• Title/Summary/Keyword: West sea

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Neotectonic Crustal Deformation and Current Stress Field in the Korean Peninsula and Their Tectonic Implications: A Review (한반도 신기 지각변형과 현생 응력장 그리고 지구조적 의미: 논평)

  • Kim, Min-Cheol;Jung, Soohwan;Yoon, Sangwon;Jeong, Rae-Yoon;Song, Cheol Woo;Son, Moon
    • The Journal of the Petrological Society of Korea
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    • v.25 no.3
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    • pp.169-193
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    • 2016
  • In order to characterize the Neotectonic crustal deformation and current stress field in and around the Korean Peninsula and to interpret their tectonic implications, this paper synthetically analyzes the previous Quaternary fault and focal mechanism solution data and recent geotechnical in-situ stress data and examines the characteristics of crustal deformations and tectonic settings in and around East Asia after the Miocene. Most of the Quaternary fault outcrops in SE Korea occur along major inherited fault zones and show a NS-striking top-to-the-west thrust geometry, indicating that the faults were produced by local reactivation of appropriately oriented preexisting weaknesses under EW-trending pure compressional stress field. The focal mechanism solutions in and around the Korean Peninsula disclose that strike-slip faulting containing some reverse-slip component and reverse-slip faulting are significantly dominant on land and in sea area, respectively. The P-axes are horizontally clustered in ENE-WSW direction, whereas the T-axes are girdle-distributed in NNW direction. The geotechnical in-situ stress data in South Korea also indicate the ENE-trending maximum horizontal stress. The current crustal deformation in the Korean Peninsula is thus characterized by crustal contraction under regional ENE-WSW or E-W compression stress field. Based on the regional stress trajectories in and around East Asia, the current stress regime is interpreted to have resulted from the cooperation of westward shallow subduction of the Pacific Plate and collision of Indian and Eurasian continents, whereas the Philippine Sea plate have not a decisive effect on the stress-regime in the Korean Peninsula due to its high-angle subduction that resulted in dominant crust extension of the back-arc region. It is also interpreted that the Neotectonic crustal deformation and present-day tectonic setting of East Asia commenced with the change of the Pacific Plate motion during 5~3.2 Ma.

The Ecological Values of the Korean Demilitarized Zone(DMZ) and International Natural Protected Areas (비무장지대(DMZ)의 생태적 가치와 국제자연보호지역)

  • Cho, Do-soon
    • Korean Journal of Heritage: History & Science
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    • v.52 no.1
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    • pp.272-287
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    • 2019
  • The Korean Demilitarized Zone (DMZ) was established in 1953 by the Korean War Armistice Agreement. It extends from the estuary of the Imjin River, in the west, to the coast of the East Sea. It is 4 km in width and 148 km in length. However, the ecosystems of the civilian control zone (CCZ) located between the southern border of the DMZ and the civilian control line (CCL) and the CCZ in the estuary of the Han River and the Yellow Sea are similar to those in the DMZ, and, therefore, the ecosystems of the DMZ and the CCZ are collectively known as the "ecosystems of the DMZ and its vicinities." The flora in the DMZ and its vicinities is composed of 1,864 species, which accounts for about 42% of all the vascular plant species on the Korean Peninsula and its affiliated islands. Conducting a detailed survey on the vegetation, flora, and fauna in the DMZ is almost impossible due to the presence of landmines and limitations on the time allowed to be spent in the DMZ. However, to assess the environmental impact of the Munsan-Gaesong railroad reconstruction project, it was possible to undertake a limited vegetation survey within the DMZ in 2001. The vegetation in Jangdan-myeon, in Paju City within the DMZ, was very simple. It was mostly secondary forests dominated by oaks such as Quercus mongolica, Q. acutissima, and Q. variabilis. The other half of the DMZ in Jangdan-myeon was occupied by grassland composed of tall grasses such as Miscanthus sinensis, M. sacchariflorus, and Phragmites japonica. Contrary to the expectation that the DMZ may be covered with pristine mature forests due to more than 60 years of no human interference, the vegetation in the DMZ was composed of simple secondary forests and grasslands formed on former rice paddies and agricultural fields. At present, the only legal protection system planned for the DMZ is the Natural Environment Conservation Act, which ensures that the DMZ would be managed as a nature reserve for only two years following Korean reunification. Therefore, firstly, the DMZ should be designated as a site of domestic legally protected areas such as nature reserve (natural monument), scenic site, national park, etc. In addition, we need to try to designate the DMZ as a UNESCO Biosphere Reserve or as a World Heritage site, or as a Ramsar international wetland for international cooperation. For nomination as a world heritage site, we can emphasize the ecological and landscape value of the wetlands converted from the former rice paddies and the secondary forests maintained by frequent fires initiated by military activities. If the two Koreas unexpectedly reunite without any measures in place for the protection of nature in the DMZ, the conditions prior to the Korean War, such as rice paddies and villages, will return. In order to maintain the current condition of the ecosystems in the DMZ, we have to discuss and prepare for measures including the retention of mines and barbed-wire fences, the construction of roads and railroads in the form of tunnels or bridges, and the maintenance of the current fire regime in the DMZ.

An Experimental and Numerical Study on the Survivability of a Long Pipe-Type Buoy Structure in Waves (긴 파이프로 이뤄진 세장형 부이 구조물의 파랑 중 생존성에 관한 모형시험 및 수치해석 연구)

  • Kwon, Yong-Ju;Nam, Bo-Woo;Kim, Nam-Woo;Park, In-Bo;Kim, Sea-Moon
    • Journal of Navigation and Port Research
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    • v.42 no.6
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    • pp.427-436
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    • 2018
  • In this study, experimental and numerical analysis were performed on the survivability of a long pipe-type buoy structure in waves. The buoy structure is an articulated tower consisting of an upper structure, buoyancy module, and gravity anchor with long pipes forming the base frame. A series of experiment were performed in the ocean engineering basin of KRISO with the scaled model of 1/ 22 to evaluate the survivability of the buoy structure at West Sea in South Korea. Survival condition was considered as the wave of 50 year return period. Additional experiments were performed to investigate the effects of current and wave period. The factors considered for the evaluation of the buoy's survival were the pitch angle of the structure, anchor reaction force, and the number of submergence of the upper structure. Numerical simulations were carried out with the OrcaFlex, the commercial program for the mooring analysis, with the aim of performing mutual validation with the experimental results. Based on the evaluation, the behavior characteristics of the buoy structure were first examined according to the tidal conditions. The changes were investigated for the pitch angle and anchor reaction force at HAT and LAT conditions, and the results directly compared with those obtained from numerical simulation. Secondly, the response characteristics of the buoy structure were studied depending on the wave period and the presence of current velocity. Third, the number of submergence through video analysis was compared with the simulation results in relation to the submergence of the upper structure. Finally, the simulation results for structural responses which were not directly measured in the experiment were presented, and the structural safety discussed in the survival waves. Through a series of survivability evaluation studies, the behavior characteristics of the buoy structure were examined in survival waves. The vulnerability and utility of the buoy structure were investigated through the sensitivity studies of waves, current, and tides.

Cultivation of Ginseng in Baengnyeongdo, the Northernmost Island of the Yellow Sea in South Korea (서해 최북단 섬 백령도의 인삼 재배 현황)

  • Cho, Dae-Hui
    • Journal of Ginseng Culture
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    • v.4
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    • pp.128-141
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    • 2022
  • Baengnyeongdo Island, which belongs to Ongjin-gun, Incheon, is an island in the northernmost part of the West Sea in South Korea. Baengnyeong Island is the 15th largest island in Korea and covers an area of 51 km2. The Korea Ginseng Corporation (KGC) investigated the possibility of growing ginseng on Baengnyeong Island in 1996. In 1997, thanks to the support of cultivation costs from Ongjin-gun, the first ginseng seedbed was built on Baengnyeong Island. In 1999, the seedlings were transplanted to a permanent field under a contract with KGC. In 2003, the first six-year-old ginseng harvest was performed, and KGC purchased all production according to the contract. Since then, KGC has signed on to grow ginseng until 2012 and purchased six-year-old ginseng until the fall of 2016. Since 2014, the GimpoPaju Ginseng Agricultural Cooperative Association has signed a ginseng production contract. According to a survey of nine 6-year-old ginseng fields (total 5,961 units) on Baengnyeong Island, the top five with good growth had a survival rate of 42.6 to 68%, and the bottom four with poor growth had an extremely low survival rate of 11.1 to 21.3%. The four fields with low survival rates were where hot peppers were planted before ginseng cultivation. It is believed that the excess nitrogen remaining in the soil due to the treatment of compost or manure during pepper cultivation causes ginseng roots to rot. The average incidence of Alternaria blight was 8.6%. Six six-year-old ginseng gardens were low at 1.1 to 4.7%, while the other three were high at 16.7 to 20.9%. It is assumed that the reason for the low survival rate and high incidence of Alternaria blight is a rain-leaking shield. Farmers used rain-leaking shields because the precipitation on Baengnyeong Island was smaller than on land. One field showed 3% of leaves with yellowish brown spots, a symptom of physiological disturbance of the leaf, which is presumed to be due to the excessive presence of iron in the soil. To increase the production of ginseng on Baengnyeong Island, it is necessary to develop a suitable ginseng cultivation method for the island, such as strengthening the field management based on the results of a scientific study of soil, using rain-resistant shading, and installing drip irrigation facilities. I hope that ginseng will become a new driving force for the development of Baengnyeong Island, allowing ginseng products and food to thrive in the beautiful natural environment of the island.

Development of Marine Ecotoxicological Standard Methods for Ulva Sporulation Test (파래의 포자형성률을 이용한 해양생태독성시험 방법에 관한 연구)

  • Han, Tae-Jun;Han, Young-Seok;Park, Gyung-Soo;Lee, Seung-Min
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.13 no.2
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    • pp.121-128
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    • 2008
  • As an aquatic ecotoxicity test method, a bioassay using the inhibition of sporualtion of the green macroalga, Ulva pertusa, has been developed. Optimal test conditions determined for photon irradiance, pH, salinity and temperature were $100\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, $7{\sim}9$, $25{\sim}35\;psu$ and $15{\sim}20^{\circ}C$, respectively. The validity of the test endpoint was evaluated by assessing the toxicity of four metals (Cd, Cu, Pb, Zn) and elutriates of sewage or waste sludge collected from 9 different locations. When the metals were assayed, the $EC_{50}$ values indicated the following toxicity rankings: Cu ($0.062\;mg{\cdot}L^{-1}$) > Cd ($0.208\;mg{\cdot}L^{-1}$) > Pb ($0.718\;mg{\cdot}L^{-1}$) > Zn ($0.776\;mg{\cdot}L^{-1}$). When compared with other commonly used bioassays of metal pollution listed on US ECOTOX database, the sporualtion test proved to be the most sensitive. Ulva sporulation was significantly inhibited in all elutriates with the greatest and least effects observed in elutriates of sludge from industrial waste ($EC_{50}=6.78%$) and filtration bed ($EC_{50}=15.0%$), respectively. The results of the Spearman rank correlation analysis for $EC_{50}$ data versus the concentrations of toxicants in the sludge presented a significant correlation between toxicity and four heavy metals(Cd, Cu, Pb, Zn). The method described here is sensitive to toxicants, simple to use, easy to interpret and economical. It is also easy to procure samples and maintain cultures. The present method would therefore probably make a useful assessment of aquatic toxicity of a wide range of toxicants. In addition, the genus Ulva has a wide geographical distribution and species have similar reproductive processes, so the test method would have a potential application worldwide.

Variations in subtidal surface currents observed with HF radar in the costal waters off the Saemangeum areas (새만금 연안역에서 HF radar에 의해 관측된 조하주기 표층해류의 변화)

  • Kim, Chang-Soo;Lee, Sang-Ho;Son, Young-Tae;Kwon, Hyo-Keun;Lee, Kwang-Hee;Choi, Byoung-Hy
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.13 no.1
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    • pp.56-66
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    • 2008
  • Subtidal surface currents are derived from HF radar measurements in the Saemangeum coastal ocean of the Yellow sea in July 2002 and from September to November 2004. The surface current field is analyzed to examine the effect of wind, river plume and coastline change on the spatial distribution and temporal variation of the surface currents. In July 2002, average wind speed was 0.5 m/s and freshwater discharge from the Keum River was $0.88{\times}10^7\;ton/day$. Temporal mean currents ($\overline{U}$) flow to the northwest with speed of $7{\sim}10\;cm/s$ near the Keum River estuary, to the west as fast as 13 cm/s near the opening gap of the Saemangeum $4^{th}$ dyke, and to the northwest off the Gogunsan-archipelago. This flow pattern is a result of the Keum River plume dispersal and tide-residual currents from the opening gap of the Saemangeum $4^{th}$ dyke. Time series of spatially-averaged current (<$U-\overline{U}$>) direction is highly (r=0.98) correlated with wind direction. From September to November 2004, the opening gap of the Saemangeum $4^{th}$ dyke was closed, northwesterly wind blew with speed of 2.5 m/s on average and the Keum River discharge was $1.19{\times}10^7\;ton/day$. Temporal mean current field ($\overline{U}$) has weak surface flow in most of the coastal ocean and relatively strong currents flow to the southwest with speed of 10 cm/s along the shape coastline of the Gogunsan-archipelago and the Saemangeum $4^{th}$ dyke. The strong flow is generated by the prevailing northwesterly wind which pushes the Keum River plume toward the Saemangeum $4^{th}$ dyke. The residual currents from the opening gap of the Saemangeum $4^{th}$ dyke disappeared and correlation coefficient between time series of spatially-averaged current () direction and the wind direction is 0.69.

Contents of Heavy Metals in Marine Invertebrates from the Korean Coast (한국 연안산 해산 무척추동물의 중금속 함량)

  • Mok, Jong-Soo;Lee, Ka-Jeong;Shim, Kil-Bo;Lee, Tae-Seek;Song, Ki-Cheol;Kim, Ji-Hoe
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.39 no.6
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    • pp.894-901
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    • 2010
  • To measure the heavy metal contents of marine invertebrates, we collected 239 individuals representing 52 species from the eastern (Pohang), western (Gunsan), and southern (Tongyeong) coasts of Korea: 34 species of molluscan shellfish (Gastropoda and Bivalvia), 6 species of Cephalopoda, 8 species of Crustacea, and 4 other species. The mean levels of the heavy metals in the samples taken from the edible portion of each Gastropoda were high in the order of Zn ($21.471\;{\mu}g/g$), Cu ($4.115\;{\mu}g/g$), Mn ($0.868\;{\mu}g/g$), Ni ($0.254\;{\mu}g/g$), Pb ($0.238\;{\mu}g/g$), Cd ($0.154\;{\mu}g/g$), and Cr ($0.110\;{\mu}g/g$). The heavy metals in the Bivalvia were high in the order of Zn ($35.655\;{\mu}g/g$), Mn ($5.500\;{\mu}g/g$), Cu ($3.129\;{\mu}g/g$), Cd ($0.423\;{\mu}g/g$), Ni ($0.402\;{\mu}g/g$), Cr ($0.233\;{\mu}g/g$), and Pb ($0.232\;{\mu}g/g$). The heavy metals in the Cephalopoda were high in the order of Zn ($18.380\;{\mu}g/g$), Cu ($3.594\;{\mu}g/g$), Mn ($0.630\;{\mu}g/g$), Cr ($0.150\;{\mu}g/g$), Pb ($0.068\;{\mu}g/g$), Cd ($0.034\;{\mu}g/g$), and Ni ($0.030\;{\mu}g/g$). The heavy metals in the Crustacea were high in the order of Zn ($25.333\;{\mu}g$/g), Cu ($9.042\;{\mu}g/g$), Mn ($0.659\;{\mu}g/g$), Cr ($0.592\;{\mu}g/g$), Cd ($0.207\;{\mu}g/g$), Pb ($0.126\;{\mu}g/g$), and Ni ($0.094\;{\mu}g/g$). Therefore, the mean levels of the harmful heavy metals (Cd and Pb) in marine invertebrates were high in the order of Bivalvia>Crustacea=Gastropoda>Cephalopoda. The average daily intakes of the heavy metals from the fisheries products were as follows: Cd ($6.88\;{\mu}g$), Cr ($19.13\;{\mu}g$), Cu ($137.02\;{\mu}g$), Mn ($156.13\;{\mu}g$), Ni ($11.39\;{\mu}g$), Pb ($7.01\;{\mu}g$) and Zn ($1,025.94\;{\mu}g$). The average weekly intakes of Cd, Cu, Pb and Zn from the fisheries products were 11.47%, 0.46%, 3.27% and 1.71% respectively, as compared with PTWI (Provisional Tolerable Weekly Intakes) established by FAO/WHO Expert Committee for Food Safety Evaluation.

Synthesis and Biological Activities of Myomodulin E and its Analogs (Myomodulin E 및 유도체들의 합성 및 생리활성)

  • Go, Hye-Jin;Seo, Jung-Kil;Seo, Hae-Jeom;Lee, Min-Jeong;Park, Tae-Hyun;Kim, Gun-Do;Park, Nam-Gyu
    • Journal of Life Science
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    • v.22 no.4
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    • pp.499-507
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    • 2012
  • Previous work has characterized myomodulin A (MMA, PMSMLRLamide) and myomodulin E (MME, GLQMLRLamide) purified from the central nervous systems of the sea hare, $Aplysia$ $Kurodai$, using the anterior byssus retractor muscle (ABRM) of the mussel, $Mytilus$ $edulis$. The amino acid sequences of MMA and MME were the same as those of the myomodulin family peptide found in other mollusks. In this study, we synthesized MME, its derivatives, and other neuropeptides to investigate the relationship between the structure and biological activity of MME. The primary structures of MME's derivatives, Des[$Gly^1$]-MME, Des[$Gly^1,Leu^2$]-MME, and Des[$Gly^1,Leu^2,Gln^3$]-MME, were LQMLRLamide, QMLRLamide, and MLRLamide, respectively. MMA and synthetic peptides were tested on ABRM in $M.$ $edulis$ as well as muscle preparations in $Achatina$ $fulica$. MME displayed an inhibitory effect on phasic contraction of the ABRM at $1{\times}10^{-9}$ M or higher. MME also had a relaxing effect on the catch-tension of AMRM at $1{\times}10^{-8}$ M. Both MMA and its analogs stimulated a contractile response on the crop and relaxed the catch-relaxing response on the penial retractor muscle of $A.$ $fulica$. These results suggest that MME and its analogs have modulatory effects on various muscles of mollusks. This study has also laid the groundwork for future neural and circuit modulation studies during animal behavioral changes.

Factors Affecting the Conservation and Distribution of Migratory Waterbirds in the Southern Tidal Flats of Ganghwa Island, Korea (강화도 남단 갯벌에 도래하는 물새류의 분포요인 및 보전방안)

  • ;;;;Colin Levings
    • Korean Journal of Environment and Ecology
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    • v.16 no.1
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    • pp.34-45
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    • 2002
  • Of the four tidal flat areas(Yeocha-ri, Dongmak-ri, Sundu-ri and Donggum-ri) on Southern Ganghwa Island, the distribution of migratory waterbirds showed a difference in the numbers of individuals and species. Higher numbers of individuals and species were observed on the Yeocha-ri tidal flat. The dominant waterbirds species at the four areas was the Dentin(Calidris alpina). This species showed an occupancy rate(42.0-79.1%) on the Yeocha-ri tidal flat, which was much higher relative to the other areas. The Yeocha-ri tidal flats were higher relative to MSL than the other tidal flats. When the Dongmak-ri tidal flat was covered by sea water, the Yeocha-ri tidal flat was 0.0317$\textrm{km}^2$ in area and on this space we observed many resting waterbirds. The biomass of the waterbirds' potential prey on the Yeocha-ri tidal flat was higher(1.6~2.5$\times$) than other tidal flats. Twenty-three species and 266 individuals were found on the Yeocha-ri tidal flat, which was higher than the tidal flats. The food of Dunlin, which was the dominant species in these four areas, was mainly Reticunassa festiva and Umbonium thomasi(Gastropoda) and Perinereis aibuitensis(Polychaeta). A Dunlin(38.11g) used to eat 1,295 individuals of these food items for daily basal energy. Gastropod, its density was highest on Yeocha-ri tidal flats. The distribution of waterbirds seemed to be closely related with the distribution of the benthos, space and safety of resting site. We suggest that the environments of tidal flats, which are rich foraging habitats, are important factors for conservation of waterbirds.

Comparison of growth, condition index and mortality of manila clam (Ruditapes philippinarum) between originated from China (Liaoning Dandong) and Chungnam (Taean) in Gochang tidal flats (고창 갯벌에서 중국산 및 충남산 바지락의 성장, 비만도 및 폐사 특성 비교)

  • Ahn, Hyun-Mi;Ki, Hun-Jong;Jeong, Hee-Do;Lee, Hee-Jung;Han, Hyung-Kyun;Park, Kwang-Jae;Song, Jae-Hee
    • The Korean Journal of Malacology
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    • v.32 no.3
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    • pp.175-184
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    • 2016
  • In this study, we transplanted Chinese (Liaoning Dandong) and Chungnam (Taean) manila clam seeds to Gochang tidal flats in Jeonbuk province, and compared growth, mortality, and condition indices from May 2015 to August 2016. Within 2 months after transplantation, clam mortality of Chungnam and Chinese origin were $6.9{\pm}4.3%$, $16.9{\pm}7.9{\sim}21.0{\pm}6.3%$, respectively. We supposed that higher mortality of Chinese manila clams might be due to higher stress and weakening of physiological functions by air-exposure and unavailability of food intake for 5 days harvesting, transportation, quarantine procedures. Unlike the local clam farmer's opinion based on their field experience, growth of Chungnam clams in shell length and total weight were a little better than Chinese without statistical significant difference (P > 0.05). Condition indices of Chinese clams showed declining tendency after reaching a peak in May 2014, and in June 2015, respectively. Meanwhile, Chungnam clams has reached its peak of condition indices in May 2014 and in April 2015, respectively. From this result, we supposed that there might be at least one month difference in reproduction between the Chinese and Chungnam manila clams during the first-transplanted year. Because the mortality of adult clam have sharply increased from June 2015 (due to high temperature, few rainfall and spawning) in Gochang tidal flat, it would be recommendable that farmers harvest the clams before June when its shell length are larger than 40 mm. In conclusion, we could directly compare the productivity of Chinese and Chungnam manila clam at Gochang tidal flats by field experiment, and these results are also meaningful to manila clam farmers.