• Journal of fish pathology
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• v.24 no.2
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• pp.53-64
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• 2011

In quantitative studies of clinical signs, rock bream of adults and juveniles infected with Megalocytivirus IVS-1 isolated from rock bream (Oplegnathus fasciatus) in Korea showed average $4.49{\pm}1.13$ and $4.85{\pm}1.06$ of spleen index respectively. In challenge experiments, Megalocytivirus IVS-1 induced 100% cumulative mortality in both adult and juvenile rock bream. However we found 60% cumulative mortality in juvenile red sea bream (Pagrus major) even after 30 days of injection, which contradicted with the results of other laboratories. Interestingly, IVS-1 infected red sea bream of the same juvenile size with rock bream showed lower spleen index compared to that of rock bream. In real-time PCR, there was continuous increasing of the numbers of viral copies ($2.03{\times}10^7$ copies/mg) in the spleen of juvenile rock bream infected, which were different from those in adult rock bream showing plateau level after reaching to the peak level. Moreover, enlarged cell numbers in the infected spleen were also increased continuously in the juvenile but not in adult of rock bream, even decreased after reaching to peak level. Consequently, significant differences in clinical signs: cumulative mortality. spleen index and viral copy number were found between rock bream and red sea bream, but not between adult and juvenile rock bream. Certainly quantitative expression of clinical sign as in this study may be a way to compare the progression of megalocitiviral disease more accurately in different species or physiological conditions.

• Korean Journal of Ecology and Environment
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• v.46 no.3
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• pp.395-408
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• 2013

Environmental condition can induce changes in early life-history traits in order to maximise the ecological fitness. Here I investigated how temperature change and variation in human aquatic activity/behaviour affect early life-history consequences in fish using a dynamic-state-dependent model. In this study, I developed a general fish's life-history model including three life-history states depend-ing on foraging activity, such as body mass, mass of reproductive tissue (i.e., gonadal development) and accumulated stress (i.e., cellular or physiological damage). I assumed the level of foraging activity maximises reproductive success-ultimately, fitness. The model predicts that growth rate, development of reproductive tissues and damage accumulation are greater in higher temperature whereas higher human aquatic activity rapidly reduced the growth rate and development of reproductive tissue and increased damage accumulation. While higher foraging activity in higher temperature is less affected by human aquatic activity, the foraging activity in lower temperature rapidly declined with human aquatic activity. Moreover, lower survival rate in higher temperature or human aquatic activity was independent on mortality rate due to human aquatic activity or mortality rate when foraging activity, respectively. However, the survival rate in lower temperature or human aquatic activity was dependent on these mortality rates. My findings suggest that including of early life-history traits in relation to climate-change and human aquatic activity on the analysis may improve conservation plan and health assessment in aquatic ecosystem.

• Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.7.1-7.8
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• 2020

Background: To minimize the use of antibiotics and to obtain a more sustainable fish culture and aquaculture industry, development of alternative natural source of immunostimulant to replace antibiotic in aquafeed is highly needed. Objective: Dietary inclusion effect of yacon (YC), ginger (GG), and blueberry (BB) on growth, body composition, and disease resistance of black rockfish against Vibrio anguillarum was compared to ethoxyquin (EQ). Methods: Four hundred eighty juvenile (an initial weight of 4.2 g) fish were randomly distributed into 12 of 50 L flowthrough tanks (forty fish per tank). Four experimental diets were prepared; the control (Con) diet with 0.01% EQ inclusion, and YC, GG, and BB diets at 1% each additive inclusion. Each additive was included into the experimental diets at the expense of wheat flour. Each diet was assigned to triplicate tanks of fish and hand-fed to satiation twice daily for 8 weeks. At the end of 8-week feeding trial, 20 fish from each tank fish were artificially infected by intraperitoneal injection with 0.1 mL of culture suspension of pathogenic V. anguillarum containing 3.3 × 10⁶ cfu/mL respectively. Fish were monitored for the following 8 days after V. anguillarum infection and dead fish were removed every 6 h for the first 4 days and 12 h for the rest of the study. Results: Weight gain, specific growth rate (SGR), and feed efficiency ratio (FER) of fish fed the YC diet was higher than those of fish fed all other diets. However, feed consumption, protein efficiency ratio, and protein retention was not affected by dietary additive. Moisture, crude protein, and crude lipid content of the whole body of fish were affected by dietary additive. Analysis of the Kaplan-Meier survival curves showed that survival of fish fed the YC, BB, and GG diets was higher than the Con diet. Conclusion: Oral administration of YC can improve not only weight gain, SGR, and FER of black rockfish, but lower mortality of rockfish at occurrence of V. anguillarum.

• Journal of fish pathology
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• v.17 no.3
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• pp.213-216
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• 2004

To confirm the possibility of a wild marine crab, Gaetice depressus, as a carrier for white spot syndrome virus (WSSV) and to develop an alternative experimental model for WSSV in winter season, the susceptibility of the crab to WSSV was assessed by artificial challenge and subsequently tested for infection by PCR assay. The results revealed that the crabs were as highly susceptible as penaeid shrimps. WSSV caused 100% mortality in G. depressus within 16 days after intramuscular injection. The presence of WSSV in the moribund crabs was confirmed by PCR and was found in gills and muscle tissue. These results suggest that G. depressus can be naturally infected by WSSV via moribund shrimps, and can act as a potential carrier of WSSV. In addition, G. depressus can be used as an alternative experimental animal for WSSV.

• Journal of fish pathology
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• v.24 no.1
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• pp.19-27
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• 2011

The production of surf clam, Mactra veneriformis, an important fishery resource in Korea, has recently been decreasing. This study was carried out to examine effects of spawning on immune functions of this species. Total hemocyte count (THC), phenoloxidase (PO) activity, phagocytic activity, neutral red retention (NRR) time and antibacterial activity were assessed. Spawned clams showed reduction in THC, PO, phagocytic activity and NRR times compared with unspawned ones. While spawning event did not elicit any change of antibacterial activity in both spawned and unspawned ones. This study indicates that spawning process decreases immune functions in the surf clams which could cause mortality increment and yield reduction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.11 no.1
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• pp.1-3
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• 1978

When frozen sandeel Ammodytes personatus which had been stored for a long time, was given to yellowtail for 70 to 80 days, some mortality of the rearing fish began to appear. The liver of the diseased fish showed some yellowish brown discoloration and histopathological study revealed that fatty degeneration of the liver cells was obvious, and this degeneration was especially heavy around bile-duct. The cell nuclei showed atrophy.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.403-410
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• 2015

Viral nervous necrosis (VNN) is a serious disease of sevenband grouper Epinephelus septemfasciatus in Korean aquaculture farms. However, we suggest the following preventative methods for hatcheries: 1) disinfecting rearing water, 2) selecting spawners via ELISA and PCR, 3) selecting eggs via PCR, 4) disinfecting fertilized eggs, and 5) proper facilities management. When these methods are implemented, nervous necrosis virus (NNV)-free fish are produced because vertical and horizontal transmission is prevented. However, horizontal transmission of NNV through rearing seawater sourced from the environment during grow-out stages in sea cages can still occur. Live NNV vaccines with a low rearing temperature or Poly(I:C) immunization are very effective at preventing horizontal transmission of NNV in rearing farms. Furthermore, even after VNN is contracted, fish mortality can be reduced by administering Poly(I:C).

• Journal of fish pathology
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• v.16 no.1
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• pp.31-38
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• 2003

The mortality of wild mullet, Mugil cephalus was detected in Kwang- Yang bay on February, 2002. The mullet were infected with Myxobolus sp., the cysts of Myxobolus sp. were found in the mesentery, liver, gill and pharyngeal pocket. The histological findings suggested a systemic infection by the Myxobolus sp.. The spores were measured 10-12 (10.9)${\mu}m$ in length, 9-10 (9.4) ${\mu}m$ in width, 6.4-7.2 (6.8) ${\mu}m$ in thickness, with polar capsules of 4-5.2 (4.4) ${\mu}m$ in length and 2.5-3.3 (2.9) ${\mu}m$ in width.

• Journal of fish pathology
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• v.6 no.2
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• pp.87-92
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• 1993

In February of 1990, an epizootic disease to masu salmon. Onchorynchus masou cultured at the hatchery of trout in Samchuk. Kwangwondo have broken out and induced heavy mortality. An infectious hematopoietic necrosis virus(IHNV) was isolated from diseased masu salmon fry by the use of fish cell line, CHSE-214. This IHNV isolated from masu salmon was compared with USA isolates of IHNV, SRCV and RB-76 by analysis of virion proteins in sodium dodecyl sulfate poly-acrylamide gel electrophoresis (SDS-PAGE) and neutralization tests with two monoclonal antibodies raised against SRCV(MAb SRCV/A4) and RB-76(MAb RB/B5). In the antigenicity and the size of structural proteins. this IHNV, SCS atrain was smilar to RB-76 belonged to the electropherotype I proposed by Hsu et al.(1986).

• Environmental Engineering Research
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• v.22 no.4
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• pp.426-431
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• 2017

Some phototoxicity of titanium dioxide nanoparticles ($TiO_2$ NPs) has been reported in recent years in studies with fish embryos or larvae. However, it is necessary to focus on the potential effects of embryonic exposure due to irreversible abnormalities and mortalities observed in sac-fry, and to expand various fish embryos to generate multiple test species. The aim of this study was to evaluate the effects of $TiO_2$ NPs under different irradiation conditions in exposed Oryzias latipes (O. latipes) at the embryonic and sac-fry stages. The effects of different irradiation conditions were observed using ultra-violet (UV) and visible light, and the corresponding effects were monitored by determining cumulative mortality and abnormality. O. latipes were exposed for 8 d to 0, 1, 5, 10, or 50 mg/L $TiO_2$ NPs under UV ($4,818.86mW/m^2$ at the bottom of clear vials) or visible light, after which the embryos were transferred to NP-free embryo-rearing solution until 16 days post fertilization (dpf). Abnormalities of embryos and sac-fry increased at high $TiO_2$ NP concentrations under UV irradiation, compared to control samples treated with visible light or UV irradiation alone. This work provides information regarding the phototoxicity of $TiO_2$ NPs using O. latipes at the embryonic and sac-fry stages.