• Korean Journal of Ichthyology
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• v.10 no.2
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• pp.207-215
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• 1998

Just after hatching the embryo has a yolk sac and straighted digestive tract. Just after parturition in 5.0mm TL the mouth and anus were opened. In the larval stage of 5.2mm TL, digestive tract could be divided into pharynx, esophagus, stomach, pyloric caeca and intestine of the early differentiated state. The esophagus of larvae in 5.3mm TL has a PAS positive mucous cell. From over 5.7mm TL, PAS positive goblet cell recognized in the intestine. PAS positive absorptive cell began to appear in the intestine from 5.9mm TL. Yolky materials were absorbed completely in 6.0mm TL. In the larvae of B.5mm TL, gastric glands were observed in the mucosa, but the surface epithelium did not have PAS positive granules. From over 9.0mm TL, the histological structure of esophagus showed similar to adult. In the juvenile stage from 13.0mm to 15.0mm TL, histological structure of the stomach, pyloric caeca and intestine showed similar to adult. From the ultrastructural and histochemical study, it is concluded that the functional digestive tract is present in the juvenile stage from 18.0mm to 20.0mm TL.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.6
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• pp.812-817
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• 2017

This study evaluated the effects of dietary inclusion of soybean (SM) and fermented soybean meal (FSM) on growth promotion in juvenile abalone Haliotis discus. Six hundred and thirty juvenile abalone were distributed into nine plastic containers. Three diets were prepared with 22% fish meal, 2% casein, and either 25% SM or FSM used as the protein sources in the experimental diets, and Undaria was used as a control diet to compare the effects of the experimental diets on the growth performance of abalone. The diets were assigned to three containers each and fed to the abalone once daily to satiation for 16 weeks. Weight gain and specific growth rate (SGR) were higher in abalone fed the SM diet than in those fed the FSM diet. Weight gain and SGR of abalone fed the SM and FSM diets were higher than those of abalone fed Undaria. The crude protein and lipid contents of the edible portions of abalone fed the SM and FSM diets were higher than those of abalone fed Undaria. SM was superior to FSM as a protein source in abalone feed. The SM and FSM diets facilitated greater growth than Undaria.

• Fisheries and Aquatic Sciences
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• v.21 no.9
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• pp.26.1-26.8
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• 2018

Inclusion effect of soybean meal (SBM) and fermented SBM (FSM) in extruded pellet for juvenile abalone (Haliotis discus) was compared in abalone farm. Dietary inclusion effect of the combined macroalgae (MA) (Undaria pinnatifida and Hizikia fusiforme) and a single Saccharina japonica on abalone was also compared. Three thousand six hundred juvenile abalone were purchased from a private hatchery and acclimated to the experimental conditions for 2 weeks. Six 5-ton flow-through raceway tanks were used, and abalone were randomly distributed into tanks (n = 600 per tank). Three experimental diets were prepared in duplicate. Fish meal, FSM, corn gluten meal, and shrimp meal and wheat flour and dextrin were used as the protein and carbohydrate sources, respectively, in the FSM diet. MA was also included in the FSM diet. FSM and MA in the FSM diet were substituted with SBM at the expense of wheat flour and S. japonica, referred to as the SBM and SJ diets. The experimental diets were pelletized by an extruded pelleter. Water stability of nutrients in the experimental diets was monitored at 12, 24, and 48 h after seawater immersion. The experimental diets were fed to abalone once a day to satiation with a little leftover for 120 days. The retained crude protein and lipid and ash content of the extruded pellets were changed over all period of time. Weight gain and specific growth rate (SGR) of abalone fed the SBM diet were greater than those of abalone fed the FSM and SJ diets. Weight gain and SGR of abalone fed the SJ diet were also greater than those of abalone fed the FSM diet. The longest shell length, widest shell width, highest shell height, and greatest soft body weight were obtained in abalone fed the SBM diet, followed by the SJ and FSM diets. Proximates of the soft body of abalone were not different among the experimental diets. In conclusion, SBM was a superior protein source to FSM in extruded pellet for growth performance of abalone. Dietary inclusion of a single S. japonica was superior to the combined inclusion of U. pinnatifida and H. fusiforme in the production of abalone.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.5
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• pp.408-412
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• 2000

The juvenile Bobiids, Faronirobius gymnauchen, were reared for 40 days under $0{\~}33.6{\%_{\circ}}$ salinity conditions to examine the effects of various salinity on its survival, growth and oxygen consumption rates, Survival rate was significantly declined below $6.7{\%_{\circ}}$ salinity, and daily growth rate was also reduced below $10.1{\%{\circ}}$. Body length and weight of gobiids reared below $10.1{\%_{\circ}}$ were smaller than those of gobiids reared above $20.2{\%_{\circ}}$. Oxygen consumption rate in the salinity conditions ${\leq}13.4{\%_{\circ}}$ was significantly reduced with decreasing salinity than that in natural seawater ($33.6{\%_{\circ}}$), This study revealed that low salinity reduced survival, growth and oxygen consumption rates of the juvenile gobiids suggesting potential influence on the natural mortality of F gymnauchen in the coastal areas.

• Korean Journal of Ichthyology
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• v.31 no.4
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• pp.214-221
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• 2019

This study suggests basic data for taxonomic research among similar species by observing osteological development of larvae of Hemibarbus longirostris. Newly hatched yolk-sac larvae were 8.10±0.02 mm (n=5) in mean total length, and frontal, parasphenoid, and basioccipital in the cranium were ossified. On the 6 days after hatching, flexion-larvae were 10.9±0.26 mm (n=5) in mean total length, hyomandibular, sympletic, and ectopterygoid in the cranium were ossified. On the 12 days after hatching, post-larvae were 12.2±0.55 mm (n=5) in mean total length, interopercle in operculum region and postclavicle in shoulder girdle bone were ossified. On the 25 days after hatching, post-larvae were 16.1±0.27 mm (n=5) in mean total length, epihyal and interhyal in hyoid arch, two epural in caudal skeleton, interneural processes, and interhaemal processes were ossified. On the 40 days after hatching, juvenile were 27.9±3.74 mm (n=5) in mean total length, all skeletal development completed with hypural bone in the caudal skeleton region fused in three forms (1, 2+3, 4+5).

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.3
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• pp.191-196
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• 2011

Naphthalene was composed of a substantial fraction of polycyclic aromatic ydrocarbons(PAHs) in crude oil and causes acute toxicity. In this study, we examined the toxicity of different kinds concentrations 0, 1000, 1800, 3200, 5600, $10000{\mu}g/L$ of naphthalene to juvenile flounder, Paralichthys olivaceus for 24h to determine 24-median lethal concentration($LC_{50}$) and acute effect on the hematological properties. 24h-$LC_{50}$ value of this species was $3600{\mu}g/L$. Hematocrit value significantly increased at 5600 and $10000{\mu}g/L$ naphthalene exposed group by 24h compared to control fish. Plasma. Glucose was significantly higher in the $10000{\mu}g/L$ (P<0.05). Plasma osmolality was significantly higher in the 3200, 5600 and $10000{\mu}g/L$. Plasma [$Na^+$] and [$K^+$] significantly increased in the 5600 and $10000{\mu}g/L$, however [$Cl^-$] was not affected by acute naphthalene exposure. The results of this study suggest the acute exposure to naphthalene affects both ionoregulation and osmoregulation in juvenile flounder.

• Journal of Marine Life Science
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• v.7 no.2
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• pp.180-186
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• 2022

This study was conducted to investigate the effects of different salinity on growth, survival and hematological parameters of juvenile chum salmon (Oncorhynchus keta). The fish were tested at salinity 0, 10, 20 and 30‰ for 30 days with three replicated groups. After the 30 days, the survival rate was 87.5% or more for 0, 10, 20‰ and significantly decreased to 75% at 30‰. Weight gain, specific growth rate, feed efficiency, daily feed intake, daily protein intake and protein efficiency ratio were the highest at 10‰. In the plasma components, the alanine aminotransferase (ALT) was significantly decreased at 10, 20 and 30‰ in compared with 0‰, whereas sodium (Na⁺) and chloride (Cl^-) was significant increased and there was no significant change in the total protein (TP) and potassium (K⁺). In conclusion, the optimal salt concentration for the growth of juvenile chum salmon (11~33 g) was confirmed to be 10‰, but the association with the change in blood composition should be further studied.

• Journal of Aquaculture
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• v.21 no.4
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• pp.278-284
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• 2008

Artificially-produced juvenile black sea bream Acanthopagrus schlegeli (total length $8.3{\pm}1.0\;cm$, body weight $11.2{\pm}4.2\;g$) were released in eelgrass, Zostera marina bed and their initial food organism and changes of body compositions were investigated for one month after release. Predation rates in fish sampled on 1st and 3rd days were 79%, increased up to 100% on 7th and 10th days, and then decreased on 30th days as 75%. Major prey organisms was composed of mainly Amphipoda and Gastropoda. Ratio of Amphipoda and Gastropoda in stomach were highest in fish sampled on 15th and 1st days after release, respectively. Crustacea and Algae were maintained about 20% during a sampling period. Visceral weight index (VWI) offish sampled 20th and 30th after release were significantly higher than that of initial. Carcass crude protein and lipid contents of released fish were showed significantly decreasing; however carcass n-3 HUFA composition was showed increasing tendency with the passage of time after release. Eelgrass bed was supposed to be helpful for the released fish to adjust their feeding habits and biochemical metabolism to the natural environment within a short period after release.

• 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.

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.154-159
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• 2007

The oblong rockfish, Sebastes oblongus has recently drawn attention from aquaculturists because of its marketable value and tolerance against winter water temperature in the southern coastal waters of the Korean peninsula. In the study of temperature effect on growth, water temperature $16^{\circ}C$ showed best growth. The upper temperature of the fish showed feeding activity was $27^{\circ}C$ over which the fish showed no longer feeding activity. Stocking density was also a critical factor affecting the growth and survival of the juvenile fish. The best growth was in the density of 200 juveniles/L, while the highest survival was in the density of 100 juveniles/L. A feeding experiment was conducted to determine the effects of feeding frequency on growth and survival. A feeding scheme of twice a day was good enough in the sense of growth, survival, and economy. These results indicate that parameters such as water temperature, density, tank size and feeding frequency are consideration for best seed production of the fish.