• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.735-745
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• 2022

In this study, a health assessment was conducted using the Benthic Health Index (BHI) to assess fish cage farms, where a fishery environment assessment was also performed. A total of 43 farms were evaluated located in the East Sea, West Sea, and South Sea in Korea. The results of the BHI health evaluation included 8 grade 1 farms, 4 grade 2, 12 grade 3, and 19 grade 4. The grade 1 farms included sandy sediment farms and those with low intensity aquaculture, while the grade 2 farms included those located in areas with active seawater circulation. The fish cage farms belonging to grade 3 and 4 included the majority of farms with high-intensity aquaculture activities. There was no significant difference in total organic carbon between grade 3 and 4 farms, but the results of polychaete community analysis show that organic matter concentration was significantly higher in grade 4 farms.

• Journal of Food Hygiene and Safety
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• v.22 no.3
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• pp.179-191
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• 2007

The purpose of this study was to monitor and compare the contamination levels of heterotrophic bacteria and pathogenic bacteria (total coliforms, Escherichia coli O157:H7, Salmonella spp., Vibrio parachaemolyticus, Staphylococcus aureus and Bacillus cereus). The samples collected at fish farms located in the Jeju-island were investigated from March to August in 2006. The contamination levels of S. aureus, B. cereus and Salmonella spp. ranged $0-3.3{\times}10^2 CFU/ml,\;0-2.2{\times}10^2 CFU/ml\;and\;0-5.1{\times}10^1CFU/ml$, respectively, and 85% of moist pellet feeds were contaminated with S. aureus, B. cereus and total coliforms. But total coliforms and E. coli O157:H7 were not detected in oliver flounder (Paralichthys olivaceus). For the production of safe oliver flounder (Paralichthys olivaceus), education of sanitation for employees, control of fish feed, and continuous monitoring for microorganism will be required.

• Korean Journal of Ichthyology
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• v.30 no.3
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• pp.131-136
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• 2018

Decrease in seawater temperature during winter is one of the most important and serious issues confronted by fish net-cage aquaculture farms. This can become the cause of the manifestation of diseases and ensuing mass mortality. The present study was conducted to assess the survival rate, the range of limited low-temperature, the response of oxidative stress in the blood of red sea bream Pagrus major with decrease of water temperature. Low-lethal temperature for 7 days of P. major ($7day-LT_{50}$) was $6.54^{\circ}C$ (confidence limit: $6.31{\sim}6.71^{\circ}C$). Oxygen consumption rate was decreased with lower temperature. It showed the minimum value at the range of low-lethal temperature. Osmolality at $5^{\circ}C$ and $6^{\circ}C$ experimental group was higher significantly than control group. SOD (superoxide dismutase) activity was increased significantly at $5^{\circ}C$ experimental group compared to control group. This study data will be used to determine the appropriate area for aquaculture of red sea bream. It also manage fish net-cage farm to cope with the mass mortality occurring frequently during winter season.

• 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.

• Journal of fish pathology
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• v.27 no.2
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• pp.133-137
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• 2014

We examined the cause of a disease outbreak in rainbow trout Oncorhynchus mykiss, which were adapting to a seawater in an aquaculture farm in Jeju on April, 2013. Most of the diseased fish showed a severe ulcer on the skin, enlarged spleen, expanded stomach and hemorrhage of abdominal and pyloric region. Although no parasites, fungi or viruses were isolated from diseased fish, over 200 same bacterial colonies were isolated from liver, spleen and kidney. Nucleotide sequences of the 16S rDNA gene of the bacterium in this study showed 100% identity with Vibrio anguillarum. This study is the first report of V. anguillarum infection in rainbow trout during sea adaption in Korea.

• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.269-274
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• 2020

It has used buoy for efficient domestic farm operations and fishermen fish. Buoy uses IoT-based communication to transmit water temperature, salinity, humidity, wind speed, etc. to fishers in real time. In this paper, we utilize LoRa, which enables communication in the marine environment, to construct a network and apply it to an actual buoy for monitoring. The implemented LoRa uses the 900MHz band to configure the network. The sensor consisted of a sensor that can monitor the atmospheric environment and a sensor that can monitor the marine environment. In addition, the information received in real time will be provided to the fishing village host. The fishermen were fully aware of this and took appropriate measures to conduct sea trials.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.47-57
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• 2007

Real-time oceanographic information system was developed using platforms of aquaculture farms to examine causes of mass mortality of hatchery fishes, and to reduce the damage of mass mortality which has been occurred frequently off coast by abnormal change of ocean conditions. The system had the advantages of direct data distribution to fishermen at the farm and instant maintenance of equipments due to easy access to the farms and residents at the farms in comparison with offshore mooring buoy system. To avoid discontinued measurement of the system, repairs caused by malfunction of equipments, bimonthly preventive maintenances and daily monitoring of measured data were systematized. Confidence intervals calculated by a statistical method using accumulated data were applied to data management. Such activities could minimize discontinuance of measurement and keep information more trustful. In addition, the system has various ways of data distribution. Through homepage and e-mail in the internet, information was provided to public. Display units which were connected to equipments at the farm gave the measured data directly to fishermen, which guided them to run their farm scientifically. Finally large display unit was installed at a fish market and showed the measured data at the nearest station with tide and weather information. Proper region for aquaculture and wintering region were studied using temperature data obtained by the system in 2006. The system will contribute to reduce economic damage of coastal fishery and to understand coastal marine environment.

• Journal of fish pathology
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• v.34 no.2
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• pp.185-199
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• 2021

Vibriosis is an important septicemic bacterial disease that affects a variety of commercial fish species, including cultured Dicentrarchus labrax. Nanotechnology has become an important modern tool for fish diseases prevention. Furthermore, nanomaterials have the ability to prevent and treat fish diseases. The current study was aimed to identify the causative agent of massive mortality of D. labrax commercial farm in Alexandria, Egypt. Experimental infection and the median lethal dose (LD50) of pathogenic isolate were assessed. Also, the effect of ginger nanoparticles (GNPs) and Sacchromyces cerevisiae as feed additives for prevention of vibriosis in D. labrax was carried out. Similarly, the tissue immunstimulant genes, IL-1β and TLR2 were measured in the spleen of feeding groups. The clinical signs of naturally diseased D. labrax showed corneal opacity and paleness of gills with excessive mucous secretion. The post-mortem abnormalities were severe hemorrhage and adhesion of internal organs. After bacteriological isolation and identification, the causative agent of mortality in the current study was Vibrio alginolyticus. The LD₅₀ of V. alginolyticus was 1.5×10^5.4 CFU/ml. The experimentally infected D. labrax showed ulceration, exophthalmia and skin hemorrhages. The post-mortem findings of the experimentally infected D. labrax revealed internal hemorrhage, spleen darkness and paleness of liver. There is no mortality and 100% RPS in groups fed GNPs then injected with V. alginolyticus, in those fed a combination of GNPs and S. cerevisiae and a group fed normal diet then injected with physiological saline (control negative), respectively. Contrarily, there was 10% mortality and 87.5 RPS in the group fed S. cerevisae then injected with V. alginolyticus. On the other hand, the control positive group showed 79% mortality. The spleen IL-1β and TLR2 immunostimulant genes were significantly increased in groups of fish fed GNNP, S. cerevisiae and a combination of GNPs and S. cerevisiae, respectively compared to control group. The highest stimulation of those immunostimulant genes was found in the group fed a combination of GNPs and S. cerevisiae, while fish fed S. cerevisiae had the lowest level. Dietary combination of GNPs and S. cerevisiae was shown to be efficient in preventing of vibriosis, with greatest stimulation of spleen IL-1β and TLR2 immunostimulant genes.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.159-169
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• 2007

Excessive input of organic matters from fish cage farms to the coastal waters has been considered as one of the major factors disturbing their benthic ecosystem. Sediment samples were taken from around the two fish cage zones (A and B) in Tongyeong coast in June and August 2003, to evaluate the ecological impacts of fish cage farming activity on the macrobenthic polychaete communities. Polychaete accounted for $81{\sim}87%$ of the total macrofauna individuals from each of the sampling stations. The number of species, abundance, diversity and dominant species of polychaete were rapidly changed with the distance from the fish cages. Within 10 m from the fish cages, Capitella capitata, which is a bio-indicator for the highly enriched sediments, was a dominant species and the lowest diversity was recorded. In particular, the maximum density (${\sim}18,410\;ind.m^2$) of C. capitata was found at Farm A where fish cages were more densely established within a semi-enclosed bay system. The sampling zone between 10 m and 15 m showed a rapid decrease of C. capitata with a rapid increase of the numbers of species, implying that this zone may be an ecotone point from a highly to a slightly enriched area. In the sampling zone between 15 m and 60 m, a transitional zone, which represents slightly enriched condition before normal one, was observed with additional increase and maintenance of the number of species and density of polychaete. In addition, the potential bio-indicators of organic enrichment, such as Lumbrineris longifolia and Aphelochaeta monilaris were the predominant species in the sampling zone. Multidimensional scaling (MDS) ordination plots and k-dominance curves confirmed the above results on the gradual changes in the macrobenthic polychaete communities. Our findings suggest that the magnitude of impact of fish cage farming activity on polychaete communities is probably governed by a distance from fish cage, density of fish cage and geomorphological characteristics around fish cage farm.

• 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.