• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.3
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• pp.456-463
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• 2020

The diet of the walleye pollock Gadus chalcogrammus, was studied by examining the stomach contents of 864 individuals. Using gill nets, samples were collected monthly from January to December 2017 in Jugwang, Sokcho, Yangyang, Uljin, Ganggu, and Gampo, Korea. The specimens ranged in total length (TL) from 16.6 to 75.2 cm. G. chalcogrammus fed mainly on Euphausia pacifica (Euphausiacea) and less on Cephalopoda, Pisces, Mysidacea, and Macrura. The results indicated that G. chalcogrammus is a specialist feeder, feeding mainly Euphausiacea. With growth, however, its diet shifted from Euphausiacea to Cephalopoda, Macrura and Pisces. Smaller individuals (<40.0 cm TL) consumed mainly Euphausiacea. The proportion of Euphausiacea decreased with increasing body size, whereas the consumption of Cephalopoda and Macrura increased gradually.

• Journal of Fisheries and Marine Sciences Education
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• v.15 no.2
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• pp.166-175
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• 2003

In order to offer fundamental data for the standard of comfilation of the budget on the compensation money for the reduction of fishing baot and index of investigation for computation on the average earnings of reduction of fishing boat, the fluctuation of actual outputs, expenses, earnings and the difference by type of coastal and off-shore fishery was investigated and analyzed. The results are as follows : 1. The average ouput money by large powered purse seine fishery was much with about 3,510 million won, but the average output money by off-shore gill nets fishery was little with about 8.4 million won. 2. The average catch by large powered purse seine fishery was many with about 296,000 M/T, but the average catch by eastern sea danish seine fishery was few with 4,600 M/T. 3. The average expense by large powered purse seine fishery was much with about 3,360 million won, but the average expense by diving fishery was little with 6.3 million won. 4. The average earning by large powered purse seine fishery was much with about 240million won, the average earning by offshore long line fishery was little with 18 million won. 5. The average earning rate by diving fishery was much with 31.62%, but the average earning rate by large powered purse seine fishery was little with 7.30%.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.4
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• pp.766-774
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• 2013

Biodegradable polybutylene succinate(PBS) is a kind of environmentally friendly plastics for fisheries, because it can mitigate the ghost fishing problem caused by gill-net and trap fisheries. To evaluate durability of PBS monofilament, each of different diameter 3 types of monofilaments were spun and exposed to 56 month outdoor and then their gravity, modification of surface, breaking strength, and elongation were analysed. The gravity of PBS monofilament was estimated to be approximately 1.24 when spinning ratio from 4.8 to 6.1. PBS monofilaments did not show any crack after 56 month exposed to outdoor and load-elastic elongation curve was showed sigmoid type. Decreasing ratio of elongation was appeared in the thinnest monofilament 0.2mm diameter and breaking strength was in the thickest monofilament 0.4mm diameter. Breaking strength and elongation at break were decreased rapidly after 48 month exposed to outdoor. Breaking strength reduced linearly after 48 month exposure, while no such linear relationship was found in the case of elongation at break. In results, it was investigated that the durability of PBS monofilament nets for gillnet and trap were 24, 50 month when keep to land, respectively.

• Fisheries and Aquatic Sciences
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• v.21 no.3
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• pp.12.1-12.15
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• 2018

A preliminary investigation of length-weight relationship, condition factor and reproductive ecology of African pike fish, Hepsetus odoe, was conducted between June to August 2010 in Lake Eleiyele. A total of 90 samples of the fish species were caught by fishermen using gill nets. The results obtained showed that fish species had isometric growth pattern (contrary to negative allometry expected) with the growth exponent, b value of 2.64, that is not statistically different from 3 and with high statistical power of 0.866 when tested. The mean condition factor, K, was found to be 2.6, indicating that the fish species were in good condition in the study area. For reproductive biology, mean fecundity and gonadosomatic index were found to be 1349 eggs and 3.53% respectively. This study was necessary to fill the knowledge gap and provide information for management and conservation of the investigated species in the lake system. This study recommended that further research needs to be conducted because the sampling was carried out in the rainy season period and within a quarter of a year.

• The Korean Journal of Zoology
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• v.18 no.3
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• pp.115-126
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• 1975

In order to know the fauna of Korean Caprellidae, the authors examined the materials which were collected from many places of East Sea, South Sea and YelloW sea in 1955, 1964 and during the period from 1969 to 1975. Collections were made chiefly by hand with pincette at intertidal zones and with gill nets at subtidal zones. The results of the identification were found to be 11 species of Caprella of which the following 9 species were hitherto unrecorded from Korean waters. 1. Caprella californica Stimpson, 1857 2. C. danilevskii Czerniavski, 1868 3. C. decipiens Mayer, 1890 4. C. equilibra Say, 1818 5. C. kroeyeri De Haan, 1849 6. C. polyacantha Utinomi, 1947 7. C. scaura Templeton, 1836 8. C. tsugarensis Utinomi, 1947 9. C. verrucosa Boeck, 1871

• 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 the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.81-87
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• 2021

Many merchant ships sail in the waters surrounding Jeju Island and many fishing vessels catch fish using gill nets, trolling lines, and so on. Meanwhile, marine waste has collected in the coastal waters of Jeju Island. However, there has been little research on the collection of marine waste in coastal waters. In this study, marine waste deposited in Jeju Island's northwest sea was collected using Jeju National University's training ship, and related vessels were analyzed for each gear type. According to the results, most coastal waters had abandoned fishing grounds, which were from fishing vessels, and a large proportion of them was gill net and trap fishing gear. To analyze how much marine waste is accumulating in a certain area and ship's stay time, we use automatic identification system (AIS) data to extract the time spent in the target sea, and the amount of marine waste per hour was analyzed in a unit distance of 1 ㎢. The average amount of marine waste generated per hour in the unit area was found to be 0.94 kg for gillnet fishing gear, 3.49 kg for trap fishing gear, 0.10 kg for trawl fishing gear, 0.11 kg for longline fishing gear, and 0.02 kg for other fishing gear.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.520-524
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• 2023

Regalecus russellii, which spends most of its life in the deep sea, occasionally appears in coastal waters. However, the reasons for its appearance remain unclear. In Korea, R. russellii mainly appears along the eastern coastal waters, and most of them are caught in fishing gear, such as gill nets, or are stranded on the shore; nevertheless, the frequency of appearance is extremely low. Even if found, this species is often identified to be morphologically similar to Trachipterus ishikawae, and comprehensive analysis to identify the species through sample collection is limited. Consequently, information on the biological characteristics of R. russellii appearing in the coastal waters of Korea is scarce. Herein, the anatomical characteristics of R. russellii caught in a gill net off the Gangwon-do coast on March 14, 2023, were analyzed, and coastal water temperature was measured using an ocean buoy. Our results showed that the individual was male, its total length was 320 cm, body weight was 27.52 kg, body length was 26.62 cm, gonad weight was 619.45 g, and liver weight was 218.71 g. The stomach was full of euphausiids. The water temperature changed drastically at 15-30 m roughly a week before the R. russellii individual was caught, and the subsurface water temperature was lower than 10 ℃. Our findings provide baseline data to understand the ecological characteristics of R. russellii appearing along the eastern coast of the Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.3
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• pp.255-263
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• 2014

We investigated the reproductive characteristics of Lycodes tanakae in the coastal waters of the middle East Sea to elucidate the species' population structure. We investigated Lycodes tanakae maturation and spawning based on samples collected by Danish seine and gill nets from January 2012 to December 2013. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), egg diameter, fecundity, and total length at 50% group maturity. The spawning period was December to February, while fecundity ranged from 1,677 eggs at 57.3 cm (total length;TL) to 6,445 eggs at 75.7 cm. The relationship between TL and fecundity (F) was $F_e=6E-05TL^{3.127}$ ($R^2$ = 0.516), and F increased with increasing TL. We estimated the TL at 50% group maturity as 60.4 cm for females and 59.8 cm for males. This study is the first report of Lycodes tanakae reproductive characteristics in the coastal waters of the middle East Sea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.3
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• pp.278-286
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• 2017

The age and growth of marbled flounder Pseudopleuronectes yokohamae in coastal waters of the East Sea of Korea off Pohang were determined, by evaluating monthly samples of commercial catches, caught by gill nets and longlines from February 2013 to January 2014. New annuli from annually in P. yokohamae otoliths, and the boundary between the opaque and translucent zones forms from March to May. The relationships between total length (TL) and total weight (TW) were $TW=0.009TL^{3.128}$ ($R^2=0.969$) for females and $TW=0.008TL^{3.150}$ ($R^2=0.964$) for males. The TLs at the time of annulus formation, back-calculated from the otolith-length relationship by reference to the von Bertalanffy growth curves, were $L_t=52.63$ ($1-{\exp}^{(-0.231(t+0.033))}$) for females and $L_t=36.22$ ($1-{\exp}^{(-0.400(t+0.117))}$) for males. Commencing at the age of 3 years, females grew faster than males (P<0.05).