• Journal of Aquaculture
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• v.9 no.2
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• pp.169-178
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• 1996

This experiment was conducted to develop an experimental model and a semipurified diet for vitamin C requirement study in juvenile Korean rockfish, Sebastes schlegeli. Prior to the start of the feeding trial, fish were fed the control diet for four weeks to deplete their body reserves of vitamin C, Then fish were divided into six groups and given one of the laboratory developed semipurified diets supplementing either 0 (control), 25, 50, 75, 150, o. 1500 mg L-ascorhic acid (AA)/kg diet for eight weeks. Fish fed control diet had lower hematocrit than did fish from groups fed the other diets (P<0.05). Also these fish had significantly lower percent weight gain (WG), feed conversion ratio (FCR) and muscle AA than did fish fed diets containing 150 and 1500 mg AA/kg diet (P<0.05). Diet analysis of vitamin C showed that the control diet had 39,7 mg AA/kg diet. Therefore, these fingings suggest that the experimental model and the semipurified diet can be useful for vitamin C requirement study, and the dietary vitamin C requirement is greater than 40 mg AA/kg diet, but 150 mg AA/kg diet is adequate for the maximum growth in juvenile Korean rockfish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.2
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• pp.146-152
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• 2017

A growth trial was conducted to determine the optimal supplement of dietary magnesium hydrogen phosphate (MHP, $MgHPO_4$) which was manufactured from swine manure and phosphorus (P) requirements of juvenile carp Cyprinus carpio. Graded MHP of 0.5, 1.0, 1.5 and 2.0%, each was added to the basal diet (control) in lieu of cellulose to become the range of available P from 0.4 to 0.7%. The lowest weight gain (WG) and highest feed conversion ratio (FCR) were found in the control group (P<0.05). The group fed a diet supplemented with 2.0% MHP showed the highest WG, which was not significantly different from those of fish groups that received 1.0% and 1.5% MHP (P>0.05). The lowest FCR was observed in fish groups fed 1.5% and 2.0% MHP. Plasma inorganic P was significantly higher (P<0.05) in all fish groups fed MHP-supplemented diets than in control group. A second-order regression analysis on WG revealed that the optimum dietary MHP level and the available P (AP) requirement were found to be 1.85 and 0.66%, respectively. Expressed in terms of 'g AP intake per kg $BW^{0.8}$ per day', the AP requirement was found to be approximately 0.032 g/kg $BW^{0.8}/d$.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.1
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• pp.111-119
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• 2015

A growth trial was conducted to determine the optimal incorporation level of dietary magnesium hydrogen phosphate (MHP, $MgHPO_4$), which was manufactured from swine manure and phosphorus (P), required by juvenile far eastern catfish (Silurus asotus). Graded MHP of 0.5%, 1.0%, 1.5%, and 2.0%, and 2.0% monocalcium phosphate (MCP) each was added to the basal diet (control) in lieu of cellulose to become the range of available P (AP) from 0.4% to 0.8% of which diets were designated as control, MHP0.5, MHP1.0, MHP1.5, MHP2.0, and MCP, respectively. Control diet contained fish meal (20%), soybean meal (40%), wheat flour (27%), corn gluten meal (5%), fish oil (2%) and soy oil (2%) as main ingredients. Following a 24 h fasting, 540 fish with a mean body weight of 11.8 g were randomly allotted to 6 groups in triplicate, whereby 18 tanks ($0.4{\times}0.6{\times}0.36cm$, water volume of 66 L) were prepared. The feeding experiment lasted for 8 weeks. Fish group fed the control diet showed the lowest weight gain (WG) and feed efficiency (FE) among treatments. The WG was, however, not significantly different (p>0.05) from that of fish group fed MHP0.5. Fish group fed MHP2.0 showed the highest WG and FE of which values were not significantly different from those of fish groups fed diets MHP1.0 and MHP1.5 as well as MCP (p>0.05) except fish groups fed control and MHP0.5. Aspartate aminotransferase was significantly decreased with an increase in available P, while alanine aminotransferase did not show a significant difference among treatment. The highest inorganic P in plasma was observed in fish fed MHP2.0. From the present results, a second-order regression analysis revealed that the optimal dietary MHP level and the AP requirement were found to be 1.62% and 0.7%, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.5
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• pp.454-457
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• 2003

A feeding trial was carried out to investigate the utilization of dietary soybean meal and wheat flour as substitutes for fish meal and alginate in different dietary types (powder, pellet and flake) for juvenile snail (Semisulcospira gottschei). After 10 weeks feeding trial, survival was not affected by formulation and type of diets (P>0.05), but weight gain was significantly affected by dietary formulation (P<0.001) and type (P<0.05). In the same dietary formulation, weight gain of the snail fed the flake type of diets was lower than that of the snail fed the powder or pellet types. However, the type of diet did not affect weight gain when snail fed diets containing $37\%$ soybean meal and $18\%$ alginate. The weight gain was lower in the snail fed diets containing $25\%$ fish meal compared with that of the snail for diets containing $33-37\%$ soybean meal at the same dietary type. When soybean meal was used as main protein source in diets, weight gain was not affected by dietary alginate $(0\;and\;18\%)$ and wheat flour $(36\;and\;58\%)$ contents. Crude protein and ash contents of whole body of the snail was not affected either by formulation or by type of diet. Moisture and crude lipid contents of the whole body were significantly affected by dietary formulation, but not by the type. These results indicate that $25\%$ fish meal could be replaced by $37\%$ soybean meal as dietary protein source, and pellet and powder could be desirable dietary type for the optimum growth of the snail.

• Reproductive and Developmental Biology
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• v.34 no.2
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• pp.89-94
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• 2010

Melatonin is induced by light information through the retina and leads to growth factor activation. Thus, we investigated the effects of melatonin by controlling the photoperiod of growing young rats. Male Sprague-Dawley rats (n=6; 4 weeks old) were divided into two experimental groups: the L/D group (normal photoperiod; light/dark: 12/12 h; lights on at 9:00 a.m.) and the L/L group (light/light: 24 h). Rat body weight and food consumption were measured daily for 8 weeks. After 8 weeks, the rats were anesthetized with a mixture of ketamine (50 mg/kg) and xylazine (10 mg/kg) and sacrificed. Tissue was then collected for RNA isolation (from brain, heart, liver, kidney, adrenal gland, testis, tibia, hind limb muscles). Also, serum was isolated from blood using a centrifugal separation. The L/L group had significantly lower body weight than the L/D group from 4 to 6 weeks (p<0.05). The L/D group had increased tissue mass, compared with the L/L group, but the difference was not statistically significant. The L/D group had a significantly higher melatonin concentration than the L/L group between the hours of midnight and 2:00 a.m (p<0.01). These results indicate that photoperiod length may affect the secretion of melatonin from the pineal gland. Also, the reduction of nocturnal melatonin secretion may retard the development of growing young rats. In future studies, we plan to compare exogenous melatonin administration with endogenous melatonin concentration induced by photoperiod control. Moreover, we will confirm whether the effects seen in pathological animal models can be reversed by controlling the photoperiod.

• Journal of Sericultural and Entomological Science
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• v.20 no.2
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• pp.20-25
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• 1978

Research on the hormones of insect has followed by the special opportunities and problems arising from pollution. Since then, the main frame of it has been energetically exploited by ligation, decapitation and so on. In the meanwhile, knowledge of the biochemistry of hormone action as well as other aspects of biochemistry in insects has been gradually disclosed. Since 1966, practical use of active analogs of the hormones has been also worked out as an insecticide and brought the features of it to the light. On the other hand, it is expected to afford the increase of silk productivity resulted from control of the fifth larval period by delaying normal development. With these regards, some of analogs have been tried to apply practically to the silkworm. One of them is "Manta" produced by Zoecon Chemical Company and it is presently used for the increase of silk productivity in Japan. Another one is "R-20458", not registered one, issued by Stuffer Chemical Company. It is still pending for the silkworm growth regulator For the possibility of practical use, two chemicals are tested on the increase of silk productivity by topical application and the obtained results are summarized as follows. 1. It is evident that the fifth larval period was extended by topical application of the tested chemicals "Manta"and "R-20458"at the fifth instar after 51 hours of the last ecdysis, ranging from 12 hours to one day, as compared to. the control 2. In survival rates, there is no significance at 5% level between control and treatments. It proved that there was no toxity to silkworm by topical aprication. 3. There is an increase of cocoon yield in both chemical treatments. It was resulted from increase of weight of single cocoon. "Manta"2.5ppm produced 22.2kg of cocoon. It is equal to 9% increase in index, as compared to that of control. In case of R-20458, the increasing rates were varied at the different concentration; 21.4kg of cocoon production with 5% increase at 5ppm, 20.9kg of it with 2% increase at 2.5ppm and 20.6kg of it with 1% increase at 1. 25ppm in index, respectively, as compared with that of control. 4. Percentage of cocoon shell was increased by topical application. In case of "Manta" 2.5ppm, it is 25.6% which is equal to 6% increase in index, as compared with that of control. For "R-20458", the increasing rates of percentage of cocoon shell were varied with the different level of chemical concentration. They are 25.0% of 4% increase at 2.5ppm, 24.9% of 3% increase at 1.25ppm and 24.7% of 3% increase at 5ppm. 15% increase was attained at "Manta" 2.5ppm in the weight of cocoon layer based on cocoon yield and percentage of cocoon shell in index, as compared with that of control. The rates for "R-20458"are 5% increase at 2.5ppm and 4% increase at 1. 25ppm in index.

• Korean Journal of Ichthyology
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• v.35 no.1
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• pp.30-38
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• 2023

The feeding ecology of the eight barbel loach, Lefua costata, were investigated in the Jusucheon (Stream), Namyang-ri, Okgye-myeon, Gangneung-si, Gangwon-do, Korea from January to December 2013. L. costata mainly fed from March to December when the water temperature was higher than 5℃, and the feeding rate peaked in April~May and September~October. Their main food organisms analyzed by the index of relative importance (IRI) were Diptera (77.1%), Ephemeroptera (20.3%), Trichoptera (1.7%) and Odonata (0.4%) in Insecta. Other food organisms were various, such as Arhynchobdellida (0.6%) and Tubificida (0.1%) of Annelida, Nematoda (0.2%), fish (Actinopterygii, 0.1%), and Veneroida (0.01%) of the Mollusca. Major seasonal food organisms were Diptera (55.4%) and Ephemeroptera (41.6%) in spring, Diptera (92.7%) and Anelida (6.8%) in summer, Diptera (70.8%), Ephemeroptera (9.0%), Trichoptera (8.1%) and Annelida (7.7%) in autumn. By age, juvenile (0+) tended to eat only Diptera (mainly Chironomidae, 98.2%) that were relatively small in prey size. However, as it grew, the proportion of Diptera gradually decreased, and the proportion of relatively large Mayflies and Annelids increased. The size of the prey organisms showed rapid growth, with 2.5±1.05 mm for juvenile (0+), 3.2±1.29 mm for one year (1+), 3.7±2.05 mm for two years (2+), and 6.8±4.97 mm for three years or more (≥3+).

• Korean Journal of Ichthyology
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• v.35 no.2
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• pp.75-82
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• 2023

The samples used in this study were collected on two occasions (April 21 and May 16, 2021) from Liobagrus mediadiposalis and spawned egg masses located under rocks in Daeseocheon, Yeongdeok-gun, Gyeongsangbuk-do. Fertilized eggs ranged in size from 3.30~3.92 (average 3.57±0.19) mm (n=30), and it took 152~155 hours to hatch at water temperatures of between 17.0 and 20.0℃. Newly hatched larvae immediately post-hatching had a total length of 6.43~6.67 (6.55±0.07) mm (n=30), and were characterized by the retention of a yolk sac and an incompletely open mouth and anus, consistent with the yolk. On the 9 days post-hatching, the postflexion larvae had grown to length of between 11.0~13.8 (12.3±0.70) mm (n=30), and the caudal bone at the tip of the tail was bent upwards at an angle of 45°, thereby indicating the transition to the late larval growth stage. On the 16 days post-hatching, the total length of juvenile had increased to between 15.8~18.2 (16.8±0.77) mm (n=30), and the number of fins reached a fixed number of 8 dorsal, 17 anal, and 8 pelvic fins. On the basis of the findings of this study, we were able to confirm differences in the size of hatching larvae and fin mottle patterns in the early life history of related species.

• Journal of Korean Society of Forest Science
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• v.88 no.1
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• pp.73-85
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• 1999

This study was conducted to reveal the characteristics of the early growth by locality for Korean white pine planted in Gapyung and Kwangju, Kyunggi-Do and Youngdong, Choongchungbuk-Do. The effects of local climatic conditions as one of environmental factors on the growth were also analyzed. For this, several stand variables such as number of trees survived, mean DBH, mean height, basal area per hectare, and volume per hectare by stand age were measured and summarized for each locality. Based on these statistics, periodic annual increments for 8 years from stand age 10 to 18 were calculated for each of stand variables. A topoclimatological technique, for the estimation of local climatic conditions, which makes use of empirical relationships between the topography and the weather in study areas was applied to produce reasonable estimates of monthly mean, maximum, minimum temperatures, relative humidity, precipitation, and hours of sunshine over remote land area where routine observations are rare. From these monthly estimates, 17 weather variables such as warmth index, coldness index, index of aridity etc. which affect the tree growth, were computed for each locality. The periodic annual increments were then correlated with and regressed on the weather variables to examine effects of local weather conditions on the growth. Gapyung area provided the best conditions for the growth of Korean white pine in the early stage and Kwangju area ranked second. On the other hand, the growth pattern in Youngdong ranked last overall as expected. It is also found that the local growth patterns of Korean white pine in juvenile stage were affected by typical weather conditions. The conditions such as low temperature, high relative humidity, and large amount of precipitation provide favorable environment for the growth of Korean white pine. Especially, the diameter growth, basal area growth, and volume growth are mainly influenced by the amount of precipitation. However, it is proved that the height growth is affected by both the precipitation and temperature.

• Journal of Aquaculture
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• v.9 no.4
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• pp.311-320
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• 1996

In order to compare the growth and survival rates of grey mullet (Mugil cephalus) juveniles in different salinities, the fish reared in seawater (SW) abruptly were transferred to each experimental rearing water of $0\%SW\;(0\%_{\circ}),\;25\%SW\;(7.7\%_{\circ}),\;50\%SW\;(16.1\%_{\circ})$ and $100\%SW (32.8\%_{\circ})$. Growth rates in total length and body weight of fish in $25\%$ SW, $50\%$ SW and $75\%$ SW were greater than that in $0\%$ SW (P<0,05). Decreased salinity appeared to have an acute, but appetite depressive effect in short term in the experimental groups. Survival rate was low in $0\%$ SW (P<0.05), although those were more than $81\%$ in all salinities. There were no differences in thickness of epidermis and dermis layers in fish skin among the all experimental groups at the end of experiment. But the thickness of lipid layer in $0\%$ SW fish showed the significant differences to those in $50\%$ SW and $100\%$ SW (P<0.05). With decreased salinities, oxygen consumption was found to be decresed in the other experimental groups compared to the group in $100\%$ SW. The levels of lethal dissolved oxygen in $0\%$ SW to $100\%$ SW were 1.18, 0.30, 0,28 and 0.31 ppm, respectively.