• Journal of Aquaculture
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• v.21 no.1
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• pp.26-33
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• 2008

This study investigated the synergistic effects of dietary supplementation of quartz porphyry(QP) and a laboratory developed feed stimulants, BAISM(BS) on growth performance and utilization as the additives for juvenile eel Anguilla japonica. Six isoenergetic experimental diets(18.2 kJ/g) were formulated to contain 50% crude protein, 15% lipid with or without dietary QP(Song-Gang stone, Davistone, Korea) and BS supplementation. QP and BS were provided at 0% in the control diet($Q_0B_0$) and at 0.7% QP+0% BS($Q_{0.7}B_0$), 0.7% QP+0.3% BS($Q_{0.7}B_{0.3}$), 0.7% QP+0.5% BS($Q_{0.7}B_{0.5}$), 0.7% QP+0.75% BS($Q_{0.7}B_{0.75}$) and 0.7% QP+1.0% BS($Q_{0.7}B_{1.0}$) in experimental diets on dry matter basis. After four weeks of adaptation, triplicate groups of 30 fish initially averaging $15{\pm}0.1g(mean{\pm}SD)$ were randomly distributed into each aquarium, and they were fed one of the experimental diets for 8 weeks. By the end of the feeding trial, weight gain(%), specific growth rate(%), feed efficiency(%) and protein efficiency ratio of fish fed diet $Q_{0.7}B_{0.5},\;Q_{0.7}B_{0.75}\;and\;Q_{0.7}B_{1.0}$, were significantly higher(P<0.05) than those of fish fed the other diets. But, $Q_{0.7}B_{0.5},\;Q_{0.7}B_{0.75}\;and\;Q_{0.7}B_{1.0}$ were no significant differences(P<0.05). In challenge test, fish were infected by intraperitoneal injection of 0.1 mL bacterial suspension with Edwardsiella tarda per fish after the feeding trial. As a result, fish fed QP and BS supplemented diets have a significantly higher cumulative survival rate than those of fish fed control diet(P<0.05). In conclusion, these results indicated that the optimum dietary supplementation level of QP and BS could be approximately 0.7% quartz porphyry+0.5% BAISM($Q_{0.7}B_{0.5}$) of diet based on WG, FER, SGR, PER, cumulative survival rate in juvenile eel A. japonica.

• Journal of Aquaculture
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• v.11 no.2
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• pp.223-230
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• 1998

This study was carried out for the purpose of developing environmental friendly and effective chemical treatment method for the disease control in the land-based flounder culture which is industrially popular in the coastal area in Korean. The chemicals such as flounder, Paralichthys olivaceus and their effects on the fish based on the 24hr-$LC_{50}$, $LT_{50}$, 24-hour survival rate at each experimental concentration, recovery rate of the survived individual from chemical treatment, and the histological change of the gill after chemical treatment were investigated and analyzed. The 24hr-$LC_{50}$ was 321.65 ppm for formalin, 419.62 ppm for chlorine dioxide, and 395.97 ppm for hydrogen peroxide, respectively. The $LT_{50}$ was 15-hour for formalin, 17-hour for chlorine dioxide and 24-hour for hydrogen peroxide, respectively. Fishes exposed to the experimental concentration of three chemicals were quickly susceptible in the order of formalin, chlorine dioxide and hydrogen peroxide with a trend of shorter half lethal time at higher concentration. Initial survival rate of the flounder soon after chemical treatment was the highest in the hydrogen peroxide treatment compared with the other two chemicals. The histological damage by the hydrogen peroxide treatment was negligible compared with the other two chemicals. Accordingly, hydrogen peroxide treatment showed the lowest toxicity compared with the other two chemicals to the experimental fishes.

• Journal of Aquaculture
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• v.14 no.3
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• pp.157-163
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• 2001

The antibacterial effect of fish diet soaked in the extract of Salvia miltiorriza was tested to determine its levels of antibacterial activity, minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). The extract showed strong activity against gram positive bacteria, but was weak against gram negative bacteria. Concentration levels of 13.4~40.3 and 67.2~403.0 $\mu\textrm{g}$/ml were determined as the MIC and MBC, respectively. However, levels above 403.0 $\mu\textrm{g}$/ml was neither bacteriostatic nor bactericidal against Edwardsiella tarta, a gram negative strain. The fish diet, soaked in the extract of Salvia miltiorriza, inhibited the growth of all strains of Streptococcus genus and Vibrio anguillarum. The relationship formula between weight of fish diet and Salvia miltiorriza extract absorbed into the fish diet was Y＝2.4953X＋3.3276 ($R^2$= 0.9999). The antibacterial activity of the fish diet, soaked in the extract, was stable from 10 to 35$^{\circ}C$ during the storage period of 28 days.

• Journal of Aquaculture
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• v.10 no.2
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• pp.171-178
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• 1997

Infectious pancreatic necrosis virus (IPNY) is an economically important fish pathogen since it causes the high-mortality disease in early stage of hatchery-reared fishes. In order to develop a rapid, sensitive and highly specific detection method for IPNV, reverse transcription-polymerase chain reaction (RT-PCR) was carried out using the oligonucleotide primers selected from the sequence of VP2, a major capsid polypertide of IPNV. As little as 40ng of purified IPNV dsRNA was detected by RT-PCR amplification, but no amplification products were obtained when nucleic acid genomes from other fish pathogens such as IHNV were used as RT-PCR templates. in situ RT-PCR methods are useful for the rapid and sensitive identification of IPNV.

• Journal of fish pathology
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• v.27 no.2
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• pp.107-114
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• 2014

For the treatments and protection of bacterial fish disease, many requirements are needed for aquatic probiotics so that they are effective in aquaculture animals but are also harmless to humans. In the present study, among 17 candidate probiotic bacteria (CPB) obtained from the edible part of the shellfish, Bacillus sp. CPB-St (CPB-St) were selected and in vitro evaluated for the possibility as a probiotic strain for the control of fish streptococcosis which frequently occurs in the olive flounder farms. CPB-St showed inhibitory effects on the growth of various fish pathogenic bacteria, Streptococcus sp., S. parauberis, S. iniae, Lactococcus garvieae and L. piscium by the double layer test ranging about 18~26 mm of clear zone. Inhibitory activity of CPB-St to Streptococcus sp. was observed 6 hours after and the growth of Streptococcus sp. was decreased to 8~55 folds in the co-culture of CPB-St with Streptococcus sp.. The safety of CPB-St to fish and survival of CPB-St in the intestine were assessed in the olive flounder, Paralichthys olivaceus. Fish mortality was not observed in artificial infection with CPB-St for 2 weeks. CPB-St was entirely excreted from the stomach and intestine 24 hours after oral injection. This results indicate that CPB-St has potential applications as a probiotic for the control of fish streptococcosis in aquaculture.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.3
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• pp.165-170
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• 1981

Recently an unknown microbial desease and some parasitic crustaceans are prevailing in the sea-weed farms of Uudaria pinnatifida along the south-eastern coast of Korea.(1) Green spots probably caused by the microbial pathogens were found on the fronds of Undaira Pinnatifide. Particularly they were densely distributed on the distal half of the fronds. The tissues of the green spot area rot off, and small holes with green colored margin are formed. The holes at the distal part of the fronds are enlarged and they finally coalesced each other. Then this process accelerates decaying of the distal ends of the fronds.. The fronds growing in the central part of the farms are usually severely damaged, whereas in the marginal area of the farm toward the open sea side the damage is less serious. An examination revealed that the deseased fronds bore a number of viable bacteria, $6.8\times10^5\;to\;1.2\times10^6$ per gram at $15^{\circ}C$, whereas the healthy fronds $1.1\times10^4$. Twenty-six kinds of colonies, 247 strains of bacteria, were isolated from deseased fronds, belonging to Moraxella, Achromobacter, Vibrio, Flavobacterium, Acinetobacter, Pseudomonas, etc. (2) Pinholes occurred in one series on the frond. They were probably caused by a harpacticoid copepod, Thalestris sp. Seven years ago when the disease was first found to occur the copepod was observed on the fronds from March of the year. Recently, however, they have been found as early as December of the previous year. (3) A gammarid amphipod, Ceinina iaponica, invades the pith of the midrib through holdfast of thalli. This rarely causes the longitudinal seperation of the entire frond through the midrib as they bore a tunnel in the pith. Sometimes holdfasts of tile heavy damaged thalli make the frond departed from the substrate.

• Journal of Aquaculture
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• v.11 no.2
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• pp.203-212
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• 1998

As seed production program is growing prosperously in various fishes in southern Korea, disease problems in larval and juvenile stages have emerged as a new research object. The following results were obtained from investigation about environmental factors related to mass mortalities of young Kinki red seabream, Pagrus major in process of artificial seedling production. Total length of red seabream larvae hatched was 2.93mm, and became 18.83~20.12mm at day 40. The first noticeable mortality of red seabream larvae (7.98~9.37mm) occurred in 25~30 day-old fish with the survival rates of 59.8~60.3%. Thereafter the mortality of larvae decreased, survival rate was 20.5~25.45% in day 40. After 20~30 days, the quality of pond water was bellow II class. During the experimental period COD, $PO_4$-P, $NO_2$-N, $NO_3$-N and $NH_$-N increased up to 3, 7, 34, 6 and 8 times, respectively, compared to initial ones. The number of viable bacteria in pond water and seabream larvae were $6.3{\times}10^6$~$2.3{\times}10^7$ cfu/ml, 4.3~$7.4{\times}10^6$ cfu/g in day 25, respectively. Among the isolated bacteria from the diseased red seabream in day 25, Vibrio spp. was considered to be the causative organism. External symptoms of this disease were floated, spined near the surface and inflated abdomen. When the isolated strain of the Vibrio was bathed to seabream larvae, $LD_50$ of seabream larvae was over $10^6$ cfu/ml of Vibrio spp.

• Journal of fish pathology
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• v.23 no.3
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• pp.357-367
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• 2010

The pharmacokinetic properties of amoxicillin trihydrate (Amox) were studied after single oral administration and single intravenous injection to cultured eel, Anguilla japonica, respectively (average $220{\pm}10\;g$, $28{\pm}1^{\circ}C$). Plasma samples were taken at 3, 5, 10, 15, 24, 30, 48, 96 and 144 h post-dose. The kinetic profile of absorption, distribution and elimination of Amox in plasma were analyzed fitting to a two-compartment model by WinNonlin program. In oral dosage of 40 and 80 mg/kg body weight, the peak plasma concentrations of Amox, which attained at 3~12 h post-dose, were 3.4 and $3.3\;{\mu}g/ml$, respectively. In intravenous injection with 1 mg/kg, the peak plasma concentrations of Amox, which attained at 9 h post-dose, was $7.2\;{\mu}g/ml$. The following parmeters were calculated for a single oral dosage of 40 and 80 mg/kg body weight, respectively: AUC (the area under the concentration-time curve)= 464 and $667\;{\mu}g{\cdot}h/ml$; $T_{max}$ (time for maximum concentration)= 2.1 and 3.6 h; $C_{max}$ (maximum concentration)= 3.04 and $3.4\;{\mu}g/ml$. Following intravenous injection at 1 mg/kg, this parameters were AUC= $748\;{\mu}g{\cdot}h/ml$; $C_{max}=4.2\;{\mu}g/ml$. The apparent oral bioavailability at 40 and 80 mg/kg were 1.6 and 1.1%, respectively. Despite using the trihydrate form of amoxicillin, the oral bioavailability was low in eel.

• Journal of fish pathology
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• v.30 no.2
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• pp.79-88
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• 2017

At the present, fish farms are suffering a lot of economic losses due to infectious diseases caused by various pathogens including aeromonad. Aeromonad is ubiquitous bacteria that causes infectious diseases. At least 26 species in the genus Aeromonas have been reported to cause fatal infections not only in salmonid fishes, but also in other freshwater and seawater fishes. Molecular techniques based on nucleic acid sequences of 16S rDNA and housekeeping genes can be used to identify the Aeromonas species. In this study, The genus Aeromonas was isolated from salmonid fishes of sixteen fish farms in Gangwon-Do, Korea and phylogenetically identified based on the sequences of 16S rDNA and housekeeping genes for Aeromonad, i.e. RNA polymerase sigma factor ${\sigma}^{70}$ (rpoD) or DNA gyrase subunit B (gyrB). Consequently, 96 strains were collected from Atlantic salmon (Salmo salar), coho salmon (Oncorhynchus kisutch), masou salmon (Oncorhynchus masou) and rainbow trout (Oncorhynchus mykiss), and 36 isolates were identified as the genus Aeromonas by 16S rDNA analysis. Thirty six Aeromonad isolates were further analysed based on rpoD or gyrB gene sequences and found Aeromonas salmonicida (24 isolates), A. sobria (10 isolates), A. media (1 isolates) and A. popoffii (1 isolates), indicating that A. salmonicida is a main infectious bacteria in Salmonid fishes in Gangwon-Do. It was also proved that the phylogenetic identification of Aeromonas species based on the sequences of housekeeping gene is more precise than the 16S rDNA sequence.

• Journal of Aquaculture
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• v.19 no.4
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• pp.231-235
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• 2006

The effects of mycelium cultural extract supplemented diet, hematology and disease resistance against Vibrio anguillarum in juvenile flounder, Paralichthys olivaceus were evaluated. Fish were fed the Phellinus linteus with Coriolus militaris versicolor mixed mycelium cultural extract supplemented diet, Phellinus linteus mycelium cultural extract supplemented diet and Coriolus militaris tmycelium cultural extract supplemented diet a commercial diet for 12 week. The body weight and length gain from the fish fed on daily the phellinus with coriolus versicolor mixed mycelium cultural extract supplemented diet, phellinus linteus mycelium cultural extract supplemented diet and Coriolus versicolor mycelium cultural extract supplemented diet of each mycelium cultural extract were higher than the control and the Glutamic oxalacetic transaminase (GPT) were of lower than the control. The relative precent survival rate (RPS) after an artificial challenge with $7{\times}10^5\;CFU$ of Vibrio anguillarum per fish was higher than the control.