• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.3
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• pp.231-241
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• 2023

This study was investigated in order to find composition and density of fisheries resource using bottom trawl in April, July, August, and November 2022 in the East China Sea. The average density of fisheries resource was estimated using the swept area method. As a result, 35 species were collected from the East China Sea. These included 21 fishes, six crustaceans, six cephalopods and two echinoderms. Seasonally, the average density of crustacean individuals per unit area were highest in November (692.1 inds./km²), while cephalopod individuals per unit area were highest in August (39.4 inds./km²). The average density of fish individuals per unit area were highest in August at 355.0 (inds./km²).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.59-73
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• 1982

Differences of lipids, especially total lipid composition, fatty acid and sterol composition of the flesh lipids between three species of cephalopods were investigated, since available researches concerning lipids in flesh tissues of the cephalopod are very limited. Extracted total lipid from the flesh tissues were fractionated by silicic acid column chromatography into three lipid classes of neutral lipids, glycolipids and phospholipids. The lipid compositions of total lipid and neutral lipids were estimated by the method of thin layer chromatography and TLC-scanner. The sterol compositions of unsaponifiable matters from total lipid were determined by using thin layer chromatography and gas-liquid chromatography. The fatty acid composition of each lipid class was also determined by gas-liquid chromatography. Total lipid contents of flesh tissues from three species of the cephalopods were 0.5 in Octopus vulgare, 0.8 in Octopus variabilis and $0.6\%$ in Loligo beka based on wet weight, the contents of total fatty acid in total lipid were 19.3, 47.8 and $38.4\%$, and the contents of unsaponifiable matters were 10.9, 18.8 and $41.1\%$, respectively. Total lipid was mainly composed of sterols and polar lipid-pigments as major components in each sample and the proportion of sterols and polar lipid-pigments to total lipid ranged from 27.0 to $35.5\%$ and 38.3 to $63.4\%$, respectively. The other lipid components of total lipid, e.g. triglycerides, free fatty acids, and carbohydrate-esterified sterols were determined as a minor components. The major component fatty acid in total lipid was palmitic acid and additionaly it chiefly consisted of the other unsaturated acids such as oleic, linoleic, octadecatetraenoic and eicosapentaenoic acid as major components of the acid. The compositions of sterol in three species of cephalopod were found to contain mainly cholesterol for its proportion to total sterols was 82.4 to $89.1\%$. However the other sterols such as 22-dehydrocholesterol and 24-methylenecholesterol were determined in addition to cholesterol as a minor components. The result of fractional composition of lipid class in total lipid was that total lipid had large .amount of polar lipid and small amount of nonpolar lipid i, e, neutral lipid in each sample, and the contents of phospholipid were higher than that of glycolipid in polar lipid. Neutral lipid was mainly composed of free sterol as major components in each sample and its proportion of free sterols to total neutral lipid was 50.0 to $70.5\%$. The other lipid components of neutral lipid showing similar in quantity, esterified sterols, free fatty acids and triglycerides were determined as a minor components. The major components fatty acid in neutral lipid were palmitic, oleic and hexadecadienoic acid. Palmitic acid was the most abundant and additionaly oleic, linoleic, octadecatetraenoic and myristic acid were the major component fatty acid in glycolipid. But, especially, glycolipid of Loligo beka contained a higher amount of arachidonic acid which also consists of major component in addition to those of acids. Palmitic acid was the most abundant and additionaly, oleic, linoleic and octadecatetraenoic acid were the major component fatty acids in phospholipid.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.4
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• pp.272-281
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• 2008

Seasonal and annual variation in the species composition of bag-net catch in the coastal waters of Incheon, Korea were examined from April 2000 to November 2004. To analyze seasonal variation of the fisheries data, we implemented a self-organizing map(SOM), an unsupervised artificial neural network, with the catch amount of 97 species. Over 5 years, we caught 68 species of fish, 23 species of crustaceans and six species of cephalopods. The total number of fish species were gradually increased during the study period. The number of species was higher during the spring than the autumn. The SOM identified four groups of the sampling months based on seasonal changes in communities. In the spring, the dominant species were Leptochela gracilis and Pholis fangi; whereas, in the autumn, Engraulis japonicus and Portunus trituberculatus were dominant species in bag-net catch. Our results will be used to estimate seasonal and annual variation in fisheries resources of Korean coastal waters.

• Korean Journal of Ichthyology
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• v.17 no.4
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• pp.258-263
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• 2005

Feeding habits of Hapalogenys mucronatus (10.1~22.1 cm) collected from coastal waters off Sori Island, Yeosu, from June 2003 to May 2004 were studied. H. mucronatus is a carnivore which consumes mainly caridean shrimp, crabs, polychaetes, and amphipods. Its diet includes small quantities of bivalves, cephalopods, seagrass, hermit crabs, isopods, eggs, mysids, gastropods, and copepods. H. mucronatus undergoes significant size-related changes; smaller fish (10~11.9 cm) prey mainly on amphipods, shrimps and bivalves, while the proportion of caridean shrimp increases with fish size (12~17.9 cm). The larger fishes (18~22.1 cm) eat caridean shrimps and polychaetes.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.191-199
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• 2009

Fisheries resources collected by set net in the Mizo fishing ground off Namhae Island were studied from March to December 2004 to determine species composition and catch variation. The water temperature of the fishing ground ranged $10.9{\sim}25.1^{\circ}C$ A total of 69,147.5 kg comprising 39 species was caught during the survey period. Most of the catch was fishes (33 species); others included cephalopods (5 species) and crustaceans (1 species). The dominant species were migratory, such as Trichiurus lepturus, Ammodytes personatus, Engraulis japonicus, and Scomberomorus niphonius, and accounted for 81.2% of the total catch. Sub-dominant species were Sardinops melanostictus, Acanthopagrus schlegeli, shrimps, and Todarodes pacificus, but they accounted for only 12.1% of the total. The catch by set net during the fishing period was much higher in spring and in autumn than in summer, relating to the recruitment of dominant species. Although the number of species had a tendency to decreased after summer, the catch in autumn was also higher than that in spring due to high temperatures (>$17^{\circ}C$ and seasonal variation of dominant species. The dominant species in spring were A. personatus and E. japonicus and in autumn were T. lepturus, S. niphonius, and E. japonicus.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.45 no.4
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• pp.211-222
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• 2009

The fisheries resources by a set net in the coastal waters off Neungpo, Goeje Island from 2003 to 2004 were studied to determine species composition and catch variation. The main fishing period by a set net were from April to December in 2003 and from May to December in 2004. A total weight of 48 species caught through the survey period was 540,688.0kg. Most of them were 44 species of fishes and a few were 4 species of cephalopods. Dominant species was Trachurus japonicus accounting to 57.5% in total catch. Sub-dominant species were Trichiurus lepturus(12.9%), Engraulis japonicus(10.6%), Scomber japonicus(6.9%), Clupea pallasii(4.5%), Todarodes pacificus(2.8%) and Parapristipoma trilineaturm(1.3%). The remnant species showed a low catch, indicating the catch had less than 1% in total, respectively. T. japonicus and T. lepturus were caught throughout the survey period, but C. pallasii, Gadus macrocephalus, Oncorhynchus keta in low temperature season and Thunnus obesus in high temperature season. The fishing ground temperature was 11.7-24.0${^{\circ}C}$ in range and the catch by a set net was higher in autumn than in spring and in summer with the variation of fishing ground temperature. The annual catch by a set net was much higher in 2004 than in 2003 due to high temperature(>17${^{\circ}C}$) and the recruitment of T. japonicus from offshore seas. Therefore we concluded that the catch of Neungpo fishing ground by a set net was highly related to the variation of T. japonicus catch with fishing ground temperature.

• Korean Journal of Ichthyology
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• v.24 no.1
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• pp.35-40
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• 2012

The feeding habits of yellowback seabream, $Dentex$ $tumifrons$, were studied using 317 specimens collected in the coastal waters of Busan, from January to December, 2004. The size of the specimens ranged from 10.2 to 27.8 cm in standard length (SL). D. tumifrons had turned out a carnivore and opportunistic predator that consumed mainly shrimps. Fishes were next important prey items. Its diet also included anomurans, amphipods, crabs, echinodermata and cephalopods. Polychaetes, stomatopods, bivalves, ostracods, mysids and so on were minor preys. The individuals of smallest size class (10~13 cm SL) fed mainly on shrimps. In the next size class (13~16 cm SL), the proportion of shrimps decreased, whereas the consumption of anomurans, echinodermata and crabs increased. The proportion of these prey items decreased as body size increased, whereas the consumption of fishes gradually increased. Fishes accounted for almost stomach contents of larger individuals (more than 25 cm SL).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.719-729
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• 1997

Stomach contents of bigeye tuna, Thunnus obesus, and yellowfin tuna, Thunnus albacares, caught by longlining in the western tropical Pacific were analyzed to examine their foods and to compare their feeding behavior. The food species of both bigeye and yellowfin tunas were primarily fishes, crustaceans, and cephalopods. A total of 15 fish, 6 crustacean, and 1 cephalopod species were identified from their stomach contents, of which lantern fish (Myctophum sp.) was the most important food for both tuna species. No significant differences in species composition of food items between bigeye and yellowfin tunas were observed, indicating that in the same habitat the tunas have a similar feeding behavior. However, while they showed a remarkable similarity in diet composition, significant quantitative differences on the basis of IRI values were observed in several diet species, such as Myctophidae, Alepisauridae, Oplophoridae, Gammaridae, and Onychoteuthidae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.6 no.1_2
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• pp.1-19
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• 1973

Heavy metal concentrations have been determined in fishes and shellfishes sampled from October 1971 to April 1972 in Korea. In general, fish viscera, shellfish muscle and crustacean exoskeleton contained high concentrations of the metals. With regard to the regional variations of the metals, samples of the west coast of Korea contained relatively high concentrations of mercury, copper, cadmium and lead, but those of the south coast contained high levels of cadmium and lead. In particular, the concentrations of copper in the samples of the west coast were almost twice as much those of the other coasts. The concentrations of mercury in the samples, as a whole, ranged from 0.02 to 0.58 ppm with an average of 0.16 ppm. The concentrations of cadmium were higher in the fish viscera and shellfish than the fish muscle, ranging from less than 0.02 to 0.78 ppm with an average of 0.12 ppm in the fish and shellfish muscle samples. The lead concentrations were slightly high in the fish viscera. In the muscle and bone of fish and shellfish, the range was 0.06-4.84 ppm with an average of about 1 ppm. The concentrations of copper were very high in the viscera of fish and shellfish. The shellfish muscle contained almost four times as much copper as in the fish muscle, particularly cephalopods, i. e., squid and octopus, contained very high levels of copper, and oysters collected from Gunsan area on the west coast contained the highest levels of copper. The concentrations of copper ranged from 0.12 to 28.7 ppm with an average of 1.4 ppm in the fish muscle and of 5.9 ppm in the shellfish muscle.

• Korean Journal of Ichthyology
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• v.32 no.3
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• pp.143-147
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• 2020

The feeding habits of ocellate spot skate (Okamejei kenojei) were studied by analysis of stomach contents. Specimens of O. kenojei (n=379) were collected in the cosatal waters five west Islands of the Korea, monthly from January to December 2019. The size of O. kenojei ranged from 5.9 to 34.5 cm in disc width (DW). O. kenojei was consumed mainly macrura (77.9%) and pisces (21.9%) in % IRI. But, brachyura, stomatopoda, cephalopods, and others showed a low ratio. The macruara feeding rate was highest in summer, whereas the proportion of pisces was the higher in winter than other seasons.