• Journal of Aquaculture
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• v.13 no.4
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• pp.339-351
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• 2000

Optimal environmental conditions, that sustained fastest growth, lowest mortality and abnormality of the scallop Patinopecten yessoensis, were identified from field experiments undertaken at Chumunjin during 1991-1998. Temperature within the water column 10~30 m depth ranged between 5 and 23$^{\circ}C$; high temperature and daily fluctuation resulted in growth retardation and heavy mortality of the scallop. Optimal salinity range was between 31.5 and 34.5%0 and water transparency 6.0 and 18.1 m, which was significantly affected by phytoplankton density. Chlorophyll concentration ranged between 0.04 and 3.51 f.lgfL. Low temperature and high chlorophyll concentration appear to support faster growth of the scallop. Optimal periods of transplantation for intermediate culture were between mid July and early November: cultured under high density during July-August as a first step and under low density during mid September through early November as a second step. Optimal stocking density in square net cage (<35${\times}$35 em) for intermediate culture was 30-40 individuals per cage for main culture using lantern net and 80 -100 individuals of the size of 1.5 ~ 3.0 em shell height per cage for sowing culture. During the intermediate culture, the highest growth was realized, when the cage was held at water depth between 10 and 15 m. Water depth below 25 m, however, was best to avoid mass mortality during the periods of abnormally high water temperature and high variation of water temperature. The daily growth rate during the intermediate culture was between 0.019~0.381 mm; low in January and February but high in March and April. It is suggested that the main culture is commenced before June under low stocking density to avoid the possibility of mass mortality during summer by high water temperature.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.3
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• pp.108-116
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• 2006

To investigate the factors controlling the spring population of Acartia hongi, egg production, hatching time of egg and predation pressure were measured. Egg production was maintained the superior position between winter and spring. Egg production was positively correlated with not only water temperature when water temperature was below $7^{\circ}C$ but also chlorophyll-a concentration when it was from $7^{\circ}C$ to $21^{\circ}C$. A regressive equation of development time$(D_e,\;day)$ of eggs derived from water temperature$(T,\;^{\circ}C)$ was obtained as $D_e=18.9(T-0.4)^{-1.0}$, showing longer development time at water temperature below $5^{\circ}C$. In Cross Correlation Analysis(CCA) to examine the time-lag relationship among abundances of developmental stages of A. hongi, egg production rate calculated by multiplying population egg production rate by hatching time showed more significant correlation with nauplii abundance than population egg production rate. Therefore, it suggests that hatching time is also recognized by a factor controlling formation of population and especially, in winter, high abundance of egg derived from high daily egg production rate and delayed hatch by low water temperature become the origin of initial spring population of nauplii. Egg predation by Noctiluca scintillans, suggesting a negative factor in formation of A. hongi spring population, was observed. During spring, A. hongi eggs were found in $2.9\sim21.1%$ of individuals of N. scintillans. It was deduced that $1.2\sim49.5%$ of the eggs produced by A. hongi was preyed on by N. scintillans. In conclusion, the factors controlling spring population of A. hongi were regarded as high egg production by winter generation, the delayed development time of egg by low temperature, and egg predation of N. scintillans.

• Journal of Appropriate Technology
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• v.6 no.1
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• pp.21-27
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• 2020

The ASF, which originated in Africa and threatens the world, landed in Asia in 2018 in China, and became a stern threat to the security of the Korean Peninsula when North Korea officially reported the ASF to the OIE in May 2019. In 1921, Montgomery, a British veterinary pathologist, made headlines by naming the African swine fever "African Swine Fever," or ASF, a disease caused by a high fatality virus that existed in East Africa. The ASF, which was a pandemic of endemic diseases in Africa, landed in Portgal around 1957 and swept through farms in Lisbon, Portugal. The ASF continued to settle in Spain and Portugal, causing 40 years of damage until the end of the 1990s, and is now in progress after landing on the Italian island of Sardinia in 1978. The virus, which landed in Portiport of Georgia on the Black Sea coast of the Black Sea in 2007, spread to Russia and caused massive damage to China in 2018, then rapidly spread to Vietnam, Laos and Myanmar in May 2019 and spread across the country, causing massive damage to the pork industry and is now in progress. Just three months after confirming the outbreak in North Korea, the outbreak at farms in Paju and Yeoncheon was confirmed on Sept. 16, 2019, leaving South Korea with the stigma of ASF-causing countries, and although the ASF's nationwide expansion has been blocked, it is currently underway in wild boars. If the ongoing ASF in the two Koreas becomes indigenous, it would be a major disaster not only for the pork industry but also for the Korean Peninsula economy. Under the current circumstances, it is impossible to focus only on veterinary areas limited to South Korea, ruling out risk factors from the ASF outbreak. Currently, it is difficult to prevent damage to the pork industry due to the ASF outbreak due to the poor water defense reality in North Korea, and as it is adjacent to China, which has a high risk of developing various epidemic diseases, there is a need for the two Koreas to jointly conduct quarantine and quarantine on the border areas. First of all, I think rapid exchange of information and education on ASF and other diseases is necessary before establishing a joint defense system on the Korean Peninsula. It is important to conduct thorough quarantine and disinfection of ASF-generated areas in North Korea, and areas bordering China and Russia, and jointly conduct thorough quarantine and control of livestock and livestock products in circulation. Cooperation by the South and North Korean water defense industries to prevent the protracted ASF on the Korean Peninsula by all means and methods is essential.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.1
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• pp.1-8
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• 2015

To evaluate accuracy and precision of determination of total alkalinity ($Alk_T$) and carbon dioxide ($TCO_2$) derived from present study, experiment was applied with $CO_2$ CRM (Batch 132, Scripps Institution of Oceanography; $Alk_T=2229.24{\pm}0.39{\mu}mol/kg$, $TCO_2=2032.65{\pm}0.45{\mu}mol/kg$). As the result, average concentration of $Alk_T$ and $TCO_2$ was $2354.09{\mu}mol/kg$ (~5.6% difference with $CO_2$ CRM) and $2089.60{\mu}mol/kg$ (~2.3% difference with $CO_2$ CRM), respectively. For previous method (Gran Titration) by addition $NaHCO_3$ to deionized water($Alk_T$ $2023.33{\mu}mol/kg$), average concentration was $2193.39{\mu}mol/kg$ (sd=57.15, n=7). Whereas, average concentration was $2017.02{\mu}mol/kg$ (sd=10.98, n=7) for the present study. Recovery yield experiments of total alkalinity in deionized water and seawater were implemented by addition of $NaHCO_3$. The recovery yield of deionized water in the range 0 to $4952.39{\mu}mol/kg$ was 100.8% ($R^2$=0.999), and seawater in the range 0 to $2041.32{\mu}mol/kg$ was 102.3% ($R^2$=0.999). Comparison of $pCO_2$ sensor (PSI $CO_2-Pro^{TM}$) with present method showed very meaningful correlation coefficient ($R^2$=0.977) in the range of 427 to $705{\mu}atm$ and 9.16 to $15.24{\mu}mol/kg$ throught elapsed time for two weeks. Field experiment of diurnal variation of total carbon dioxide was accomplished at Sachon harbor in the coastal waters of East Sea of Korea. Concentration of $Alk_T$ and $TCO_2$ was increased during night, and decreased during daylight hours. The results showed mirror type between $TCO_2$ and dissolved oxygen, which was attributable to photosynthesis and respiration of phytoplankton. Also, open ocean field study was performed to obtain vertical profile of $Alk_T$ and $TCO_2$ in C-C zone (Clarion-Clipperton Fracture Zone), Northeastern Pacific. Average concentrations of $Alk_T$ in the surface mixed layer (0~60 m) and deeper layer below 200 m were $2422.38{\mu}mol/kg$ (sd=78.73, n=20) and $2465.87{\mu}mol/kg$ (sd=57.68, n=103), respectively. And average concentrations of $TCO_2$ were $2134.47{\mu}mol/kg$ (sd=65.4, n=20) and $2431.87{\mu}mol/kg$ (sd=65.02, n=103) in the same depth ranges such as $Alk_T$. Vertical distributions of $Alk_T$ and $TCO_2$ concentrations tended to increase with depth, and analyzed concentrations showed slightly higher than those of previous studies in this area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.259-266
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• 1998

A study on the biological and chemical characteristics in the middle last Sea of Korea was carried out at 31 stations in October $11\~18$, 1995 on board the R/V Tam-Yang. The chlorophyll a concentration, new and regenerated production, and the vertical diffusion of nitrate from the thermocline structure were investigated. From the vertical distribution of chlorophyll a, subsurface maxima were observed near the thermorline at most stations including the frontal zone, except at the southern stations where the maximum chloropyll a concentration occurred at the surface, The nanophytoplankton was the most dominant fraction comprising $83.5\%$ of total phytoplankton cell numbers, but netphytoplankton were common at the southern stations where the dominant species were Rhizosolenia sp. Nitrogenous new production and regenerated productions were measured using the stable isotope $^{15}N$ nitrate and ammonia uptake method. The vertically integrated nitrogen production varied between 8.470 and $72.945\;mg\;N\;m^{-2}\;d^{-1}$. The f-ratio, which is the traction of new production from primary production, waried between 0.03 and 0.72, indicating that $3\%$ to $72\%$ of primary production was supported by the input of nutrients from below the euphotic zone and the rest are supported by ammonia recycled within the euphotic layer. This range of f-ratio encompasses from extremely oligotrophic to eutrophic area characteristics. The differences in productivity and f-ratio among stations were related to frontal structure and the bottom topography. The values were high near the frontal zone and low outside of it, and the station near Ulleng Island showed the highest f-ratio. Vertical diffusion coefficients were calculated from both the water column stability (Kz-1) of King and Devol's equation (1979) and new nitrogen requirement (Kz-2). The values of Kz-2 ($0.11\~0.55\;cm^2/s$) were relatively low compared to the values reported previously.

• Korean Journal of Ichthyology
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• v.22 no.3
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• pp.168-178
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• 2010

Fish assemblages associated with rock reef and non-rock reef were studied using specimens collected at three sites in Geomun Island waters of the Southern Sea, Korea, in February, May, August and October, 2006. Two survey methods for the study were followed: collection by a gill net, and video observation by scuba diving. The gill-net survey was conducted during the night, the scuba-diving observations were conducted during the day. From the gill-net survey, a total of 40 species, 380 inds. and 71,426.9 g was caught at the three sites. The dominant species was Trachurus japonicus; other species were Raja kenojei, Dasyatis akajei, Stephanolepis cirrhifer, Narke japonica, Pagrus major, Sebastes inermis, and Sphyraena pinguis. At the rock-reef site, a total of 26 species, 264 inds. and 46,776.7 g was caught by gill net, and the dominant species was T. japonicus. A total of 17 species, 45 inds., 10,535.1 g was caught at the flat-bottom 1 site, and 19 species, 71 inds. and 14,115.1 g were caught at the flat-bottom 2 site. The scuba-diving survey resulted in 13 species and 1,749 inds. observed at the three sites through the survey period. The main observed fishes were rock-dwelling species such as Chromis notatus, Microcanthus strigatus, S. cirrhifer, Ditrema temmincki, Evistias acutriostris, Girella punctata, Halichoeres poecilopterus, Hexagrammos agrammus, Prionurus scalprum, Sebastes inermis, and Semicossyphus reticulatus. Seven species and 1,739 inds. observed at the rock-reef site comprised 99.4% of the inds. of the three sites. Therefore, the fish community in Geomun Island waters included many rock-reef. species, but a few were migratory species like T. japonicus and Scomber japonicus. The abundance of fish at the rock-reef site was high in comparison with those at two non-rock reefs. The dominant species were very different between the day and the night, although rock-reef species comprised the main part of the fish community. We conclude that the high abundance of fish in Geomun Island waters is most closely related to physical structure, such as rock reefs, which is the main habitat of many fishes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.3
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• pp.129-137
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• 1989

Sand fish, Arctoscopus japonicus (Steindachner) is distributed in the coastal waters of East Sea of Korea, Japan, and Alaska. On December 1, 1987, matured adult of sand fish were collected from the shore of Ok-kye, Myongju-gun, Kangwon-do, Korea. The authors carried out artificial insemination on boat. The fertilized eggs were incubated and the larvae were reared in laborato교. The eggs of this species were demersal and adhesive, and their diameter were varied within $3.1\~3.4$mm (mean 3.3 mm, n= 10). They have a number of small oil globules. The spawned eggs in nature were formed the egg mass which were measured ca. 4 m in dia-meter. The hatching took place in 65 days after fertilization at the water temperature of $8.7\~12.3^{\circ}C$. The newly hatched larvae were $8.5\~10.2$ mm in total length with 11 (abdominal) +40 (caudal) = 51 myomeres. 24 days after hatching, the larva attained 19.4 mm in total length, at this time the larvae absorbed the yolk completely, and become postlarvae. 32 days after hatching, the larva attained 23.4 mm in total length, and become juvenile. 56 days after hatching, the juvenile reached 29.9 mm in total length and had adult form. 5 spines of preopercle bone were formed at 24.4 mm in total length. At ca. 15 mm in total length, the form of the pectoral fin was transformed into the adult form.

• Korean Journal of Heritage: History & Science
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• v.52 no.1
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• pp.242-257
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• 2019

The Demilitarized Zone (DMZ) stretches two kilometers north and south from the Military Demarcation Line (MDL) of South and North Korea. This area was established as a weapons-free buffer zone when an armistice agreement was signed in 1953. However, there have been several very high-tension military standoffss over the past 65 years. On the South Korean side, civilian access to the Civilian Control Line (CCL) and beyond to the north has been restricted, and natural heritage has been well maintained. Natural heritage is defined as living things, their habitat and non-living things of the ecosystem which deserve to be protected. Research shows that a variety of flora and fauna, their habitat, marshes and geographical structures are found across the DMZ region. Although the DMZ region has not been such a good place for habitat conservation, we can say that this area may be the best location for restoration in terms of its variety of ecosystems and considerable land size. Restoration of course depends on future plans and management policies. This area, including the DMZ and the well-protected north of the CCL, will be the best habitat for endangered species of wild fauna and flora if we classify the various habitat types and create a habitat map. In doing this project, we need to include the estuary of the Han River and the lagoon (brackish water lake) of the East Sea coast. In addition, we must establish long-term plans for conservation and sustainable use and do international scientific research across the DMZ region in collaboration with scientists of South and North Korea and international experts. Mutual cooperation between the two Koreas for investigation and conservation efforts is paramount.

• Korean Journal of Ichthyology
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• v.21 no.1
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• pp.1-6
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• 2009

The effect of water temperature on fasting and post-prandial total ammonia excretion (TAN) of the starry flounder Platichthys stellatus (mean body weigh : $42.4{\pm}3.4g$) was studied. The fasting and post-prandial TAN excretions were measured under three different water temperatures (10, 15 and $20^{\circ}C$) for 24 hours using a recirculating system. In each treatment three replicates were set up and total 45 fish were used. Fish were taken to the indoor aquarium, acclimated over 10 days at three temperatures, and transferred to TAN measuring system for measurements of TAN excretion at the same temperatures. After 3 days of starvation, fasting TAN excretion was measured at each temperature. To investigate post-prandial TAN excretion, fish were hand-fed to satiation level with a commercial diet containing 50.2% crude protein for 7 days, two times daily 08 : 00 and 16 : 00 h. The fasting and postprandial TAN excretion increased with increased water temperature (p<0.05). Mean fasting TAN excretion rates at 10, 15 and $20^{\circ}C$ were 10.9, 11.2 and $12.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$, respectively. The value at $20^{\circ}C$ was higher than those at 10 and $15^{\circ}C$ (p<0.05), but there was no significant difference between $10^{\circ}C$ and $15^{\circ}C$. Mean post-prandial TAN excretion rates at 10, 15 and $20^{\circ}C$ were 33.0, 43.4 and $55.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$, respectively. Two peaks of post-prandial TAN excretions were observed, and the second peak was always greater than the first. The post-prandial TAN excretion rate reached to the maximum after 10 hours from the first feeding at $10^{\circ}C$($45.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$), $15^{\circ}C$ ($64.5mg\;TAN\;kg\;fish^{-1}\;h^{-1}$) and $20^{\circ}C$ ($83.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$), respectively. The TAN loss for ingested nitrogen at $20^{\circ}C$ (48.8%) was higher than that for $10^{\circ}C$ (43.0%) and $15^{\circ}C$ (45.7%). This study provides empirical data for estimating ammonia excretion and managing culture management of starry flounder under given temperatures.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.37-46
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• 2016

This study describes the spatio-temporal distributions in phytoplankton community such as species composition, standing crops and dominant species from April to November 2008 in the Uljin Marine Ranching Area (UMRA). A total of 123 species of phytoplankton belonging to 67 genera was identified. In particular, diatoms and dinoflagellates were occupied more than 60.5% and 34.6% of total species, respectively. The annual dominant species were Thalassiosira sp., Pseudo-nitzschia pungens in spring, Leptocylindrus danicus, Guinardia striata in early summer, Cheatoceros cirvisetus, Ch. decipiens in early autumn and Skeletonema costatum -ls (like species), Pn. pungens in autumn. Phytoplankton cell density fluctuated with an annual mean of $48cells{\cdot}mL^{-1}$ between the lowest value of $1.8cells{\cdot}mL^{-1}$ in early autumn and the highest value of $240cells{\cdot}mL^{-1}$ in spring. According to the cluster analysis, the phytoplankton community of the UMRA was characterized by the nutrient supply from land side and water movement as current.