• Journal of Aquaculture
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• v.18 no.1
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• pp.19-25
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• 2005

This study was performed to investigate the optimum density for the intensive mass production of cyclopoid copepod, Paracyclopina nana in terms of nauplii and adults production. Effect of three development stages on the fecundity of adult female for nauplii production, survival rate of P. nana nauplii with different initial nauplii culture densities for adults production and cannibalistic feeding behavior of P. nana was examined, respectively. The fecundity of adult female by different female, copepodite ana nauplii density in 2 ml water volume decreased with the density of adult female, but was not affected by the density of either copepodite or nauplii. The average daily nauplii production for a adult female in 8 L water volume was $2.3{\times}10^5$ individuals with the incubation density of 7 adult females/ml, and this average value was significantly higher than those values of 0.6 to $1.7\times10^5$ individuals with the incubation density of 1,3,5, 10 adult females/ml (P<0.05). Survival rate of P. nana nauplil with different initial nauplii culture densities in 5 L vessels for 15 days were 32.7, 30.7, 28.9 and $23.0\%$ with the culture density of 50, 100, 150 and 200 inds./ml, respectively, but these were significantly higher than those of values 19.7 and $18.4\%$ with the culture density of 250 and 300 inds./ml (P<0.05). Cannibalistic behavior of P. nana adults on their offspring was observed, but the behavior decreased when phytoplankton was supplemented though there was no statistical difference (P>0.05). These results may indicate that P. nana is adaptable to the hatchery conditions and this species is cultured at the high densities. Optimum culture density for nauplii and adults production of P. nana were 7 adult females/ml and 200 nauplii/ml, respectively.

• Journal of Aquaculture
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• v.18 no.4
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• pp.236-244
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• 2005

Experiments were performed to investigate the effects of the different anesthetic MS-222 and lidocaine-HCl doses on the blood physiological responses, on the time required for anesthesia and recovery, and on the survival rates of black rockfish (Sebastes schlegeli). Plasma cortisol was its highest levels (96.1$\pm$12.1 ng/ml) at 6 hours after the administration of 300 ppm of MS-222, and in all groups, plasma cortisol levels were higher than the initial levels during the anesthetic experiment. Fish receiving lidocaine-HCl also exhibited higher than initial plasma cortisol levels at almost experimental intervals. The middle size fish exhibited the highest glucose level (143.3$\pm$14.5 mg/dl) at 50 ppm of anesthesia after 1 hour, and every level was significantly higher than the initial level for at least 12 hours. Glucose levels in fish to which lidocaine-HCl was administered were comparable to the levels seen in conjunction with MS-222 treatment. In fish anesthetized with MS-222, K+ levels in the small size fish were significantly elevated after 1 hour, while Na+ levels did not change in any of the groups throughout the experiment. Anesthetic time was significantly attenuated with increases in the concentrations of MS-222 and lidocaine-HCl. We also noted a correlation between anesthetic time and fish size, in that larger fish took a longer time, followed by the middle size and then the small size fish. The all fish size groups showed above $95\%$ survival rates at every experimental concentration in MS-222 and 300-400 ppm in lidocaine-HCl. The results may indicate that 100-200 ppm MS-222 and 400 ppm lidocaine-HCl are the most effective doses as sedatives for the black rockfish and these doses could be used as the suitable anesthetics doses.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.6
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• pp.659-670
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• 2017

Oxidative stress and inflammation are key factors responsible for progression of liver injury. A variety of functions of oyster hydrolysate (OH) are affected by their antioxidant and anti-inflammatory activities. However, little is known regarding the effects of OH on a liver injury model. This study was performed to evaluate the effects of OH on acute liver injury induced by lipopolysaccharide/D-galactosamine (LPS/D-GalN) in mice. Experimental groups were divided into six groups as follows (each group, n=10): control (saline), LPS/D-GalN, LPS/D-GalN+OH (100 mg/kg), LPS/D-GalN+OH (200 mg/kg), LPS/D-GalN+OH (400 mg/kg), and LPS/D-GalN+silymarin (25 mg/kg, positive control). The experimental acute liver injury model was induced with LPS ($1{\mu}g/kg$) and D-GalN (400 mg/kg). We first analyzed antioxidant and anti-inflammatory activities in OH. OH showed high DPPH and ABTS radical scavenging activities and reduced ROS generation in Chang cells in a dose-dependent manner. In addition, OH showed anti-inflammatory activities, such as inhibition of cyclooxygenase-2 and 5-lipooxygenase. Treatment with OH down-regulated tumor necrosis factor $(TNF)-{\alpha}$, interleukin (IL)-6, and $IL-1{\alpha}$ expression levels in LPS-stimulated RAW264.7 cells. OH significantly reduced LPS/D-GalN-induced increases in the concentrations of alanine transaminase and aspartate aminotransferase in serum. In the LPS/D-GalN group, liver tissues exhibited apoptosis of hepatocytes with hemorrhages. These pathological alterations were ameliorated by OH treatment. Consistently, hepatic catalase activity was low in the LPS/D-GalN group compared to the control group, and catalase activity was significantly restored by OH treatment (P<0.05). Furthermore, OH markedly reduced the LPS/D-GalN-induced increase in $TNF-{\alpha}$, $IL-1{\beta}$, and IL-6 levels in liver tissue. Taken together, these results show that OH has hepatoprotective effects on LPS/D-GalN-induced acute liver injury via inhibition of oxidative stress and inflammation, suggesting that OH could be used as a health functional food and potential therapeutic agent for acute liver injury.

• ALGAE
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• v.32 no.2
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• pp.101-130
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• 2017

The ichthyotoxic Cochlodinium polykrikoides red tides have caused great economic losses in the aquaculture industry in the waters of Korea and other countries. Predicting outbreak of C. polykrikoides red tides 1-2 weeks in advance is a critical step in minimizing losses. In the South Sea of Korea, large C. polykrikoides red tide patches have often been recorded offshore and transported to nearshore waters. To explore the processes of offshore C. polykrikoides red tides, temporal variations in 3-dimensional (3-D) distributions of red tide organisms and environmental parameters were investigated by analyzing 4,432 water samples collected from 2-5 depths of 60 stations in the South Sea, Korea 16 times from May to Nov, 2014. In the study area, the vegetative cells of C. polykrikoides were found as early as May 7, but C. polykrikoides red tide patches were observed from Aug 21 until Oct 9. Cochlodinium red tides occurred in both inner and outer stations. Prior to the occurrence of large C. polykrikoides red tides, the phototrophic dinoflagellates Prorocentrum donghaiense (Jun 12 to Jul 11), Ceratium furca (Jul 11 to Aug 21), and Alexandrium fraterculus (Aug 21) formed red tides in sequence, and diatom red tides formed 2-3 times without a certain distinct pattern. The temperature for the optimal growth of these four red tide dinoflagellates is known to be similar. Thus, the sequence of the maximum growth rates of P. donghaiense > C. furca > A. fraterculus > C. polykrikoides may be partially responsible for this sequence of red tides in the inner stations following high nutrients input in the surface waters because of heavy rains. Furthermore, Cochlodinium red tides formed and persisted at the outer stations when $NO_3$ concentrations of the surface waters were < $2{\mu}M$ and thermocline depths were >20 m with the retreat of deep cold waters, and the abundance of the competing red-tide species was relatively low. The sequence of the maximum swimming speeds and thus potential reachable depths of C. polykrikoides > A. fraterculus > C. furca > P. donghaiense may be responsible for the large C. polykrikoides red tides after the small blooms of the other dinoflagellates. Thus, C. polykrikoides is likely to outgrow over the competitors at the outer stations by descending to depths >20 m and taking nutrients up from deep cold waters. Thus, to predict the process of Cochlodinium red tides in the study area, temporal variations in 3-D distributions of red tide organisms and environmental parameters showing major nutrient sources, formation and depth of thermoclines, intrusion and retreat of deep cold waters, and the abundance of competing red tide species should be well understood.

• Korean Journal of Environmental Biology
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• v.30 no.1
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• pp.15-25
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• 2012

From April to November 2009, we performed field investigation to survey the characteristics of fish fauna and fish community structure inhabited in Yongdam reservoir in the upper Geumgang, which is changed into flat-water zone from flow-water zone by blocking the continuity by the gigantic submerged weir built in the upstream of Geumgang. 15 species belonging to 8 families were collected from natural habitat (St. 1) where its natural characteristics is well preserved, and 11 species were korean endemic fish species. 24 species belonging to 10 families were collected at the down region of Yongdam dam (St. 3), which might be affected by the change of water environment due to the dam, and 11 species were korean endemic fish species. On the other hand, 20 species belonging to 7 families were collected inside Yongdam reservoir (St. 2) which is changed into flat-water zone from flow-water zone by the dam reservoir, and 6 species were korean endemic fish species. In the dam reservoir, due to Yongdam dam built in the upper Geumgang, the original flow-water zone fish such as $Acheilognathus$ $koreensis$, $Pseudopungtungia$ $nigra$, $Coreoleuciscus$ $splendidus$, and $Gobiobotia$ $macrocephala$ were disappeared, and instead, the kinds of fish habitating in the flat-water zone tend to increase rapidly, such as $Carassius$ $auratus$, $Opsarichthys$ $uncirostris$ $amurensis$, $Hemiculter$ $eigenmanni$, $Zacco$ $platypus$, and $Lepomis$ $macrochirus$. Relative abundance of the insective fish was 66.7% at St. 1, 40.0% at St. 2, and 54.2% at St. 3. In order to preserve endemic fish species and aquatic ecosystem, it is desirable to minimize the artificial installation in the upper river, such as a large scale dam which can affect the habitat and if inevitable, it is required to prepare preservation measures when building facilities.

• Journal of Life Science
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• v.26 no.11
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• pp.1237-1244
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• 2016

A comprehensive analysis of the genetic diversity and relationship of the cold-water fishery walleye pollock (Theragra chalcogramma), the most abundant economically important fishery resource in the East sea of Korea, has not been carried out, despite its importance in Korea. The present study assessed the genetic diversity and relationship between five walleye pollock populations (Korean population, Russian population, USA population, and Japanese populations) of T. chalcogramma using eight microsatellite DNA (msDNA) markers to provide the scientific data for the preservation and management of the Pollock fishery resource. The results of the analysis of 186 individuals of the Pollock revealed a range of 7.13-10.63 numbers of alleles (mean number of alleles=9.05). The means of observed heterozygosity ($H_O$), expected heterozygosity ($H_E$) were 0.732 and 0.698, respectively. The results of genetic distance, Pairwise $F_{ST}$, UPGMA (UPGMA: un-weighted pair-group method with an arithmetical average) (the phylogenetic tree), PCA (PCA: Principal Coordinate analysis) analysis pointed to significant differences between the Korean population, Russian population, USA population, and Japanese populations, although small (p<0.05). These results shed light on the genetic diversity and relationships of T. chalcogramma and can be utilized for research on the evaluation and conservation of Korean T. chalcogramma as genetic resources.

• Journal of Aquaculture
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• v.13 no.3
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• pp.267-275
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• 2000

To evaluate the characteristics and efficiency of oxygen transfer rate of a polystyrene foam bead as media in a packed column aerator was tested. This media has more surface area and cheaper than other ordinary plastic media. The polystyrene foam media was a sphere-shaped bead with 2.5 mm in diameter and specific surface area was 1,350 $m^2$/$m^3$. Oxygen transfer rate and standard aeration efficiency were tested under different hydraulic loading rates, depths of the media and temperatures. Experiment 1 was performed using a small packed column aerator with 10 cm in diameter and 1 m in length. The aerator filled with 0, 4.5, 9.0 and 18.0 cm of the media was tested under hydraulic loading rates of 2.0, 4.0 and 5.6 $m^3$/$m^2$/min at temperatures of 20, 25 and 3$0^{\circ}C$, respectively. In this experiment, standard oxygen transfer rate (SOTR) increased with the hydraulic loading rate and depth of the media increased. The maximum SOTR was reached at 5.6 $m^3$/$m^2$/min of hydraulic loading rate with 9 cm in depth of the media. However, standard aeration efficiency (SAE) decreased with the hydraulic loading rate increased because electricity consumed by pump increased as hydraulic loading rate increased. The highest SAE was reached at hydraulic loading rate of 2.0 $m^3$/$m^2$/min with 9.0 cm in depth of the media. Therefore, the highest SOTR and SAE were achieved at 9.0 cm in depth of the media regardless of the hydraulic loading rate. The maximum SAE was about 1.8 kg $O_2$/kW-hr with the hydraulic loading .ate of $m^3$/$m^2$/min at temperature of 20 $^{\circ}C$.Experiment 2 was performed using a larger aerator, 20 cm in diameter with 2 m in height. The aerator filled with 0, 9, 18, 27 and 36 cm of the media was operated under hydraulic loading rate of 2.0, 4.0 and 5.6 $m^3$/$m^2$/min at temperature of 27 $^{\circ}C$. The SAE reached to the highest efficiency (1.9 kg $O_2$/kW-hr) at 2.0 $m^3$/$m^2$/min of hydraulic loading rate and 36 cm in depth of the media. According to the above results, the polystyrene foam bead as a media in a packed column aerator was effective to increase oxygen transfer rate.

• Journal of Aquaculture
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• v.19 no.1
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• pp.1-6
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• 2006

The tryptic enzyme activities from hepatopancreas, foregut, midgut and feces were examined to optimize the feeding method in whiteleg shrimp, Litopenaeus vannamei. The highest tryptic enzyme activity was found in hepatopancreas. The enzyme activities of hepatopancreas were 4 times higher than those of foregut per mg dry weight at 30 minutes feeding. Post feeding period, the activities of hepatopancreas increased continuously up to 30 hours after feeding. Trypsin activities of foregut showed about 3 times higher than did those of midgut. Average activity of foregut reached the pick with $303{\pm}68\;(mean{\pm}SE)$ nmol/mg/min at two hours after feeding and kept the activity up to 4 hours after feeding and thereafter the activity decreased. Average tryptic enzyme activity of midgut increased to $96{\pm}26nmol/mg/min$ up to two hours after feeding and it decreased to $52{\pm}17nmol/mg/min$ at five hours after feeding eventhough the gastric evacuation rate was still 50% by then. Foregut clearance occurred in 30 minutes after feeding and midgut weight increased up to 2 hours after feeding. Also we found that the maximal food ingestion in foregut was equivalent to the average 0.3% of its body weight by 30 minutes after feeding. Up to 5 hours after feeding, the weight ratio of midgut to body weight reduced, but still the weight ratio of foregut to body weight kept the similarity until then. These indicated that the tryptic enzyme activity and the clearance rate are different among the digestive organs and between forgot and midgut during the post feeding period in whiteleg shrimp.

• Journal of Aquaculture
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• v.19 no.1
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• pp.25-32
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• 2006

An experiment was carried out to investigate changing of water quality during the seed production of dark-banded rockfish Sebastes inermis in large scale tanks. Ten broodstock of dark-banded rockfish were held in three circular tanks (diameter 6.5 m; depth 2 m; water volume 50 ton) each (stocking density $0.061kg/m^3$). During the experiment the temperature ranged from 14.2 to $16.1^{\circ}C$. The fingerlings were 134 with rotifers only during 1 to 9 days after parturition, rotifers with Artemia nauplii during 10 to 20 days after parturition, Artemia nauplii only during 21 to 35 days after parturition, Artemia nauplii with commercial diet during 36 to 80 days after parturition and commercial diet only during 81 to 85 days after parturition. Water quality (dissolved oxygen, pH, $NH_4^+-N,\;NO_2^--N,\;NO_3^--N\;and\;PO_4^{3-}-P$) in rearing tanks measured every 5 days in long term monitoring investigation or every 2 hours in diurnal monitoring investigation. In 85 days after parturition, the body weight of fish grew up to 0.88 f and specific growth rate was 8.0%/day in body weight. In long term monitoring investigation, with the increase of the amount of supplied commercial diet, the concentration of dissolved oxygen (DO) and pH decreased, but the concentration of $NH_4^+-N\;(4.5\;to\;76.3{\mu}M),\;NO_2^--N\;(0.02\;to\;0.06{\mu}M),\;NO_3^--N\;(3.0\;to\;5.9{\mu}M)$, and $PO_4^{3-}-P\;(0.41\;to\;0.59{\mu}M)$ increased. In the diurnal monitoring investigation, the concentration of $NH_4^+-N$ showed great fluctuation and ranged from 3.0 to $9.1{\mu}M$ when fed rotifers, 16.3 to $45.8{\mu}M$ when fed Artemia nauplii and 36.5 to $120.1{\mu}M$ when fed commercial diet. After daily feeding with each of feed, the amount of dissolved inorganic nitrogen (DIN) and phosphorus (P) wastage were 7.0 g and 0.7 g when fed rotifers, 24.7 g and 0.7 g when fed Artemia nauplii and 140.9 g and 2.2 g when 134 commercial diet. The amount of DIN and phosphorous wastage during 134 commercial diet was significantly higher than that of fed rotifer and Artemia nauplii (P<0.05). Results will provide valuable information far water quality management and culture of dark-banded rockfish in commercial seed production systems.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.6
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• pp.712-726
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• 1994

Feeding trials were conducted to determine the essentiality of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and to compare the efficiency between EPA and DHA for juvenile Korean rockfish. Fish averaging 2.1 g were fed experimental diets containing different levels of EPA or DHA, and different combinations of EPA and DHA in two separate experiments. Graded levels ($0.0{\sim}l.75\%$) of dietary EPA or DHA as ethyl esters were substituted for a part of the $8\%$ beef tallow in the basal diet. After 5 weeks of the experimental period, weight gain, chemical composition of whole body, protein and lipid retention efficiency, hepatosomatic index, and fatty acid composition of liver were measured. Daily growth rate and feed efficiency were the lowest in fish fed the diets without EPA arid DHA. These responses were effectively improved by increasing EPA or DHA in the diets up to $1.0\%$ levels, and then reached a plateau between 1.0 and $1.75\%$ levels of either EPA or DHA. Protein and lipid retention efficiency were also improved with the high levels of dietary EPA or DHA. DHA was superior to EPA at the same level of each in weight gain, feed efficiency, and protein and lipid retention efficiency. Hepatosomatic index tended to decrease with increase of the dietary EPA or DHA levels. Lipid contents of whole body were increased with levels of EPA or DHA in the diets. Dietary EPA and/or DHA levels affected directly the fatty acid composition of liver polar lipid. EPA or DHA in the liver polar lipid were increased with levels of dietary EPA or DHA, respectively, whereas those in nonpolar lipid were not affected by the dietary levels of EPA and/or DHA. These finding indicate that either of the EPA or DHA is essential for normal growth of Korean rockfish, and the essential fatty acid requirement is $1.0\%$ of EPA and/or DHA in the diet. DHA is superior to EPA as essential fatty acid, and the dietary EPA/DHA ratio of less than 1.0 may be adequate for normal growth of Korean rockfish fed a diet enough n-3HUFA (EPA and DHA).