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The present study investigated the virulence and expression of innate immunity genes in isolates of infectious hematopoietic necrosis virus (IHNV) in Gangwon province, South Korea, by challenging rainbow trout, Atlantic salmon, and coho salmon. Eight IHNV isolates were used to infect RTG-2 cells for viral replication using plaque assays. Three isolates with the highest replication rates, the RtPc0314g and RtPc0314c isolates of the JRt-Shizuoka type and the RtPc0816g isolate of the JRt-Nagano type, were experimentally infected into the fish. In rainbow trout, both RtPc0314c and RtPc0314g isolates showed 100% cumulative mortality while the RtPc0816g isolate showed 60% cumulative mortality for 14 days. In contrast, all three isolates showed

Starry flounder (Platichthys stellatus) is a commercially important cold-water fish. Our aim was to investigate the effects of fluctuating water temperature on flounders after periods of starvation and feeding. Fish were divided into starvation and feeding groups. The water temperature was increased stepwise in experiment 1; more focused variations, based on the results of experiment 1, were studied in experiment 2. At temperatures ≤27 °C, there was no significant difference observed in survival. At 28 °C, mortality increased, survival was lower (21%) in the starvation group than in the feeding group (46%), and weight loss was the highest (15%) in the starvation group. In experiment 2, survival was ≥86%, and there was no significant difference between the starvation/feeding groups. However, when the water temperature was increased to 27 °C after being decreased to 12 °C, weight loss was the highest (11%). Glucose, cortisol, superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels increased with increasing water temperature, and then gradually decreased. Glutamic pyruvic transaminase (GPT)/glutamic oxaloacetic transaminase (GOT) levels showed large variations among individuals. Triglyceride, cholesterol, and protein levels gradually decreased with long-term starvation. Survival was not affected by water temperature drop ≤27 °C after starvation/feeding. These results indicate that 27 °C is the upper limit of tolerable water temperature for the survival of starry flounders. Therefore, aquaculture farms should ensure maintaining water temperatures at ≤27 °C during high-temperature periods.

The ability of enriched live food, such as Artemia, to improve the growth performance of Pacific cod (Gadus macrocephalus) larvae during larviculture has yet to be fully established. Thus, the effects of feeding differentially enriched Artemia to Pacific cod larvae were investigated here, specifically the effects on the survival, growth, fatty acid composition, and air exposure stress response of the larvae. Three different commercial Artemia enrichment emulsion oils were used: commercially available enrichment 1, 2, and 3, referred to as ER1, ER2, and ER3, respectively. Although ER2-treated Artemia contained the most eicosapentaenoic acid (EPA) and ER3-treated Artemia contained the most docosahexaenoic acid (DHA) and highly unsaturated fatty acid (HUFA), the ER1 enrichment improved overall survival, growth, and survival after air stress test to the greatest extent in larval Pacific cod. Furthermore, the levels of DHA and HUFA observed in larvae fed the ER1 diet were higher than the respective concentrations of these nutrients observed in larvae fed the other diets. Thus, under the experimental conditions applied in the present study, ER1 provided Artemia with DHA and EPA ratio of 4.1 for early feeding of Pacific cod larvae.

The walleye pollock Gadus chalcogrammus is an important commercial species in Japan whose larvae and eggs may be negatively affected by the cold water mass from the coastal Oyashio current that is present in the spawning ground of the Japanese Pacific stock of this species. Therefore, we investigated egg and larval specific density, larval mortality, and behavioral response to temperature change during the ontogenetic development of the walleye pollock to understand the effect of this cold surface water mass (&lt, 1.5 °C). Egg and larval specific density varied during development but were lower than the corresponding values from the coastal Oyashio waters. Within our study temperature range (0.3 °C–10.0 °C), the number of days to 50% mortality (D50) was high at 3.1 °C. Below and above this temperature, the D50 showed a decreasing trend. Regarding larval response, at 1.5°C and 5.0°C, newly hatched larvae occurred abundantly in the surface layer, irrespective of the surface and rearing temperatures. When these larvae were released into a thermally stratified water column (surface: 1.5 °C, bottom: 5.0 °C), larvae reared at 5.0 °C with the mouth open and yolk sac completely absorbed moved to the lower layers. However, larvae reared at 1.5 °C remained in the surface layer. These results suggest that the cold water mass could negatively affect larval survival and may limit the escape ability of larvae from unfavorable cold conditions.

The effect of dietary substitution of Undaria pinnatifida with carrot leaf by-product (CLB) on the growth performance and soft body composition of juvenile abalone (Haliotis discus) was determined. A total of 1080 juvenile abalone were randomly distributed into 18 cages (60 per cage). Five formulated diets and dry U. pinnatifida were prepared in triplicate. The 20% U. pinnatifida was included in the control (CLB0) diet. The 25, 50, 75, and 100% of U. pinnatifida were substituted with an equal amount of CLB, referred to as the CLB25, CLB50, CLB75, and CLB100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare the effect of formulated diets on growth performance of abalone. Abalone were fed with one of the experimental diets once a day at a satiation level with a little leftover for 16 weeks. Water stability of dry matter content in all formulated diets was changed over all the observation periods, and their significant interaction was also observed. The retention of dry matter content in all formulated diets was significantly (P 0.05) different from those of abalone fed the CLB0 diet. Shell height, width, and length of abalone fed all formulated diets were significantly (P

An 8-week feeding trial was conducted to investigate the effects of dietary protein level on growth performance, feed utilization, body composition, plasma chemistry and antioxidant parameters of juvenile walleye pollock (Gadus chalcogrammus). Two-hundred and forty juvenile pollock, averaging 4.5 g, were randomly distributed between 12 400-L flow-through circular tanks (20 fish per tank). Four experimental diets with increased crude protein levels (40, 45, 50, and 55 %) were formulated, and referred to as the P40, P45, P50, and P55 diets, respectively. Each diet was assigned to three tanks and the fish were hand-fed to satiation twice daily. At the end of feeding trial, weight gain and specific growth rate increased with increasing dietary protein up to 50 %, and then decreased with further increase in dietary protein. The feed intake of the fish fed the lowest protein diet (P40) was greater than those of fish fed the higher protein diets (P45, P50 and P55). The feed efficiency was the lowest in the P40-fed fish. The protein retention tended to increase with dietary protein, from P40 to P45, and then decline when the dietary protein level was further increased to P55. The whole-body composition, except for the crude protein content, was not affected by the dietary protein content. Antioxidant response was also not affected by the dietary protein content. In conclusion, based on a second-order polynomial regression analysis of weight gain, the optimum dietary protein level for juvenile pollock was estimated to be 48.2 %.

Our aim was to study the relationship between the sex-determining genes, sox9a and cyp19a, and water temperature in Gadus chalcogrammus. We assessed the sex ratio based on the expression levels of sox9a and cyp19a at different water temperatures (5, 8, 11, and 14 &deg, C) and at different stages of walleye pollock development (embryos, larvae, and juveniles). Next, we used immature walleye pollock to assess sox9a expression in males and cyp19a and vitellogenin (VTG) expression in females at different water temperatures. Males expressed sox9a in the gonadal tissues, while females expressed cyp19a in the gonadal tissues and VTG in the blood plasma. In the first experiment, cyp19a expression was higher at 5 &deg, C and 8 &deg, C, and sox9a expression was higher at 11 and 14 &deg, C. In the second experiment, sox9a expression remained relatively stable, but cyp19a expression decreased with increasing temperature, decreasing significantly after 14 &deg, C. Similar patterns were also observed for VTG expression. These results indicate that lower water temperatures increase cyp19a expression, which increases the female ratio. Higher water temperatures increase sox9a expression, which increases the male ratio. Therefore, this study highlights the potential of the sex-determining genes and the influence of water temperature.

A feeding trial was conducted to assess the effect of dietary inclusion of various aquatic animal protein sources on growth performance, feed utilization, body proximate composition, and plasma chemistry in grower walleye pollock (Gadus chalcogrammus, Pallas 1811). A total of 180 grower fish averaging 154.0 g in weight were chosen randomly and distributed into 12 flow-through tanks of 300 L (15 fish per tank). Four experimental diets were prepared in triplicate. Pollock meal (PM), anchovy meal (AM), krill meal (KM), and jack mackerel meal (JM) were used as the main protein source in the experimental diets, denoted PM, AM, KM, and JM diets, respectively. These diets were fed to fish twice a day at a satiation level for eight weeks. The weight gain and specific growth rate (SGR) of fish fed the KM and JM diets were higher than were those of fish fed the other diets. Daily feed intake (DFI) and daily protein intake (DPI) of fish fed the KM and JM diets were higher than were those of fish fed the PM and AM diets. The strong second polynomial correlation between the contents of 4 free amino acids (arginine, glutamic acid, histidine and leucine) in protein sources and WG, SGR, DFI and DPI were observed. The experimental diets had no effect on proximate composition of the muscle and liver. Plasma analysis did not differ between the experimental diets. In conclusion, KM and JM showed the greatest protein sources than among the ingredients assessed, and consequently KM and JM yielded the higher growth (WG and SGR) and feed intake (DFI and DPI).

We evaluated effects of dietary lipid level on growth performance, feed utilization, fatty acid composition, plasma chemistry, and antioxidant responses in juvenile walleye pollock (Gadus chalcogrammus). Two-hundred forty juvenile pollock averaging 4.4 g in weight were randomly distributed between 12 400-L flow-through circular tanks (20 fish per tank). Fish were fed four isonitrogenous experimental diets with crude lipid levels of 8.1%, 12.6%, 16.7%, or 20.8% for 8 weeks. Each diet was assigned to three tanks, and the fish were hand-fed to satiation twice daily. At the end of the trial, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio were increased with increasing dietary lipid up to 16.7%, and then decreased with a further increase in dietary lipid. The hepatosomatic index showed an increasing trend with increasing dietary lipid. The crude lipid content in liver increased with increasing dietary lipid. Saturated fatty acid levels in the muscle and liver decreased, whereas essential fatty acids and polyunsaturated fatty acids in the muscle and monounsaturated fatty acids in the liver increased with increasing dietary lipid. The hematological and antioxidant parameters were not affected by the dietary lipid content. In conclusion, on the basis of a second-order polynomial regression analysis of weight gain, the optimum dietary lipid level for juvenile walleye pollock was estimated to be 15.8%.

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 (HO), expected heterozygosity (HE) were 0.732 and 0.698, respectively. The results of genetic distance, Pairwise FST, 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

This study was performed to determine the effect of water temperature condition on survival rate and growth of juvenile geoduck ( Panopea japonica ). Panopea japonica juveniles were bred for 6 weeks at 12, 15, 18, 21, 24 and 27℃ on incubator. Juveniles median lethal times (LT50) were 29 hours in 27℃, 14.5 day in 24℃, 37.4 day in 21℃. Survival rate of water temperature 12, 15 and 18℃ showed a high survival rate in 95.0%, 95.0% and 93.3% at 6 weeks. As a result of culturing for 6 weeks at 12, 15, 18, 21 and 24℃, a daily growth of shell length and total weight was 0.10 mm, 0.12 mm, 0.13 mm, 0.16 mm and 0.14 mm, and 2.21 mg, 2.65 mg, 2.84 mg, 3.13 mg and 2.93 mg. Juvenile shell length and total weight have significantly increased at 15-21℃. However, mortality rate has significantly increased at more than 21℃. As a result, appropriate water temperature for juveniles culturing considered 15-18℃.Key words: Juvenile geoduck, Panopea japonica , Culture, Water temperature, Median lethal time

We examined the effect of warm temperature on the survival of larvae of walleye pollock and on their swimming behavior during the four days of post-hatch. Observations were conducted on larvae in Petri dishes and in 85 cm tall, cylindrical tanks that had a warmer upper layer and cooler lower layer separated by a small thermocline. Mortality was carried out in four temperature ranges from to . The number of days to 50 % mortality () was longest (18.7 days) at and decreased with increasing temperature to 10.3 days at . And were similar level to that at temperature 3.1 and (17.9 days). Larval responses to warmer temperatures varied depending on developmental stages. 2dph larvae changed the distribution to the thermocline of the water column. And, 3dph larvae had a ability for escaping from the unfavourable warmer temperature. These results suggest that the warmer water negatively affects the larval survival.

The Pacific oyster, Crassostrea gigas, is the main oyster species cultivated in Korea. Despite a long history of hatchery practices, little is known about the population genetics of native populations of C. gigas in Korea. This study examined the population structure and genetic diversity of 297 individuals of C. gigas in six populations, representing two major geographically separated habitats along the coast of Korea, using multiplex assays with nine highly polymorphic loci. All populations showed very high genetic diversity, with a deficit of heterozygotes and a recent bottleneck. No significant differences were found in the genetic diversity of the two geographically separated oyster groups, although significant, but minimal, genetic differentiation was observed (FST = 0.003, p = 0.002). This was mainly due to genetic differences between the oyster populations from Taean and Gaduk, suggesting that the oyster is not panmictic. This result was corroborated by an analysis of molecular variance (AMOVA) and multidimensional scaling analysis. It was inconsistent with a previous finding of no population differentiation using mitochondrial sequence analysis, implying rather recent separation of the two geographic populations. This genetic differentiation might have resulted from the combined of various factors, such as historical dispersal, the local environment, and ocean currents. Nonetheless, these results mean that the two geographical groups should be treated as independent units for proper resource management. Our results provide critical information on the ecological and economic potential of the Korean Pacific oyster.

Large amounts of the manila clam, Ruditapes philippinarum, have been imported from Dalian (China) recently to meet the increasing demand in Korea. To ensure the quality and safety of the domestic marine product, it is necessary to be able to distinguish between domestic manila clams and clams that are imported from Dalian, China. We developed expressed sequence tags (ESTs)-derived single nucleotide polymorphism markers using 454 pyrosequencing. A total of 780,000 ESTs were assembled, and 49,540 putative SNPs were identified from 46,405 contigs. Twenty-one polymorphic SNPs from 11 primers were finally selected as diagnostic markers. Genotype analysis showed that 21 SNP markers had the opposite alleles (transitions or transversions) between domestic and imported samples, which were useful for distinguishing clam origins. The GENECLASS 2.0 program was used to estimate the ability of the markers in the discrimination between domestic and imported populations. The 21 SNP markers had 98.96% ability to discriminate domestic manila clams and 100% ability to identify those imported. These markers could be useful for discriminating between domestic and imported manila clams and can contribute to the prevention of falsified labeling of this species.

In Pleuronectiformes, blind-side malpigmentation (hypermelanosis) is common in cultured flatfishes, and is economically important. To understand the mechanism of blind-side hypermelanosis in flatfishes, we examined when the malpigmentation initially occurred, and studied how the symptoms proceeded during early development of the starry flounder, Platichthys stellatus. To assess quantitative pattern changes of blind-side skin, we observed morphological development of the whole body from 22 (total length [TL] 10.0±0.2 mm and body weight [BW] 8.8±0.57 mg) to 110 days (TL 23.4±0.7 mm, BW 193.6±23.3 mg) after hatching (DAH), and also examined the malpigmented area rate of blind-side skin and the malpigmented fish ratios. The experimental animals were reared in fiberglass-reinforced plastic (FRP) tanks in water at a temperature of 18.9±1.9°C and salinity of 32.6±0.6 psu and were fed with rotifer and Artemia nauplii from 22 to 48 DAH, and with A. nauplii and commercial feed from 49 to 110 DAH. As results, the first staining patch seen by the naked eye was observed around the area between the anus and pelvic fin or caudal edge of the trunk at 80 DAH (TL 20.6±0.5 mm, BW 112.5±8.8 mg). The pigmented area and the pigmented fish ratios were significantly increased from 80 to 110 DAH. These results indicated that malpigmentation on the blind side of starry flounder was initially observed at about 2 cm in length and 100 mg in weight, and the pigmented domain on the blind-side skin was continually broadened by the differentiation of pigmented cells (melanophores and xanthophores) with growth.

This study examined the influence of water temperature on the induction of vitellogenin (VTG) in walleye pollocks (Gadus chalcogrammus) in aquaculture. The full-length VTG-A (or VTG-I) gene of walleye pollock was cloned using RACE (Rapid amplification of cDNA ends)-PCR method from liver tissue and recombinant VTG protein (wpVTG) was expressed in E. coli. The wpVTG protein was used to construct polyclonal antibodies to specifically detect VTG in blood; the antibodies were verified using western blotting. The VTG in blood plasma was determined by ELISA. The relationship between GSI (gonadosomatic index), VTG and body length were all positively correlated, and the results indicated that VTG can be used as an indicator of sex and/or maturation of female G. chalcogrammus in aquaculture. When VTG was measured in by the aqua-cultured female pollocks raised in water temperature of 5 °C, 8 °C, 11 °C, and 14 °C, VTG was detected only at 5 °C and 8 °C. In the histological analysis of VTG-inducing individuals, vitellogenesis was found in ovaries. In those same samples, E2 (17beta-estradiol) was detected in the blood by LC-MS. On the other hand, there was no significant difference in level of VTG induction when E2 of same concentration was treated to hepatocyte culture in different water temperatures. These results seemed to indicate that VTG is not directly affected by water temperature. However, we considered that the water temperature indirectly affect VTG induction by affecting the E2 concentration level.

We determined the effects of neuroactive compounds known as synthetic larval settlement inducers on the settlement of the Pacific oyster C. gigas pediveliger on the larval collector. Six types of the inducers, serotonin (5-HT), γ-amino butyric acid (GABA), L-3,4-dihydroxyphenylalanine (L-DOPA), norepinephrine, epinephrine and methyl bromide (MB) were tested. All the chemicals induced larval settlement, MB being the most effective with settlement rate of 42.7 ± 2.7%, followed by GABA (35.4 ± 2.0%), 5-HT (29.1 ± 2.2%), L-DOPA (19.2 ± 2.1%), epinephrine (15.2 ± 0.9%), and norepinephrine (11.0 ± 1.2%). The chemicals γ-amino butyric acid and methyl bromide were also better in terms of settled density on the collector with their respective density of 1.97 ± 1.42 and 2.37 ± 1.86 ind/cm 2 , reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery. Keywords : Neuroactive compounds, Induce settlement, Settlement rate, Larvae, Crassosterea gigas

The genetic variation of Ark Shell, Scapharca broughtonii black was estimated using six polymorphic microsatellite (MS) loci in 443 individuals collected from five populations in Korea. The mean numbers of alleles per locus in five populations were 10-28. The mean number of alleles per locus in Jinhae Hatchery (JHH) population showed the least value as 15.5, but that in Gangjin (GJ) population showed the most value as 20.3. The mean expected heterozygosity in Saryangdo (SR) population showed the least value as 0.817, but that in Gangjin (GJ) population showed the most value as 0.831. In Jinhae hatchery(JHH) population, the mean expected heterozygosity was 0.822, there was no significant difference from those of wild population. The FST values in Gangjin (GJ) population showed significant difference from those of the other populations, which revealed Gangjin (GJ) population is genetically different from the other populations. The FST values among Jinhae Hatchery (JHH) population, Jinhae (JH) population and Saryangdo (SR) population showed lower values than the others, which implies there was a gene flow among these three populations. The FST value and genetic distance between Jinhae (JH) population and Saryangdo (SR) population showed the least value as 0.0001 and 0.0386, indicating that these two populations were genetically the same.

The study describes growth and survival on different kinds of sediment improvements of early spats of the hard clam, Meretrix petechialis . Specimens of the mature hard clam were collected in the intertidal zone of Yeonggwang, Korea, July 2011. After transportation, early spats(shell length 196 ± 14 μm) collected in mature hard clam were used. Experiment period were July 7 to August 6 in 2011 (30 days). Sediment improvements used iodine(10 ppm), hydrogen peroxide(H 2 O 2 , 5 ppm), sodium hypochlorite (NaClO, 100 ppm), chlorine dioxide(ClO 2 , 100 ppm) and potassium permanganate (KMnO 4 , 5 ppm). After cultured during 30 days, shell length growth of hard clam were observed 1.04 ± 0.26 mm in sodium hypochlorite 100 ppm, 1.03 ± 0.25 mm in chlorine dioxide 100 ppm and 1.01 ± 0.28 mm in iodine 10 ppm. Survival rate were 31.4% in chlorine dioxide 100 ppm, 12.1% in sodium hypochlorite 100 ppm, 11.6% in iodine 10 ppm, 1.5% in hydrogen peroxide 5 ppm and 0% in potassium permanganate 5 ppm.

This study is the result of examining the growth and survival rate of larva and spat when supplied with Enriched live food by adding B12, chitosan, PSB, and polysaccharides to microalgae (Chaetoceros gracilis, Isochrysis galbana) to raise the survival rate of larva and spat during artificial clam seed production. Microalge (Chaetoceros gracilis, Isochrysis galbana) was strengthened for nutrition with B12 0.1 ppm, chitosan 0.2 ppm, PSB 3 ppm and polysaccharides 1 ppm and was daily supplied for 3 × 10 3 -15 × 10 3 Cells/mL and the growth and survival rates were measured. As the result of experiment, the growth of larva did not show much difference with PSB test section 199 ± 0.59 μm, B12 test section 198 ± 0.64 μm, and chitosan 197 ± 0.52 μm, survival rate was highest at PSB test section with 99.3%, followed by B12 test section 95.9%, and chitosan 94.5%. Growth of early spat was the highest for PSB test section at 2.74 ± 0.58 mm, followed by polysaccharides 2.67 ± 0.55 mm, B12 2.54 ± 0.48 mm, and chitosan 2.49 ± 0.51 mm, and the survival rate was the highest for PSB test group at 32.1%, followed by B12 test section 31.6%, chitosan 28.5%, and polysacharrides 21.4%. From such results, PSB is found to be very effective with low-quality improvement when breeding early spat of clams, and especially for floor-type early spat breeding, it had the effect of suppressing protozoan and germs so that detailed studies from various perspectives should be conducted with various chemicals in the future.

To produce cupped oyster sprat consistently, we investigated the efficiency of nine settlement substrates using selective breeding of Pacific oyster Crassostrea gigas, with the goal of popularizing off-bottom culture on the west coast of Korea. We also compared the growth and survival of selectively bred sprat (diploid) with triploid sprat from an off-bottom culture system. Considering, the attachment rate and detachment efficiency, producing cupped oyster in a polypropylene gunny bag proved to be the most effective method. There were no differences in shell growth or total weight between the diploids from selective breeding and triploids from off-bottom culture for 5 months. However, the survival rate was 8 times higher in the diploids than the triploids. Transplanting sprat from selective breeding is one way to restore oyster farms and nurture off-bottom culture along the west coast.

Spawning behavior and early life history of the tuman river sculpin, Cottus hangiongensis were studied in the laboratory and in the field at Wangpi Stream, Gyeongsangbuk-do, Korea, from January to December, 2007. The spawning ground was in the lower Wangpi Stream, which is a shallow region about 40cm or less in depth. During the spawning period, from March to April, mature males made nest cavities under stone 10 which they led a gravid female. The male and female then turned upside down, and spawning and fertilization occurred onto the ceiling of the nest cavity. After spawning, the male chased the female from the nest and mated with several other females. Fertilized eggs were spherical in shape, demersal, adhesive, transparent and yellow in color, measuring 1.86 mm (1.79~1.93 mm) in diameter. A mean of 17(12~22) various-sized oil globules were counted in the yolk. Granular materials formed a mass in the yolk. Fertilized eggs hatched at 256 hrs, 10 minutes after the morula stage under water temperature of . Newly hatched larvae 9.34 mm (9.02~9.69 mm. n

Diel rhythm of oxygen consumption (OC) of the starry flounder Platichthys stellatus was measured at different water temperatures in a closed recirculating seawater system with a respiratory chamber. The fish consumed 70.5, 79.7, and 90.6 mg at 15, 20, and , respectively, showing a linear increase in OC with water temperature. The OC of fish showed a clear diel rhythm, with lower values during the day and higher values at night, in accordance with the light (09:00-21:00) and dark (21:00-09:00) phases of the diel cycle (12L:12D) in water at 15 and . However, the OC of the fish showed an unclear diel rhythm with the light and dark phases of the diel cycle at . The respective OC at 15, 20 and was 63.8, 72.4, and 88.4 mg during the light phases and 77.2, 87.1, and 92.8 mg during the dark phase. The starry flounder is thought to be a nocturnal fish with a higher OC at night, while it rests during the day. Its OC was the most stable in the light, when it did not feed. Consequently, the night-time OC is the active OC and the day-time OC is the resting OC in the starry flounder.

Blood physiological responses, growth and survial rates were examined in juvenile starry flounder, Plotichthys stellatus exposed to different salinities (5, 10, 20, 33 ppt) for 90 days. At the end of the experiment, the plasma levels of Na+and osmolality were similar at 10, 20, 33 ppt, however, the values were significantly lower at 5 ppt compared to those at other salinities. Stress responses such as plasma levels of cortisol, glucose, hematocrit (Ht) and hemoglobin (Hb) levels in all groups showed no significant difference. Although no differences in growth were observed, body weight at 20 ppt tended to be higher than others. Survival in all groups was greater than 99% with no significant differences. These results suggest that starry flounder is euryhalin species, thus this fish can be reared with normal growth and survival rate at 5-33 ppt salinity without osmoregulatory disturbance and stress.

Starry flounder (Platichthys stellatus) is an important sport and food fish found around the margins of the North Pacific. Aquaculture production of this species in Korea has increased because of its commercial value. Microsatellite DNA markers are a useful DNA-based tool for monitoring the genetic variation of starry flounder populations. In this study, 12 polymorphic microsatellite DNA markers were identified from a partial genomic starry flounder DNA library enriched in CA repeats, and used to compare allelic variation between wild and hatchery starry flounder populations in Korea. All loci were readily amplified and demonstrated high allelic diversity, with the number of alleles ranging from 6 to 18 in the wild population and from 2 to 12 in the farmed population. A total of 136 alleles were detected at the 12 microsatellite loci in the two populations. The mean observed and expected heterozygosities were 0.62 and 0.68, respectively, in the hatchery samples and 0.67 and 0.75, respectively, in the wild samples. These results indicate lower genetic variability in the hatchery population as compared to the wild population. Significant shifts in allelic frequencies were detected at eight loci, which resulted in a small but significant genetic differences between the wild and hatchery populations (FST = 0.043, P < 0.05). Further studies with additional starry flounder sample collections are needed for comprehensive determinations of the genetic varieties between the wild and hatchery populations. These microsatellite loci may be valuable for future population genetic studies, monitoring the genetic variation for successful aquaculture management and the preservation of aquatic biodiversity.