• 한국발생생물학회지:발생과생식
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• 제24권3호
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• pp.225-230
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• 2020

This study reports the presence of mature and bi-sexual phase gonads in red spotted grouper, Epinephelus akaara after less than a year of cultivation in a commercial indoor tank and a net cage. In December 2018, juveniles were placed in an indoor tank and cultured for five months. In June 2019, the fish were transferred to a net cage and cultured until September. The rearing temperatures ranged from 19.86℃-24.65℃ in the indoor tank and 21.86℃-27.65℃ in the net cage. During the net cage culture period, specimens were randomly selected for histological gonad examination. The highest gonadosomatic index (GSI) value was measured in July (3.38±2.53), and dramatically decreased in August (0.44±0.21) and September (0.42±0.30). In July, some mature fish showed signs of vitellogenic stage oocyte development (vitellogenic and oil droplet stage oocytes), but immature fish were in an early developmental stage containing peri-nucleolus stage (PNS) oocytes. Bi-sexual phase gonads containing spermatocytes and spermatids were observed in the lumen and several PNS oocytes. By August and September, most specimens showed early-stage ovary development. However, mature testis (in August) and bi-sexual phase gonads (in September) were also observed. These results provide evidence for early puberty and hermaphroditism in the red spotted grouper.

• 한국어병학회지
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• 제4권2호
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• pp.87-94
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• 1991

1. 자연감염(自然感染) 능성어는 외관적으로 먹이를 먹지 않고 분색이 옅은 밤색이나 짙은 밤색으로 변하며 몸이 휘어져 힘없이 가두리 바닥이나 수면에 누워서 폐사(斃死)하였는데, 해부(解剖)를 해보면 뇌출혈(腦出血)과 비장(脾臟) 및 담관(膽管)이 팽대(膨大)되어 있었다. 2. 자연감염어(自然感染魚) 아가미에서 Trichodina sp. 기생충(寄生蟲)이 다수 검출(檢出)되지만 대량(大量) 폐사(斃死)의 직접(直接) 원인생물(原因生物)은 아니며, 또한 병어(病魚)의 장기(臟器)에서 우점적(優占的)으로 분리(分離)되는 Vibrio속(屬) 세균(細菌)은 병원성(病原性)이 없는 해수상존(海水常存) Vibrio 균(菌)이었다. 3. RTG-2 및 CHSE-214 어류(魚類) 주화세포(株化細胞)에서 바이러스는 분리(分離)되지 않았지만, 병어(病魚)의 장기마쇄여과액(臟器磨碎濾過液)으로 인위감염(人爲感染)시켰을 때 자연감염어(自然感染魚)와 유사(類似)한 증상(症狀)을 나타내면서 폐사(斃死)하였다. 4. 자연감염어(自然感染魚) 및 인위감염어(人爲感染魚)의 간(肝) 세포질내(細胞質內) 공포부위(空胞部位)에 크기가 45-60nm 정도되며 육각형(六角形) 내지 다각형모양(多角形模樣)을 한 virion들이 무수히 존재하였다. 5. 따라서 1990년(年)과 1991년(年) 고수온기(高水溫期)에 우리나라 남해안(南海岸) 일원 해상가두리 양식장에서 사육중이던 능성어가 대량(大量) 폐사(斃死)한 것은 바이러스성(性) 질병(疾病)에 의한 것으로 생각된다.

• 한국수산과학회지
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• 제53권4호
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• pp.499-505
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• 2020

We investigated growth, survival and stress response depending on salinity changes in hybrid grouper (Epinephelus fuscoguttatus ♀×E. polyphekadion ♂, BCG) juvenile. Experiment I (Exp I), the hybrids were stocked at 32 psu and reared for 30 days under decreasing salinity at a rate of 5-7 psu per day (25, 20, 15, 10, 5 psu). Experiment II (Exp II), the salinity was decreased from 32 psu to 5 psu during a period of 24, 48 and 72 h. Experiment III (Exp III), acclimatized BCGs were exposed from 5 psu to decreasing salinity at 0, 1, 2, 3, 4 psu. In the Exp I, 90% survival only in the 5 psu. Growth were 5 and 32 psu had significantly low growth than other treatment. In the Exp II 100% survived by the end of the experiment. The plasma cortisol level was highest in the treatment the salinity rapidly dropped, but all the treatment recovered quickly after 24 h of salinity reduction. In the Exp III, the lower the salinity, the faster the mortality occurred in salinity below 5 psu. It is therefore concluded that the BCGs are highly tolerant of low salinity and the salinity tolerance threshold is 5 psu.

• 한국수산과학회지
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• 제48권4호
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• pp.403-410
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• 2015

Viral nervous necrosis (VNN) is a serious disease of sevenband grouper Epinephelus septemfasciatus in Korean aquaculture farms. However, we suggest the following preventative methods for hatcheries: 1) disinfecting rearing water, 2) selecting spawners via ELISA and PCR, 3) selecting eggs via PCR, 4) disinfecting fertilized eggs, and 5) proper facilities management. When these methods are implemented, nervous necrosis virus (NNV)-free fish are produced because vertical and horizontal transmission is prevented. However, horizontal transmission of NNV through rearing seawater sourced from the environment during grow-out stages in sea cages can still occur. Live NNV vaccines with a low rearing temperature or Poly(I:C) immunization are very effective at preventing horizontal transmission of NNV in rearing farms. Furthermore, even after VNN is contracted, fish mortality can be reduced by administering Poly(I:C).

• 한국수산과학회지
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• 제55권2호
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• pp.129-136
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• 2022

The nutrient composition of the muscle of the hybrid grouper (Epinephelus fuscoguttatus×E. lanceolatus, HG) and the hybrid longtooth grouper (E. moara×E. lanceolatus, HLG) was measured as a function of body weight in this study. The crude protein and lipid levels in HG were 21.0-21.2 g/100 g and 1.9-3.4 g/100 g, respectively. HLG contained 20.6-20.7 g/100 g protein, and 3.9-5.5 g/100 g crude lipid. The total amino acid contents of HG were 18,829.7-18,980.2 mg/100 g and that of HLG was 17,793.7-19,293.7 mg/100 g. The mean saturated fatty acid content was 0.61-1.09 g/100 g for HG and 1.27-1.77 g/100 g for HLG. Monounsaturated and polyunsaturated fatty acid levels were 0.59-1.02 g/100 g (Monoene), 0.67-1.11 g/100 g (Polyene) in HG, which were lower than the 1.21-1.78 (Monoene), 1.22-1.69 g/100 g (Polyene) found in HLG. The highest mineral content (K and P) of HG was 510.13-517.05 mg/100g and 231.59-247.67 mg/100 g, while that of HLG was 518.81-523.59 mg/100 g and 257.51-248.84 mg/100 g, respectively. In conclusion, there is potential for expanding the commercial utilization of HG and HLG as food resources as they are both nutrient-rich.

• Fisheries and Aquatic Sciences
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• 제23권2호
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• pp.4.1-4.9
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• 2020

Growth of fish is controlled by various environmental factors, including water temperature (WT). WT is also a major factor that affects the eating behavior of fish. In this study, we studied the relationship between WT and expression profiles of factors involved in appetite regulation and digestion in red spotted grouper. Fish were divided into three groups with 30 fish per group and reared for 2 weeks in a recirculating system at three different WT (natural WT, 20 ℃, and 25 ℃). After 2 weeks, they were sacrificed immediately after food intake (+ 0 h), 3 h after (+ 3 h), 6 h after (+ 6 h), and 3 h before being fed the next day (- 3 h). Fish samples were obtained for analysis of mRNA expression levels of cholecystokinin (CCK), leptin A (LepA), leptin B (LepB), and neuropeptide Y (NPY) in the brain, liver, and intestine. Expression of CCK and NPY mRNA was significantly higher at 25 ℃ compared to that at natural WT and 20 ℃, but no difference was observed for leptin. This suggests that the red spotted grouper shows characteristics typical of subtropical fish and has higher levels of feeding and digestion when reared at 25 ℃ water temperature condition.

• Fisheries and Aquatic Sciences
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• 제24권7호
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• pp.235-242
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• 2021

The present study investigated the critical thermal maxima (CT_max) of red-spotted grouper, Epinephelus akaara under different acclimation temperatures (T_acc). Fish were acclimated at 24℃, 28℃, and 32℃ water temperature for 2 weeks. Water temperature was increased at a rate of 1℃/h and CT_max level was measured following the critical thermal methodology (Paladino et al., 1980). The results showed that CT_max values of E. akaara were 35.61℃, 36.83℃, and 37.65℃ for fish acclimated at 24℃, 28℃, and 32℃, respectively. The acclimation response ratio (ARR) was 0.26. The CT_max values were significantly correlated with body size. Collectively, it is said that the CT_max value of red-spotted grouper can be affected by different adaptation temperature (24℃, 28℃, and 32℃) and the fish acclimated to a higher temperature has a higher CT_max level. Besides, the CT_max value of 35.61℃-37.65℃ indicating the upper thermal tolerance limit for E. akaara under different T_acc (24℃, 28℃, and 32℃). Understanding the thermal tolerance of E. akaara is of ecological importance in the conservation of this species.

• 한국어병학회지
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• 제25권2호
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• pp.111-116
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• 2012

본 연구에서는 2006-2008년 남해안 일대의 해상가두리에서 사육중인 능성어에서 발생하는 viral nervous necrosis (VNN)의 발생양상을 조사하였다. VNN은 사육 수온이 $24-26^{\circ}C$ 범위인 8월부터 발생하기 시작하여 수온이 $20-25^{\circ}C$ 범위인 9-10월까지 지속되었고, 성어보다는 치어에서 폐사율이 높게 나타나는 것으로 확인되었다. 폐사되는 패턴으로는 급성으로 인한 대량폐사와 소량으로 지속적으로 폐사되는 경우가 확인되었다. 능성어로부터 분리된 NNV 분리주들의 coat protein gene을 계통분석한 결과, 분리주들은 모두 RGNNV 유전자형에 속하였다. 이상의 결과로 능성어 양식장에서의 VNN은 RGNNV type의 NNV에 의해 여름철 7-9월(사육수온: 약 $24^{\circ}C$)에 치어뿐만 아니라 성어에서 발생하는 것으로 확인되었다.

• 한국발생생물학회지:발생과생식
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• 제22권4호
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• pp.369-378
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• 2018

We determined the morphologic characteristics (body weight and degree of abdomen inflation) of the red spotted grouper, Epinephelus akaara, mother fish producing healthy eggs. Experimental fish were chosen from fish reared in a sea cage. The fish were divided into four size groups by body weight: 400~600, 600~800, 800~1,000, and 1,000~1,200 g and four stages (I~IV) of the degree of abdomen inflation. After hormone treatment, we observed the amount of ovulation-induced eggs, and rates of buoyancy, fertilization, embryonic survival, and hatching. As a result, mother fish with a body weight of 600 g or more spawned, and the fertilization rate, embryonic survival rate, and hatching rate were high in the 800~1,000 g range, thus showing effective ovulation induction. As a result of dividing the degree of abdomen inflation based on the anal fin of the mother fish into I-IV stages and determining hormone treatment time, the GSI was $0.9{\pm}0.2%$ at stage I, $2.3{\pm}0.2%$ at stage II, $5.6{\pm0.2%$ at stage III, and $7.9{\pm}0.9%$ at stage IV. The flotation rate and hatching rate were highest at stage III, and the fertilization rate and embryonic survival rate were highest at stage IV. Therefore, in terms of egg quality, the amount of eggs collected per mother fish, maturation, and histology were different depending on the degree of abdomen inflation. At stage III, where the abdomen inflation degree of the mother fish was based on the basal part of the dorsal fin relative to the height of the anal fin was 1, the egg quality was highest.

• 한국어류학회지
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• 제26권1호
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• pp.70-73
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• 2014

Interspecific hybrids between tiger grouper Epinephelus fuscoguttatus and giant grouper E. lanceolatus were genetically identified based on the partial sequence analysis of mitochondrial cytochrome c oxidase I (COX I) gene and nuclear recombination activating gene 2 (RAG 2) gene. Out of 585 base positions of RAG 2, a total of five nucleotide substitutions were detected between the two parental species (E. fuscoguttatus and E. lanceolatus). The hybrids had two distinct types of RAG 2 sequences corresponding to those of both parental species. Mitochondrial COX I gene sequencing showed that hybrids had sequences identical to E. fuscoguttatus. Molecular data clearly demonstrate that hybridization does occur between E. fuscoguttatus and E. lanceolatus, but with E. fuscoguttatus as the maternal parent.