• Journal of Environmental Science International
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• v.30 no.7
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• pp.585-595
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• 2021

We used seawater temperature data, measured in the Garolim Bay, to analyze temperature variation on an hourly and daily basis. Lagrange's interpolation using before and after data was applied to restore nonconsecutive missing temperature data. The estimated error of the data restoration was 0.11℃. Spectral analyses of seawater temperature showed significant periodicities of approximately 12.4 h (semidiurnal tide) and 15.0 d (long-period tide), which is close to those of M₂ and M_f partial tides. Variation in seawater temperature was correlated more with tidal height than with air temperature around the Garolim Bay. In June and December, when the seawater temperature difference between the inside and outside of the Garolim Bay was very large, the periodicities of 12.4 h and 15.0 d were highly prominent. These results indicate that the exchange of seawater between the inside and outside of the Garolim Bay induced variations in seawater temperature owing to tide. Understanding temperature variation because of tide helps to prevent abnormal mortality of cultured fish and to predict seawater temperature in the Garolim Bay.

• Animal cells and systems
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• v.2 no.4
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• pp.521-527
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• 1998

The turnover of epidermal cells after seawater adaptation of the freshwater fishwas studied in the guppy (Poecilia reticulata) by means of Proliferating cell nucleus antigen (PCNA) immunocytochemistry and transmission electron microscopy. The number of PCNA-immunoreactive cells in the epidermis of the seawater-adapted guppies, which becomes thinner than that in the fresh-water, generally increases four times as much. Degeneration of filament-containing cells by necrosis or apoptosis occurs mainly in epidermal cells. Apoptotic filament-containing cells seem to be shed into the water in the environment instead of phagocytosis by adjacent macrophages. The apoptotic chloride cell has a highly condensed cytoplasm and the lumen of tubular system is distended. The apoptotic mucous cell, which has an electron-dense cytoplasm, is characterized by the presence of a large multivesicular body of different electron densities. Macrophages contain many electron-dense lysosomal bodies and large vesicles filled with cellular debris. It is concluded that mitosis and apoptosis of epidermal cells are greatly stimulated when fish are adapting to seawater. This result reflects an increase in epidermal cell turnover by change of environmental salinity.

• Journal of Food Hygiene and Safety
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• v.38 no.5
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• pp.381-389
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• 2023

Vibrio vulnificus, the most fatal waterborne and foodborne pathogens of 50% fatality rate in the world, is common in seawater and occurs particularly in warmer months. In this study, we investigated the toxin genes using reverse transcription-polymerase chain reaction (RT-PCR), antibiotic resistance status using Vitek, and genetic characteristics using pulsed-field gel electrophoresis (PFGE) of different V. vulnificus strains isolated from the Jeju Island seawater, distribution fishery products, and fish tanks. We examined a total of 487 samples and isolated a total of 46 strains (including overlapping strains) of V. vulnificus, 44 strains from seawater and 1 strain each from fishery products and fish tank. We detected toxin gene vvhA in all 46 strains and rtxA, viu in 8 strains (17.4%) and 9 strains (19.6%) strains, respectively. Antibiotic resistance tests indicated 100% resistance to cefoxitin antibiotics. The PFGE analysis of the 46 strains identified a total of 6 types showed 100% homology and the degree of similarity was 81.3-98.0%; however, there were no similarity between the regions and samples. These results indicate that V. vulnificus isolated from the seawater, fishery products, and fish tanks should be continuously monitored as cases of food poisoning caused by V. vulnificus with toxin genes have been reported in Jeju Island.

• Journal of fish pathology
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• v.35 no.2
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• pp.185-193
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• 2022

This study investigated carnival behavior in the nursery stage of Fenneropenaeus chinensis. In order to suppress the carnival behavior and improve the survival rate, it was examined whether there was a carnivalism inhibitory effect according to the rearing water of shrimp. In addition, their blood physiological changes were observed. As a result, in the experimental group with the size difference of F. chinensis, the survival rate was the highest in the biofloc technology (BFT) rearing water of olive flounder (75%), and in the experimental group without the size difference, the survival rate was the highest in the seawater experiment group (93%). In both experimental groups, rate of carnival behavior was observed to be low in the fed experimental group regardless of the size difference of F. chinensis. As a result of blood cell analysis of F. chinensis according to the rearing water, the percentage of granulocytes was the highest in the BFT rearing water of flounder (75%) and the lowest in the filtered seawater group (66%). The proportion of semi-granulocytes was the highest at 11% in the shrimp BFT rearing water, and the lowest at 7% in the filtered seawater. The proportion of hyalinocytes was highest in filtered seawater (27%) and lowest in flounder BFT rearing water (16%). These results suggest that carnival behavior and blood composition of F. chinensis may be different depending on the conditions of the rearing water in the nursery stage.

• Journal of Aquaculture
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• v.20 no.2
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• pp.121-126
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• 2007

Comparison of fish number on routine oxygen consumption (OC) of black porgy (Acanthopagrus schlegeli) reared in seawater (SW) versus freshwater (FW) was performed in closed water-recirculating system containing respiratory chamber. Fish acclimated in separate indoor tanks with SW or FW were sampled as two groups (one or three of fish used, $mean\;{\pm}\;S.D.=36.4{\pm}9.8$). OC of fish reared in both SW and FW showed clear temporal rhythms, with higher values in the daytime and lower values at night, in accordance with light (09:00-21:00 h) and dark (21:00-09:00 h) phases of the diel cycle (12L:12D). The OC of the fish increased linearly with the water temperature. The OCs of black porgy reared in SW and FW at 15, 20, $25^{\circ}C$ were 140.0, 174.8, 282.3 mg $O^2{\cdot}kg^{-1}{\cdot}h^{-1}$ and 177.5, 307.8, 413.1 mg $O^2{\cdot}kg^{-1}{\cdot}h^{-1}$ for the one of fish used, and 200.5, 274.7, 339.1 mg $O^2{\cdot}kg^{-1}{\cdot}h^{-1}$ and 118.2, 188.2, 252.8 mg $O^2{\cdot}kg^{-1}{\cdot}h^{-1}$ for three of fish used, respectively. Black porgy reared in SW had higher ventilation rates than those in FW. These results indicate that black porgy reared in FW had higher OC than those in SW at the one of fish used, but the fish reared in SW had higher OC than those in FW at the three of fish used.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.203-204
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• 2003

Ammonia in aquaculture system may lead to suppression of fish growth, sublethal histopathological changes, and even death thus ammonia is considered toxic to fish. Tricking filter and submerged filter have many advantages include: low construction cost, easy management and maintenance, and well adaptation to different water and waste loading rates. (omitted)

• Korean Journal of Ichthyology
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• v.12 no.2
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• pp.111-117
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• 2000

There were observed the histomorphological alterations such as chloride cell hyperplasia, branchial lamellar epithelial separation, the increased cellular turnover of chloride cells, glomerular shrinkage and blood congestion in rainbow trout (Oncorhynchus mykiss) during the seawater adaptation. The ultrastructure by scanning electron microscope (SEM) indicated that the gill secondary lamella of rainbow trout exposed to seawater, were characterized by rough convoluted surfaces during the adaptation. There were observed a large number of mitochondria with the elongate and well-developed cristae in chloride cells exposed to seawater by transmission electron microscope (TEM). The presence of two mitochondria- rich cell types is discussed with regard to their possible role in the hypoosmoregulatory changes which occur during seawater-adaptation. Glomerulus shrinkage and blood congestion were occurred higher in nephrons of seawater-adapted fish than those living in freshwater. Our findings demonstrated that rainbow trout tolerated moderately saline environment and the increased body weight living in seawater was relatively higher than that living in freshwater in spite of histopathological changes.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.97-100
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• 2008

Various flyers in nature have attracted great interests with a recent need for developing versatile and small-size flight vehicles. In the present study, we focus on the flying fish which has been observed to glide a long distance just above a seawater surface. Since previous studies have depended on the field observation or measurement of the physical parameters only, quantitative data of the flying fish flight has not been provided so far. Therefore, we evaluate the wing performance of the flying fish in gliding flight by directly measuring the lift, drag and pitching moment on real flying fish models (Cypselurus hiraii) in a wind tunnel. In addition, we investigate the roles of wing morphology like the enlarged pectoral and pelvic fins, and lateral dihedral angle of pectoral fins. With both the pectoral and pelvic fins spread, the lift-to-drag ratio is larger and the longitudinal static stability is enhanced than those with the pelvic fins folded. From the glide polar, we find that the wing performance of flying fish is equivalent to those of medium-size birds like the petrel, hawk and wood duck. Finally, we examine the effect of water surface underneath the flying fish and find that the water surface reduces the drag and increases the lift-to-drag ratio.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.1
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• pp.79-88
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• 2002

13%Cr martensitic stainless steel has been used mainly with a material for fish pre-processing machinery. However, it has not very nice cutting section because of little of the carbon content. Therefore, SUS420J2 steel that contents 0.3%C with high-strength in spite of the rust is used with a material for fish pre-processing machinery. However, studies on the corrosion characteristics of SUS420J2 steel are relatively rare. Especially, the corrosion phenomenon may cause serious degradation because the fish pre-processing machinery is exposed always to seawater environment. In this paper, the immersion corrosion test was carried out at seawater environment (pH=7.52) on SUS420J2 steel specimens that have various post-treatment conditions and its corrosion characteristics were evaluated. From test results, the specimens such as base metal, vacuum heat treatment, electrolytic polishing and tempering after quenching tend somewhat sensitive from the corrosion. In the case of vacuum heat treatment specimen of continuous immersion during 360 days, the weight loss ratio was high about seven times when compared with the different specimens. On the contrary, SUS420J2 steel specimen that has the heat treatment of tempering after quenching and the electrolytic polishing was less sensitive from the corrosion, and the weight loss ratio was very low.

• Journal of Aquaculture
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• v.3 no.2
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• pp.127-133
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• 1990

Growth Comparisons of two age groups of coho salmon, Oncorhynchus kisutch, underyearling and age one, were made at Chungmu Experimental Fish Culture Station from December 17, 1988 to April 26, 1989. During the first 66 days of experimental period, the fish of underyearling group grew from 167.0 g to 633.1 g in average weight and the feed coefficient (FC) and daily growth rate (DGR) were 1.1 and $2.0\%$, respectively. In the same period, the fish of age one group grew from 396.0 g to 854.6 g in average weight and the FC and DGR were 1.1 and $2.0\%$, respectively. During the second 63 days, the fish of underyearling and age one group grew up to 1171.9 g and 1239.7 g respectively. FCs of these two groups were 1.5 and 2.6, respectively and DGRs were $1.0\%$ and $0.7\%$, respectively. Underyearling fish consumed more feed and performed better FC and DGR than age one fish. FC and DGR sharply decreased as the fish weight increased. Therefore under-yearling fish of this species seems better as seeds for seawater cage culture. For this purpose it is necessary to increase smolting rate in the underyearling group fish within a single season.