• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.60 no.2
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• pp.101-113
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• 2024

This study investigated the species composition and community structure of aquatic organisms captured using coastal beam trawling in Gomso Bay, Jeollabuk-do, from January to December 2022. Throughout the experimental period, a total of 20,246 individuals belonging to 94 marine species were captured, with a combined biomass of 602,828 g. Fish exhibited the highest abundance, comprising 56 species, followed by crustacea (21 species), bivalvia (8 species), cephalopoda (5 species), gastropoda (3 species), and holothuroidea (1 species). The dominant species was Leiognathus nuchalis, constituting 14.0% of the total individuals, followed by Portunus trituberculatus at 12.1%, Oratosquilla oratoria at 10.4%, Crangon hakodatei at 9.9%, and Metapenaeus joyneri at 7.9%. The diversity index ranged from 1.72 to 2.55, with the lowest diversity observed in March and the highest in July. Cluster analysis based on species composition of the 27 most common species showed that aquatic organisms were divided into three groups: spring and summer organisms (Group A) and summer organisms (Group B) and autumn and winter organisms (Group C).

• Korean Journal of Ichthyology
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• v.19 no.4
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• pp.318-323
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• 2007

The feeding habits of Pacific cod (Gadus macrocephalus) were studied based on the examination of stomach contents of 192 specimens collected from November, 2005 to January, 2006 in the coastal waters off Gadeok-do, Korea. The size of Pacific cod ranged from 35 to 82 cm in standard length (SL). Pacific cod mainly consumed shrimps such as Eualus spathulirostris, Crogon hakodatei and C. affinis and fishes. Its diet also included small quantities of cephalopods, amphipods, hermit crabs and crabs. Individuals between 35 cm and 45 cm SL mainly consumed shrimps. The portion of shrimps decreased with increasing fish size, and this decrease was paralleled with increased consumption of fishes and cephalopods. In this study we found Syngnathus schlegeli in the stomach contents of many Pacific cod specimens. S. schlegeli is a typical seagrass fish species which inhabits in seagrass beds, This fact means that Pacific cods stay in the seagrass beds during spawning period. Therefore migration of Pacific cod to coastal waters off Gadeok-do during spawning period seems to be a survival strategy for its larvae and small juveniles to stay in seagrass beds which provide with abundant foods and shelters to many commercial fish species.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.177-190
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• 2009

Species composition and abundance of marine organism in the Nakdong River estuary were investigated seasonally from November 2007 to November 2008. During the study period, a total of 169 species, 93 families, and 6 taxa were collected in the study area. Species included were 2 species in Bivalvia, 11 in Cephalopoda, 43 in Crustecea, 8 in Echinodermata, 6 in Gastropoda, and 99 in Pisces. The seasonal dominant species in number of individuals were Acropoma japonicum in autumn, Apogon lineatus in winter, Siphonalia spadicea fuscolineata in spring, and Crangon hakodatei in summer. Dominant species in abundance were Chelidonichthys spinosus in autumn, Liphius litulon in winter and spring, and Raja kenojei in summer. The number of species and their abundance, the species composition, and the diversity indices fluctuated with seasons. The organisms were divided into 17 groups by seasonal variation using a self-organizing map.

• Applied Microscopy
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• v.30 no.3
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• pp.295-301
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• 2000

Five kinds of sensory cells, called A1-, A2-, B-, C-, and D-type cell, respectively, are observed in the epithelial tissue of suker's infundibulum of Cephalopoda, Octopus minor. The A1-type cells lie side by with the B-type cell in the epithelium of sucker's infundibulum. In the A1-type, the nucleus shapes irregularly and the karyolymph appears dark due to its high electron density. The cytoplasm is filled with many vacuoles of various sizes ($0.04\sim0.4{\mu}m$ in diameter), which move to the apical portion of the cell to be secreted via glycocalyx. The A2-type cells are mainly found at the basal portion of the epithelium. The shape of its nucleus is similar to that in the A1-type cell, and the cytoplasm, filiform or in reticular form, shows high electron density. The B-type cell contains an ovoid nucleus and the cytoplasm where lots of vacuoles which resemble the endoplasmic reticulum and electron-dense round granules of various sizes $(0.25\sim0.6{\mu}m)$ are found. The vacuoles and granules are secreted into the free surface via glycocalyx. The C- and D-type cells in simple or stratified layer are observed at the folded portion of the sucker's epithelium. The C-type cell contains a low electron-dense elliptical nucleus, while the D-type cell has an irregular nucleus where beterochromatin is well developed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.241-248
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• 2002

The combined hydroacoustic and demersal trawl surveys to investigate the distribution characteristics of fish schools in the Yellow Sea and the East China Sea were carried out during the spring of 1997 by the training ship "Nagasaki Maru" of Nagasaki University. Fish samples were collected by bottom trawling from 9 trawl stations randomly selected in the survey area, and the species and length compositions of trawl catches are examined. Hydroacoustic data were collected by using a Furuno FQ-50 scientific echo sounder operating at 50KHz and the data stored in field were later processed in the laboratory. The results obtained can be summarized as follows ：1. In the 9 trawl surveys conducted in the Yellow Sea and the East China Sea, 78 species including 80 species of fishes, 4 species of Cephalopoda and 6 species of Crustacea, were identified. The most abundant species in these stations were swimming crab(Portunus trituberculatus), Japanese horse mackere(Trachurus japonicus), redlip croaker(Larimichthys polyactis) and the catch per one hour in each station ranged 7.7 to 182.5 kg/hour. 2. The mean volume backscattering strength for the entire water column and the bottom layer of the 0-10 m from bottom friction were -74.6 ㏈ and -68.2 ㏈, respectively. That is, the mean volume backscattering strength for the bottom layer was 6.4 ㏈ higher than that for the entire water column 3. In the surveys during the spring of 1997, the geographical distribution characteristics of fish schools suggests a trend of decreasing fish abundance toward the coast area of Korea and the highest demersal concentrations appeared in waters between the Cheju Island and the Tsushima Island 4. The distribution density of fish school in the East China Sea and Yellow Sea during the 1997 acoustic survey were estimated to be 6.65$\times$10$^{-5}$ kg/㎥ in the entire water column and 2.86$\times$l0$^{-4}$ kg/㎥ in the bottom layer, respectively.pectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.4
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• pp.387-400
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• 2012

Species composition and seasonal variation of aquatic organism in the coastal waters off Taean, Korea were investigated using catches by commercial fishing of the pot and gill net from April 2010 to January 2011. A total of 58 species, 10,602 individuals and 547,569g of aquatic organism were collected during the study. Aquatic organism were composed of 22 species of Pisces, 20 species of Crustacea, 8 species of Gastropoda, 3 species of Echinodea, 2 species of Cephalopoda and Bivalvia, and 1 species of Holothuroidea. 41 species in 9 orders and 22 families were collected by the pot, and 28 species in 15 orders and 22 families were collected by the gill net. Volutharpa ampullacea was the most dominant in the pot, while Okamejei kenojei was the most dominant in the gill net. These two species accounted for 73.9% in the number of individuals, and 64.4% in biomass. The number of species was high in spring in the pot, and autumn in the gill net. The number of individuals and biomass were highest in winter and summer respectively in the pot, and summer in the gill net. The number of species of the consignment quantity caught by commercial fishery of the pot and gill net in Mohang was 12 and 14 respectively. Cluster analysis based on species composition of the 18 most common species showed that the species were separated into 3 different group. Group A was composed of species which were abundant in spring, group B was composed of species which were abundant in summer and autumn, and group C was composed of year-round residents.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.4
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• pp.452-468
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• 2012

Marine organisms were collected by the stow nets and the stow net on boat fisheries from April 2010 to November 2011 in the Han River Estuary and categorized as 126 species, 61 families, and 5 taxa. The species were consisted with 34 in Crustacea, 5 in Cephalopoda, 79 in Pisces, unidentified jellyfishes in Cnidaria, and Finless porpoise in Mammals. The major species were composed of fish and crustaceans in the Han River Estuary. The dominant species in Crustacea were Chinese ditch prawn (Palaemon gravieri), blue crab (Portunus trituberculatus), Ridgetail prawn (Exopalaemon carinicauda), and mantis crab (Oratosquilla oratoria), and those in Pisces were Korean anchovy (Coilia nasus), and Japanese grenadier anchovy (Coilia mystus). The length structures of the six dominant species have more than one mode in the Han River Estuary. It reflects that the species inhibit during a part of and/or whole lifetime in the Han River Estuary where they utilize as spawning and/or nursery grounds. Freshwater fishes were collected from station D where is the closest location to the Han River stream, and their appearances were well matched with the large amount of freshwater discharge due to flood periods. Principal components analysis (PCA) was carried out with species compositions and showed temporal and spatial differences by the variations of species.

• Journal of Environmental Science International
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• v.21 no.10
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• pp.1275-1286
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• 2012

Coastal marine ecosystem plays important role of spawning and nursery grounds for fisheries resources. Yongil Bay is one of major coastal marine ecosystems, which is located in the southwestern East Sea of Korea. Species composition and abundance of marine organism in the Yongil Bay were investigated by season from March to November 2009. Gill net and pot fisheries were used for survey of pelagic and demersal species composition, and collected 106 species, 67 families, and 7 taxa of fisheries resources from the coastal ecosystem. Species were included 2 species in Ascidiacea, 2 species in Bivalvia, 6 in Cephalopoda, 22 in Crustacea, 5 in Echinodermata, 12 in Gastropoda, and 57 in Pisces. Diversity indices (Shannon index, H') showed seasonal variation with low value of 2.11 in winter, and high value of 2.63 in autumn. Main dominant species were Asterias amurensis, Pleuronectes yokohamae, Siphonalia spadicea fuscolineata, Trachurus japonicas, Sillago japonica, Conger myriaster, Volutharpa ampullaceal, Engraulis japonicus, Asterina pectinifera, and Portunus (Portunus) sanguinolentus that were occupied over 71.5% of total individuals, and 52.9% of wet weight. Seasonal variations of fisheries resources composition were discussed on correlationships with those of environmental factors in the coastal ecosystem of the Yongil Bay in Korea. Those results from this study will provide scientific data and information to develop the ecosystem-based coastal fisheries assessment and management system in Korea.

• Journal of Marine Life Science
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• v.8 no.1
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• pp.1-7
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• 2023

This study was performed to understand the reproductive ecology of cephalopods, described the microanatomical structure of the male reproductive organs and spermatophore in the common squid, Todarodes pacificus, a major cephalopods in Korea. The common squid was gonochorism and had sexual dimorphism, the color of the reproductive organs reflected on the mantle and the presence of the hectocotylus. Male reproductive organs were composed of testis, primary vas deferens, spermatophoric gland (seminal vesicle), spermatophoric sac (Needham's sac) and secondary vas deferens. The male has specialized reproductive organs such as the spermatophore forming organ, spermatophoric gland. Testis was histologically a seminiferous tubule type. The primary vas deferens was a thin and inverted triangular spring-like form that connected from the rear of the testis to the spermatophoric gland. Inside, it was filled with sperm of basophilic in H-E stain. The spermatophoric gland is an irregular oval connected to the primary vas deferens and spermatophoric sac, and there were a number of tubular glands. The spermatophoric sac is a tubular structure located between spermatophoric gland and secondary vas deferens, and a number of spermatophores have been identified in the lumen. The secondary vas deferens was connected to the posterior of the spermatophoric sac and had a spermatophore inside. The spermatophore was a long, transparent tube about 22 mm long, with a sperm mass inside.

• Korean Journal of Ichthyology
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• v.35 no.2
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• pp.113-120
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• 2023

The diet composition of chub mackerel Scomber japonicus were studied using 959 specimens collected in the coastal waters of Jeju Island, Korea from January to November 2022. The size of the specimens ranged from 22.8 to 45.8 cm in total length. S. japonicus were fed mainly on euphausiids that constituted 77.7% in IRI. Fishes were the second largest prey component. Its diet also includes small quantities amphipods, copepods, shrimps, crabs and cephalopods. The diet composition of S. japonicus showed changes in season. The euphausiids feeding rate was highest in summer, whereas the proportion of fishes was higher in winter than in other seasons. The proportion of fishes has increased as the body size of S. japonicus increased, whereas the proportion of euphausiids decreased gradually. As the body size of S. japonicus increased the mean weight of prey per the stomach (mW/ST) tended to increase significantly (One-way ANOVA, P<0.05).