and an increase in cortisol, ALT, and AST compared with the control levels. Abnormal ultrastructural changes in the gills and liver tissues were observed in fish exposed to 700 mg/L nitrite for up to 96 h compared with the control tissues. Ultrastructural changes included atrophic gill mitochondria and hepatocytes that developed smooth endoplasmic reticulum and atrophic mitochondria. Although no rockfish mortality occurred at 500 mg/L nitrite, all the hematological parameters examined responded adversely to a nitrite dose of 200 mg/L for 96 h. These results show that although the acute toxic concentration of nitrite for the dark-banded rockfish is > 700 mg/L, sublethal concentrations of nitrite also negatively affect its hematological parameters.

• Journal of fish pathology
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• v.13 no.1
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• pp.7-13
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• 2000

Beginning in the summer of 1993, a serious mortality among cultured penaeid shrimp occurred in the western sea of Korea. The typical sign of this disease was white spots inside the surface of the carapace. Cytopathic effect (CPE) were not observed by virus in CHSE-214, RTG-2, but not by pH 11. A nonoccluded rod-shaped form virus was observed by electron microscopy in the lymphoid organ. The virion was bacilliform virus and sourrounded by a virion envelope. Its virion protein was found to be similar to hypodermal and hematopoietic necrosis virus (HHNBV) by analysis of virion proteins in SDS-PAGE. The genome of virus is double stranded DNA molecule whose full length was about 114kb. It was similar to penaeus acute viremia (PAV) of Japan.

• Journal of fish pathology
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• v.3 no.1
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• pp.11-19
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• 1990

Yellow tail (Seriola quinqueradiata) infected by Pasteurella piscicida have been occurred to mass mortality without showing apparent surface lesions in cage culture farms. In this case, it is necessary to consider countermeasure by rapid diagnosis of infected fish. The purpose of the present study was to investigate usefulness of the direct fluorescent antibody technique(FAT) for rapid diagnosis of pseudotuberclosis of cultured yellowtail caused by P. piscicida. Antibody produced by inoculating rabbit with formalin killed pseudotuberclosis bacteria antigen(strain KNP-2). Immunoglobulin-G(IgG) was purified from antisera by DEAE-cellulose column chromatography and conjugate with fluorescein isothiocyanate. Fluorescein-labeled antisera was purified by sephadex G-25 gel column chromatography. The fluorescein/protein molar ratio of labeled antisera was determined as 8.8-9.5. Diagnosis of cultured yellowtail was examined in cage culture farms which located in Tongyung, kyungnam from July to October 1990. The causative bacteria of pseudotuberclosis could be detected within two hours after the specimens were transferred to the laboratory for FAT, and it showed that FAT could be adapted as a rapid and accurate diagnostic method of pseudotuberclosis in yellowtail.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.411-419
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• 2018

This study investigated the survival rates and physiological responses of Korean rockfish, Sebastes schlegeli, in live fish containers ($8^{\circ}C$, 33 psu) for 18 days. The survival rate was 99% and 97% in the control and experimental groups, respectively. Hematocrit and hemoglobin did not differ significantly between the control and experimental groups. Glucose and cortisol rose immediately on the first day of containment, but both gradually normalized. Aspartate aminotransferase and alanine aminotransferase did not differ significantly between the two groups after recovery. $NH_3$ continued to rise after the first day, but decreased to a level not significantly different from that of the control group during the recovery period. Plasma ions and osmolality did not change abnormally. The hemocyte population was not significantly different from that of the control. The ratios of apoptotic and necrotic cells indicated no specific variation in hemocyte viability. The histological changes in the skin and gills were not significantly different from those seen in the control. The experimental data obtained in this study suggest that live fish containers may be used to transport Korean rockfish without significantly affecting their physiology or survival.

• Journal of fish pathology
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• v.12 no.1
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• pp.56-62
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• 1999

Since 1998, mass mortality of the Japanese flounder has widely occurred in the south and west coastal area of Korea. A new serotype birnavirus was isolated during the investigation of the cause of the disease. By the electromicroscopic examination, the isolated virus particles appeared hexagonal and unenveloped with an average diameter 52 to 56 nm. Birnavirus specific fragment was amplified by RT-PCR. High yield of virus (10.3 to 10.8 log $TCID_{50}/ml$) was produced in CHSE-214. RTG-2 and RTE-2 cells. Typical birnavirus CPE was observed in these cells. On the contrary, the virus CPE was not shown in the FHM and EPC cells. By a cross-neutralization test with IPNV Ab, IPNV Sp, IPNV VR-299 and MBV Y6, the isolated virus was closely related to marine birnavirus (MBV).

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.731-737
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• 2016

To understand the characteristics and strength of the cold water that has caused damage to marine-culturing farms around Guryongpo, in the southwestern part of Korea, surface and water column temperatures were collected from temperature loggers deployed at a sea squirt farm during August-November 2007 and from a Real-time Information System for Aquaculture environment operated by NIFS (National Institute of Fisheries Science) during July-August 2015 and 2016. During the study period, surface temperature at Guryongpo decreased sharply when south/southwestern winds prevailed (the 18-26th of August and 20-22nd of September 2007 and the 13-15th of July 2015) as a result of upwelling. However, the deep-water (20-30m) temperature increased during periods of strong north/northeasterly winds (the 5-7th and 16-18th of September 2007) as a result of downwelling. Among the cold water events that occurred at Guryongpo, the mass death of cultured fish followed strong cold water events (surface temperatures below $10^{\circ}C$) that were caused by more than two days of successive south/southeastern winds with maximum speeds higher than 5 m/s. A Cold Water Index (CWI) was defined and calculated using maximum wind speed and direction as measured daily at Pohang Meteorological Observatory. When the average CWI over two days ($CWI_{2d}$) was higher than 100, mass fish mortality occurred. The four-day average CWI ($CWI_{4d}$) showed a high negative correlation with surface temperature from July-August in the Guryongpo area ($R^2=0.5$), suggesting that CWI is a good index for predicting strong cold water events and massive mortality. In October 2007, the sea temperature at a depth of 30 m showed a high fluctuation that ranged from $7-23^{\circ}C$, with frequency and spectrum coinciding with tidal levels at Ulsan, affected by the North Korean Cold Current. If temperature variations at the depth of fish cages also regularly fluctuate within this range, damage may be caused to the Guryongpo fish industry. More studies are needed to focus on this phenomenon.