• Korean Journal of Ichthyology
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• v.36 no.2
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• pp.174-181
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• 2024

This study examines the community characteristics of fish species collected by fyke net from the eastern coastal waters of Yeosu, Korea, during the period from 2020 to 2021. A total of 4,539 fish were sampled and classified into 43 species, 28 families, and 7 orders. The dominant species included Mugil cephalus (14.4%), Konosirus punctatus (10.9%), Lateolabrax japonicus (8.3%), Acanthopagrus schlegelii (7.9%), and Pennahia argentata (7.2%). The diversity index was highest in October (H'=2.888) and lowest in February (H'=2.075). Furthermore, the dominance index was highest in March (DI=0.524) and lowest in December (DI=0.178). Hierarchical cluster analysis (HCA) revealed that fish communities could be divided into three groups based on Bray-Curtis similarity. Group 1, consisting mainly of species collected from June to October, formed one cluster. Group 2, including winter spawning species such as Pseudopleuronectes yokohamae, Clupea pallasii, and Hexagrammos otakii, sampled from November to February, formed another cluster. Group 3, which included species such as Larimichthys polyactis, Amblychaeturichthys hexanema, and Sebastes inermis, formed a cluster collected from March to May. The eastern coast of Yeosu is considered a suitable habitat for fisheries resources, including highly economically valuable species, and it is also assumed to be an important spawning and nursery ground for many fish species.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.461-473
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• 2015

Jinhae Bay located in the southern of Korean Peninsular is an important spawning area in Korea. By some preliminary studies it was measured several times that adult Pacific codes (Gadus microcephalus) were passed (swimming layer: 15 to 18 m) over a submerged sea tunnel (sea bottom: about 30 m) rather than another immigration route when the Pacific codes were tagged surgically with an acoustic transmitters and released inside of the Bay. There is a possibility that the Pacific codes and the other fishes use the route on the sea tunnel as an immigration route are affected by a human-generated underwater noise around the sea tunnel due to the sea tunnel traffic. On this study the 25-hour measurements of the underwater noise level by water layer were conducted with a hydrophone attached on a portable CTD and an underwater noise level meter during four seasons, and the acoustical characteristics of the underwater noise was analyzed. The mean traffic volume for one hour at the sea tunnel on the spring was shown the largest value of 1,408 [standard deviation (SD): 855] vehicles among four seasons measurement. The next one was ordered on the autumn [1,145 (SD: 764)], winter [947 (SD: 598)] and summer [931 (SD: 558)] vehicles. Small size vehicle was formed 84.3% of the traffic volume, and ultra-small size, medium size, large size and extra-large size of the vehicle were taken possession of 8.7%, 3.2%, 2.0% and 1.8%, respectively. On the daily change of the noise level in vertical during four seasons the noise level of 5 m-layer was shown the highest value of 121.2 (SD: 3.6) dB (re $1{\mu}Pa$), the next one was 10 m-layer [120.7 (SD: 3.5)], 2 m- and 15 m-layer [120.3 (SD: 3.5 to 3.7)] and 1 m-layer [119.2 (SD: 3.6)] dB (re $1{\mu}Pa$). In relation with the seasonal change of the noise level the average noise level measured during autumn was shown the highest value of 123.9 (SD: 2.6) dB (re $1{\mu}Pa$), the next was during summer [121.4 (SD: 3.2)], spring [118.0 (SD: 3.4)] and winter [116.5 (SD: 5.1)] dB (re $1{\mu}Pa$). In results of eigenray computation when the real bathymetry data (complicate shape of sea bed) was applied the average number of eigenray was 2.68 times (eigenrays: 11.03 rays) higher than those of model bathymetry (flat and slightly sloped sea bottom). When the real bathymetric data toward inside (water depth becomes shallow according to a distance between the source of noise and hydrophone) of the Bay was applied on the eigenrays calculation the number of the eigenray was 1.31 times (eigenrays: 12.49 rays) larger than the real bathymetric data toward outside (water depth becomes deep with respect to the distance). But when the model bathymetric data toward inside of the Bay was applied the number of the eigenray was 1.05 times (eigenrays: 4.21 rays) larger than the model bathymetric data toward outside.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.8
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• pp.1069-1075
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• 2009

Conger eel (Conger myriaster) is used as a well-being food in the foodservice industry in Korea. We analyzed not only the proximate composition but also the taste components affecting conger eel, which are fatty acids, nucleotides, amino acids, etc. Concerning the composition, the crude lipid was the lowest in summer at 3.2%, which is considered due to spawning period. The major fatty acids were $C_{16:0},\;C_{16:1},\;C_{18:0},\;C_{18:1},\;C_{20:5},\;and\;C_{22:6}$. The $C_{18:1}$ content was the highest among the fatty acids and the content varied between 36.76 and 45.11% by season. Seasonal change in the content of poly-unsaturated fatty acids was increased from spring to winter in conger eel. Among the nucleotides, the contents of IMP (3.617$\sim$5.524 $\mu$mol/g) and Hx (0.913$\sim$2.238 $\mu$mol/g), which is closely related to taste, and the concentrations of IMP and Hx were the highest (7.219 $\mu$mol/g) in winter, and HxR (0.625$\sim$1.652 $\mu$mol/g) was higher than ATP (0.058$\sim$0.083 $\mu$mol/g), ADP (0.145$\sim$0.161 $\mu$mol/g), and AMP (0.166$\sim$0.179 $\mu$mol/g). In conger eels, the major total and free amino acids were glutamic acid (14,178.7$\sim$7,802.6 mg%), aspartic acid (4,669.2$\sim$8,259.0 mg%), lysine (4,198.3$\sim$7,540.8 mg%), leucine (3,843.6$\sim$6,782.1 mg%), and histidine (199.6$\sim$644.4 mg%), glycine (94.8$\sim$152.2 mg%), alanine (35.3$\sim$71.2 mg%), glutamic acid (44.1$\sim$70.6 mg%), respectively, but the concentration of amino acids was different by season. The content of free amino acids, which is related to the taste component, was detected as high in summer and winter at 1179.2 and 1,605.2 mg%, respectively.

• Journal of Fisheries and Marine Sciences Education
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• v.3 no.2
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• pp.73-82
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• 1991

In recent years, the communication and the trade between the Republic of Korea(South Korea) and the Communist bloc has been activated. The simultaneous entrance of South Korea and North Korea to the United Nations will accelerate the political dialogue and also the trade which is indirectly carried out through a third country at present will be turned into direct way. Fisheries products are also treated as one of the important trade goods and there is a hopeful prospect that the amount of trade will be steeply increased in the near future. Furthermore, there is a great possibility of development up to the joint utilization of fishing grounds or the joint investment in fisheries projects. Concerning such points, since it is very much important to understand the present status of fisheries in North Korea, the author made a study on this field as requested by the Board of Unification, and report a part of the study here. The prominent character of North Korea's ruling sea area is that the sea is completely separated into two regions-the East Sea Region and the West Sea Region-and no continuity exists between them. The East Sea Region locates in the fringe of the biggest fishing ground of the world-the North Pacific Ocean-and very rich in resources not only warm water fishes but also cold water fishes. Especially alaska pollack, Theragra chalcogramma, is caught abundantly in this region. Contrary to that, fishing activity in the West Sea Region seems to be interrupted in winter. Even though some valuable warm water fishes-yellow corvenia, Pseudosciaena manchurica, and hair tail, Trichiurus lepturus, and so forth-come to this region from spring to summer along the coast line of this region for spawning, and vigorous fishing activity is carried out. But the most of them migrate southward to the neighboring waters of Cheju Island for wintering from autumn to winter, and so the fishing activity in this region seems to be interrupted greatly during winter. The total number of fishing boats in North Korea is estimated at 36 thousand and the rate of mechnization at about 70% compared with 99 thousand and 78% in South Korea. North Korea proclaimed an exclusive economic zone of 200 nautical miles in 1977. Specific character of this zone is setting of military boundary zone, up to 50 miles from the base line in the East Sea Region and also it covers whole region of the economic zone in the West Sea Region. Especially in the East Sea Region she set up a straight base line which can not be permissible by the international law. North Korea's statistics on fisheries product has not been announced officially on account of her unique isolationism, but it can be estimated through several data procured. At the first, the amount of fisheries products in the North Korea is reported as about 1.7 million ${\frac{M}{T}}$ by Fisheries Statistics which issued by the FAO in 1987, but a North Korea's trade organization announced the amount as 3.5 million ${\frac{M}{T}}$ in 1988. The former seems to be underestimated and the latter must be an exaggeration. According to Chikuni, who is a Japanese worker for FAO, prepared the unofficial statistics based on the evidence which he collected through the fineries development plan of the FAO/UNDP, and estimated the mean amount between 1982 and 1984 was 2.4 million ${\frac{M}{T}}$ or so. The Board of Unification estimated on the basis of various factors that the amount was 2.2 million ${\frac{M}{T}}$ or so in 1987 and in 1988. This seems to be the most reasonable. To solve the chronic lack of foreign currency, North Korea makes effort on the development of fisheries, and has even aimed fisheries product at 11 million ${\frac{M}{T}}$ by 1993, but this target looks unrealistic under the present circumstances. Somehow, we can exploit her extreme policy which has gone so far as to establish such an excessive and impractical target. Nevertheless this will be helpful to promote the joint development of the fishery activity between South Korea and North Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.5
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• pp.423-435
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• 1984

The reproductive cycle of the small filefish, Rudarius ercodes was investigated based on the annual variations of gonadosomatic index(GSI) and hepatosomatic index(HSI) by electronic and photic microscophy. The specimens used were collected at the coastal area of Benden island, Sizuokagen, Japan, from September 1982 to August 1983. GSI began to increase from March, starting season of longer daylength and higher water temperature, and reached the maximum value between June and August. It began to decrease from September with the lowest value appearing between November and February without any evident variation. The annual variations of HSI were not distinct in male filefish and were negatively related to GSI in female : HSI decreased in the summer season when the ovary was getting mature and reached the maximum in the winter season when the ovary was getting retrogressive. The ovary consisted of a pair of saccular structure with numerous ovarian sacs branched toward the median cavity. Oogonia divided and proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophile cytoplasm showed several scattering nucleoli along the nuclear membrane. when the oocytes growing to about 300 ${\mu}m$, nuclear membrane to disappear with nucleus migrating toward the animal pole. The regions of protoplasm were extremely confined within the animal hemisphere in which most of cytoplasms were filled with yolk materials and oil drops. After ovulation, residual follicles and growing oocytes remaining in the ovarian sacs degenerated. But perinucleatic young oocytes without follicles formed were not degenerated, and growing continuously still in the next year. Mitochondria and endoplasmic reticula in the cytoplasm remarkably increased with oocytes maturing and yolk accumulating. Those were considered to be functionally related to the yolk accumulation. Five or six layers of possible vitellogenin, oval-shaped disc structures with high electron density, appeared in the apex of follicular processes stretching to the microvilli pits of mature oocytes. Testis consisting of a pair of lobular structures in the right and left were united in the posterior seminal vesicle, Cortex of testis was composed of several seminiferous tubules, and medulla consisting of many sperm ducts connected with tubules. Steroid hormone-secreting cells with numerous endoplasmic reticula and large mitochondria of well developed cristae were recognized in the interstitial cells of the growing testis. Axial filament of spermatozoon invaginated deeply in the central cavity of the nucleus and the head formed U-shape with acrosome severely lacking, mitochondria formed large globular paranuclei at the posterior head, and microtubular axoneme of the tail represented 9+9+2 type. The annual reproductive cycles could be divided into five successive stages : growth(March to July), maturation(May to September), Spawning(mid May to early October) and resting stages(October to February). The spawning peak occurred from June to August.

• The Korean Journal of Malacology
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• v.30 no.2
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• pp.107-116
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• 2014

Gonadal development and maturation mechanism were studied on the freshwater marsh clam Corbicula papyracea (Heude), which is the endangered species in Korea. The specimens were collected in the rearing ponds and waterway of NFRDI in Gapyeong-gun, Gyeonggi-do from January to December 2004, and then investigated by condition factor, relative growth, gonadal development phases and gonad histological characters based on 30-50 individuals every month. Comparing with the freshwater marsh clam, C. papyracea is small, light olive brown shell and violet interior. The hermaphrodite individuals of C. papyracea take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The average water temperature of inhabit area was in range of $1.8-27.0^{\circ}C$ and usually took great effects on the gonad maturation of C. papyracea. The condition factor ranged from 0.14 to 0.21 throughout the year, which was the lowest during winter season (December-February), and gradually increased to the highest value of 0.21 in May. The ratio of meat weight to total weight was 25.9-38.7%, indicating the similar trend with condition factor. The highest values of condition factor and the ratio of meat weight appeared 1-2 months later than gonadosomatic index reached the peak value, it was probably because that the ovoviviparous eggs would spend a long period before hatching from the foster-sack in the gills. To synthesize the characters of meat weight, condition factor and gonad development by histological study, reproductive cycle of C. papyracea could be divided into five successive stages: multiplicative stage (December to February), growing stage (February to May), mature stage (June to August), spawning stage (August to November), recovery stage (November to December). The smallest shell length of matured C. papyracea was 12.6 mm, and individuals, larger than 16 mm, was formed the nursery in the gills.

• Korean Journal of Ichthyology
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• v.11 no.1
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• pp.62-71
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• 1999

The seasonal distribution of Maurolicus muelleri eggs and larvae were determined using samples collected from the Korea Strait and the southern part of the East Sea in May and November, 1992, August, 1993, and January, 1994. The eggs were most abundant in summer and the larvae in spring, while, their abundance was low in winter. The eggs were mainly found from in all season around sea of the front area of latitude $35{\sim}36^{\circ}N$ and the West Channel of the Korea Strait found the middle or bottom water lower than $15^{\circ}C$. The seasonal distribution of the eggs in the western Korea Strait varied according to the structure of the bottom cold water of the Korea Strait. The M. muelleri larvae in different stage were most abundant in the front area of latitude $35{\sim}36^{\circ}N$. The spawning and hatching area of the M. muelleri was considered to be the front area located in the shelf break, and some eggs can be transported into the Korea Strait by westward cold bottom current in summer. The Korea Strait would be the southern margin of the distribution of Maurolicus muelleri eggs and larvae of the East Sea.

• Journal of Wetlands Research
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• v.10 no.1
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• pp.39-47
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• 2008

An eco-washland is increasingly getting attentions as a new alternative plan for management of water resources because of role as flooding control and ecological park without social and ecological side effects. However, there is a lack of study regarding technological development and ecological guidelines to create eco-washland. This study was carried out to suggest ecological guidelines necessary for engineering process to create eco-washland. A study site was the lower reach of Seokjang stream connecting to Yimjin river, a candidate of new eco-washland, and Kumsa area in Namhan river was selected as a reference site. The analysis of ecological characteristics focused on vegetation, fishes, and birds. Major vegetation communities, composed of dominant species such as Salix koreensis, Salix gracylistyla, Miscanthus sacchariflorus, Phragmites communis, etc., formed physical conditions along with other land uses including open water, sandbar, cultivated land, etc. Dominant species of fishes were some species belonging to Cyprinidae and Acheilognathinae, and in case of birds Anser albifrons, Anas platyrhychos, Anas poecilorhyncha belonging to waterbirds and Paradoxornis webbinanus dependent to forest edge were dominantly distributed. The results showed that complex wetland types associated with partially deep water and upland was the optimal eco-hydrological condition of washland. Cyprinidae and Acheilognathinae in case of fish and Egretta spp. (spring season) and Anas spp. (winter season) in case of bird were selected as target species for the these wetland types. Finally, a detail planning criteria to create habitats of these target species were discussed in terms of spawning, breeding, feeding, resting, refuge, nesting, etc.

• Korean Journal of Ichthyology
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• v.11 no.2
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• pp.117-125
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• 1999

We investigated the reproductive cycles of two freshwater fishes, Moroco oxycephalus and M. lagowskii, in Korea. Seasonal changes in gonadosomatic index (GSI) and gonads were investigated histologically from April 1998 to April 1999. The reproductive cycles of two species were not shown any differences. The reproductive cycle can be divided into 5 phases : phase I (spent phase), phase II (immature phase), phase III (early developing phase), phase IV (late developing phase), and phase V (ripe phase). In phase I, the gonads of two species began to lose distinctly their weights from mid April, and reached the lowest GSI in late July (phase II). In September, the GSI values of testis and ovary increased very slowly (phase III) and gonadal developments rested during the winter season (phase IV). In March, the GSI values of M. oxycephalus and M. lagowskii began to increase, and reached the maximum in April (phase V). From the cyclic changes in the GSI and histological analyses, the spawning period was between mid April and mid May.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.352-360
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• 2005

Acheilognathus signifer is distributed widely in high density in the Naechon-stream. The order of this-stream was 2 ${\sim}$ 4 and the water width is wide but the depth is relatively shallow and the sinuosity is 1.83, which indicates a meandering stream. The water width/stream width ratio is 1.59, which suggests moderate entrenchment. Naechon-stream was classed as B type by Rosgen (1995). The natural habitat of A. signifer is a slow flow velocity pool, like a backwater pool, which is made up of piled up boulders that restricts the flow of water. The stream bed is made up of boulders and sands that enable the spawning host to inhabit. A. signifer selects a microhabitat where the boulders furnish hiding places. The Habitat of A. signifer is strongly affected by the existence or not there of U. douglasiae sinuolatus. After hatching from the mussel, A. signifer inhabits the surface of the water. It then moves to the low layer once it acquires swimming ability. While A. signifer inhabits the river in summer, A. signifer moves to the deeper layers in winter, where there are the refuge like rocks and boulders. In spring A. signifer moves from the deep water to the river line where the mussels reside.