• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.186-194
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• 2020

In this study, spectral analysis was conducted to identify environmental factors af ecting short-term changes in water temperature in the East, West and South coasts of Korea. The data used in the spectrum analysis is the 2016 summer water temperature, air temperature, tide level and wind data provided by Korea Hydrographic & Oceanographic Agency. In power spectrum results, peaks of water temperature and tide level were observed at same periods in West Sea (Incheon, Pyeungteak, Gunsan and Mokpo) and South Sea (Wando, Goheung, Yeosu, Tongyeong and Masan) where mean tidal range was more than 100 cm. On the other hand, periodicity of water temperature did not appear in East Sea and Busan where the mean tidal range was small. Coherence analysis showed that water temperature was highly correlated with tide in West Sea and three stations(Wando, Goheung and Tongyeong) of South Sea. Especially, correlation between water temperature and tide level in Wando and Tongyeong presented 0.96 at semi-diurnal period. Water temperature in Yeosu seems to have influenced by tide and inflow of fresh water. In Masan, water temperature is influenced by south wind, tide and inflow of fresh water. In East Sea, influence of tide on water temperature is small due to current and small tidal range. As a result of comparing the time series graph, stations where the correlation between water temperature and tide is high show that relatively cold water was inputted at flood tide and flow out at ebb tide. short-term variation of water temperature was affected by tide, but long-term variation over a month was affected by air temperature.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.277-285
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• 2003

Temperature profiles were observed to understand seasonal variation of thermal structures in the Juam reservoir from March 2000 to May 2001. Heat flux which affects thermal structures was calculated by observed water temperature and meteorological data. Temperature became homogeneous vertically by convection due to the surface cooling in winter. Maximum heat loss through the surface (109.45W/$m^2$) occurred in December. There was a horizontal gradient of water temperature in winter. The temperature was $3^{\circ}C$ at upstream and $5^{\circ}C$ near the dam. The surface temperature increased by the increase of solar radiation in spring and summer. Maximum heat gained through the surface was 101.95 W/$m^2$ in July. Maximum surface temperature was $29^{\circ}C$ in August, whereas the bottom water was $7^{\circ}C.$ Surface mixed layer became thicker and its temperature decreased by surface heat loss in fall and winter.

• Korean Journal of Ichthyology
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• v.31 no.4
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• pp.201-207
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• 2019

Temperature is one of the most important criteria considered in species preference for aquaculture. Acute drop in temperature during winter is a cause of disease and mass mortality in farmed fish. This study was carried out the low water temperature tolerance, oxygen consumption, hematologic and histological responses to use as basic data for the management of fish farming which frequently cause death due to winter water temperature drop. Low-lethal water temperature for 4 days of file fish Thamnaconus modestus (4day-LT₅₀) was 6.97℃ (6.69~7.27℃). Oxygen consumption rate decreased with decreasing water temperature, showing a significant difference between water temperatures. SOD activity increased significantly at 6℃ experimental group than control group (10℃) (p<0.05), but CAT did not show any significant difference between experimental temperatures (p>0.05). Cortisol increased with decreasing experimental water temperature compared to control group. Histological changes in the liver include decreased blood vessels in the blood vessels, proliferation of acid cells, condensation of the nucleus, atrophy of pancreatic exocrine gland cells, and enzyme source granules.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.4
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• pp.509-518
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• 2019

Analyses with various Sea Surface Temperature (SST) products indicate that the interannual variability of the area-averaged SST in the East/Japan Sea (EJS) is well correlated to that of Pacific Decadal Oscillation (PDO) during 1979-2018, especially in the autumn. The regression analysis with the wind vectors at 200 hPa, where the strongest jet stream flows, suggests that the long-term variability of the intensity as well as the meridional movement of the jet stream are related to the coupling of the autumn EJS SST and PDO. When the axis of the jet stream moves poleward (equatorward) with its weakening (strengthening), both the EJS SST and North Pacific SST increase (decrease). This suggests that both the intensity and meridional movement of the jet stream are possibly related to the coupling of the autumn EJS SST and PDO. However, effects of a weak jet stream during the summer and the strong East Asian winter monsoon make weak coupling between the EJS SST and PDO.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.329-332
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• 1982

A Series of trials for the spawning induction of the Israeli strain of common carp were carried out at the fish culture research station of National Fisheries University of Pusan from 1978 to 1981. 1, During 3 years up to the first periods in 1980 carp pituitaries and/or commercial gonadotropic hormone was used to induce the brood fish to spawn without success. In the trials in the later periods in 1980 and in 1981, water temperature increase method was used with success in 40 females of 16 trials leaving a single failure with 2 females. 2. Brood fish had been kept in a small circular tank ($7\;m^2$) continuously supplied with cool well water enough to keep the water temperature in the tank relatively cool, ranging from 16.9 to $20.2^{\circ}C$, and the water in the spawning tank ($15\;m^2$) was 3.0 to $6.5^{\circ}C$ higher than in the brood fish holding tank. 3. It could be said that the spawning of Israeli strain of common carp in Korea hardly occur without water temperature increase even though treated with hormone.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.2
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• pp.91-97
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• 2001

The effects of sudden changes of water temperature (WT) on the stress response and physiological change of the cultured olive flounder in large (FL) and small (FS) size, and fat cod (FC) were examined by manipulating WT (2 types) in a flow through seawater culture system with 6 tanks (water vol. 270 L/tank). The WT was decreased from $20^{\circ}C$ to $10^{\circ}C$ within 5 hours ($2^{\circ}C/hour$) and maintained at $10^{\circ}C$ for 21 hours (Exp. I), and it was raised from $20^{\circ}C$ to $30^{\circ}C$ within 5 hours and maintained at $30^{\circ}C$ for 21 hours (Exp.II). In Exp. I, the levels of blood hematocrit at 5 hours ($10^{\circ}C$) in FS was significantly decreased from $13.5\pm2.0\%\;to\;11.3\pm2.3\%$, but FC at 2.5 hours ($15^{\circ}C$) ($19.0\pm0.3\%\;to\;23.2\pm3.8\%$) was increased, The blood hemoglobin concentration of all fish in Exp, II was significantly increased until 8 hours after raising WT from $20^{\circ}C$ to $30^{\circ}C$. In Exp. I and II , the levels of plasma cortisol in FL, FS and FC was changed from $5.2\pm8.5ng/mL,\;4.4\pm4.5ng/mL\;and\;2.7\pm0.4ng/mL$, respectively, before sudden drop and rise of WT. The levels of plasma cortisol of in FL ($164.0\pm53.1ng/mL$) and FC ($207.9\pm25.4ng/mL$) were significantly increased by the lowering WT sharply during whole experiment. The FL ($12.6\pm2.0ng/mL$) and FS ($4.0\pm3.9ng/mL$) showed no significant differences in cortisol level according to sudden rise of WT (5 hours). But it in FC ($44.7\pm18.2ng/mL$) was increased. In Exp. I, the plasma glucose levels of all fish groups were decreased after 5 hours ($10^{\circ}C$), The plasma lactic acid concentration of FL and FS showed no significant differences until 5 hours after raising WT from $20^{\circ}C$ to $30^{\circ}C$, But it in FC was significantly increased with WT raise.

• 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.

• Korean Journal of Environmental Biology
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• v.36 no.2
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• pp.131-139
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• 2018

The warming of water as a result of climate change affects fish habitat. Variations in water temperature affect fish physiology almost totally. The rise in water temperature due to climate change leads to hypoxia following decreased oxygen solubility and decreased binding capacity of oxygen-carrying hemoglobin. This study was conducted to evaluate the health status of Atlantic salmon (Salmo salar) fry at elevated water temperatures($20^{\circ}C$) compared with optimum water temperature ($15^{\circ}C$). The method facilitated the detection of biomarker genes using NGS RNAseq analysis and evaluation of their expression pattern using RT-qPCR analysis. The biomarker genes included interferon alpha-inducible protein 27-like protein 2A transcript variant X3, protein L-Myc-1b-like, placenta growth factor-like transcript variant X1, fibroblast growth factor receptor-like 1 transcript variant X1, transferrin, intelectin, thioredoxin-like, c-type lectin lectoxin-Thr1-like, ladderlectin-like and calponin-1. The selected biomarker genes were sensitive to changes in water temperature based on NGS RNAseq analysis. The expression patterns of these genes based on RT-qPCR were similar to those of NGS RNAseq analysis.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.236-243
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• 2023

This study aimed to investigate the survival rates, hematologic responses, and histological responses of juvenile Korean rockfish (Sebastes schlegelii) exposed to artificial increase of water temperature. The water temperature was incrementally raised from the initial 23℃ to 26℃, 28℃, 30℃, and 31℃, with a 1℃ increase every 24 hours. The fish were exposed to each water temperature setting for a period of seven days. No mortality was observed at 26℃ and 28℃. However, at 30℃, mortality began on the 4th day of exposure, with an overall survival rate of 1.5% at the end of the seventh day. At 31℃, mortality occurred as early as the first day of exposure, and all fish had perished by the second day. Plasma cortisol and glucose concentrations increased as water temperature rose, with a significant decrease observed at 31℃. No significant difference in plasma GPT concentration was observed across the various experimental temperatures. In contrast, plasma GOT concentration significantly increased at 31℃. Histological examination revealed that both the liver and gills exhibited normal histology at the initial temperature of 23℃ and at 26℃. However, at 28℃ hepatocellular hypertrophy and gill lamellar epithelial hyperplasia and epithelial cell lifting were observed. At 30℃, hepatocellular condensation and gill lamellar fusion were noted. Finally, at 31℃, severe histological changes were observed, including hepatocellular necrosis, liver congestion, and gill filament necrosis.

• Proceedings of the Korean Aquaculture Society Conference
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• 2005.05a
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• pp.106-107
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• 2005