• Korean Journal of Ecology and Environment
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• v.55 no.1
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• pp.49-59
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• 2022

Total of 325 estuaries in Korea were surveyed to analyze the effect of presence of sluice gate on the estuary environment and fish community from 2016 to 2018. Fish community in closed and open estuaries showed differences generally, and the relative abundance (RA) of primary freshwater species in the closed and migratory species in the open estuaries were high. The result of classifying species by habitat characteristics in closed and open estuaries showed similar tendencies at the estuaries of south sea and west sea. The relative abundances of primary freshwater species in the closed estuaries at the estuaries of south sea and west sea were the highest, but estuarine and migratory species were high in both closed and open estuaries at the estuaries of east sea. Primary freshwater species showed higher abundances in the closed estuaries with reduced salinity due to blocking of seawater since they are not resistant to salt. However, primary freshwater species in open estuaries at east sea was higher than that of the closed estuaries, which is considered to be the result of reflecting the characteristics (tide, sand bar, etc.) of the east sea. Korea Estuary Fish Assessment Index (KEFAI) was showed to be higher at open estuaries than closed in all sea areas (T-test, P<0.001), the highest KEFAI was observed in closed estuaries at south sea, and open estuaries in east sea. Fish community of closed and open estuaries in each sea areas showed statistically significant differences (PERMANOVA, East, Pseudo-F=3.0198, P=0.002; South, Pseudo-F=22.00, P=0.001; West, Pseudo-F=14.067, P=0.001). Fish assemblage similarity by sea areas showed a significant differences on fish community in closed and open estuaries at east sea, south sea, and west sea (SIMPER, Group dissimilarity, 85.85%, 88.36%, and 88.05%). This study provided information on the characteristics and distribution of fish community according to the types of estuaries. The results of this study can be used as a reference for establishing appropriate management plans according to the sea areas and type in the management and restoration of estuaries for future.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.637-656
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• 2023

River estuaries are dynamic and productive ecosystems with high regional biodiversity. Environmental DNA (eDNA) has become a useful approach to assessing biodiversity in aquatic ecosystems. This study was conducted to investigate fish community characteristics and species diversity in two river estuary ecosystems, the Taehwa River and Changwon Stream. We further compared conventional and eDNA metabarcoding analyses of the fish communities. The conventional survey was performed in May, July, and October 2022, while the eDNA analysis was conducted only in May. We observed various fish species with different life histories, including carp, goby, and marine fish. We also found that migratory fish, such as dace Tribolodon hakonensis, sweetfish Plecoglossus altivelis, and eel Auguilla japonica, occurred in the Taehwa River, suggesting high river connectivity. Marine fish species were predominant in the Changwon Stream, as this river is located close to the sea. The diversity indices showed that the Taehwa River generally had higher species richness, evenness, and diversity values than the Changwon Stream. A total of 9-19 species were detected in the conventional survey for the three sites, whereas 11-18 species were found from eDNA analysis. The findings indicate that the sensitivity of eDNA was similar to or higher than that of the conventional method. Our study findings suggest the efficiency and efficacy of eDNA-based fish community monitoring, although with some shortcomings in applying the genetic marker to Korean fish, including no clear-cut distinction for Korean endemic species and/or genetically closely related species groups.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.191-199
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• 2007

Seasonal variation in species composition of fish in the Saemangeum Reservoir was determined using seasonal samples collected by an otter trawl from April 2006 to February 2007 after the dike construction, and compared with the data obtained during the dike construction in 2001-2002. A total of 35 species, 8,960 individuals and 53,084.4 g of fish were collected during the study. Of the fish collected, brackish and coastal fishes such as Konosirus punctatus, Synechogobius hasta and Repomucenus lunatus, and migrant fishes such as Engraulis japonicus and Scomberomorus niphonius predominated in abundance accounting for 95% in the total number of individuals. Fish species composition and abundance showed a similar seasonal trend to those in the other western coastal waters of Korea. The resident species were mainly collected in spring and in autumn. The number of species and biomass were high in summer by the large amount of catch of migrating species. Catch was low in winter and only 2 species were collected. A brackish and coastal fish, K. punctatus and two migrant fishes, E. japonicus and S. niphonius were abundantly collected after the dike construction. However, the dominant fishes during the dike construction such as Leiognathus nuchalis, Neosalanx jordani and Chaeturichthys stigmatias were rarely collected. Fish density was $1,149\;inds./10,000m^2\;and\;12,644g/10,000m^2$ during the dike construction, and increased 6 times in the number of individuals ($7,467\;inds./10,000m^2$) and 3 times in biomass ($44,237g/10,000m^2$) after the dike construction. Annual species richness (R) and species diversity (H') decreased from R=0.0160 and H'=2.47 during the dike construction in 2001-2002 to R=0.0038 and H'=1.11 after dike construction in 2006-2006, respectively. These changes seemed to be related to the reduction of the saline area and degradation of water quality in Semangeum Reservoir after the dike construction.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.298-304
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• 1999

Toxic effect of landfill leachate on the larvae and juvenile stage of the river puffer fish, Takifugu obscurus, were investigated in order to assess severity of environmental impact of leachate effluent on the general population of estuarine fishes. A short-term toxic experiment was designed to test both laboratory hatched larvae and juveniles (5, 10 and 15 mm in length) and in-situ juveniles (30 and 45 mm in length) using the leachate concentrations between 0 and 16%. Lethal concentrations of 50% mortality ($LC_{50}$) were observed using Spearman-karber Method. 24hr-$LC_{50}$ appeared at the leachate concentrations ranging from 3.03 to 8.57%, 48hr-$LC_{50}$ at 2.73 to 6.21 %, 72hr-$LC_{50}$o at 2.45 to 5.53%, and 96hr-$LC_{50}$ at 2.38 to 4.93%, respectively. Leachate concentrations between 0.69 and 1.51% induced 96hr-$LC_1$. Respiratory frequency was significantly affected even at low leachate concentrations between 0.5 and 1.0% (P < 0.05). These results suggest that the leachate effluents may cause a harmful impact on the physiology of river puffer fish, especially for younger cohorts.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.874-881
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• 1997

In order to estimate toxicity of copper, radmium and chromium on survival, growth and oxygen consumption of the estuarine mysid, Neomysis awatschensis, adult and juvenile, the experiments were conducted by renewal bioassay method at $20{\pm}1^{\circ}C\;and\;20{\pm}1\%_{\circ}$ salinity. The $96hr-LC_{50}$ of the mysid exposed to cadmium, copper and chromium was 20.2, 11.3 and $670.4\;{\mu}g/\ell$ in adut and 3.4, 1.9 and $49.4\;{\mu}g/\ell$ in juvenile, respectively, and were ranked in order of toxicity : copper >cadmium >chromium. Survival rates of the mysid exposed to the sublethal concentrations of heavy metals for 40 days were significantly affected by cadmium $\geq1.0\;{\mu}g/\ell$ and copper $\geq0.6\;{\mu}g/\ell$ concentrations. The growth rate of the mysid exposed to $cadmium\geq2.0\;{\mu}g\ell$ and copper $\geq1.2\;{\mu}g/\ell$ concentrations were significantly reduced than that exposed to normal condition, but there was no affect on intermoult period. Oxygen consumption rate of the mysid exposed to heavy metals was significantly reduced with increasing heavy metals concentrations. The results of the present study led us to conclude that concentrations levels cadmium$\geq1.0\;{\mu}g\ell$ and copper $\geq0.6\;{\mu}g\ell$ of the estuarine could markedly affect the distribution and population of the mysid by reduced survival, growth and oxygen consumption rate.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.795-798
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• 2008

An estuary is very important that the seawater and the freshwater meet and they formed wide foreshore and estuarine which is used as the habitat of various living thing and spawning bed of fish. Masan bay is typical closing bay in Korea. It is located 9 km from the open sea and most inside of Jinhae bay. The width of bay entrance is less than 1 km, where the flow velocity is very low. The large scale industrial complex of Masan bay is located in near Masan and Changwon city whose population is about 100 million. Because of low tidal velocity, the pollutants from the land are accumulated, which makes the water quality worse in Masan bay. The purpose of this study is to analyze the various hydraulic characteristics using RMA-2 model. The advection and diffusion of pollutant is also simulated using RMA-4 model according to the inflow of Changwon-stream and Nam-stream. The hydraulic simulations include the effect of tide which can be characterized by the tide data of Masan bay tide observatory.

• 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.