• Journal of Aquaculture
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• v.10 no.1
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• pp.55-61
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• 1997

The experiment was conducted to understand the effect of HCG upon ovulation induction and egg maturation in the sevenband grouper, Epinephelus septemfasciatus, as a part of the research for its resources management and seed production. Three different size groups of sevenband groupers showing 300~400g, 1,500~2,000g and 2,500~4,000g, were collected from June to August, 1996. They were treated two or three times with HCG (500~1,000 IU/kg). Gonadal development of the sevenband groupers were examined using the paraffin section method and then stained with haematoxylin and eosin. When smaller groups of sevenband grouper having 300~400g, 1,500~2,00g and 2,500~3,200g in weight were treated two or three time with HCG 9500~1,000 IU/g), their gonads contained oogonia, oocytes with the size of 20~30${\mu}{\textrm}{m}$, and stroma tissues. However, in case of two HCG treatments with a dosage of 1,000 IU/kg on sevenband groupers of 3,400~4,000g, both healthy eggs of $800\mu$m in diameter and regressing eggs were ovulated. A sevenband grouper of 4,000g obvulated 4,252 eggs in total. Of these, healthy and regressing eggs turned out to be 20.8% and 79.2%, respectively. In addition, previtellogenic oocytes of around $50\mu$m, oocytes of 20~$30\mu$m, and ovulation trace were also observed in the gonad.

• Development and Reproduction
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• v.17 no.4
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• pp.369-377
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• 2013

The fertilized eggs of E. septemfasciatus are spherical and transparent with buoyancy at 790 to $890{\mu}m$ (average $821.8{\pm}2.0{\mu}m$) in diameter with 170 to $230{\mu}m$ oil globules (average $192.9{\pm}0.93{\mu}m$). Hatching began approximately 46 and 35 hours after fertilization at $22.0^{\circ}C$ and $25.0^{\circ}C$ water temperature, respectively. The average total length of newly hatched larvae was $1.75{\pm}0.03mm$. Most of the yolk and oil globules were absorbed within 3 to 4 days after hatching. The larvae reached 2.48 to 2.72 mm in total length, and their mouths and anuses opened at 3 to 4 days after hatching. In this time, the mouth diameters of the larvae were 0.209 to 0.238 mm. The larvae reached 3.24 to 4.15 mm in total length at 11 to 17 days after hatching, and began to metamorphose at the time the second dorsal and pelvic spines appeared and elongated. The abdominal cavity was densely lined with melanophores. The larvae reached 5.12 mm in total length at 24 days after hatching.

• Journal of fish pathology
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• v.12 no.2
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• pp.107-113
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• 1999

The pathogenicity of the fish nodavirus causing viral nervous necrosis (VNN) of sevenband grouper, Epinephelus septemfasciatus was examined in sevenband grouper and other marine fish by intramuscular injection. Sevenband groupers of 27~104 g in body weight were highly susceptible to the fish nodavirus, but yellowtail (537 g in body weight), red seabream (207 g), rock bream (43 g), flounder (41 g), tiger puffer (27 g) and rockfish (94 g) of the sizes used to this experiment were not. The pathogenicity of the viral agent to the sevenband grouper was high without regard to fish sizes at rearing water temperature over $20^{\circ}C$, but not at $15^{\circ}C$. Therefore, susceptibility of sevenband grouper to the viral agent causing VNN was thought to be water temperature-dependent rather than fish size (age-dependent). Compared to the infectivity of the viral agent to sevenband grouper with artificial infection methods, fish were successfully affected by intramuscular, intraperitoneal, oral, dipping and cohabitation administrations although there were slight differences in mortalities among infection methods. And survival sevenband grouper after infection with the fish nodavirus was resistant to the reinfection for a long time.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.4
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• pp.981-989
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• 2015

This study aims to investigate how ovulation induction of sevenband grouper, Epinephelus septemfasciatus varies when treated with different hormonal substances such as ovaprim, pimozide, LHRHa, and HCG. As for LHRHa, we injected it in different concentrations: $50{\mu}g/kg$, $100{\mu}g/kg$, $150{\mu}g/kg$, and $200{\mu}g/kg$. All hormonal substances including LHRHa were injected into back muscles. As a result, ovulation occurred in all sample groups. The sample group injected with HCG released the largest amount of eggs, and the dimeter of eggs and oil globules were also significantly bigger than those of others. Fertilization rate, embryonic survival rate, and hatching rate were the highest in a LHRHa ($100{\mu}g/kg$) +pimozide ($1,000{\mu}g/kg$) group and buoyant rate in a LHRHa group. Ovulation rate was 100% when LHRHa was injected in different concentrations. The largest amount of eggs was released in $200{\mu}g/kg$. The diameter of eggs and oil globules were the biggest in $200{\mu}g/kg$ and the smallest in $50{\mu}g/kg$. Fertilization rate showed no significant difference through all different levels of concentration: 94.6-95.3%. Buoyant rate was the highest in $100{\mu}g/kg$ and embryonic survival rate and hatching rate in $150{\mu}g/kg$. Based on these experimental results, we concluded that LHRHa in $100{\mu}g/kg$ is the most efficient for the ovulation induction of sevenband grouper.

• Journal of fish pathology
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• v.4 no.2
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• pp.87-94
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• 1991

In the late summer of 1990 and 1991, mass mortality occured among cage-cultured grouper, Epinephelus septemfasciatus in south cost of Korea. The moribund fish didn't feed and became pale or dark chestnut colour and irregularly swimmed due to the loss of equilibrium, finally the diseased fish fell down side away on the bottom or the surface of cage showing the bent of body and died. The diseased fish showed the extensive hemorrahge in brain, the swelling of spleen and bile duct as the specific syptoms of internal organs. So the gill, skin and other organs of the diseased fish were examined for the presence of pathogenic parasites and bacteria. The parasitic Trichodina sp. were detected only from the gill lamella of the diseased fish, but these parasites seemed to be not a direct causative agents that induced the gross mortality of the cultured grouper. because these parasites were also observed in normal grouper, yellowtail, red seabream and rock bream co-cultured with the diseased grouper in same or near cages. In the viral examination, although isolation of the causative agent by the use of estabilshed cell Lines, RTG-2 and CHSE-214, was not succeed, the normal grouper inoculated intramuscularly with the filtered homogenate of the organs of the diseased fish showed the same external and internal signs with the naturally infected grouper. They died within a week. By using the naturally and the artificially infected fishes, electron microscopic observation revealed numerous hexagonal or polygonal particles in the cytoplasm of liver cells. Based on the these results, we suggest that the mass mortality of the cultured grouper would be occurred by the infection of a viral agent.

• Korean Journal of Ichthyology
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• v.28 no.4
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• pp.229-238
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• 2016

This study aims to investigate egg quality and amino acid composition of buoyant and non-buoyant eggs and evaluate egg quality of sevenband grouper, Epinephelus septemfasciatus. Amino acid analysis of eggs was conducted to investigate what elements were necessary for the survival and good quality of egg depending on farming condition and different diet. We analyzed amino acid from buoyant eggs and non-buoyant eggs, farming conditions (tank and sea cage), and different dietary conditions (formulated feed, formulated feed+raw fish-based moist pellets, and raw fish-based moist pellets). Egg quality was the best in a sea cage and when raw fish-based moist pellets (MP) were fed. In addition, egg quality with formulated and MP was better than that with formulated feed. As a result of amino acid analysis of eggs, buoyant eggs were containing more free amino acid than non-buoyant eggs. Also, eggs with MP were containing more free amino acid than those with formulated feed and MP. Eggs with mixed formulated feed and MP were containing more free amino acid than formulated feed. In conclusion, amino acid was helpful to improve egg quality, and egg quality can be controlled by farming conditions and feed.

• Korean Journal of Ichthyology
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• v.28 no.4
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• pp.260-266
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• 2016

We determined the morphologic characteristics (body weight and abdomen inflation degree) of the mother fish of sevenband grouper, Epinephelus septemfasciatus producing the healthy eggs. Experimental fish were chosen from the reared fish in the sea cage for 6 years. The fish were divided into four size groups by body weight: 4.0~5.0, 5.0~6.0, and 6.0~7.0 kg and four stages (I~IV) by the abdomen inflation degree. After hormone treatment, we observed the ovulation amount of induced eggs, rate of buoyant, fertilization, embryonic survival, and hatching. Egg and oil globule diameter was measured. In order to observe gonadal development, we calculated gonadosomatic index (GSI) and conducted its historical analysis. The ovulation occurred from all experimental fishes over 5.0 kg. The rate of buoyant, fertilization, and embryonic survival was the highest in 6.0~7.0 kg. Hatching rate was the highest in 5.0~6.0 kg. Stage I and II did not induce ovulation. GSI was $0.31{\pm}0.10%$ in stage I, $0.74{\pm}0.25%$ in stage II, $4.68{\pm}0.40%$ in stage III and $6.86{\pm}0.12%$ in stage IV. The rate of buoyant, fertilization, embryonic survival and hatching was the highest in stage III.

• Journal of Microbiology and Biotechnology
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• v.25 no.10
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• pp.1761-1767
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• 2015

Sevenband grouper, Epinephelus septemfasciatus, is becoming an important aquaculture species in Korea. However, viral nervous necrosis disease is a large problem causing mass mortality in sevenband grouper aquaculture. Recombinant protein vaccines are one of the best methods to reduce these economic losses. However, the cell-based expression method mainly produces inclusion bodies and requires additional procedures. In this study, we expressed a recombinant viral coat protein of sevenband grouper nervous necrosis virus (NNV) using a cell-free protein synthesis system. The purified recombinant NNV coat protein (rNNV-CP) was injected into sevenband grouper at different doses followed by a NNV challenge. Nonimmunized fish in the first trial (20 μg/fish) began to die 5 days post-challenge and reached 70% cumulative mortality. In contrast, immunized fish also starting dying 5 days postchallenge but lower cumulative mortality (10%) was observed. Cumulative morality in the second trial with different doses (20, 4, and 0.8 μg/fish) was 10%, 40%, and 50%, respectively. These results suggest that rNNV-CP can effectively immunize sevenband grouper depending on the dose administered. This study provides a new approach to develop a recombinant vaccine against NNV infection for sevenband grouper.

• Development and Reproduction
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• v.18 no.1
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• pp.13-23
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• 2014

This study is conducted to monitor the morphological developmental features of the egg development, larvae and juvenile of Epinephelus septemfasciatus, the fertilized eggs were gotton using artificial insemination. Matured parents are collected from marine caged fish farms in Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanamdo Korea in June 2012. The fertilized eggs were pelagic eggs containing one oil globule, and measured 0.81~0.89 mm ($0.85{\pm}0.04mm$, n=50) in diameter. In regard to rearing environment, the water temperature is $21.0{\sim}23.0^{\circ}C$ and the salinity is 32.0~33.2‰. Hatching was observed from 48 hours after fertilization, the mouth and anus of prelarvae was not opened but had egg yolk at newly hatched. 4 days after hatching, the mouth and anus of postlarvae was opened and began to eat Rotifer and was measured 2.40~2.49 mm ($2.45{\pm}0.03mm$ n=10) in total length. 12 days after hatching, postlarvae was measured 3.77~4.67 mm ($4.27{\pm}0.33mm$) in total length, its the second pole tide of dorsal fin and the first pole tide of pelvic fin was extended longitudinally. 71 days after hatching, juvenile was measured 40.5~45.4 mm ($42.6{\pm}2.04mm$) in total length. Seven bands were observed in body, and pole tides of dorsal and pelvic fins were shortened.

• Journal of Aquaculture
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• v.18 no.3
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• pp.167-172
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• 2005

Sex reversal to a functional male of sevenband grouper $(41.0{\pm}1.3cm\;TL,\;1.4{\pm}0.1kg\;BW)$ was induced by $17{\alpha}-methyltestosterone\;(MT,\;0.5\sim2.0mg/kg\;BW)$ implantation from March 17 to May 12,2002. Gonad of control group was composed of genial cells and peri-nucleolus oocyte during the experimental period. Gonad of fish treated with 0.5 mg MT/kg BW had peri-nucleolus oocytes, spermatogonia, spermatids and spermatozoa at the late stages of spermatogenesis, while the fish group treated with 1.0 and 2.0 mg MT/kg BW contained spermatoza in the efferent duct. Sperm were obtained from the experimental groups treated with a dose of $1.0{\sim}2.0mg$ MT/kg BW. In the MT treated groups, testosterone and 11-ketotestosterone levels were higher than those in the control group during the $2{\sim}6$ weeks of the experimental period (P<0.05). $Estradiol-17{\beta}$ was detected from fish in the experimental fish.