• Fisheries and Aquatic Sciences
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• v.26 no.10
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• pp.605-616
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• 2023

Scuticociliatosis, caused by the parasitic pathogen Miamiensis avidus, poses a significant threat to olive flounder farms in South Korea. Infected fish suffer from severe systemic infections affecting various organs, with potential secondary bacterial diseases. This study investigated the emergence of different M. avidus serotypes in 20 olive flounder farms on Jeju island, South Korea, from 2015 to 2020. Additionally, we identified Tenacibaculum maritimum as a co-infecting bacteria. Based on serotyping and monitoring data, we developed a trivalent vaccine targeting two serotypes of M. avidus and one strain of T. maritimum. The efficacy of the vaccine was evaluated under laboratory conditions and demonstrated a relative percentage of survival (RPS) of 75%, 80%, and 93% for M. avidus serotype I, M. avidus serotype II and T. maritimum, respectively. Furthermore, successful field trials conducted on four different olive flounder farms resulted in significantly higher survival rates (52%-76% RPS) and weight gains in vaccinated fish. Overall, this study presents an effective vaccine against M. avidus and T. maritimum infections in farmed olive flounder, making a valuable contribution to sustainable aquaculture in South Korea.

• Journal of Aquaculture
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• v.11 no.4
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• pp.495-503
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• 1998

The present study investigated the effects of Bisroot, that contains live bacteria (Bacillus polyfermenticus, Bacillus mesentericus, Streptococcus faecalis, & Bifidobacterium breve) and digestive enzymes (protease, lipase), on the growth, body composition and immune response of Nile tilapia fingerlings. One percent of the Bisroot was added to the experimenta feed. All exprimental fish were fed for 60 days. The weigh gains among the experimental fish were not significntly different (P>0.05). Hematocrit value, hemoglobin, total protein, glucose, GOT, and GPT were unaffected by Bisroot treatment. However, it was observed that glucose, GOT, and GPT value in the fish that were fed Bisroot, were lower than the control. The complement activity ($CH_50$) tended to be significantly increased by Bisroot treatment, but not lysozyme activity. Phagocytosis and respiratory burst activities of macrophages in the head kidney were enhanced by Bisroot. Therefore, the Bisroot diet enhances the cellular immune activities were enhanced by Bisroot. Therefore, the Bisroot diet enhances the cellular immune activities of non-specific immune responses. When fish were challenged with a virulent strain of Edwardsiella tarda, the Bisroot treated fish were more resistant than the control. The present results suggest that the introduction of Bisroot into the diet of Nile tilapia could increase their resistance against bacterial infection, reduce fish mortality, and offers economic benefits.

• Journal of Veterinary Clinics
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• v.26 no.3
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• pp.226-230
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• 2009

We evaluated the efficacy of $\beta$-hemolytic Streptococcus(S.) iniae vaccine on cultured olive flounder. Three hundred flounders(weight $50{\pm}5$ g) were obtained from two farm at Wando and Taean in the southern and western coast of Korea at May and June 2007, respectively. Twenty of flounders moved in 0.5 tons aquaria in land-marine tank system of National Veterinary Research and Quarantine Service. Seawater was transported from the sea of Inchon in western Korea, and water temperature maintained to $22^{\circ}C$ and $25^{\circ}C$ during the vaccination and challenge test, respectively. We used the formalin-inactivated $\beta$-hemolytic S. iniae vaccine produced by domestic manufacturers. The vaccine was intraperitoneally administered to fish. The vaccinated and control group were challenged with intraperitoneal injection by virulent S. iniae SI-36 isolates with $5.0{\times}10^8$ CFU/fish at 3 weeks after vaccination. We evaluated the vaccine efficacy by calculating numbers of dead fish, and observing of clinical signs, exterior and gross lesions, and examining bacteria isolation and identification. Thirty-four(25.2%) of 135 control and vaccinated group fish were dead with serious anemia, abdominal extension, and hernia of intestine during 3 weeks post vaccination. We isolated Neoheterobothrium hirame from the buccal cavity and Edwardsiella tarda from kidney of dead and diseased fish. When infected fish with these agents were challenged with S. iniae SI-36 isolates, the cumulative mortality of control and vaccinated group were 86.7, and 46.7%, respectively. However, significant differences(p<0.05) were observed on cumulative mortality between control(20.0%) and vaccinated group(95.0%) at second trials with 40 healthy, and relative percent survival(RPS) was 78.0%. We confirmed that the efficacy of $\beta$-hemolytic S. iniae vaccine on olive flounder were impacted by health condition such as bacterial and parasitic diseases.

• Journal of Life Science
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• v.18 no.3
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• pp.395-402
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• 2008

Level of microbial contamination was examined in four fish farms of Jeju east coast for sanitary indication of bacterial contamination such as heterotrophic bacteria, Escherichia coli O157:H7, Salmonella spp., Vibrio parahaemolyticus, Staphylococcus aureus, Bacillus cereus and total coliforms. The samples were collected and investigated from June to October in 2007. Bacterial species of S. aureus, B. cereus and Salmonella spp. were frequently detected from the seawater of above fish farms. Salmonella spp., S. aureus, B. cereus were detected in the range of $0{\sim}4.3{\times}l0^3,\;0{\sim}2.7{\times}l0^4,\;0{\sim}7.6{\times}l0^3$ CFU/ml, respectively, from the fish feed used in all four selected farms. Additionally, Salmonella spp., S. aureus, B. cereus were detected in oliver flounder (Paralichthys olivaceus) of these farms, however total coliforms and E. coli O157:H7 were not detected during our experimental period. For the production of microbiologically safe and healthy oliver flounder, proper quality control of feed, sanitation programs, and continuous monitoring of microorganism are essential practices, which required to include in the farm management system.

• Journal of Marine Life Science
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• v.5 no.2
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• pp.51-57
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• 2020

Disinfection and maintenance of rearing water in aquaculture is an essential element for the prevention of fish diseases. This is especially important in recirculating aquaculture systems (RAS) in which fish are reared at high density using recycled water. In this study, tilapia was reared in two different RAS (one with plasma generator - PW system, another without plasma generator - No PW system). In plasma treated group, UVT% of water was improved clearly, and the number of heterotrophic bacteria decreased significantly after 40 days. Total weight gain of tilapia in PW system was significantly higher, and other growth indicators were also relatively higher although not statistically significant. In addition, the fish in PW system had a 100% survival rate, and there were no histological differences between fish from both systems. Fish did not seem to be affected by the toxicity of ROS. In conclusion, it is expected that plasma water can effectively deactivate fish pathogens and improve the quality of rearing water.

• Journal of fish pathology
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• v.35 no.1
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• pp.57-63
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• 2022

Vibrio parahaemolyticus and V. vulnificus are known to be infected to human via fisheries products. Therefore, food safety of fisheries products is important for public health and fish industry. This paper was conducted to know how well these human isolates can survive in olive flounder (Paralichthys olivaceus). The growth of V. parahaemolyticus and V. vulnificus showed about 50~60% reduced rates at 25℃ than at 37℃ and did not show any differences according to NaCl concentration of media except the increasing in the growth of V. vulnificus in medium containing 3% NaCl. Artificial infection of 1×10⁶ CFU/fish was carried out to confirm the sensitivity of olive flounder against V. parahaemolyticus and V. vulnificus. After 1 week from injection, no fish was dead. To evaluate nonspecific defense of olive flounder against V. parahaemolyticus and V. vulnificus, the antibacterial potency of serum and epidermal mucus were tested. The number of the vibrios exposed to serum obtained from olive flounder significantly decreased after 3 hours, and epidermal mucus showed decrease of the bacteria over than 90% until 12 hours from exposure. Phagocytosis of head kidney leucocytes of healthy olive flounder against V. parahaemolyticus and V. vulnificus showed in over 70% of leucocytes at the 2 hours. Therefore, cultured olive flounder only as vehicle for human pathogen in environmental water is well developed its antibacterial potency against human pathogens, so the viability of V. parahaemolyticus and V. vulnificus in cultured olive flounder was considered very low.

• Food Science and Preservation
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• v.15 no.6
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• pp.922-926
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• 2008

The effect of UV-C irradiation on microbial growth and the quality of imported dried filefish and octopus during storage was examined. Samples of imported dried filefish and octopus were irradiated at 0, 5, 10 and $20\;kJ/m^2$ and stored for 3 months at $20^{\circ}C$ or for 6 days at $4^{\circ}C$. Exposure times of 5 min 33 sec, 11 min 6 sec, and 22 min 12 sec were used. UV-C treatment of the imported dried filefish and octopus decreased the populations of aerobic bacteria, yeasts and molds in proportion to radiation dose. Compared to the control, total aerobic bacteria, and yeast and mold populations were significantly lower (1-2 log CFU/g) with UV-C treatment of $20\;kJ/m^2$. UV-C irradiation caused negligible changes in the Hunter color L, a and b values. These results indicate that UV-C irradiation could be useful in inhibiting microbial growth on imported dried fish without impairing quality during storage.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.3
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• pp.138-146
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• 1989

This experiment was conducted to utilize the water soluble protein from the fish meal in wastewater as nitrogen source by alkaline protease producting bacteria and to investigate the culture condition of the production. G-12 and G-14 strains having the strong activity of the alkaline pretense were isolated from sea water. These strains were identified as Pseudomonas chlororaphis and Pseudomonas alcaligenes according to physiologycal characteristics, respectively. In enzyme production, galactose and casein for G-12 strain, and raffinose and the water soluble protein of the fish meal wastewater for G-14 strain was favorable as carbon and nitrogen source. An action of inhibition appeared in all of the metal salts used. The optimal temperature of enzyme production was $30^{\circ}C$ for all strains. Optimal initial pH for the enzyme formation in G-12 and G-14 strains was pH 10.0 and 8.0. When these two strains were incubated for $30\~35$ hours in the optimal production medium, the enzyme production reached at maximum.

• Journal of Aquaculture
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• v.17 no.2
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• pp.109-114
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• 2004

The effects of different concentrations (0, 0.3, 0.6 and 0.9%) of fish feed additives (Hanbangchun and Olyukchun) utilizing effective microorganisms and herb medicine on activity of liver function were examined in olive flounder, Paralichthys olivaceus, Moreover, we investigated the characteristics of the additives. Total number of microorganisms (Lactic acid bacteria, Bacillus subtilis, Saccharomyces cerevisiae, Photosynthetic bacteria and Azotobactor) in the additives was 5.6${\times}$10$^{8}$ CFU/g in the Hanbangchun and 3.0${\times}$10$^{8}$ CFU/g in the Olyukchun. Levels of three typical pathological microorgamisms (Edwardsiella tarda, Vibrio anguillarum and Streptococcus sp.) in moist pellets (MP) were significantly decreased by the additives in a concentration-dependent way. Hepatosomatic index of fish in the 0.3% group was significantly increased. Total serum protein was increased in all the groups containing additives, but the protein content in liver was higher in the control group. Higher activities of catalase and superoxide dismutase which are involved in physiological defense mechanisms were found in the dietary groups containing 0.3% and 0.6%, respectively. These results suggest that the additives, Hanbangchun and Olyukchun, can increase tolerance of olive flounder against stress and hypoxic conditions by increasing activities of body antioxidant enzymes.

• Korean Journal of Ichthyology
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• v.29 no.1
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• pp.62-68
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• 2017

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.