• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.4
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• pp.360-369
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• 1987

The relationship between the catches of tuna and hydrographic conditions in South-East Pacific region (latitude $5^{\circ}N-12^{\circ}S$, longitude $135^{\circ}W-115^{\circ}W$) was investigated by using the catch data of tuna and Digital Bathythermograph (DBT) data from December 9, 1980 to April 2, 1981. The results are as follows : The study area were located in South Eguatorial Current regions including equatorial upwelling regions in $5^{\circ}N\;to\;12^{\circ}S$. The horizontal mean temperature at the depth of 10m on the first quarter months in the study area was about $25^{\circ}C$C and the salinity of those fishing areas ranged from 34.8 to $35.0\%_{\circ}$. Yellowfin tuna and bigeye tuna were mainly caught in SW vertical temperature profile type, which the depth of thermocline ranged from loom to 300m, and temperature difference of thermocline was about $12^{\circ}C$. The deeper the depth of thermocline, the more the catches of tuna. While albacore tuna was caught well in SS vertical temperature profile type which the temperature of thermocline ranged from $9^{\circ}\;to\;26^{\circ}C$ and its gradient was very smooth. The depth of 1 ml/l surface of dissoved oxygen content ranged from loom to 200m in the South-East Pacific between longitude $140^{\circ}W-100^{\circ}W$, but it was shallower than 100 m near the North-South American continent. The catches of bigeye tuna were larger than those of yellowfin tuna in South Equatorial Current region. As approaching to the South and North American continent, the catches of yellowfin tuna and bigeye tuna decreased because the thermocline becomes shallower and steeper and the depth of the 1 m1/1 surface of dissolved oxygen content became shallower.

• 한국해양학회지
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• v.30 no.4
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• pp.279-287
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• 1995

The vertical profiles of natural ²¹⁰Pb, ²¹⁰Po and ²³⁴Th activities were measured for the upper 100 m of water column at three stations in the middle region of the Korean East Sea during May 1992. And the distribution of these radionuclides was discussed associated with the formation of warm eddy or water mass. The main thermocline was maintained between the depth of 50 and 100 m at the southern station (Sta. A1), and between the depth of 10 to 50 m at the coastal station of Sockcho (Sta. B10). Contrastingly, a main thermocline at Sta. A10, which locates near the center of warm eddy, was observed below 230 m depth. Between 50 and 220 m depth of Sta. A10 is there a relatively homogeneous water mass of 10.1${\pm}$0.5$^{\circ}C$, which is significantly higher in temperature and lower in nutrient than the other two stations. It seems to be due to sinking of the warm surface water in which nutrients were completely consumed. Both ²¹⁰Pb and ²¹⁰Po show the highest concentration at Sta. A1 and the lowest at Sta. B10 among the three stations. Also, the ²¹⁰Pb activity is generally higher in the upper layer than in the lower layer, while ²¹⁰Po activity represents the reversed pattern at all three stations. At Sta. A1 and Sta. B10, the activities of ²¹⁰Po relative to its parent ²¹⁰Pb were deficient in the water column above the main thermocline, but were excess below the thermocline. However, the station near the center of warm eddy(Sta. A10), shows no excess of ²¹⁰Po in the depths below 50 m, although its defficiency is found in the upper layer like the other stations. At Sta. A1 and b10. ²³⁴Th activities are slightly lower in the surface mixed layer than in the deeper region However, at Sta. A10, ²³⁴Th activity in the upper 30 m is higher than below 50 m or in the same depth of the other stations, probably because of the high concentration of particulate matter. The residence time of ²¹⁰Po in the surface mixed layer at Sta. A10 is 0.4 year, much shorter than at the other two stations(about one year). Above 100 m depth, the residence times of ²³⁴Th range from 18 to 30 other two stations(about on year). Above 100 m depth, the residence times of ²³⁴Th range from 18 to 30 days at all stations, without significant regional variation. The percentages of recycled ²¹⁰Po within the thermocline are 39% and 92% at Sta. A1 and Sta. B10, respectively. Much higher value at Sta. B10 may be due to a thin thickness of the mixed layer as well as the slower recycling rate of ²¹⁰Po in the main thermocline.

• Proceedings of the KSRS Conference
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• v.1
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• pp.174-179
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• 2006

Information on the distribution characteristics of tuna resources in Kiribati EEZ waters in three zones (Zone 1: west Gilbert region, Zone 2: central Phoenix region, and Zone 3: east Line region) as well as their relationship with the ocean environment is critical for sustainable managing the migratory tuna resource and fishing practices in this region. Therefore, this study is designed to investigate the spatial and temporal distribution and concentration of bigeye (BET) and yellowfin tuna (YFT) in Kiribati EEZ waters in relation to sea surface temperature (SST) and thermocline depth so as to better understand the tuna resources management basis in Kiribati waters. The geographic and temporal distribution and concentration were first displayed. Paired t-test was utilized to compare the distribution between the two tuna species based on Catch per Unit Effort (CPUE) derived from the Korean longliners during 1996 to 2004, and also among the three zones of Kiribati EEZ waters. Environmental conditions of the three zones were then compared and correlated with the CPUE of YFT and BET. In addition, the effect of ENSO phenomena on the environmental conditions and the distribution of YFT and BET within the three zones were also examined. The BET was relatively higher in the Zone 3 whereas YFT predominate in the Zone 1 and the Zone 2 due to oceanographic differences among the three zones and the ecological habitats of the two tuna species. It was suggested that El Ni?o/Southern Oscillation (ENSO) phenomena altered the oceanographic conditions of the three zones that in turn change the distribution of the two tuna species. During El Ni?o, the warm phase of ENSO, resulted in having more BET in all the three zones and the opposite observed during La Ni?a (cold phase) replacing by having relatively higher catch rate for YFT, particularly in the Zone 2. Although the results of the study are from short periods (1996 to 2004) in considering oceanographic anomality, these environmental variations should be considered into sustainable fisheries management of tuna fisheries in Kiribati EEZ waters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.4
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• pp.355-361
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• 2007

A giant jellyfish (Nemopilema nomurai), which is presumed developing in the East China Sea, is recently one of major issues in the Northeast Asia region due to its fatal damage to the fishery. The biomass estimates have generally been conducted by trawl sampling and sighting survey methods. The biological research is also needed to clarify such environmental origin or diurnal migration patterns. While trawl sampling or sighting survey methods are effective to investigate its density estimates in its distributed community of near bottom or surface, they have a problem in investigation on the vertical distribution of jellyfishes. In this case, an echo sounding detection would have an advantage to survey it more extensively and effectively. This trial was conducted to observe the vertical distribution of giant jellyfish, where thermocline strongly formed, during mooring at each station of the East China Sea and southern coastal area using acoustical and optical methods. By the results, they were observed to exit and move at the water column under the thermocline using the optical camera and echo sounder system, and the information was analyzed to find out the acoustical sound scattering characteristics relatives to 120kHz frequency. These results can be utilized effectively to estimate the vertical distribution and biomass of Giant jellyfish with comparing results from trawl sampling and sighting survey methods, hereafter.

• Ocean and Polar Research
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• v.35 no.2
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• pp.171-179
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• 2013

The long-term variability of sea surface temperature in the East China Sea was reviewed based mainly on published literatures. Though the quantitative results are not the same, it is generally shown that sea surface temperature is increasing especially in recent years with the rate of increase about $0.03^{\circ}C$/year. Other meaningful results presented in the literatures is that the difference of water properties between layers upper and lower than the thermocline in summer shows an increasing trend both in temperature and salinity, suggesting that the stratification has been intensified. As a mechanism by which to evaluate the wintertime warming trend in the region, the weakening of wind strength, which is related to the variation of sea level pressure and atmospheric circulation in the western North Pacific and northern Asian continent, is suggested in the most of related studies.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.549-556
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• 2001

Heat flow characteristics during hot water extraction process was studied experimentally. Data were taken at various outlet port type for the fixed inlet port type, inlet-outlet temperature differences and mass flow rates. In this study, the temperature distribution in a storage tank and an outlet temperature were measured to predict a flow pattern in the storage tank, and a hot water extraction efficiency was analysed with respect to the variables dominating a extraction process. Experimental results show that the extraction efficiency is high in a low flow rate in case of using modified distributor I(MDI) as a outlet port type.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.111-116
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• 1983

Temperature inversions are investigated by using the oceanographic data (1965-1979) obtained in the Southern Sea of Korea. The temperature inversions in winter occur about six times more frequently than those in sumner. In the west region of the Southern Sea, the inversions are found at any depth in winter. In the east region of the Southern Sea, however, they usually appear in surface layer in winter. Such inversion phenomena in winter can be explained by surface cooling effects associated with a net heat loss at the sea surface and a southward advection of surface cold water due to north-westerly monsoon. In summer the inversion layers are usually formed below the thermocline in the west region of the Southern Sea, and in surface layer in the east region. The former results from the mixing between the Tsushima Warm Current and the Yellow Sea Bottom Cold Water, and the latter is generated by an offshore flow of cold water near coast due to southwesterly wind.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.332-344
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• 1996

The vertical profiles of the natural $^{210}Po,\;^{210}Pb\;and\;^{234}Th$, activities were measured at the upper 150 m or 200 m of water column from west-east intersection in the east-southern coastal area of the Korea Peninsula during the period from 26 to 29 April 1994 to compare the removal rates (residence time) and removal processes for $^{210}Po\;and\;^{234}Th$. At the inshore stations, the $^{210}Po$ activity was generally higher in the thermocline and its under layer than in the surface mixed layer, while represented the reversed pattern at the offshore stations. However, the $^{210}Pb$ activity decreased generally with depth. Also, the activity of $^{210}Po$ relative to its parent $^{210}Pb$ was deficient in the water column above the main thermocline, but was slightly excess or close to equilibrium in the thermocline and its under layer. The vertical profiles for the activity of $^{210}Pb$ relative to its parent $^{226}Ra$ showed the reversed pattern with the vertical variation of $^{210}Po$ excess (or deficiency). The $^{234}Th$ activity was significantly lower in the surface mixed layer and thermocline than in the deeper layer. The residence time of $^{210}Po$ ranged from 1 to 4 years at the five stations except station E8 that showed yet long residence time (approximately 10 years). The long residence time at the station E8 may resulted from the thicker surface mixed layer and subsequent the vertical mixing of $^{210}Po$ which was recycled in the lower surface mixed layer compared to at the other stations. Also, the residence time of $^{210}Po$ was shorter at the inshore stations than at the offshore stations. However, the residence time of $^{234}Th$ ranged from 52 to 74 days at all station without the significant variation, was very much shorter relative to the residence time of $^{210}Po$. The correlation between the removal rate of dissolved $^{234}Th$ and the concentration of total suspended matter (TSM) was generally positive. Therefore, it seems that the major route of the removal mechanism of $^{234}Th$ from seawater in the surface mixed layer is via adsorption onto suspended particle surfaces (most likely inorganic particles) and subsequent settling to the bottom layer. Between the removal rate of dissolved $^{210}Po$ and the concentration of chlorophyll-a was positively good correlation. Consequently, most likely the removal of $^{210}Po$ may be occurred by uptake to organisms (mainly such as planktonic debris or fecal pellets) and subsequent settling.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.2
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• pp.91-96
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• 1982

Temperature inversions are investigated by using the oceanographic data obtained in the Yellow Sea from 1965 to 1979. The temperature inversions are found in every depth in almost all areas of the Yellow Sea. While in summer, they frequently occur below thermocline in the west region of the Jeju Island. Such phenomena in winter can be explained by surface cooling effects associated with a net heat loss at the surface and a southward advection of cold water, and those in summer result from the process of mixing between the Yellow Sea Warm Current and the Yellow Sea Bottom Cold Water.

• Ocean and Polar Research
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• v.37 no.2
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• pp.107-117
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• 2015

Thorpe scale analysis was performed using two sets of 25-hour-long hourly CTD data. Raw density profiles collected on the continental slope of the southwestern East Sea were post-processed to reduce instrument noises and measurement errors. Density inversions were detected by applying the overturn ratio test proposed by Gargett and Garner (2008). The value of $K_z$ below the main thermocline estimated with the Osborn parameterization was $5.3{\times}10^{-4}(1.1{\times}10^{-4})m^2s^{-1}$ and that with the Shih parameterization was $5.9{\times}10^{-5}(2.4{\times}10^{-5})m^2s^{-1}$during the spring (neap) tidal period. This result suggests that internal tides can enhance vertical mixing in the observation region.