• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.4
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• pp.281-290
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• 2007

This study was aimed not only to develop the gill net and trap made of biodegradable monofilaments in order to prevent a ghost fishing and to protect marine ecosystem, but also to analyze their spinning process and physical properties. Results showed that the spinning speed of biodegradable polybutylene succinate(PBS) monofilament was estimated to be approximately 100m/min when spinning temperature and cooling water temperature were adjusted at $180^{\circ}C$ and $3^{\circ}C$, respectively. The breaking loads of PBS monofilaments were estimated to be $35.3kg/mm^2$ at ${\phi}0.2mm$, $46.5kg/mm^2$ at ${\phi}0.3mm$, and $49.7kg/mm^2$ at ${\phi}0.4mm$ in the dry condition, respectively. However, its breaking loads in the wet condition were reduced by 2.4-5.5%, compared to those in the dry condition. The knotted strength of PBS monofilament at ${\phi}0.2mm$ was estimated to be 98.6% of PE in the dry condition. The breaking load of PBS monofilament at ${\phi}0.3mm$ was evaluated to be 81.8% of PA, and its softness showed 3 times less than that of PA in the wet condition. The breaking load of PBS monofilament at ${\phi}0.4mm$ was 95.3% of PA, and its softness showed 1.6 times less than that of PA in the wet state. However, the load elastic elongations of two kinds of monofilaments were estimated to be 1% higher than that of PA.

• Journal of Aquaculture
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• v.20 no.1
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• pp.26-30
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• 2007

Resources of the sea cucumber, Stichopus japonicus in the west coast of Korea are decreasing sharply due to overfishing and severe marine pollutions. Artificial seed production and release of this species need to be conducted to maintain sea cucumber stock in the region. In this study, to provide basic information for such works, reproductive cycle of sea cucumber collected from Anmyondo in the region was histologically studied for a year from October 2004 to September 2005. This species was dioecious, and its gonads was composed of a number of gametogenic follicles. The gonadosomatic index (GSI) was reached the maximum in June (7.91), and the minimum in October (0.42). The main spawning occurs between June and August. The reproductive cycle of the sea cucumber could be divided into five stages: multiplicative stage (January to March), growing stage (March to April), mature stage (April to July), spawning.

• Journal of Aquaculture
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• v.20 no.1
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• pp.47-50
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• 2007

The primordial germ cells of the oblong rockfish, Sebastes oblongus were buried under fibrous mesenchymal tissues between gut and mesonephric duct of pre-larva with 4.0 mm total length (TL) at 1 day after the parturition. In the juvenile of 22.0 mm TL at 71 days after the parturition, the gonad composed of a large number of gonial cell and formed of cavity along the lateral side of the gonad, differentiated to the ovary. At this time, the gonad formed seminiferous tubules by somatic cells, was differentiated to the testis. The smallest oblong rockfish that possessed primary oocytes was about 42.1 mm TL at 141 days. Spermatogonia remained quiescent until most fish were over 42.1 mm TL at 141 days. The oblong rockfish the differentiated directly into male or female without an intermediate female phase at the early indifferentiated stage. Therefore, the oblong rockfish belongs to the differentiated type of gonochoristic teleosts.

• Korean Journal of Environment and Ecology
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• v.31 no.5
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• pp.455-460
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• 2017

Since a new (unrecorded) species was reported in 2016, a total of four sea snake species are currently listed in Korean waters. Although the possibility of year-round inhabitation of sea snakes in Korean waters has increased due to climate change, the related studies are scarce because of the lack of human resources and available equipment. We placed posters and banners requesting voluntary information on sea snakes in coastal regions and Jeju Island to obtain information on sea snake distributions in the coasts of South Korea and possible specimens through volunteer activities. As a result, we received total 45 reliable reports, including photographs or video, between March 2013 and December 2016. Eighteen reports on three sea snake species and thirteen capture cases of two species were submitted from Jeju Island and southern coastal regions of Korea mostly between August and November. There were twenty-seven false reports including seven cases of terrestrial snakes, eighteen fishes, and one each of invertebrate and inanimate material. Based on the results, we proposed the effective way of sea snake surveys using volunteers.

• Journal of Wetlands Research
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• v.22 no.4
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• pp.328-336
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• 2020

In this study, the soil characteristics of peat layer in Korea were analysed to predict new peat distribution areas in Taean, Chungcheongnam-do. The soil characteristics of peat distribution areas in Taean were compared with those in other areas in Korea. In Korea, peat researches were conducted in various regions, such as Taean in Chungcheongnam-do, Pyeongtaek in Gyeonggi Province, Gangneung in Gangwon-do, Ulsan, Iksan in Jeollabuk-do and Jangheung in Jeollanam-do. We summarized a) topographic distribution, b) deposition type, c) soil drainage classes, and d) soil suborder of previously studied area to determine criteria for prediction of peat distribution area. Through a case study, the type of peat layer distribution area in Taean were divided into two; (1) a) valley, b) co-alluvium, c) somewhat poorly drained, d) aqualfs and (2) a) marine plain, b) alluvium, c) very poorly drained, d) aquepts. A field survey was conducted to confirm the distribution of the actual peat layer. All peat layer were located within 10-km from the coastal line which is similar to previous studies, and the peat layer was characterized with pH 5, humic acid content of less than 15% and dark brown color. The new peat layer in Taean was deeper, thicker and less humificated than other studied areas.

• Journal of the Korean association of regional geographers
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• v.5 no.2
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• pp.119-132
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• 1999

The Korean Peninsula, jutting southward from the Asian mainland into the Pacific Ocean, is surrounded by numerous bays and islands on three sides. The study area of this research is the coastal area surrounding the Sacheon Bay, which is located in the mid-southern tip of the peninsula. Historically, the bay region took the role of the main gate leading to the western part of Kyung-nam Do(Province) due to the fact that the bay is the nearest coast to Chinju, the central city of the province. The Sacheon Bay had provided important sea routes from the old days until the early twentieth century. Because of the bay's sea routes, the bay region has been militarily of great significance. Recently, road/rail/highway/airplane transportation functions have become gradually increased but sea transportation function has been decreased in the region. As the Sacheon Bay was rich in fishery resources, dozens of fishing villages in the bay region depended on fishery and marine product industries for long years. But the inflow of the fresh water used to cause serious damage to the fishing industry in the bay region after a drainage canal from the Nam River was constructed in 1969. As a result, the industry has dwindled gradually for last decades. Recently, a couple of industrial parks were constructed along the coast and many manufacturing factories were built on the parks. It has been expected that many jobs lost in fishery and agriculture are replaced by new opportunities in industry. More than half of the workers employed in the parks' factories commute from the city of Chinju. It is asserted in this paper that the transportation, fishery, manufacturing, and tourism functions of the Sacheon Bay region are closely associated with. The characteristics of the region can be well understood through the functional changes and associations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.232-237
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• 1999

The relationship between structure and contractile activity was studied on the three neuropeptide $\gamma$ (mammalian-, bowfin-, shark-NP$\gamma$) that were synthesized by the solid-phase method. Circular dichroism spectra showed that mammalian-, bowfin- and shark-neuropeptide $\gamma$ took an unordered structure in buffer solution and artificial liposome. The intestinal motility response was investigated with guinea-pig ileum, rat duodenum and carp intestine. In case of carp intestine, contractile activity was as follows; bowfin-NP$\gamma$> shark-NP$\gamma$>mammalian-NP$\gamma$, On the other hand, the contractile activity of mammalian-neuropeptide $\gamma$ was more potent than those of bowfin-, shark-neuropeptide $\gamma$ in the guinea-pig ileum and rat duodenum. These results suggest that NP$\gamma$ show the species-specific activity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.225-237
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• 2001

The community structure of macrobenthos was investigated around Sorido Island, southern coast of Korea between August 1996 and April 1997. Triplicate macrobenthic samples were taken seasonally at twelve stations in August and November 1996 and fourteen stations in February and April 19n by van Veen grab ($0.1m^2$). A total of 217 macrobenthic species were identified during study Period: 80 species were from polychaetes, 60 species from crustaceans, and 46 species from mollusks. The mean density of macrobenthos estimated $1,068 ind/m^2$, and polychaetes comprised $85\%$ of total density. The mean biomass was $110.2 g/m^2$, and echinoderms contributed to more than a half of the biomass. Major dominant species based on abundance were three polychaetes Tharyx sp., Lumbrineris longifolia, and Magelona japonica, which frequently occur in the coastal area enriched by organic pollution. The densities of the species were $582 ind/m^2$, $72 ind/m^2$, and $41 ind/m^2$, respectively. These species showed very low density in the offshore area. The study area was classified into four regions each sustaining specific macrofaunal assemblages by Bray-Curtis cluster analysis: a station group adjacent to the Kwangyang Bay and Yosu harbour and three station groups around Sorido Island. There were negative correlations between the concentration of PAHs in sediments and the abundance of Ampeliscidae spp. and Amphipoda. These results were discussed in terms of both environmental factors and distribution of benthic community.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.279-284
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• 2001

This paper reports the purification of myomodulin A (MMA) and myomodulin E (MME) from the sea hare. The central nervous systems of 500 sea hare were extracted in an acidified solvent, after which four HPLC column systems were used to obtain pure peptides, The phasic contraction bioassay using a Mytilus edulis anterior byssus retractor muscle (ABRW) was applied to monitor all collected fractions. The pure peptides were submitted to Edman degradation based automated microsequencing. Mass spectrometry and chemical synthesis confirmed the sequence. The primary structures of MMA and MME were Pro-Met-Ser-Met-Leu-Arg-Leu-$NH_2$, (847.41 Da) and Cly-Leu-Gln-Met-Leu-Arg-Leu-$NH_2$, (830.50 Da), respectively. Synthetic peptides showed a modulating activity of phasic contraction in the ABRM of Mrtilus edulis.

• Korean Journal of Ichthyology
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• v.20 no.1
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• pp.13-20
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• 2008

Internal and external reproductive parameters of the striped bitterling, Acheilognathus yamatsutae were compared. Internal reproductive parameters was used gonadosomatic index (GSI), hepatosomatic index (HSI) and gonadal development stage. External reproductive parameters was used ovipositor in female and pearl organ, dorsal and caudal fin nuptial color in male. The GSI and HSI of the female and male showed highest in February. Gonadal development was observed mainly ripe and spawning/spent stage in February to May. The ovipositor length index (OLI) of the female showed highest in March to April. Pearl organ number and expression rate of the male showed highest in February to May. Dorsal fin nuptial color expression rate and index (NCI-DF) showed highest in February to May. Caudal fin nuptial color expression rate and index(NCI-CF) showed highest in February to April. The study suggested same change of internal and external reproductive parameters in female and male.