• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1303-1304
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• 2005

The sea water and the soil of surface zone in lagoon have many physical relations between each other by both physical phenomena such as tidal motion and wave action, and activity of a creature which lives in soil zone. The soil zone has an activity of filtering the sea water at lowering tide and also the organic materials in sea water are supplied into the soil. And small creatures such as small crab eat organic materials. Usually the surface zone of lagoon becomes under the sea water in two times of a day and also is coming in two times under the sunshine and it becomes dries up conditions. Authors made the field observation at Sanbannse lagoon in Tokyo bay in several times between 2002 to 2004. The observation has been done in a half period of tide in October and November 2002 and also full tide observation is made in July 2, 2003 in summer and November 26, 2003 in autumn. In 2004, three times observations of full tide has been made in three times as June 22, July 20 and December 14. This report is the summary of results on these observations focusing on the soil surface zone and sea water at under ground and wave breaking zone.

• Korean Journal of Ichthyology
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• v.9 no.2
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• pp.221-227
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• 1997

Feeding habits of Leiognathus nuchalis collected from the eelgrass bed in Kwangyang Bay from January 1994 to December 1994 were studied. Leiognathus nuchalis was a carnivore which mainly consumed copepods and crab larvae. Its diets included small quantities of polychaetes, amphipods, mysids, caridean shrimps. It showed ontogenetic changes in feeding habits. In an initial feeding stage, copepods were major food organisms. However, crab larvae and polychaetes were heavily selected with increasing fish size. Although copepods and crab larvae were major prey organisms for all seasons, the relative proportion of these two food items changed with season.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.45 no.4
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• pp.267-275
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• 2009

According to the recent statistics of marine casualties in Korea, fishing boats are more likely to be ended in the casualties, and small fishing boats especially cause much more accidents in sinking and capsizing than any other big vessels. These casualties were mainly produced from the ignorance on the lack of own ship stability. From this view, this study aims to analyze the characteristics of stability on the crab trap fishing boat receiving transverse wave by means of carrying out the water tank test. The rolling angle of the model ship was affected largely with the displacement and the wave period of it, and the trends were shown that the magnitude of the angle was proportional to the displacement, but inversely to the wave period. And the wave height had effect on the rolling angle just in the specific range of the wave period. The force of steady wind didn't have influence on the rolling variation significantly.

• The Korea Journal of Herbology
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• v.39 no.2
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• pp.1-9
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• 2024

Objectives : Paeng-hwal is described as an insect herbal medicine used for digestive diseases in the Dong-ui-bo-gam. The origin of this herbal medicine is limited to several small crabs, such as Helice tridens. These crab species cohabitat in the same environment and share similar morphological characteristics, making it very difficult to distinguish and collect the individual species for use in dietary supplements or herbal medicines. This study was conducted to develop a genetic identification tool for discriminating among these closely related small crab species. Methods : CO1 DNA barcode regions of 15 samples from 6 species of small crabs were analyzed to obtain the individual sequences. To identify the correct species, comparative analyses were carried out using the database of the NCBI GenBank and the NIBR. SCAR primers were designed to develop simple and rapid assay methods using inter-species specific sequences. Optimal SCAR assay conditions were established through gradient PCR, and the limit of detection (LOD) was determined. Results : Six species of small crabs (Helicana tridens, Macrophthalmus abbreviatus, Helicana tientsinensis, Helicana wuana, Chiromantes dehaani, and Hemigrapsus penicillatus), which are distributed as Paeng-hwal, were identified through CO1 sequences analysis. We also developed SCAR markers to distinguish between six small crabs at the species level. Furthermore, we established the optimal PCR assay methods and the LOD of each individual species. Conclusions : The rapid and simple SCAR-PCR assay methods were developed to identify the species and control the quality of herbal medicines for Paeng-hwal based on the genetic analyses of CO1 DNA barcodes.

• Korean Journal of Ichthyology
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• v.13 no.4
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• pp.223-229
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• 2001

Feeding habits of juvenile Sillago maculata, collected from the tropical seagrass beds in Cockle Bay, Queensland, were studied. S. maculata (0.5~9.5 cm SL) was a carnivore which consumed mainly gammarid amphipods, crabs and copepods. Its diets included small quantities of polychaetes, shrimps, fishes, isopods and cumacean. S. maculata showed ontogenetic changes in feeding habits. Small individuals preyed mainly on copepods, crab larvae and gammarid amphipods. While the portion of the stomach contents attributable to polychaetes, crabs and fishes increased with increasing fish size, consumption of copepods and crab larvae decreased progressively. Gammarid amphipods were the most selected prey item for all size classes.

• Animal Systematics, Evolution and Diversity
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• v.31 no.2
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• pp.107-113
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• 2015

Two diogenid hermit crab species, Dardanus lagopodes and Diogenes deflectomanus, are newly reported from Korea. Dardanus lagopodes is distinguished from the other species of genus Dardanus in Korea by having setae with cream-colored tips on the cephalothorax and the following characteristics: ocular peduncles somewhat longer than antennular peduncles, and the pereopod without a longitudinal sulcus and scute-like projections. Diogenes deflectomanus is similar to D. nitidimanus but can be distinguished by having the fixed finger of the left cheliped bent slightly downwardly and the following characteristics: slightly shorter ocular peduncle, elongated left cheliped with small granules on the surface, right cheliped without calcareous teeth on the cutting edge of the dactylus, and the minute spine of post-median margin of the telson is not well developed. The geographical distributions of these two species are extended by the present study. In particular, D. deflectomanus in the current study is the first report outside Chinese waters. Now, 20 species of the family Diogenidae are known in Korean waters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.2
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• pp.143-151
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• 2003

A series of fishing experiments was carried out in the waters off the east coast of Korea from January, 2002 to March, 2003, using gill nets of different mesh sizes (m = 180, 210, 240, 270, and 300 ㎜) to determine the size selectivity of gill net for male snow crab Chionoecetes opilio. The maximum carapace length (RL) of each male snow crab caught in the fishing experiment was measured. The master curve of mesh selectivity was estimated by applying the extended Kitahara's method. Two kinds of functional models, quadratic function and cubic function were used to express logarithmic selectivity curve and were fitted to the data using the method of least squares. The obtained results were summarized as follows; 1. The cubic function of asymmetry was chosen to determine the selectivity curve of gill net for male snow crab from the model deviance comparison. 2. The result of size selectivity showed that the catch number of small male crab was getting decreased according to the increase of mesh size. 3. The optimum value (RL/m) was 0.549 and the RL/m was estimated to be 0.281, 0.296, and 0.356 when the retention probability were 0.2, 0.25 and 0.5, respectively.

• Journal of Ecology and Environment
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• v.43 no.1
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• pp.31-42
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• 2019

Background: Han River estuary is a national wetland reserve near the Demilitarized Zone (DMZ) between South Korea and North Korea. This trans-boundary estuary area has been well preserved and shows distinctive plant communities along the salinity gradient. To elucidate energy flows and nutrient cycling in this area, we studied trophic relations between the dominant sesarmid crab, Sesarma dehaani, and food sources in three wetlands with different environments along the estuarine gradients. Results: Stable isotope signatures (${\delta}^{13}C$ and ${\delta}^{15}N$) of the crabs were significantly different among the sites and body size classes. Seasonal changes in ${\delta}^{13}C$ of small crabs were distinct from those of large individuals at all the sites. The isotopic values and fatty acid profiles of the crabs were more different among the sites in September than in May. In May, large-sized crabs utilized more plant materials compared to other dietary sources in contrast to small-sized crabs as revealed by a stable isotope mixing modeling, whereas contributions to diets of crabs were not dominated by a specific diet for different body size in September except at site 1. Based on PCA loadings, fatty acid content of $18:3{\omega}3$, known as a biomarker of plant materials, was the main factor to separate size groups of crabs in May and September. The ${\delta}^{13}C$ value of sediment had high correlation with those of small-sized crabs at site 1 and 2 when 1-month time lag was applied to the value for crabs during the surveyed period. Conclusions: Based on the stable isotope and fatty acid results, the consumption habits of S. dehaani appear to be distinguished by sites and their size. In particular, smaller size of S. dehaani appears to be more dependent on fewer food sources and is influenced more by the diet sources from the sediments in Han River estuary.

• Korean Journal of Environmental Biology
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• v.27 no.3
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• pp.297-305
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• 2009

The Asian paddle crab, Charybdis japonica (A. Milne-Edwards) is an important fishery resource in Korea. Despite its common occurrence and commercial importance, few studies have been carried out on the life cycle and trophic ecology of these populations inhabiting on the tidal flat. Food habits of C. japonica populations were investigated on the Jangbong tidal flat, Incheon, Korea. Monthly samples were taken using a modified otter trawl from November 1999 to January 2001. Based on the examination of stomach contents from 257 individuals, the frequencies of occurrence and the relative volumes of food items were analysed. As a result, the crustaceans (the brachyura, the cirripedia and the harpacticoid copepoda), the echinoderms (the ophiuroidea) and the molluscs (the cephalopoda Loligo beka, the bivalves Bivalvia unid. and Mytilus galloprovincialis) were important food for this species. To examine ontogenetic shifts in diets, individuals of C. japonica were categorized into 2 different size classes (${\leq}60mm$ and ${\geq}61mm$ in carapace width) representing sexually premature and mature stages. The food items of the small crabs (${\leq}60mm$) were dominated by the crustaceans with the harpacticoid copepods constituting 84.6% of total prey number. The next group was the bivalves and the brachyurans. On the other hand, the large crabs (${\geq}61mm$) mainly feed on the bivalvia (Mytilus galloprovincialis and Bivalvia unid.), the brachyurans (Crab unid.) and occasionally the cephalopods and fishes. The difference in proportions of the main prey items among these two size classes was statistically significant. Therefore, the feeding habits of the portunid crab, C. japonica changed with growth.

• Journal of Fisheries and Marine Sciences Education
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• v.18 no.3
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• pp.209-217
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• 2006

In this study, chemical compositions of Helice tridens tientsinensis(Htt, sea crab) and changes of chemical compositions in fermented sea crab tested according to different storage days(10, 16, 20, 25, 29, 55, 61, 67). The average amount of chemical compositions in raw Htt, it contains 77.12% of moisture, 1.96% of ash, 18.93% of crude protein, 0.26% of crude lipid. During storage time the amount of moisture and crude protein decreased, but crude lipid and ash increased. The amount of volatile basic nitrogen in Htt showed 6.56 mg/100g. The fermented sea crab in brine stored at the temperature of $5^{\circ}C$ showed 23.72 mg/100g of freshness even after 55 days. It showed first stage of decomposition(31.69 mg/100g) after 61 days. it is most efficient to store fermented sea crab at a low temperature. The amount of free amino acid composition in fresh Htt, was measured as follow ;arginine(1140.88 mg/100g), alanine(311.26 mg/100g), prorine(214.63 mg/100g), serine(113.56 mg/100g), taurine(90.80 mg/100g). The amount of amino acid in fermented sea crab increased as the storage days increased. Fatty acid contents in fresh Htt showed the largest amount of erucic acid (27.39 area%) and pentadecenoic acid (19.44 area%), oleic acid (17.68 area%), palmitic acid (11.00 area%), stearic acid (6.89 area%), and elaidic acid (6.15 area%) in order. In fermented sea crab, a small change was noticed in quantity, but the obvious increased composions were palmitoleic and heneicosanoic acid etc.