• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.31-38
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• 2014

The fish community and upstream of glass eels (Anguilla japonica) in the Imjin River estuary Gyeonggi-do, Korea was investigated from 2008 to 2012. During the surveyed period 43 species belonging to 18 families were collected. Korean endemic species was Microphysogobio jeoni which showed a ration of 0.04% in collected species. Exotic fishes were Carassius cuvieri and Ctenophayngodon idellus, and comprised 0.06% of the total individual number. Among the fish species observed, 17 species of the freshwater fish (40.5%), 6 species of migration fish (14.2%), 8 species of the brackish water fish (19.1%) and 11 species of sea water fish (26.1%). In terms of composition ration, Anguilla japonica (glass eels, 49.8%), Coilia ectens (23.3%), Saurogobio dabryi (8.1%), Repomucenus olidus (3.3%), Lateolabrax maculata (2.9%) and Chelon haematocheilus (2.8%) were found to display high individual number. On the other hand, C. ectens (33.6%), C. haematocheilus (14.2%), Cyprinus carpio (10.5%), Mugil cephalus (9.1%) and S. dabryi (7.6%) were dominated of biomass. The dominant species of individual was A. japonica (glass eels), and subdomint species included C. ectens. The fish biomass catched of fisherman in the Imjin River (Paju-si) were 83.6~240.3 t by each year. The year 2011 and 2012 were decreased rapidly. Among these, M. cephalus (48.0~80.0%), C. carpio (6.7%), Carassius auratus (4.9%), Silurus asotus (3.9%), Takifugu obscurus (2.5%), Anguilla japonica (adult, 2.2%) and Pseudobagrus fulvidraco (2.1%) dominated of biomass. Body weight of glass eels at each year were 0.03~ 1.13 t, average 212.0 kg and 1,325,000 individual by 0.16 g each one individual.

• Journal of Marine Life Science
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• v.5 no.2
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• pp.72-80
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• 2020

A sea dike in the Yeongsan River estuary was constructed in 1981 to supply water and reclaim tidal flats for agriculture, separating the estuary into the freshwater and seawater zones. However, the sluice gates are frequently opened and freshwater is discharged in summer when more rainfall is recorded than other seasons, then converting the estuary to brackish water system. In this study, the direct effect of freshwater discharge was investigated by monitoring daily variation in water properties and phytoplankton size structure before and after the freshwater discharge events from 2013 to 2015. Freshwater discharge resulted in a sharp decrease in salinity and dissolved oxygen (DO) at surface water whereas it increased the turbidity of water column. However, salinity did not decrease sharply in 2014 when freshwater was discharged one day before the monitoring and salinity remained low prior to the monitoring. Levels of nutrients especially dissolved inorganic nitrogen (DIN) increased after the discharge and this contributed to potential limitation of nutrients such as P or Si rather than N in the estuary. Freshwater discharge also caused the changes in phytoplankton biomass (chlorophyll a) and size structure although their responses were different between years. The changes may affect growth of grazers and thus structure of marine food web by alternating food availability in the Yeongsan River estuary.

• Korean Journal of Environment and Ecology
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• v.32 no.6
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• pp.591-602
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• 2018

Clithon retropictus has been designated as an endangered wildlife Class II due to its high value as a biological indicator species capable of judging environmental quality such as salinity, water flow, and ground conditions. However, basic research on its physiological and ecological characteristics is still lacking. As such, this study intended to examine the impact of environmental conditions such as salinity and soil particle size on the size and density of Clithon retropictus at the Yeoncho river estuary. The investigation of the salinity, which is a key variable that affects the distribution of organisms in the estuary, showed that Clithon retropictus could grow at a salinity ranging from 0#x2030; (freshwater) to 25‰ (brackish water). The coarse gravel (19-75mm) tended to increase nearer the upper stream (under the Yeoncho weir), while the proportion of particles smaller than sand (less than 19mm) increased toward the downstream. The population and the size of the individuals decreased rapidly in the downstream where water stagnated near the Yeoncho weir, and the salt water joined. The results indicated that Clithon retropictus had a high tolerance to salinity, but the adaptability was weaker toward the extremes since the population, and the size tended to decrease as the salinity increased. The correlation analysis revealed that both salinity and soil particle size affected the population and individual size. The correlation between the individual size and salinity was -0.242 (P <0.01), indicating that the size decreased with increasing salinity. The correlation between individual size and coarse gravel having a particle size of 19mm or more was 0.420 (P <0.01), indicating that the size increased with increasing the particle size.

• 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 Ecology and Environment
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• v.54 no.3
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• pp.247-256
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• 2021

Understanding the selective feeding behavior of zooplankton on phytoplankton is essential for evaluating the nutrient cycle and energy flow in the food web. Although many studies have been conducted regarding the feeding behaviors of zooplankton through gut content analyses, there are limitations in the visual identification of digested contents using a microscope. DNA techniques have been applied to overcome these limitations since they can detect and amplify small amounts of prey DNA remaining in the gut contents. We designed a method to extract prey DNA from the gut contents of the whole body of the copepod specimen and tested the resolution of DNA identification for the prey phytoplankton. The common brackish species, Sinocalanus tenellus, were collected from Saemangeum Reservoir in different sites and seasons, and gut content DNA was extracted using 2.5% bleach treatment for 2 min for removal of potential contamination sources existing in preserved specimens without dissolution of the body. The sequences of the extracted gut contents were confirmed using BLASTn suite based on the NCBI database. The phytoplankton species detected in the gut showed temporal and spatial differences. Although DNA analysis of small copepod gut contents has been suggested as an effective method to examine the dynamics of primary prey sources at the genus or species level, uncertainties such as misidentification and limitations in the detailed information of the composition still exist.

• Journal of Korean Elementary Science Education
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• v.40 no.1
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• pp.113-125
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• 2021

In this study, a problem-centered learning based STEAM field experience learning program was developed and the effects of applying it were investigated. The program was composed of 8 sessions by using problem-centered learning education method and integrating STEAM elements between disciplines. The contents of program are as follow. In the step of sharing problems and making a problem-solving plan, they understood the various examples and meanings of endangered species, explored the project activities, and made an inquiry plan. In the search and re-exploration phase, a smart device was used to investigate the appearance, habitat environment and cause of extinction for Clithon retropictus, and a site inquiry plan was established for each group. Then, they moved to the field to explore brackish-headed gallops and discuss ways to protect endangered species. In the step of creating a solution, a web-based report was produced as the final product using smart devices based on the results of the inquiry. In the presentation and evaluation stage, the produced web-based report was used to present each group, conduct mutual evaluation, and organize project activities. The developed program was applied to 6th grade 29 students enrolled in the J University Gifted Education Center. In order to find out the effectiveness of the program, tests of science process skill, creative problem-solving ability, and scientific attitude were conducted before and after of program learning, and the results were statistically analyzed by t-test. In addition, a STEAM program satisfaction test was conducted after project in order to find out the satisfaction of the class. As a result of application of the program, the results were significantly improved in openness, criticism, and creativity among the sub-factors of creative problem-solving ability and scientific attitude. Satisfaction with the STEAM program was also high, but no significant result was found in science process skill. Therefore, the program of this study could be influenced on improvement of creative problem-solving ability and scientific attitude of gifted students in elementary science.

• Korean Journal of Environment and Ecology
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• v.37 no.1
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• pp.59-69
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• 2023

This study was carried for the purpose of using basic data for vegetation management plans by analyzing the current status of herbaceous community and Salix spp. community at Janghang Wetland in Han-river estuary. In order to investigate the vegetation status, the 50 plots were investigated and analyzed using the quadrat and Braun-Branquet method. In the herbaceous community, were found a total of 31 taxa of 11 families, 24 genera, 28 species, and 3 variants. A total of 42 taxa of 16 families, 33 genera, 39 species and 3 variants were appeared in the Salix subfragilis community, and a total of 46 taxa with classification of 19 families, 37 genera, 43 species, and 3 varieties were founded in the Salix koreensis community. As for the analysis of life-form and dominance, the hydatophytes was relatively high in the Salix subfragilis community, the hemicryptothytes was high in herbaceous community and therophytes was high in Salix koreensis community. As a result of correlation analysis of electrical conductivity(EC) and exchangeable sodium(Na+) in the soil, hydatophytes and hemicryptothytes showed a negative correlation, and therophytes showed a positive correlation. Therefore, it was analyzed that Salix koreensis and therophytes have a high rate of appearance in relatively dry and salty soil. Salix subfragilis, hydatophytes, and hemicryptothytes have a high rate of appearance in low salt concentrations and wet areas.

• Korean Journal of Ichthyology
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• v.34 no.4
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• pp.262-269
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• 2022

A distribution survey was conducted from 2018 to 2020 to evaluate the distribution status, habitat characteristics, and extinction threat of the short ninespine stickleback Pungitius kaibarae (Gasterosteidae). Literature reports of P. kaibarae distribution have been sorted by each period, 1980~1996, 1997~2005, and 2007~2017, and the samples were collected in 32, 43, and 64 stations for each period. Among the 75 streams and 193 sampling sites investigated during the study period, 1,400 P. kaibarae individuals were collected from 26 streams at 39 sites. The main habitat of P. kaibarae was downstream or brackish water zones with a low altitude, slow water velocity, and many aquatic plants. The main reasons for the decline in population size were assumed to be drought and flood, river work for flood restoration and river maintenance, bridges construction, and predation by the exotic fish species Micropterus salmoides. Previous evidence reported a 42.6% reduction in occupancy within 10 years, a decline in habitat quality, and the spread and impact of the exotic fish species Micropterus salmoides. Therefore, P. kaibarae is now considered a Vulnerable (VU A2ace) species based on the IUCN Red List categories and criteria. Therefore, P. kaibarae should be redesignated as an endangered species by the Ministry of Environment and systematically managed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.15 no.4
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• pp.166-175
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• 2010

Seasonal variation in species composition of estuarine fauna in the Han River estuary was determined by analyzing monthly samples collected on the intertidal flat of Ganghwa Island by a fence net from April to December 2009. Total number of species was 57: 34 species of fishes, 20 species of crustacean, 2 species of cephalopods and 1 species of jellyfish. Of a total of 57 species, Portunus trituberculatus (57.2%), Palaemon gravieri (7.1%), Collichthys lucidus (7.0%), Hemigrapsus sanguineus (6.2%) and Exopalaemon carinicauda (4.7%) were predominated in abundance. Diverse species were occurred in spring and autumn, and abundance was high in autumn. Chelon haematocheilus, Synechogobius hasta, Co ilia nasus, P. gravieri and E. carinicauda were classified as the brackish residence species. P. trituberculatus, C. lucidus, Mugil cephalus and Cynoglossus joyneri were coastal migratory species which use the estuary as nursing and feeding grounds. Diadromous species (such as Takifogu obscurus, Anguilajaponica and Eriocheir sinensis) and freshwater fish (Carassius auratus) were also collected.

• Korean Journal of Ichthyology
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• v.24 no.3
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• pp.201-219
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• 2012

The estuaries bank of Nakdong River, Korea, was constructed in 1987 and many arguments have been under discussion on the subject of ecological impact on ecosystem during 20 years. In this context, however, it was not focused on the role of fish-way and the way of improvement to promote fish movement to complete its life history. This paper was the result of investigation on fish fauna of upper and lower part of the bank and the analysis of comparison of the fishes with those using fish-way which were installed in each side of bank as ladder type and fish gate. The authors discussed the importance of fish gate and its management base on the result. The number of fishes collected in this study for upper part of estuaries bank was 31 species, among them 71% was the pure freshwater residents indicating the characteristics of the area as a freshwater ecosystem. It was observed that 9 species of coastal fishes were found in this region including Coilia ectens and Neosalanx sp. which is anadromous to spawn. Excluding 6 freshwater fishes, 30 fish species collected in lower part of estuaries bank were coastal fishes indicating that former brackish ecosystem was changed into marine one. The freshwater fishes found in this region were restricted the appearance only in the season of discharging freshwater into the sea. The number of fishes found in fish-way was 39 species, more than that of river and coast. But only 19 species founded in fish ladder was comparable with the result of investigation on fish gate including 32 species. It was considered that the fish gate has more important role as a fish passage from the fact that only it allowed to movement of numerous number of fry of Neosalanx sp. and Engraulis japonicus. These results indicates that two-way movement system is more efficient than downward only one in estuaries bank for fish migration.