• Korean Journal of Ecology and Environment
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• v.53 no.3
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• pp.229-240
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• 2020

In this study, the results of fish assemblage survey for 16 reservoirs in the Yeongsan·Seomjin-River watershed were presented with fish assemblage characteristics analysis in relation to reservoir size. The survey method including number of sampling sites was followed the "Biomonitoring survey and assessment manual" of the Ministry of Environment/National Institute of Environmental Research (MOE/NIER), and the reservoirs were categorized as three size groups, small, medium or large reservoirs, based on the MOE/NIER as well. Total 13 family classified into 44 species were collected from 2018 (7 reservoirs) to 2019 (9 reservoirs), and the dominant and subdominant species were Hemiculter eigenmanni (Relative abundance, RA, 32.9%) and Lepomis macrochirus (RA, 31.4%), respectively. As a result of the analysis in relation to the reservoir size, the average (±standard deviation) number of species of the small, medium and large reservoirs were 11±2.9, 14.3±2.1, 22.7±0.6, respectively, which showed positive correlation with the reservoir size. Total 6 fish assemblage characteristics(number of species, number of individuals, richness index, herbivorous fish ratio, carnivorous fish ratio, exotic fish ratio) showed significant differences between the each reservoir size groups (P<0.05). As a result of cluster analysis, 16 reservoirs were clustered into 5 groups with 60% similarity, and the each reservoirs seems to be clustered depends on the distance from each other, watershed and their historical geology rather than size. These results are baseline information for the understanding of fish assemblage in Korean reservoirs, important for establishing management policy of reservoirs in the Yeongsan·Seomjin-River watershed.

• Korean Journal of Ichthyology
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• v.21 no.4
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• pp.262-272
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• 2009

Upstream behavior of glass eels was examined in an experimental eel-ladder at a laboratory of the National Fisheries Research and Development Institute from March to May in 2008. The study was made under various environmental factors and conditions affecting the upstream migration of glass eels in order to design a functional ladder that would allow the passage of glass eels. The experimental eel-ladder consisted of an upper freshwater chamber and a lower sea water chamber; glass eels in sea water can move up to the upper freshwater chamber through the slope (eel-ladder) between them. The optimal condition of the eel-ladder was estimated by comparing the number of glass eels that moved upstream depending on various conditions. Since the glass eels actively moved up the slope to river water rather than to reservoir water or tap water, the experiment was realized using river water. A significantly higher number of glass eels moved up during the spring tide than during the neap tide, and during night than during the day. Upstream movement was significantly higher during high tide than during low tide. Glass eels effectively moved up through a slope of less than $30^{\circ}$ and water-flow velocity lower than 0.4 m/sec. The fish preferred a coarser ladder bed covered with small gravels, brush or carpet.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.403-412
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• 2003

Temporal and spatial variations of size-structured phytoplankton (chlorophyll a) were investigated over an annual cycle (February-October, 2003) to elucidate phytoplankton dynamics in the Juam Reservoir, Chonnam. Physical properties were also measured to investigate the relationship between the properties and temporal and spatial variations of size structured phytoplankton using simple linear regression. Phytoplankton (chlorophyll a) were grouped into three size classes: micro-size(> 20 ${\mu}m$), nano-size (3-20 ${\mu}m$) and pico-size (< 3 ${\mu}m$) in this study. Physical properties included water temperature, light attenuation coefficients, PAR (photosynthetically active radiation) and turbidity. Maximum chlorophyll a was observed in April, 2003 in the lower region whereas a peak of chlorophyll a developed in October, 2003 in the upper region. Large cell-sized phytoplankton (micro-size class)were dominant in the events of the chlorophyll a peaks. Potential mechanisms in the physical properties affecting the size-structured phytoplankton dynamics in the Juam Reservoir were discussed.

• Journal of fish pathology
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• v.6 no.2
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• pp.205-218
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• 1993

On the development of hirame(Paratichtys olivaceus) culture, outbreak of scuticociliata infection was reported to cause severe damage in Japan. To establish effective measures for isolation and cultivation of this ciliate, we tried to culture this pathogenic ciliate using medium for bacteria and fish cell lines in vitro. Scuticociliata from the brain tissues of infected fish was aseptically inoculated to CHSE-214 cells cultured in MEM-10 without antibiotic. Scuticociliata grew well and the number of ciliate reached $10^6\;cells/ml$ at temperatures of $15^{\circ}C$ to $20^{\circ}C$ for 10d. The number of ciliate cultured in the cell lines is 10 times higher than the numbers cultured in the liquid medium alone. This ciliata could be cloned by dilution method. Scuticociliata isolated could grow well on 42 different cell lines that were established from marine fish, warm freshwater fish, and salmonids. This ciliate could be preserved in liquid nitrogen for more than 6 months. Subsequently, we observed the optimal temperature and salinity for growth, and tested the sensitivities of this organism to formaldehyde, flagyl(Metronidazole), Ekuteshin(Combination compound of sulfamonometoxin and ormethoprim), and ozonixation. Optimal temperature for growth was $25^{\circ}C$ and salinity was 1.0 to 1.5%. Washed scuticociliata was killed by formaldehyde at the concentration of 50ppm for 10min, but was not completely killed even at a high concentration of 400ppm for 20min in MEM-5. Flagyl and Ekuteshin can inhibit the growth of scuticociliata at the concentration of 1,000 and $100{\mu}g/ml$ in MEM-10, respectively. More than 99% of this scuticociliata could be killed by ozonization at a dose equivalent to $1.0mg/\ell$ oxidant for 30sec in sea water. Isolated scuticociliata showed the pathogenicity to the cultured hirame by artificial infection(I. P. injection, $10^5\;cells$/fish). The number of scuticociliata in the water could be counted by most probable number(MPN) method using tissue culture, and the minimum detectable number was $1.8\;cells/\ell$. The number in the reservoir tank for water supply to the culture tank was 110 cells/l. After cleaning by elimination of the sediments from of the reservoir tank and disinfected with formaldehyde, number of scuticociliata decreased and was counted less than $1.8\;cells/\ell$ and infection rate of cultured hirame was decreased.

• Korean Journal of Microbiology
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• v.38 no.1
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• pp.31-37
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• 2002

For elucidating the correlation between the eubacterial community structure and environmental parameters in Nammae Reservoir located in Kyungsan, Kyungbuk, the bacterial community structure and their structure affecting environmental parameters were analyzed using Fluorescent In Situ Hybridization (FISH) monthly over year. $\alpha$ . $\beta$ . $\gamma$-subclasses of Proteobacteria and Cytophaga-Flavobacterium (CF) group known as dominant bacterial group in freshwater were detected in 3 stations over year. The ratio of each subclass to total bacteria was determined; $\alpha$.$\beta$ . $\gamma$-subclasses and CF group varied in the range of 4.0~29.2%, 1.7~25.8%, 1.8~12.8%, 4.9~36.3%, respectively and there was no substantial differences between stations. In terms of the correlation between each group specific bacteria and environmental parameters such as temperature, SS, pH, DOC, NH$_4$-N, NO$_3$-N, PO$_4$-P, standing crops of algae, the results were as follows: 1) total bacterial numbers correlated positively with temperature, SS and DOC, 2) Eubacteria positively with DOC and Chl-$\alpha$, 3)${\gamma}$-subclass positively with DOC, and 4) CF group positively with standing crops of chlorophyceae, 5) whereas $\beta$-subclass bacteria correlated negatively with standing crop of cyanobacteria and that of total algae.

• Korean Journal of Microbiology
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• v.39 no.4
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• pp.272-276
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• 2003

Sapgyo Lake is an artificial freshwater reservoir which is located to the midwest of Korea and is the main water reservoir for industry and agriculture of the region. In this study we investigated environmental factors and the change of bacterial community with the influence of surrounding inflow water and the seasonal variation using the molecular ecological approach. Water samples were collected at front of the dike in May and August, 2001. Bacterial genomic DNAs were extracted directly and purified for the amplification of bacterial 16S rDNA. Clone libraries of the 16S rDNA were constructed using pGEM-T easy vector and RFLP analysis was performed to make a group as OTUs with 4 base recognizing enzymes (MspI and HaeIII). The estimated values of richness in August sample was higher than in May. Thirty-three of 153 clones in May and thirty-eight of 131 clones in August were sequenced from forward region of bacterial 16S rDNA for about 600~800 bp. Proteobacteria, Cytophaga, gram positive bacteria and Verrucomicrobia were observed both months. Especially, Planctomyces, cyanobacteria and chloroplast appeared in August when algal bloom occurred. On the whole investigation, Sapgyo lake showed a typical community structure of estuarine and was influenced by heterochthonous organic matters from the surrounding stream.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.4
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• pp.193-200
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• 2007

The purpose of this study is investigate to water quality, pH, turbidity, salinity, nutrients, SS, DO, COD, ${NH_4}^+$-N, ${NO_2}^-+{NO_3}^-$-N, TN, TP, ${PO_4}^{3-}$-P in ditches and seawater of the Hwawon, southwestern coastal area of Korea. Two stations of the ditch, one station at outfall from reservoir of the coastal development and 15 stations of seawater were measured in August just after a 96.5 mm rainfall and in dry season of November 2006. The sampling time were divided into a rainy and dry season based on turbidity, SS, salinity and nutrients difference of distributions that was evidence as a inflow of pollutants from the developing coastal land area. The pH, turbidity, salinity and SS were high and showed different from between surface and bottom in near the developing of coastal land than the other stations after a strong rainfall over 90 mm while it were not varied in vertical and horizontal concentration profile in dry season. The other nutrients were showed the same concentrations gradient patterns. In opposition to expectations, the SS in dry season was higher than in the rainy season due to upwelling by the wind and strong current. It appears that the researched coastal seawater qualities were mainly effected by the inflow of freshwater from the ditches and drain from the reservoir of the developing land area during strong rainfall while the seawater qualities were mainly effected by the wind and strong current in dry season.

• Korean Journal of Remote Sensing
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• v.34 no.6_1
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• pp.1119-1130
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• 2018

Soyang Lake has been contributing to economic growth by preventing flood damage in the metropolitan area, the water level in the middle to upper flow of lake has been greatly decreased due to the drought in 2015. In order to restore the existing flow rate, Bupyungbo has been built in Bupyeong-ri, Shin Nam-myeon, Inje-gun to cause artificial changes on the sedimentary environment of Bupyeong freshwater region. Therefore, this study intends to confirm the changes of sedimentary environment since Bupyeongbo has been utilized. For this study, we used the Sentinel-2 satellite image data periodically to measure the dimension of water according to the volume of water kept near Bupyung district and analyzed the particle size and the percentage of water content of the sediments through field study. The Sentnel-2 satellite images showed us how the water surface has been changed and that during the period from September 2017 to October 2018, the minimum and maximum area of water surface was observed in June 2018 and in January 2018, respectively. In addition, we find that the smaller being the particle size, the higher having the water content and that there is higher the correlation between the water content and the grain size of the sediment layer. Hereafter, if we will acquire the drone images at Bupyung district, we expect that we will be able to measure the distribution of sediments in the same area according to different time periods and observe various kinds of sediment through field work.

• Parasites, Hosts and Diseases
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• v.59 no.4
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• pp.427-432
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• 2021

The infection status of zoonotic trematode metacercariae (ZTM) was investigated in total 568 freshwater fishes (19 species) from the irrigation canal of Togyo-jeosuji (Reservoir) in Cheorwon-gun, Gangwon-do, the Republic of Korea for 3 years (2018-2020). All fishes were examined using the artificial digestion method. The metacercariae of Clonorchis sinensis (CsMc) were detected in 180 (43.8%) out of 411 fish of positive species, and their infection intensity was 38 per fish infected (PFI). Especially, in 2 fish species, i.e., Pseudorasbora parva and Puntungia herzi, the prevalence was 82.1% and 31.3%, and the infection intensity with CsMc was 88 and 290 PFI, respectively. Metagonimus spp. metacercariae (MsMc) were found in 403 (74.1%) out of 544 fish of positive species, and their infection intensity was 62 PFI. In the pale chub, Zacco platypus, the prevalence of MsMc was 98.6%, and their infection intensity was 144 PFI. Centrocestus armatus metacercariae were detected in 171 (38.9%) out of 440 fish of positive species, and their infection intensity was 1,844 PFI. Echinostoma spp. metacercariae were found in 94 (19.6%) out of 479 fish of positive species, and their infection intensity was 3 PFI. Metorchis orientalis metacercariae were detected in 43 (29.3%) out of 147 fish of positive species, and their infection intensity was 4 PFI. By the present study, it has been confirmed that some species of ZTM, including CsMc and MsMc, are prevalent in fishes from the irrigation canal of Togyo-jeosuji in Cheorwon-gun, Gangwon-do, Korea.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.315-326
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• 2021

The clear-water phase (CWP) is a notable limnological phenomenon in freshwater systems caused by predatory interactions between large filter-feeding zooplankton and phytoplankton. However, the mechanisms and factors that influence the extent of CWP, particularly in complex water systems with both fluvial and lacustrine characteristics, remain poorly understood. The present study evaluated CWP occurrence patterns at different sites in a large reservoir located in a temperate monsoon region (Lake Paldang, Korea); the relationships among factors associated with CWP occurrence, such as transparency, zooplankton diversity, and chlorophyll a concentration were investigated. Transparency exhibited significant correlations with precipitation and retention time, as well as the relative abundance of zooplankton (p<0.01), suggesting that a change in the retention time due to precipitation can alter CWP. Data collected before and after CWP occurrence were analyzed using paired t-test to determine variations in CWP occurrence based on the water system characteristics. The results demonstrated that various factors were associated with CWP occurrence in the fluvial-type and lacustrine-type sites. The correlation between zooplankton biomass and transparency was stronger in the lacustrine-type sites than in the fluvial-type sites. The lacustrine-type sites, where cladoceran emergence is common and is associated with long retention times, favored CWP occurrence. The results suggest that lacustrine-type sites, which are conducive to zooplankton development and have relatively long retention times, enhance CWP occurrence. Furthermore, CWP occurrence was notable in spring, and the present study revealed that site-specific CWP could occur throughout the year, regardless of the season.