• Journal of Marine Life Science
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• v.6 no.2
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• pp.106-116
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• 2021

To secure basic data by monitoring the growth of salmon (Oncorhynchus keta) released to the Taehwa River. After discharge, the characteristics of the young salmon distribution and migration rate habitat were investigated for two years. A total of 4 points [Sunbawi bridge (St.1), Guyeong bridge (St.2), Samho bridge (St.3), and Myeongchon bridge (St.4)] were investigated. The survey of 2017 indicating an increase of 10 mm in average length and 0.8 g in average weight, and the survey of 2018 indicating an increase of 10 mm in average length and 0.5 g in average weight. Among 39 species, 10 insectivorous and 12 omnivorous, are believed to compete with young salmon for food. 6, 5, 6 and 8 predatory fish species has emerged at each site, respectively. According to this study, it is believed that St.1 and St.2 points are more proper as discharge location of young salmon because these two points have less varied in depth, flow rate, salt concentration etc. In addition, it is thought that the night or dawn time in early January is the best discharge time of young salmon fish because predatory fish such as Korean piscivorous chub and bass etc. does not eat food actively at that time.

• Korean Journal of Ichthyology
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• v.21 no.4
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• pp.247-252
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• 2009

The egg development and early life history of the Korean endangered fish Koreocobitis naktongensis (Cobitidae) were investigated. Eggs from the females were obtained by injecting 10 IU/g of human chorionic gonadotropin and inseminated with sperm by the dry method in the laboratory. The fertilized eggs were 1.0~1.2 mm in diameter and had no oil globules. The embryo began to hatch about 38 hrs after fertilization under water temperature of $20{\pm}1^{\circ}C$. The newly-hatched larvae were 2.6~2.8 mm in total length, and their mouth and anus were not yet opened. Seven days after hatching, the postlarvae were 4.5~5.2 mm in total length, and their yolk sacs were completely absorbed. They entered the juvenile stage when all fin-rays were formed at 50 days after hatching, and their total lengths were 21~27 mm.

• Korean Journal of Ichthyology
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• v.29 no.3
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• pp.190-196
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• 2017

The egg and larval development of pale chub, Zacco platypus were determined by observation of laboratory reared larvae from hatching. The experimental adult fish were collected in Wicheon of Nakdong river in June 2016, The eggs and larvae were reared in the experimental tanks, and observed their morphological change. The egg diameter ranged from 1.68 to 1.78 mm ($mean{\pm}SD$, $1.73{\pm}0.07mm$, n =30). The eggs were hatch 70 hours after fertilization. The total length (TL) of the newly hatched larvae ranged from 5.39 to 5.42 mm ($5.40{\pm}0.02mm$, n=10). On the 8 days after hatching, 10 fin rays were formed in caudal fin at 7.89~7.93 mm TL ($7.91{\pm}0.02mm$, n=10). On the 44 days after hatching, the juveniles ranged from 16.1~16.5 mm TL ($16.3{\pm}0.28mm$, n=10).

• Journal of Aquaculture
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• v.9 no.3
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• pp.279-285
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• 1996

The effects of various concentrations of $17{\beta}-methyltestosterone$ (MT) or $17{\beta}-estradiol\;(E_2)$ on sex reversal, survival and growth rates of olive flounder, Paralichthys olivaceus were investigated. MT and $E_2$ were treated to juvenile flounder for 60 days from 30 (total length : 14.5 mm) to 90 (TL : $10.41\~11.17$ mm) days after hatching. Fish were treated with 0, 1, 10 and 100 ppb of MT or $E_2$ in the rearing water for 2 hours per day. At the time of 200 days after hatching, fish were sampled to examine sex ratio. One hundred pub of MT produced $100\%$ male, however 1 and 10 ppm MT produced 72.5 and $87.2\%$ males. One, 10 and 100 ppb of $E_2$ produced 75.5, 91.9 and $97.2\%$ females, respectively. Survival and growth rates of each experimental group at the end treatment were not significantly different from those of the control (P>0.05).

• Environmental Analysis Health and Toxicology
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• v.22 no.1 s.56
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• pp.83-90
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• 2007

This study was investigated the effort of growth and gonadal development in olive flounder, Paralichthys olivaceus exposed to PCBs Effluent Allowance Concentration, 3.0 ppb in Korea. Total length, body weight and weight gam of fish were no significant differences between two treatments (control: T.L.-110.0 mm, T.W.-9.61 g: treatment: T.L.-112.8 mm, T.W.-9.68 g), however, weight gain of fish unexposed to PCBs wat observed to increase gradually from 100 days after hatching (30 days after treatment). In the indifferentiated gonad to the juvenile stage, the differentiation of the ovary occured at 60 days after hatching (20 days after treatment) and that of the testis occured at 70 days after hatching (30 days after treatment) in two groups. In the ovary, the oogonia and ovarian lamellar appeared 130 days after hatching (50 days after treatment). The spermatogonia and resticular lobule of the testis were observed at 130 days after hatching (50 days after treatment). Testicular cyst appeared 140 days after hatching (60 days After treatment). There was no difference on the development of ovary and testis. There was no obvious difference of sex ratios. Therefore, These results considerate that PCBs have any effect for growth and gonadal development, but a little act for early growth in olive flounder.

• Journal of fish pathology
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• v.16 no.3
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• pp.183-191
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• 2003

The effect of each dietary supplements (Undaria 5%, Undaria 10%, Obosan 0.5%, Wasabi leaf 2%, Wasabi stem 2%) on the water temperature fluctuation in juvenile olive flounder (Paralichthys olivaceus) was investigated. The response to stress was assessed in terms of effects on haematological and immunological, and resistance against Edwardsiella tarda infection. Plasma glucose and cortisol levels were significantly lower in 5% undaria and 2% wasabi leaf supplement groups than the controls after the first change of water temperature (P<0.05). The plasma lysozyme activities and the survival rates from E. tarda infection were significantly higher in the 5% undaria supplement groups than the control (P<0.05). These results suggest that the 5% undaria supplement seems to be contributable to the increased disease resistance on olive flounder.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.1
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• pp.35-42
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• 2012

We investigated the effect of dietary supplementation with probiotics on growth performance, feed utilization, innate immunity and disease resistance against Streptococcus iniae in juvenile olive flounder Paralichthys olivaceus. Four experimental diets were made by supplementation with three Bacillus sp. probiotics (B. subtilis, B. pumilus and B. licheniformis) into a basal diet (control) at 0.5% each. Three-hundred fish (average BW, 20 g) were randomly distributed (25 per tank) into twelve 150 L capacity polyvinyl circular tanks with three replicates per dietary treatment. Triplicate groups of fish were fed the experimental diets to apparent satiation (twice per day, 09:00 and 17:00 h) for nine weeks. After the feeding trial, a challenge test was directly conducted against S. iniae. The results indicated that dietary supplementation with the probiotic, Bacillus sp, seemed to improve growth performance of olive flounder. Hematological parameters and innate immunity as determined by nitroblue tetrazolium, myeloperoxidase or superoxide dismutase activities were not significantly affected by the probiotic supplementation. The result from the challenge test suggested that dietary supplementation with probiotics Bacillus sp. can improve the disease resistance of olive flounder against S. iniae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.4
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• pp.307-313
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• 2010

Stanniocalcin 1 (STC1) is a glycoprotein hormone that is important in the maintenance of calcium and phosphate homeostasis in both fish and mammals. STC1 and its paralog STC2 are expressed in multiple tissues in fishes, although the physiological roles of piscine STCs are still unclear compared with those of mammals. In this study, we cloned olive flounder STC1 (ofSTC1) and ofSTC2 cDNAs into pET28a vector and used E. coli Rosetta (DE3) as the host strain for protein expression. Expression experiments were carried out using isopropyl-$\beta$-D-thiogalactoside (IPTG) and nickel affinity chromatography. We could identify the recombinant proteins as single 29.5 kDa (ofSTC1) and 33.2 kDa (ofSTC2) bands in the insoluble fraction on sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE). These results indicate that ofSTC1 and ofSTC2 were expressed as insoluble proteins in E. coli. Furthermore, the injection of ofSTC1 protein into juvenile tilapia resulted in a decrease of the serum calcium level. These results suggest that the purified fish STC1 and STC2 proteins may be used to elucidate the physiological role of STCs in fishes.

• Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.229-247
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• 2014

Seven feeding trials were conducted to determine the effects of feeding rate and frequency in the Korean rockfish Sebastes schlegeli at seven different water temperatures. Two feeding-rate experiments for 5-g Korean rockfish at $17^{\circ}C$ and $20^{\circ}C$; three feeding rate experiments for 16-g Korean rockfish at $16^{\circ}C$ and $24^{\circ}C$; and finally, two feeding frequency experiments for 93- and 100-g at $15^{\circ}C$ and $20^{\circ}C$ were conducted. Twenty fish averaging $5.5{\pm}0.2$ g ($mean{\pm}SD$) were randomly distributed into 18 indoor tanks containing 40-L seawater from a semi-recirculation system. Fish were fed a commercial diet for 4 weeks at water temperatures of $17^{\circ}C$ and $20^{\circ}C$. Two feeding trials were conducted to determine the optimum feeding frequency in growing Korean rockfish reared at temperatures of $15^{\circ}C$ and $19^{\circ}C$. Broken line regression analysis of weight gain (WG) indicated that the optimum feeding rates of 5-g growing Korean rockfish were 4.48% (BW/day; BW, body weight) at $17^{\circ}C$ and 4.83% (BW/day) at $20^{\circ}C$. Broken line regression analysis of WG showed optimum feeding rates of 16-g juvenile Korean rockfish of 3.41% (BW/day) at $16^{\circ}C$, 3.75% (BW/day) at $20^{\circ}C$, and 3.34% (BW/day) at $24^{\circ}C$. The biological performance, results, along with morphological indices and serological characteristics, suggest that a feeding frequency of 1 meal/day was optimal to improve WG in growing Korean rockfish grown from 93 to 133 g at a water temperature of $15^{\circ}C$, and 100 to 132 g at $19^{\circ}C$.

• The Korean Journal of Ecology
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• v.19 no.6
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• pp.543-562
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• 1996

Zooplankton community structure and the factors correlated with community differences were examined in sandusky Bay (SB) and the open water of Lake Erie (LE, U.S.A.). SB zooplankton communities differed from those in LE by having a greater rotifer density and species richness. Keratella spp., Brachionus spp., and Pompholyx complanata dominated SB rotifers; Brachionus and Pompholyx were rarely seen in LE. Of 19 rotifer species observed, nine species were found only at SB sites. Ordination of zooplankton species abundance by detrended correspondence analysis (DCA) showed an overlap between SB and LE sites, but indicated a portion of the space that was occupied by only SB communities. The seasonal trajectories of zooplankton dynamics in the ordination space at SB sites differed from that of LE. The zooplankton most important in forcing site separation along a DCA Axis I at SB sites were Brachionus angularis, Pompholyx complanata, Keratella valga, Keratella quadrata, Filinia terminalis (rotifers), and Eubosmina coregoni and Daphnia (cladocerans). These species had axis scores which were significantly correlated (p<0.01) with bacterial density and bacterial phosphorus, total phosphorus, and algal density. Very high baterial density and very abundant bacterivorous rotifers in SB suggest that the transport of bacterial carbon through rotifers may be a relatively important link to higher trophic leaels. We believe that this "microbial carbon flow" from the base of the food web may be important in determining the suitability of SB as a spawning site and nursery for larval and juvenile fish.nile fish.