• Ocean and Polar Research
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• v.24 no.1
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• pp.115-121
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• 2002

Yubu Island is located within the estuary of the Geum River, South Chungcheong Province $(35^{\circ}59'N,\;126^{\circ}36'E)$, Korea. The island is surrounded by a broad and sandy mudflat, which is typical in the west coast of Korea, and is located 4km off from Gunsan City. Less than 100 humans live on the island, occupying 30 houses. After we discovered that this island was a very important waterbird habitat especially for the East Asian subspecies of the Eurasian oystercatcher, Haematopus ostralegus osculans. Waterbirds were monitored once every month from August 1999 to July 2000. The highest number of oystercatchers counted was 3,200 in December 1999, and the birds seemed to remain in the area continuously from September to next February. About 200 breeding and non-breeding birds remained during the breeding season. In August, early migrants returned to the island, with the number reaching 1,060 individuals. This island is also very important for other waterbirds. Endangered or significant species occurring at this site, and their maximum counts were: chinese egret Egretta eulophotes (5), black-faced spoonbill Platalea minor (17), brant Branta bernicla (1), common shelduck Tadorna tadorna (8,000), hooded crane Grus monacha (2), spoon-billed sandpiper Ewynorhynchus pygmeus (7), dunlin Calidris alpina (6,500), great knot Calidris tenuirostris (24,000), far eastern curlew Numenius madagascariensis (2,500), spotted greenshank Tringa guttifer (4) and Saunders's gull Larus saundersi (1,200). During the 12 month survey period, we observed 52 waterbird species and the total of the maximum counts for the separate species was 73,308, implying that perhaps 150,000 birds could be using the immediate area, if a turnover rate of 2 was assumed.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.610-619
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• 2018

This study was carried out in August and September 2016 to investigate the species composition and biomass of benthic diatoms in Yubu Island, Gomso Bay, Imja Island, and Yeoja Bay tidal flat of Southwestern coast. There were 181 species of 48 genera in Yubu Island tidal flats, 194 species of 51 genera in Gomso Bay tidal flats, 224 species of 64 genera in Imja Island tidal flats and 188 species of 56 genera in Yeoja Bay tidal flats. A total of 274 species of 70 genera appeared. Pennales appeared more widely than Centrales and were dominated by Paralia sulcata and Navicula spp. Biomass of Yubu Island tidal flat ranged from $18.8-136.1mg\;m^{-2}$, $31.9-215.7mg\;m^{-2}$ in Gomso Bay, $2.9-120.2mg\;m^{-2}$ in Imja Island and $10.1-147.7mg\;m^{-2}$ in Yeoja Bay. The range of total biomass from 4 areas was $2.9-215.7mg\;m^{-2}$. The concentration of phaeopigment and degradation product of chlorophyll-a was $1.7-470.8mg\;m^{-2}$ in Yubu Island tidal flat, $52.3-277.2mg\;m^{-2}$ in Gomso Bay, $0.6-78.9mg\;m^{-2}$ in Imja Island and $39.1-346.3mg\;m^{-2}$ in Yeoja Bay. Compared with the results reported in this study area and the domestic tidal flats, it cannot be directly compared and evaluated due to various factors such as the timing of the survey, the frequency of the survey, the analysis method and geography. The southwestern coast of Korea has a variety of benthic diatoms and the high concentration of chlorophyll-a is the main determinant of primary productivity.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.483-492
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• 2019

During the breeding season, both adults and immature Eurasian Oystercatchers (Haematopus ostralegus osculans) were observed to feed on prey, such as gastropods (Umbonium thomasi) and bivalves, at the tide water line around Yubu island in Korea. To determine differences in the foraging efficiency between the adult and immature birds, we recorded the feeding behavior using digiscoping with a telescope and a smartphone. We compared the pace, the prey search rate, the proportion of prey search techniques, the feeding success rate, the handling time, and the heads-up rate between the adult and immature birds. There were significant differences in the proportion of prey search techniques when gastropods were consumed and in the prey search rate and heads-up rate when bivalves were consumed but there were no significant differences in feeding success rates. Therefore, although the immature birds on Yubu Island were inferior to adults during the breeding season and they lacked the proficiency to locate prey, their overall foraging efficiency was similar to adults. This was considered to be due to the continuous eating of bivalves during the wintering season, which requires a high level of foraging efficiency.

• Korean Journal of Ecology and Environment
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• v.51 no.2
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• pp.184-191
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• 2018

During the breeding season, some Eurasian Oystercatchers (Haematopus ostralegus osculans) in Yubu Island foraged in the open mudflat area nearby the breeding ground, instead of the tide water line area, main feeding site throughout the year. We found significant differences in foraging behavior and prey species diversity between the two different feeding site types. Even though the birds took more steps for most probably searching preys, their feeding success was much lower in the open mudflat area than the tide water line area. The multiple peck and boring methods were more frequently adopted to catch polychaetes on the open mudflat area, whereas the single peck method was dominant and gastropods and bivalves were main preys in the tide water line area. This study suggests that the bird shows flexible foraging strategy of shifting feeding site, foraging behavior and preys for better reproductive success.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.3
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• pp.11-27
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• 2016

This study is a survey of the flora distributed in Seocheon tidal flat wetland protected area of nearby island (Daejuk-do, Tokki-deung, Muk-do) and Yubo-do Seocheon-gun Chuncheongnam-do, Korea. The numbers of vascular plants were summarized as 231 taxa including 65 families, 167 genera, 204 species, 2 subspecies, 23 varieties and 2 forms. The halophytes were 33 taxa including 15 families, 29 genera, 29 species, 3 varieties and 1 form (Chenopodium album var. stenophyllum, Cnidium japonicum, Juncus haenkei and so on). The rare plants were 4 taxa including Pseudoraphis ukishiba (VU), Belamcanda chinensis (VU), Phacelurus latifolius (LC) and Polygonum bellardii (DD). The Korean endemic plants were 2 taxa including Salix pseudolasiogyne and Forsythia koreana. In the specific plants by floristic region were 24 taxa, a degree I were 19 taxa (Rhodotypos scandens, Zanthoxylum planispinum, Cynodon dactylon and so on), 2 taxa of a degree III (Elymus mollis and Asparagus oligoclonos), 3 taxa of a degree IV (Polygonum bellardii, Wisteria floribunda and Pseudoraphis ukishiba) and degree II, V were not found. The naturalized plants were 40 taxa including Phytolacca americana, Sicyos angulatus, Lactuca scariola and so on. Naturalization rate (NR) was 17.3% of all 231 taxa of vascular plants and urbanization index (UI) was 12.5% of all 321 taxa of naturalized plants. This study was performed to used as a basic data to identify the protected from plant ecosystems of type classify into analyze the vegetation characteristic of based on flora distributed in Yubu-do and nearby islands.

• Journal of Wetlands Research
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• v.21 no.1
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• pp.84-94
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• 2019

The Seocheon and Yubu Island mudflats in Geum Estuary are important stopover sites for migratory birds as energy supplementation area in the East Asia-Australasian Flyway. Benthic invertebrates in the tidal flats are important food resources for the migratory birds. In other words, benthic invertebrates in the tidal flats play an important ecological role in energy flow. This study was conducted to investigate the relationship between benthic invertebrate assemblages and environmental factors in Seocheon and Yubudo tidal flats in the Geum Estuary. As a result of the benthic invertebrate assemblage during the fall migration season, the total species number was 147, density and biomass were $1,772{\pm}1,342individuals/m^2$ and $445.1{\pm}807.6g/m^2$, respectively. Based on the appearance species and the density data, the result of analysis of mutual similarity among sampling sites was divided into two groups. Group A was the Macrophthalmus-Heteromastus community and Group B was the Spio-Urothoe-Mandibulophoxus community. Group B showed higher mean species number, density and biomass than Group A. The BIO-ENV analysis showed that the benthic invertebrate assemblages were most affected by the combination of sand content % and sediment sorting (${\rho}=0.500$). The variables of significant relationship with species number and biomass were sediment sorting (p=0.015) and the pore water DO(Dissolved Oxygen, p=0.003) in sediment, respectively.

• Parasites, Hosts and Diseases
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• v.49 no.4
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• pp.457-460
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• 2011

Adults of Maritrema obstipum (Digenea: Microphallidae) were found in the intestines of 4 species of migratory birds, including the sanderling (Crocethia alba), Kentish plover (Charadrius alexandrines), Mongolian plover (Charadrius mongolus), and red-necked stint (Calidris ruficollis), collected from Yubu Island, Chungcheongnam-do, Korea. The worms of were $451{\times}265{\mu}m$ in size, and were easily identifiable as Maritrema species by the presence of the cirrus sac, and the ring-like distribution of the vitellaria. More specifically, the ejaculatory duct curved posteromedially, and the 2 parts of vitelline follicles were found to be distinct at the posterior end. The eggs were brown-colored, and $19.8{\times}12.3{\mu}m$ in size. All these findings implicated M. obstipum as the pertinent species of the worms. Beside these, adult worms of Gynaecotyla squatarolae, Parvatrema duboisi, and Acanthoparyphium sp. were also discovered. This is the first report establishing migratory birds as the natural definitive hosts for M. obstipum.

• Parasites, Hosts and Diseases
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• v.58 no.1
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• pp.81-86
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• 2020

Trematode specimens were collected from the intestine of a herring gull, Larus argentatus, which was found in a critical condition on the shore of a small island (Yubu-do, Seocheon-gun, Chungcheongnam-do) located at the western coast of the Korean peninsula. Total 11 specimens of intestinal flukes, including 3 Cryptocotyle lingua (Heterophyidae), 1 Himasthla alincia (Echinostomatidae), 5 Cardiocephaloides medioconiger (Strigeidae), and 2 Diplostomum spathaceum (Diplostomidae), were recovered. C. lingua was morphologically characterized by the presence of a large ventrogenital apparatus and 2 obliquely tandem testes. H. alincia had an elongated body and a head collar equipped with 31 collar spines. C. medioconiger had a bisegmented body and a voluminous copulatory bursa containing the seminal vesicle and ejaculatory duct. D. spathaceum also had a bisegmented body and its vitellaria extended up to the anterior border of the tribocytic organ. It is of note that C. lingua is potentially zoonotic that can occur in birds and humans. Three of them, i.e., C. lingua, C. medioconiger, and D. spathaceum, are new trematode fauna in Korea. Studies on trematode fauna of migratory birds should be continued in Korea.

• Parasites, Hosts and Diseases
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• v.57 no.6
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• pp.705-708
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• 2019

Gymnophalloides seoi (Digenea: Gymnophallidae) is a human intestinal trematode contracted by eating raw oysters (Crassostrea gigas) in the Republic of Korea (=Korea). It has been known to be highly endemic in Aphae Island, Shinan-gun, Jeollanam-do (Province). However, recent epidemiological status of G. seoi has not been reported since the 1990s. In this study, we investigated the prevalence of G. seoi metacercariae in natural and cultured oysters collected from 3 islands and 2 coastal areas in western parts of Korea. The oysters were examined using the artificial digestion method followed by stereomicroscopy. The overall positive rate of G. seoi metacercariae in natural oysters was 66.0% (99/150), and the oysters collected from Yubu Island showed the highest infection rate (74.0%). However, the metacercarial density per oyster was relatively low (1.5-2.4 per oyster). By contrast, no metacercaria was found in cultured oysters purchased from 2 coastal areas in Chungcheongnam-do. Thus, we could confirm that natural oysters produced from 3 western coastal islands are infected with G. seoi metacercariae, whereas cultured oysters purchased from 2 coastal areas were free from infection.