• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.72-72
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• 2003

A 10-week feeding trial was conducted to investigate the effects of dietary glucose, dextrin and starch on growth and body composition of juvenile starry flounder. Triplicate groups of fish (average weight, 9.7 g) were fed iso-nitrogenous (53% CP) and iso-caloric (3.8 kcal/g diet) diets containing 20% glucose, 20% dextrin and 5-25% alpha-potato starch with 5-14% lipid levels. Survival was not affected by dietary carbohydrate. Weight gain, feed efficiency and protein efficiency ratio of fish fed the diet containing 20% glucose were the lowest among all groups. The best weight gain was observed in fish fed the diets containing 20% dextrin. Growth and feed efficiency were not affected by dietary -potato starch level. Lipid contents of whole body and liver were not affected by dietary glucose, dextrin and starch at the same level. However, the lipid contents tended to decrease with increasing dietary starch level and those of fish fed the diets containing 5% alpha-potato starch were significantly higher than those receiving 10-25% alpha-potato starch. Liver glycogen content and hepatosomatic index tended to increase with increasing dietary starch level. These results indicate that juvenile starry flounder are able to efficiently utilize dextrin and -potato starch compare to glucose in diets and that alpha-potato starch could be incorporated up to 25% in the diet for optimum growth by juvenile starry flounder.

• Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.325-332
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• 2015

An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Geomoondo and Jejudo in west of South sea, Korea by conver-net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k't as estimated by peak event analysis. The escape rate of juvenile fish in conver-net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.4
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• pp.1548-1568
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• 2015

Korea's Compulsive Shutdown System bans online game providers from offering their services to children under 16 years of age from midnight to 6 a.m. Although it was introduced only after lengthy rounds of discussion, controversy over the system still continues. The key question is whether the system, which unilaterally emphasizes juvenile protection, infringes upon the freedom of playing games for teenagers, the freedom of business for game products related business operators and the right to foster children for parents, which are basic rights under the Constitution. It is very encouraging that the State took up the issue and prepared various systems for juvenile protection through the Compulsive Shutdown System. Yet the government has to plan as comprehensive and effective of a measure as it possibly can by predicting the trends of technology development and game use, and also set detailed standards to ensure that the system should not become an excessive or inappropriate regulation. Although the State's compulsive intervention may be positive since it is hard to expect a self purification capability to exhibit itself concerning game use among teenagers, a plan to prevent game addiction among adolescents from the long-term and fundamental perspectives should be prepared as well.

• Fisheries and Aquatic Sciences
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• v.14 no.1
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• pp.62-69
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• 2011

The effects of actively stimulating devices (ASD) on juvenile flatfish escape were studied to increase escape rates from the cod end by encouraging fish to approach the net wall. Two kinds of ASD were designed: a fluttering net panel, i.e., a free-end flag-like net panel, and a double conical rope array. Escape responses of juvenile bastard halibut were observed in a circulating water channel using two model cod ends, one made with diamond-shaped 43-mm-mesh-size polyethylene (PE) as a high-contrast cod end and the other with polyamid (PA) mono-ply as a low-contrast cod end. Retention rate was significantly lower with the double conical rope-array ASD in the PE cod end than with conventional PE cod ends only or the fluttering net-panel ASD inside the PE cod end. Mean retention rate with the low-contrast PA cod end was also significantly lower than that with the high-contrast PE conventional cod end. Therefore, active fluttering devices using a double conical rope array together with less visible low-contrast netting in the cod end could help to reduce the bycatch of juvenile flatfish by weakening their optomotor response and actively driving fish to the side net panel.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.466-473
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• 2015

The juvenile red variant of the sea cucumber Stichopus japonicus is distributed worldwide. It is a valuable food source in Korea, China, and Japan. Major issues in farming the juvenile red variant sea cucumber include growth rates and disease resistance. In recent years, studies have focused on feed additives to enhance immune system and health. In this study, we used a common diet (CD), a nutritional diet (ND; mixed nutritional supplements), and an immunity diet (ID; mixed probiotics, spirulina, and levan) and compared the growth rates and immunity of juvenile red variant sea cucumbers fed the experimental diets for 12 weeks. The growth and survival rates in the ID group were significantly increased (P>0.05). This suggests that the feed additives positively influenced immunity and growth in the ID group. However, the immune activity was exhibit a stabilizing effect, and further investigation of immune effects is required.

• Fisheries and Aquatic Sciences
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• v.12 no.3
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• pp.203-208
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• 2009

A factorial feeding trial of different levels of three carbohydrate sources (wheat flour, $\alpha$-potato starch, and sodium alginate) was conducted to determine proper sources and levels of dietary carbohydrate for juvenile sea cucumbers. Three replicate groups of juvenile sea cucumbers (770 mg average weight) were fed the experimental diets once a day for 10 weeks. After feeding trial, survival of sea cucumbers was not significantly different between diets. The body weight of sea cucumbers was significantly (P<0.01) affected by both source and level of dietary carbohydrate, tending to decrease as dietary carbohydrate level increased. Body weight of sea cucumbers fed a 25% wheat flour diet was the highest but was not significantly different from that of sea cucumbers fed diet containing 10% wheat flour with 15% sodium alginate (P>0.05). No significant differences were observed in contents of moisture, crude protein, crude lipid and ash of sea cucumbers among dietary treatments. These results suggest that sea cucumbers utilize wheat flour and sodium alginate more efficiently than they do $\alpha$-potato starch, and that a formulated diet containing 43-60% carbohydrate may be suitable for juvenile sea cucumber culture.

• Fisheries and Aquatic Sciences
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• v.14 no.2
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• pp.130-137
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• 2011

Visual stimuli of nets, which affect fishing selectivity, vary by twine diameter, color, and material under different light conditions and visual geometries. In this study, two cylindrical model codends of two mesh sizes, 28 and 43 mm, were made of high-contrast, dark brown polyethylene (PE) netting twine and low contrast, light-blue polyamid (PA) monofilament twine. Each model codend was filled with juvenile seabream and set in the water channel of a light-blue circular tank under a flow speed 0.8 m/s for 30 min. Light conditions were set to relatively bright, dim, and dark. The resulting retention rates of juvenile seabream were 15-35% lower for the low-contrast codend with PA monofilament than for the high contrast PE twine netting under bright and dim light conditions, while no difference was observed under dark conditions. The effects of mesh size and netting contrast on the retention rate were dependent on the light level, while the retention rate due to netting contrast was independent of mesh size. Therefore, low-contrast nets in the codend could help to reduce juvenile bycatch by disturbing the orderly optomotor response.

• Korean Journal of Ichthyology
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• v.29 no.4
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• pp.267-271
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• 2017

Diel changes in feeding activity of juvenile Pacific herring, Clupea pallasii were investigated throughout the analysis of stomach contents of 301 fishes collected from the southeastern coast of Korea. Fish samples were collected every 3 hour over a 24 h period in summer using small bottom trawl. The ratio of empty stomach, stomach fullness, stomach contents index (SCI) and stomach fullness index (IF) of juvenile C. pallasii were varied markedly with day/night changes. The ratio of empty stomach tended be higher during nighttime, while the other values were higher at daytime, with showing peak before sunset. During daytime, the stomach contents mainly were made up of copepods and euphausiids, while the diets at midnight were composed of nearly digested and unidentifiable items.

• Journal of Ecology and Environment
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• v.41 no.1
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• pp.29-33
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• 2017

This study was conducted to clarify the size of the home range and movement distance of juvenile black-faced spoonbills from post-fledging until fall migration using a Global Positioning System (GPS)-wideband code division multiple access (WCDMA)-based telemetry system along the west coast of South Korea. The home range of juvenile black-faced spoonbills (n = 3) was $45.2km^2$ in size and the core area consisted of $8.4km^2$ within the Baeksu mudflat, Yeonggwang, South Jeolla Province, South Korea. Mean weekly movement distances were not significantly different (Kruskal-Wallis test, Z = 3.47, P = 0.18) among individuals, ranging from 0.1 to 23.9 km during the study period. The home range and movement of juvenile black-faced spoonbills were related to intertidal areas, especially to their use as feeding areas.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.6
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• pp.818-823
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• 2017

The diet composition of juvenile gold-eye rockfish, Sebastes thompsoni (40-50 mm SL), was examined based on 121 individuals collected in the Yellow Sea Bottom Cold Water in August 2016. The Yellow Sea Bottom Cold Water is characterized a by water mass of <$10.0^{\circ}C$ and 33 psu. The juvenile gold-eye rockfish fed on Amphipods [57.3% index of relative importance (IRI)] and Euphausiacea (32.9%). Most of the point in the prey-specific abundance plot indicated a high between-phenotype component (BPC).