• Journal of fish pathology
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• v.35 no.2
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• pp.157-165
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• 2022

Single-cycle viruses generated by reverse genetic technology are replication-incompetent viruses due to the elimination of gene(s) essential for viral replication, which provides a way to overcome the safety problem in attenuated viruses. Infectious hematopoietic necrosis virus (IHNV) is a major pathogen causing severe damage in cultured salmonid species. In the present study, we generated a single-cycle IHNV lacking the transmembrane and cytoplasmic domain in the G gene (rIHNV-GΔTM) and evaluated the prophylactic potential of rIHNV-GΔTM in rainbow trout (Oncorhynchus mykiss). To produce rIHNV-GΔTM, IHNV G protein-expressing Epithelioma papulosum cyprini (EPC) cells were established. However, as the efficiency of rIHNV-GΔTM production in EPC cell clones was not high, fish were immunized with a low-tittered single-cycle virus (1.5 × 10² PFU/fish). Despite the low dose, the single-cycle IHNV induced significant protection in rainbow trout against IHNV infection, suggesting high immunogenicity of rIHNV-GΔTM. No significant difference in serum ELISA titers against IHNV between the rIHNV-GΔTM immunized group and the control group suggests that the immunized dose of rIHNV-GΔTM might be too low to induce significant humoral adaptive immune responses in rainbow trout. The involvement of adaptive cellular immunity or innate immunity in the present significantly higher protection by the immunization with rIHNV-GΔTM should be further investigated to know the protection mechanism.

• Journal of Aquaculture
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• v.20 no.2
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• pp.85-89
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• 2007

This study examined the hatching rate of eyed-eggs and growth of fingerlings of USA strain rainbow trout, Oncorhynchus mykiss, which were transplanted on Nov. 17, 2005 from the USA for improvement of breeding. The diameter and weight of eyed-eggs were $4.95{\pm}0.34\;mm$ and $0.07{\pm}0.003\;g$, respectively. The eyed-eggs were hatched in 8 days later and hatching rates were $77.3{\sim}98.6%$. After 56 days from hatching, the fingerlings grew to $4.0{\pm}0.7$ cm and 0.62 g in total length and body weight, respectively. The relationships between total length (TL) and elapsed days (ED) were expressed as TL=0.0366ED+1.8645 ($r^2=0.928$, n=350). The relationships between body weight (BW) and elapsed days (ED) were expressed as following; $BW=0.0638e^{0.0408ED}\;(r^2=0.9917,\;n=350)$. And survival of rainbow trout was $64.5{\pm}1.3%$ in 56 days after hatching.

• Fisheries and Aquatic Sciences
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• v.23 no.5
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• pp.12.1-12.8
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• 2020

Background: An 8-week feeding trial was designed to evaluate the potential of yellow mealworm (MW; Tenebrio molitor) as a locally available nutrient-rich feedstuff for rainbow trout fry (Oncorhynchus mykiss). Methods: Triplicate groups of fish (mean ± SE; 1.11 ± 0.01 g) were assigned to each of the five isonitrogenous and isocaloric practical diets containing graded level of a full fat MW (0, 7, 14, 21, and 28%) at the expense of fish meal (designated as MW0, MW7, MW14, MW21, and MW28, respectively). Results: Fish growth performance in terms of weight gain and specific growth rate significantly increased with increasing dietary MW level up to 14% and then declined when dietary MW levels further increased to 28%. Significantly higher protein efficiency ratio and lower feed conversion ratio were found in fish fed with diets containing MW compared to fish fed the control MW0. Myeloperoxidase activity was significantly higher in fish fed MW7 diet compared to fish fed the MW0 diet. Fish fed the MW14 and MW28 diets had significantly higher lysozyme activities than those fed the MW0 diet. Conclusions: Overall, the efficacy of MW as promising alternative to fish meal in practical diets for rainbow trout fry has been proved not only in relation to growth rates and feed utilization, but also from the viewpoint of immunopotentiation effects.

• Journal of Aquaculture
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• v.10 no.1
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• pp.39-47
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• 1997

Induction of hybrid and allotriploid between female rainbow trout, oncorhynchus mykiss and male cherry salmon, O. masou were performed. Triploid rate in allotriploid was 92% and the survival rates of allotriploid exceeded that of their hybrid counterparts. Karyological studies revealed that the hybrid had exactly the same intermediate diploid karyotypers as that of two parental species, while allotriploid had two sets of the maternal haploid complement and one set of the paternal haploid complement. Hybrid revealed an intermediate size in celluar and nuclear size of erythrocyte, while allotriploid revealed larger cellular and nuclear size of erythrocytes than hybrid. The number of nucleolar organizer regions of hybrid were 1 or 2, while those of allotriploids were 1, 2 or 3. These results proved that allotriploidization can lead to increase cytogenetical characters compared to counterpart hybridization.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.688-696
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• 2022

Obesity could cause immune-physiological disorders in fish. Yet, little is known about the impact of obesity on stress and histological responses. This study aimed to determine histological and physiological changes in and vulnerability of overfeeding-induced obese rainbow trout Oncorhynchus mykiss exposed to stress condition. Control, intermediate and overfed groups were fed at 1.5, 2.5 and 3.09% of their body weight per day, respectively, for eight weeks. Weight gain, body mass index, hepatosomatic index and serological parameters, and histology of liver were measured in five fish from each group at week 0, 2, 4, and 8. At week 8, 20 fish from each group were exposed to heat stress by increasing water temperature at a rate of 3℃ per day from 15 to 25℃ and maintaining the final temperature for 10 days. Overall, overfed fish showed significantly higher weight gain, body mass index, and serological parameters than those of fish in the other groups. Fish in the overfed and intermediate groups displayed multifocal infiltration of inflammatory cells in hepatic parenchyma. Mortality rate and serological parameters of fish in the overfed group exposed to heat stress were significantly higher than those of fish in the other groups, indicating increased vulnerability to environmental stress.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.585-595
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• 2023

This study was conducted to optimize the rice paper roll processing conditions with frozen rainbow trout Oncorhynchus mykiss meat (RPR-FRT) treated with polysaccharide and TGase using a response surface methodology and to examine their quality characteristics. The RSM results for the RPR-FRT showed that the optimum condition for the garlic-pepper mixture was 21.2 g and that for starch was 22.6 g based on 150 g of RPR-FRT. The RPR-FRT contained 58.47 g/100 g of moisture, 8.57 g/100 g of crude protein, 3.28 g/100 g of crude lipid, and 1.00 g/100 g of ash. The vitamin E content was 1,010.91 ㎍/100 g. Based on their contents, the samples could be considered good supplements for P, Cr, and Se. The RPR-FRT contained unsaturated fatty acids (75.84%), DHA (10.33%), and EPA (2.56%). Anserine, arginine, glycine, and taurine accounted for 41.93%, 11.27%, 7.13%, and 7.00% of free amino acids in the RPR-FRT, respectively. The sulfur compounds in the RPR-FRT constituted 73.16% of the total flavor compounds. The RPR-FRT prepared using the optimum conditions was superior in masking off-flavor and showed improved nutritional content.

• Journal of fish pathology
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• v.35 no.2
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• pp.215-223
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• 2022

Disease including parasite, bacteria and virus cause serious mortality to salmonid fish in the aquaculture. In this study, we investigated the current disease status of the rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch) in Yanayang, Pyeongchang, Jeongseon and Yeongwol of Gangwon province in 2021 and performed molecular characterization of those pathogen. For parasites, Ichthyophthirius multifiliis was observed at 2 farms. For bacteria, we identified Aeromonas sobria from kidney of rainbow trout using phylogenetic analysis of gyrB gene. A. salmonicida were isolated from necrosis site of gill cover and fin in coho salmon and necrotic lesion of fin in rainbow trout. Phylogenetic analysis using vap gene indicated that A. salmonicida isolated in this study were clustered with previously reported A. salmonicida subsp. salmonicida isolates. For virus, JRt-Nagano type of infectious haematopoietic necrosis virus was detected in rainbow trout, but infectious pancreatic necrosis virus and Oncorhynchus masou virus were not detected. These results provide useful information for the prevention of disease spread and transmission when cultivating new species such as Atlantic salmon in Korea.

• Fisheries and Aquatic Sciences
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• v.8 no.3
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• pp.185-187
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• 2005

We tested the in vivo ability of a DNA chip to detect virus-specific genes from virus-infected olive flounder Paralichthys olivaceus and rainbow trout Oncorhynchus mykiss. Target cDNA was obtained from total RNA of virus infected cell lines by reverse transcription (RT) and was labeled with fluorescent dye (Cy5-dUTP). The results show the successful detection of infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicaemia virus (VHSV) genes in the virus-infected fishes.

• Journal of fish pathology
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• v.32 no.2
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• pp.91-96
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• 2019

Rainbow trout (Oncorhynchus mykiss) were treated with ultrasonic (40kHz) and microbubble. The organic serum components, glucose were decreased compared to control at microbubble single treatment (M) and ultrasonic treatment (UL), but glucose concentrations in fish serum of all experimental groups analyzed in this study were also within the normal range. The organic serum components, cholesterol and total protein were no significant change by ultrasonic and microbubble treatment. There were no significant changes in the lysozyme activity on ultrasonic and microbubble treatment. Serum bactericidal activity decreased on ultrasonic single treatment (UL) compared to the control (P<0.05), but the numbers of bacterial colonies were significantly lower than those in the negative (PBS). The results of this study indicate that ultrasonic and microbubble treatment did not have a critical effect on the serum composition and innate immunity of O. mykiss, and that it is a way to do not significant stress on the fish body as a countermeasure against sea lice.

• Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.24-29
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• 1998

Effect of extracellular calcium in vitellogenin (VTG) production in response to estradiol-17 $\beta$ $(E_2,\;2\times10^{-6}M)$ was examined in primary hepatocyte culture of rainbow trout, Onchorhynchus mykiss. Total calcium in estrogenized sera significantly increased, compared with the control, while diffusible calcium was insignificant. However, diffusible calcium in the incubation medium with $E_2$ was significantly reduced, compared with the control. The uptake of extracellular calcium by cultured hepatocytes signifIcantly increased 90 min after $E_2$ addition. Moreover, the accumulation of intracellular calcium increased in the cultures with $E_2$, regardless of the calcium concentrations in the incubation media. In addition, $E_2-primed $ VTG production was significantly decreased by withdrawal of E_2$ from the incubation medium. Moreover, VTG production by $E_2-primed$ hepatocytes was reduced by removing calcium from the incubation medium with or without $E_2$. These results suggest that the entry of extracellular calcium into the cytoplasm is an important step for VTG production in primary hepatocyte cultures in rainbow trout.