To determine the optimum water temperature (a temperature which minimizes metabolic activities and stress in fish) for long distance transportation of red-spotted grouper (Epinephelus akaara), by evaluating the behavior, survival and physiological and hematological responses to variable water temperature conditions (9, 12, 15, 18 and 21℃) for 48 hours. Fish exposed to 9℃ died at 48 hours exposure, but those exposed to 12, 15, 18 and 21℃ treatment groups all survived. Fish in the 15, 18 and 21℃ exposure groups exhibited normal swimming, while those exposed to 12℃ were observed to be stationary at the bottom of the tank. The plasma cortisol and glucose concentration were higher in fish exposed to 12℃ than at other temperature conditions. The fish in the 12 and 15℃ groups had significantly higher hematocrit (Ht) and hemoglobin (Hb) than those in the 18 and 21℃ groups (P<0.05). Levels of aspartate aminotransferase (AST), NH3 and osmolality showed a pattern similar to the levels of plasma cortisol, while alanine aminotransferase (ALT) and total protein did not significantly vary among the experimental groups. These results indicate that the optimum water temperature for long distance transportation of the red-spotted grouper is 15℃.

본 연구의 목적은 능성어와 자바리의 정자동결을 위한 간편한 실험법개발이다. 희석제와 동해 방지제가 정자동결에 미치는 효과를 파악하고자 운동성성과 생존율을 조사하였다. 동결실험에 서 300 mM glucose와 15% dimethylsulfoxide (DMSO)를 희석제와 동해방지제로 각각 사용하였 다. 동결실험결과, 능성어 정자는 동결 5개월 후 60% 이상의 운동성을 보였고, 자바리 정자는 동결 5개월후 90% 이상의 운동성을 보였다.

It is well known that fish hear a wide frequency range of sound using both laterial line and inner ear, and the sound is probably the most effective channel for long-range communication underwater than any other stimulus.The auditory threshold of svenband grouper, Epinephelus septem fasciatus was determined by conditioning method using a sound coupled with electric shock in a tank. The audio-signals and electric shock used in the experiment were pure tones of 100 to 1000Hz and DC 6n.The response of fish to the sound was observed by ECG intervals from precordial leads method (V1·V2 method). The auditory threshold curve for sevenband grouper was V-shaped, with most sensitive threshold at 350Hz in the range of 100~1000Hz. The Sevenband grouper were more sensitive to sounds of 200~400Hz than to adjacent frequencies.

Survival of embryos largely depends on yolk processing during early development. Proteolytic enzymes, cathepsin B & D (ctsb & ctsd) are known to have some important roles in yolk processing of various fish species. Mature female red spotted groupers were injected with human chorionic gonadotropin (HCG) to induce ovulation. The fertilized eggs and embryos were sampled at 0, 4 and 24 HPF (hours post fertilization). Survivals of each groups of embryos were checked at 24 and 48 HPH (hours post hatching). Transcripts of ctsb & ctsd showed the highest level at 0 HPF and relatively high at 4 HPF, but greatly decreased at 24 HPF. In bad egg quality group (BE, embryos survived until 24 HPH), transcript level of ctsb at 4 HPF were significantly lower than the transcript level at the same stage in good egg quality group (GE, embryos survived until 48 HPH) while no significant change of ctsb transcript level was observed at 0 or 24 HPF between BE and GE. Transcript level of ctsd was decreased at 24 HPF, but the difference was not as strong as the case of ctsb transcript. These results suggest that maternal ctsb transcript rather than ctsd transcript is likely to be involved in egg quality resulting in the difference of survival rate of embryos at early developmental period in this species.

Skeletal deformities are significant problems that affect the growth and commercial value of fish reared in hatcheries. However, studies of bone metabolic process related to skeletal deformities are limited. We investigated the potential correlation between bone deformities and plasma calcium, phosphorus, and estradiol-17β levels in reared red spotted grouper (Epinephelus akaara) juveniles. We collected E. akaara frys from private farms at 110, 140, 180 and 300 days after hatching (DAH), and classified the normal and deformed fish by observing their external shape and inner frame by soft X-ray. We also analyzed the calcium, phosphorous, and estradiol-17β levels in their plasma. A comparison between normal and deformed fish, indicated that calcium and estradiol-17β levels were higher in deformed fish than in the normal at 180 and 300 DAH. The level of phosphorus was also higher in deformed individuals than in normal fish, but only at 300 DAH. These results suggest that skeletal deformities are associated with increases in plasma calcium, phosphorus, and estradiol-17β levels.

This study carried out to examine the association between the haplotypes of mitochondrial control region (CR) and growth traits of two F1 progeny populations of the Red-spotted grouper. We found polymorphic patterns of the 133-bp repeat units in the CR. In the BBR01 population (70-days after hatching), a total of 1,091 F1 progeny were divided into three haplotypes (H01, H03 and H04). The significant differences were found in the levels of BL, BW and LWI (p<0.05). The F1 animals with the haplotype H01 had greater level of BL (50.815±4.586 mm) than those of H03 (47.270±6.486 mm) and H04 (47.179±6.278 mm). The H01 F1 fishes were heavier level of BW (2.270±0.559 g) than those of H03 (1.789±0.711 g) and H04 (1.797±0.706 g). In the BBR02 population (11-months after fertilization), three haplotypes H03, H04 and H05 were detected. The significant difference was found only in the BL values among three haplotypes (p<0.05). The F1 animals with the haplotype H03 had greater level of BL (19.22±2.000 cm) than those of H04 (18.64±1.964 cm) and H05 (18.86±1.512 cm). There were no significant differences in BW and LWI among haplotypes in the BBR02 population (p>0.05). These results suggested that the mitochondrial haplotypes may affect the growth traits during early developmental stage of the Red-spotted grouper. The marker-assisted selection system for broodstock animals may be helpful in improving performance traits for aquaculture of the Red-spotted grouper.

In fish, light (photoperiod, intensity and spectra) is main regulator in many physiological actions including body growth. The present study was to investigate the effect of light spectra on the body growth in red spotted grouper Epinephelus akaara. Experiment performed from December, 2016 to March, 2017 and fish (n=200, body weight 6.9±0.1, total length 7.5±0.1) was reared under different light spectra (blue, green, red and white) for 15 week under 12 hour light and 12 hour dark photoperiod and natural water temperature (13.6~16.7℃). We examined the mRNA expression levels of growth hormone (GH) in the brain with pituitary and photoreceptors mRNA expression in the retina. Red spotted grouper of BW was no different in each for the four groups (light spectra of blue, green, red and white) to five week of rearing period, but BW of rearing blue light spectra group fish was significantly increased in ten week of rearing period. After that, in 15week of rearing period, BW of four group fish was no showed difference respectively. The total length (TL) of fish was no differed in four experimental groups under the experimental duration respectively. The gh mRNA was more highly expressed in rearing blue light spectra group fish than other experimental groups in 15 weeks. The short wavelength sensitive opsin (sws) mRNA was more increased in rearing blue light spectra group fish than other groups in 15 weeks. The middle wavelength sensitive opsin (mws) and rod opsin mRNA expression was no differed in four experimental groups under all experimental durations respectively. The long wavelength sensitive opsin (lws) mRNA expression was more increased in rearing red light spectra group fish than other groups in 15 weeks. Our present results suggest that somatic growth of red spotted grouper is induced under blue light condition under low water temperature duration. Also, these results are thought to be affected of the gh and sws mRNA expression blue wavelength. However, in this experiment we did not confirm the correlation between GH and photoreceptor. Therefore, further studies are needed to clarify the correlation of the light spectra and photoreceptor with body growth in red spotted grouper.

This study analyzed the mitochondrial DNA (mtDNA) sequences of the Red-spotted grouper, Epinephelus akaara (Perciformes, Serranidae), and used for construction of molecular phylogeny and for association between maternal haplotypes and phenotypic differences of F1 progeny. This study revealed phylogenetic position of the endangered red-spotted grouper, Epinephelus akaara (Perciformes, Serranidae) based on the nucleotide sequences of complete mt genome. Complete nucleotide sequences were determined from the mt genomes of two individuals of the red-spotted grouper caught in South Korea. The mitochondrial genome had 16,795 base pairs (bp) and 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNAs, and a noncoding control region. The two mt genomes were highly homologous (99.71% similarity). The two mt genomes of E. akaara determined in this study were found in Clade I in the phylogenetic tree with those of E. awoara, E. fasciatomaculosus, E. sexfasciatus, E. diacanthus, E. sticus, and E. morio, suggesting that this may be helpful to understand phylogenetic position of Epinephelus species including red-spotted grouper. The genetic structure and phylogenetic relationship were investigated in the red-spotted grouper populations using the sequence polymorphisms of the cytochrome c oxidase subunit I(COI) gene and variable number of tandem repeats (VNTRs) of the control region (CR). A total of forty-one COIhaplotypes were found from 174 COIsequences from East Asia. The Jeju Island population (n=5) had four haplotypes, and the South Sea population (n=105) had twenty-five haplotypes. The Hong Kong population had nineteen haplotypes from fifty-nine COIsequences determined in this study. Among the COIhaplotypes, EAC_03 is commonly found in all populations (Jeju Island and South Sea of Korea, China, Hong Kong and Taiwan). In addition, there were four haplotypes (EAC_12, EAC_14, EAC_28 and EAC_35) also common among the populations tested in this study and collected from NCBI database. However, twenty haplotypes were specific in the Korean populations, and fifteen haplotypes were specific in the China and Hong Kong populations. The neighbor-joining (NJ) trees constructed from the phylogenetic analyses based on the polymorphisms of the COIhaplotypes showed the monophyletic branching pattern within the genus Epinephelus, indicating that the red spotted grouper populations had evolved from common maternal ancestors. Consequently, East Asian red-spotted grouper populations are maternally related at least in part, as well as sharing the same evolutionary history, and still affected by the East Asian ocean current (Kuroshio). From the haplotype analysis for mtDNA CR, we obtained VNTR polymor-phisms in all populations tested. We found five haplotypes for the CR VNTR patterns. The 133-bp repeat units were counted two to five. Using CR VNTR haplotypes, the statistical association was examined between mtDNA haplotypes and growth traits of aquafarming young fishes of the red-spotted grouper. A total of 386 F1 progeny, which were randomly selected from a progeny population produced by artificial insemination in the farm, were genotyped and statistically compared their body length (BL), body weights (BW) and length-weight indexes (LWI) at 11-months after hatching. There haplotypes H03, H04 and H05 were detected for CR in the parents and progeny populations. The significant difference was found in the BL values among three haplotypes (p<0.05). The F1 animals with haplotype H03 had freater level of BL (19.22±2.000 cm) than those of H04 (18.64±1.964 cm) and H05 (18.86±1.512 cm). There were no significant differences in BW and LWI among haplotypes (p<0.05). These results concluded that the maternal lineages affected the growth rates during early developmental stage in the red-spotted grouper. These findings suggested that the mitochondrial background of the fertilized eggs may play an important role in the early development, and the markerassisted selection system for broodstork animals may be helpful in improving performance traits for aquaculture industry as well as for conservation biology of the endangered red-spotted grouper. However, the results from the association analysis between haplotypes and phenotypes of F1 progeny (n=1,093) at 60-days after hatching showed that there were no significant difference (p>0.05). Consequently, the results of this study may be useful information for understanding the evolutionary relation with other species and may be good genetic markers for breeding management in the red-spotted grouper aquaculture system.

Red spotted grouper, Epinephelus akaara, is a popular aquaculture species and a protogynous hermaphrodite. Induction of artificial sex change at the time of primary sex differentiation is of interest but has not been successful due to the lack of necessary basic information. To find out the potential neuroendocrine influence on the primary sex differentiation, the expression of key genes in the brain was investigated during the formation of ovarian cavity. Expression of cyp19a1b, esr1, gnrhr1, fsh, lh and cga in the brain was positively associated with the formation of ovarian cavity, showing gradual increase as the formation proceeds. However, the expression of gnrh1 was suppressed during the early part of the ovarian cavity formation, signifying potential hypothalamic influence on the primary sex differentiation in this species.