• Journal of Aquaculture
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• v.16 no.3
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• pp.159-164
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• 2003

Effect of the benthic echiurid Urechis unicinctus juveniles on the chemical characteristics of organically enriched sediment, as well as the individual survival rate and growth in various sediments, was investigated in this study to ascertain the effectiveness of U. unicinctus in the bioremediation of organically polluted sediment. The content of acid volatile sulfide (AVS) in the sediment of three coastal areas was 0.4±0.1 mg/gㆍdry sediment in Seonso, 0.1±0.01 mg/gㆍdry sediment in Myo-do, 0.02±0.01 mg/gㆍdry sediment in Dolsan-do, respectively. 500 juveniles with average body length of 1.2±0.3 mm were bred in these sediments. After 30 days, the AVS content of three places decreased to 0.29±0.3, 0.08±0.01 and 0.0l±0.01 mg/gㆍdry. After 60 days, the content was 0.23±0.03, 0.0l±0.01, 0.0l±0.01 mg/gㆍdry. The AVS content in the control (sediment from Seonso without juveniles) was 0.39±0.75 mg/gㆍdry sediment (after 30 days) and 0.45±0.01 mg/gㆍdry sediment (after 60 days). At the same time, the chemical oxygen demand (COD) and total ingition loss (TIL) of these sediments showed the same trend with that of AVS. Furthermore, 60 days later, the survival rate and growth of juveniles were 71.2%, 11.1±l.0 mm in Seonso, 89.8%, 12.0±1.3 mm in Myo-do and 81.6%, 11.9±1.9 mm in Dolsan-do. It was suggested that U. unicinctus can survive better in less polluted environment. Under different U. unicinctus juvenile density (100, 300, 500, 700, 900 individuals), after 60 days cultivation, the AVS content decreased from 0.4±0.1, 0.4±0.1, 0.4±0.3, 0.4±0.3, 0.4±0.3 mg/gㆍdry to 0.4±0.2, 0.3±0.2, 0.2±0.1, 0.2±0.1, 0.2±0.1 mg/gㆍdry. Therefore, the higher the density of juveniles, the greater the effect in improving the sediment. In comparison to different initial AVS concentration (0.40±0.01, 0.35±0.01, [I can't find a reference to this number above], 0.29±0.02, [I can't find a reference to this number above], 0.18±0.03, [I can't find a reference to this number above], 0.06±0.02 mg/gㆍdry sediment [I can't find a reference to this number above] and the control 0.0±0.0[I can't find a reference to this number above]), after 30 days cultivation with 500 juveniles, the AVS content was 0.29±0.03, 0.19±0.0, 0.15±0.01, 0.12±0.02, 0.05±0.0mg/gㆍdry and 0(control). After 60 days cultivation, the content was 0.23±0.03, 0.12±0.4, 0.10±0.01, 0.18±0.03, 0.06±0.02 mg/gㆍdry and 0 (control). Use % decrease in AVS content to state: The impact of U. unicinctus on the sediments was greater with higher concentrations of AVS. The results of this study indicate that U. unicinctus is effective in the biological treatment of sediments polluted by AVS and other organics.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.61-70
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• 1997

The spawning season, growth and feeding habit of tubesnout, Aulichthys japonicus were examined from the samples collected by a small beam trawl in the Zostera marina belt at the coastal water off Hamduck, Cheju Island, from May 1993 to May 1994. Tubesnout was the dominant species of overall 58 species collected in the study area throughout the year. The larvae and juvenile of tubesnout in the frequency distributions of body length began to appear in the Z. marina belt in March, and adults disappeared after May in the following year. The gonad weight index (GWI) and the condition factor (K) were high from November 1993 to January 1994 for males, while females were high from February to May 1994. Although tubesnout is an oviparous fish, males have the urogenital papilla. These results suggest that they were fertilized between November and January, and then males seemed to be died or move into other places. Females were examined to spawn from February to May. The stomach contents of tubesnout were dominated by copepoda smaller than ca. 1mm, Paracalanus, Oithona, Acartia, Oncaea and Harpacticoidae, accounting for 97% of total food items. The feeding habit of tubesnout did not vary by size. The fishes fed on Calanus, Euchaeta and decapoda larvae larger than ca. 3mm in March and April during the spawning season.

• Korean Journal of Environment and Ecology
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• v.27 no.4
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• pp.429-436
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• 2013

Churyeong Stream flows 37km from the mouth of Lake Okjeong and is impeded by many weirs that hamper the active movement of land-locked sweet smelt fish (Plecoglossus altivelis) that ascend and descend between the lake and the upper stream. In late December 2006, a fishway was constructed in a weir of the lower reach of Churyeong Stream, where juveniles begin their ascent to mature upstream. At 13 sites along the stream from April to October 2007, we investigated the effects of the newly constructed fishway on sweet smelt growth. After construction of the fishway, juvenile sweet smelt were able to migrate freely upstream, something that had previously only been possible when the weir was in flood. The body size of mature sweet smelt collected during the spawning season in September 2007 was greatly increased compared to previous seasons, measuring an average of $163{\pm}21.5mm$ in standard length. These measurements were 13mm, 20mm, and 57mm longer than body length averages for mature sweet smelt collected in 2006, 2004, and 2005, respectively. Therefore, it is likely to be necessary for the construction of fishways on streams and rivers containing land-locked sweet smelt populations to increase average body sizes and viability.

• FLOWER RESEARCH JOURNAL
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• v.17 no.2
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• pp.93-100
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• 2009

This study was carried out to investigate the efficient in vitro mass propagation methods for juvenile sporophytes of Matteuccia struthiopteris. Chopped segments of pinnae, petiole and rhizome were cultured on 1/2MS with 0.1% activated charcoal. Among these explant sources only rhizome segments produced young sporophytes, regenerating vigorously on 1/2 MS medium. Adjusting sucrose concentration to 2% and supplement to $50mgL^{-1}$ $NaH_2PO_4$ in 1/2MS medium proved to be more efficient for plant regeneration. Various combinations of growth regulators such as kinetin, BA, NAA, and IBA were added to the growing media, and the best sporophyte regeneration was obtained by $1{\mu}M$ kinetin. The BA addition resulted in vigorous proliferation of meristematic tissues, but without differentiation to sporophytes. Three types of culture methods, solid using agar, liquid stationary, and liquid shaking culture, were employed with or without activated charcoal. The addition of 0.1% activated charcoal to modified 1/2MS media (2% sucrose, $50mgL^{-1}$ $NaH_2PO_4$, $1{\mu}M$ kinetin, pH 5.8 and 0.8% agar) yielded highest sporophyte regeneration in liquid shaking culture.

• Korean Journal of Social Welfare Studies
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• v.45 no.2
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• pp.5-30
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• 2014

This study sought to identify developmental trajectories of bullying victimization from late elementary school through early high school, and to examine internalizing and externalizing problem outcomes associated with the trajectory group membership. Data from Seoul Panel Study of Children were collected annually over a 7-year period from 5th grade of elementary school through 2nd grade of high school (2005~2011). Latent class growth analysis yield three trajectory classes corresponding to stable low (81.2%), stable high (3.5%), and declining bullying victimization (15.6%). Findings from analysis of covariance indicated that students in both stable high and declining trajectory groups reported significantly higher means in internalizing behavior (withdrawal, depression/anxiety, and suicide ideation), compared to those in the stable low group. For externalizing behavior such as aggression and juvenile status offense, students in the stable high group showed higher means, compared to those in the stable low and declining trajectory groups. Developmental pattern of bullying victimization over multiple development stages and associated internalizing and externalizing outcomes are discussed as are the implications for the bullying prevention.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.2
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• pp.134-140
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• 2019

A feeding trial was conducted to investigate the effects of dietary fish meal replacement by a blend of lysine cell mass, corn protein concentrate and poultry by-product meal on the growth and blood chemistry of the starry flounder Platichthys stellatus. The fish meal replacer (FMR) was prepared to have the same level of protein as fish meal (FM). With a commercial diet as a positive control, five experimental diets (basal, FM42, FM32, FM22 and FM12) were formulated to contain 52% protein and 10% lipid. The dietary FM levels decreased from 52% (basal) to 42, 32, 22 and 12% with concomitant increase in the FMR to 10, 20, 30, 40 and 50%, respectively. Juvenile starry flounder with an average body weight of 177.3 g were randomly distributed in each (30 fish/tank) of 18 plastic tanks ($139{\times}99{\times}54cm$). After a 45-day feeding trial, the survival rate ranged from 95.6% (FM22) to 100% (control and FM42), while the weight gain of the fish groups varied from 49.7 to 58.4 g. The results clearly revealed that starry flounder can grow well on a diet containing low FM (12%) with a high level of FMR (50%) without any adverse effects.

• Korean Journal of Ichthyology
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• v.33 no.4
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• pp.262-272
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• 2021

The egg development and early life history of Tribolodon hakonensis that collected from the Seomjin River were studied. The fertilized eggs of the T. hakonensis were slightly adhesive and separated with a yellow yolk and no oil globule. The size of the eggs was an average of 2.89 mm (2.79~2.96) in diameter. Fifty percents of the embryos were hatched in about 63 hrs after fertilization at water temperature of 20℃. The newly hatched larvae showed average 6.92 mm (6.09~7.60) in total length. At 8 days after hatching, they were 13.75±0.67 mm (n=10) in total length and their yolk sacs were completely absorbed, opening mouth and anus (postflexion larvae stage). At 40 days after hatching, they became juvenile and reached 26.99±1.82 mm (n=10) in total length and all their fin rays were formed. At 137 days after hatching, the young fish were 72.63±10.7 mm (n=10) in total length and their body shape, color and behavior were similar to those of adult fish. The size of eggs and the larva after hatching significantly affected the initial growth among groups of genus Tribolodon, and the hatching time of fertilized eggs and the growth rate of the early life history according to the water temperate were different.

• Journal of Aquaculture
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• v.5 no.1
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• pp.29-67
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• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.

• Journal of the Korean Society of School Health
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• v.7 no.1
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• pp.57-71
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• 1994

I investigated actual conditions of smoking of teenagers who were randomly chosen middle and high school students. 1. Juvenile smoking 1) Parents' opinions of juvenile smoking Most parents do not want their children to smoke after growth : 88.6% of fathers (middle school students: 88.9%, high school students: 88.4%) and 95.1% of mothers (middle school students: 93.4%, high school students :95.5%). 2) Teenagers' opinions of smoking after growth The rate of students who will smoke after growth is 10.8% (middle school students: 12.0%, high school students: 9.9%): students in agricultural areas show the higher rate than those in cities. 3) Parents' opinions of their children's smoking now 1.5% of fathers want their children to smoke now (middle school students: 1.3%, high school students: 1.6%) and 1.1% of mothers do (middle school students: 0.6%, high school students: 1.5%). This shows that most parents do not want their children to smoke now. 4) Students' opinions of their friends' smoking now Students who want their friends smoke now cover 7.8% (middle school students: 7.1%, high school students: 8.4%). This rates are higher than those of parents shown in (3). And more high school students and more girl students gave the positive reponse than middle school boy and girl students, respectively. 5) Students' views of smoking "Look like an adult" covers the rate of 4.0% (boy: 7.8%, girl:3.6%) 6.7% of middle school students have this view, while 3.7% of high school students have. 16.1% of students had an experience of smoking during the last one year (boy: 29.9%, girl: 8.6%): this shows that the rate of the boy students is more than 3 times greater than that of the girl students and high students who experienced smoking last year covers 20.2%, while middle school students shows 10.9%. 6) Actual conditions of students' smoking The present rate of students' smoking is 22.4% (boy:38.3%, girl:13.8%): the rate of boy students is greater than that of girl students. Students who smoke more than pack of cigarettes a day cover 8.2% (boy: 17.5%, girl: 3.2%): 5.2% of middle school students (boy:11.4%, girl: 2.1%) smoke more than one pack while 10.7% of high school students do (boy:21.5%, girl: 4.2%). This shows that the rate of boy students' smoking is greater than that of girl students' smoking. 7) The rate of smoking of students' parents 75.4% of fathers (city: 74.5%, agricultural area:75.9%) smoke: and more than a half (62.4%) smoke more than a pack cigarettes a day. On the other hand, the rate of smoking mothers is 5.2%(city: 4.3%, agricultural area: 7.3%): the rate is higher in agricultural areas. 8) Opinions of smoking population in the future 61.4% of students answered that smoking population will increase, while 27.0% have the opinion that smoking population will decrease. 2. Opinions of the effects of smoking on health 1) Have you heard that smokers are likely to suffer from tuberclosis? 78.3% of students said yes (boy: 80.8%, girl: 76.4%): it is shown that the rate of boys is greater than that of girls. 2) Have you heard that smokers are likely to get out of endurance? 76.6% of students (boy: 69.3%, girl: 49.7%) answered yes: it is shown that the rate of boys is greater than that of girls. 3) Have you heard that heart-beats get fast when one smokes? 32.5% of students (boy: 35.5%, girl: 30.9%) answered yes: 32.2% in cities(boy: 33.0%, girl: 31.8%) and 33.5% in agricultural areas(boy: 41.8%, girl: 28.8%): and 28.7% middle students and 35.5% of high school students answered yes. 4) Have you heard that smokers are likely to have heart-diseases? 35.1% of students (boy: 34.0%, girl: 34.1%) answered yes: 35.3% in cities (boy: 37.2%, girl: 34.2%) and 36.7% in agricultural areas (boy: 39.0%, girl: 33.9%): 34.8% of middle school students and 35.4% of high school students. 5) Have you heard that smokers are likely to have a lung cancer? 91.4% of students (boy: 93.2%, girl: 89.9%) answered yes: 90.35% in cities and 94.2% in agricultural areas. 6) Have you heard that the life of smokers gets shorter? 94.3% of students (boy:94.6%, girl: 92.2%) answered yes. 7) Have you heard that pregnant smokers will deliver a baby with low birth weight? 29.6% of students (boy: 29.8%, girl: 29.4%) answered yes: the rates of boys and girls almost the same. 8) Have you heard that one feels calm when one smokes? 80.1% of students (boy: 81.8%, girl: 79.2%) answered yes: boys and girls showed almost the same rate. 3. Preventive measures Smoking people continued to increase all over the world because smoking not only mitigated emotional uneasiness such as loneliness, nervousness and so on, but also could be very helpful from the social perspective. This was so because they did not consider harmful effects of smoking on health, and victims. However, because any -one can have physical disorders caused by smoking, people should always keep in mind the following preventive measures. 1) Doctors or teachers should set an example of giving up smoking. Informing patients or students of harmful effects of smoking to persuade their family and relatives not to smoke. 2) Through mass media like newspapers, periodicals or broadcasting, to make people know harmful effects of smoking and not smoke. 3) To prohibit selling teenagers cigarette by law. 4) To prohibit smoking in public places like work places, offices, lecture rooms, recreation rooms, buses, trains and so on. 5) To decrease the rate of life insurance for non-smokers as in foreign countries and to give a warming of the harmful effects on cigarette packets or ads.