• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.506-514
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• 2020

We investigated seed management and feeding regime of larval red spotted grouper Epinephelus akaara using live food organisms. Fertilized eggs were produced in March 2020 by manipulating photoperiod and water temperature. Broodstock (F0) produced approximately 0.30×10⁶ eggs, of which 0.25×10⁶ were fertilized; first-generation broodstock (F1) produced 2.00×10⁶ eggs, of which 1.90×10⁶ were fertilized. Larvae were reared at temperatures of 21.0-24.5℃. The feeding regime consisted of rotifers Artemia, and commercial pellet feed. From 5-8 days after hatching (dah), rotifers collected from high-density incubation tanks were fed to grouper larvae at a density of 10-20 individuals/mL. From 9-30 dah, rotifers collected from low-density incubation tanks were fed to larvae at a density of 10-20 individuals/mL. Newly hatched Artemia were provided from 20-24 dah and enriched Artemia from 25-50 dah. Commercial pellet feed was given starting at 13 dah. The average mouth size in hatchlings was 263.4±3.7 ㎛ at 5 dah, 406.7±21.0 ㎛ at 11 dah, and 856.9±136.6 ㎛ at 21 dah. At 1 dah, larvae had a mean total length of 1.95±0.06 mm. At 66 dah, the mean TL was 4.0 cm. The final number of surviving red spotted grouper larvae was 218,380 fishes.

• Fisheries and Aquatic Sciences
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• v.10 no.3
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• pp.113-118
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• 2007

Bromophenols are a group of compounds found only in marine organisms. They accumulate and give a sea-like aroma to marine animals. Cultivated fishes generally contain low concentrations of bromophenols compared to wild fishes. Feeding cultivated fishes with bromophenol-containing seaweed could increase their bromophenol content and thus improve their flavor quality. We evaluated the effect of an experimental feed on the bromophenol content of green grouper, Epinephelus coioides, during an 8-week feeding period. Green grouper individuals were divided into two groups and fed with conventional feed or experimental feed containing dried seaweed. Fish were collected biweekly for 8 weeks for proximate analyses and bromophenol content evaluations. Bromophenols were extracted, identified, and quantified by gas chromatography-mass spectrometry. Both moisture and lipid contents were generally higher in the controls; however, total weight and protein content were higher in the experimental group. Only 2,4-dibromophenol and 2,4,6-tribromophenol were detected in the samples. Throughout the 8 weeks, 2,4,6-tribromophenol concentrations were higher in the experimental group (9.20-32.3 ng/g dry wt) than in the control group (7.33-18.79 ng/g dry wt), but no significant difference in 2,4-dibromophenol concentration was detected between the two groups. The total bromophenol content reached a maximum at week 4 for the experimental feed and week 6 for the control. In short, experimental feed that incorporated bromophenol-containing seaweed increased the total bromophenol content in the green grouper.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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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).

• Ocean and Polar Research
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• v.25 no.4
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• pp.483-491
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• 2003

Since the red grouper was declared overfished, the Gulf of Mexico Fishery Management Council must prepare a rebuilding plan considering the following alternative management policies: a Total Allowable Catch (TAC), 5-month season closure, 1800-pound trip limit, and a 50-fathom longline boundary. This study was aimed at evaluating the effects of proposed policies for rebuilding the red grouper stock in a 10-year period by developing a bioeconomic model. Under the assumption that the recreation sector was held to its share of TAC (24% of the total quota), the target stock biomass goal was attained in all policies. The NPV was the largest in the 5-month season closure policy if the output price did not fall. There were distributional effects on the different components of the fleets in the 1800-pound trip limit and the 50-fathom longline boundary policy.

• Korean Journal of Ichthyology
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• v.27 no.1
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• pp.10-15
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• 2015

Giant grouper (Epinephelus lanceolatus) is a endangered species considered as a vulnerable grade-organism in the International Union for Conservation of Nature (IUCN) red list. As a fundamental baseline study for establishing a giant grouper broodstock management system, the efficiency for parentage analysis was evaluated by using microsatellite makers previously available in this species. The eight microsatellites generated a total 52 alleles from 32 individuals, the mean expected heterozygosity was 0.663, and mean inbreeding coefficient was 0.011, consequently suggesting that the present broodstock has retained the high level of genetic diversity. However, our analysis also recommended the collection of more broodfish for more stable brood line, since the estimated value of the effective population size was proven to be 35. The average probability of identity was $6.85{\times}10^{-11}$. NE-2P and NE-PP of paternity non-exclusion probabilities were 0.00835 and 0.00027, respectively. As the result of principle coordinate analysis, the genotype of broodstock was not overlapped, suggesting that the management system of giant grouper based on eight selected microsatellite markers might be effective, although further validation with extended number of broodfish might also be needed in future. Data of present study could be a useful basis to avoid the unwanted selection of broodfish that possess close genetic relationship with current broodstock, and consequently to establish effective broodstock management system allowing the production of progeny with high genetic diversity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.572-576
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• 2020

As grouper aquaculture production intensifies worldwide, hybrids are increasingly produced to induce heterosis of traits such as rapid growth and strong environmental adaptability. In this study, we compared the morphological characteristics of a hybrid grouper to those of its parent species Epinephelus moara and E. lanceolatus. The coefficients of external and skeletal traits evaluated using soft X-rays did not differ significantly among groups; however, several patterns were detected among measured traits. The body depth (BD), length of caudal peduncle (LCP), and pre-anal fin length (PAL) of the hybrid were the same as those of E. moara, whereas the pre-pectoral fin length (PPL) and interorbital width (IOW) of the hybrid were the same as those of E. lanceolatus. Traits that did not differ significantly among the three groups included pre-dorsal fin length (PDL), pre-ventral fin length (PVL), length of anal fin (LAF), and length of dorsal fin (LDF), whereas the depth of caudal peduncle (DCP) and snout length (SNL) showed intermediate traits, and eye diameter (ED) was significantly smaller in the hybrid. Therefore, intermediate traits such as DCP and SNL and specific traits such as ED may be used as indices for hybrid classification.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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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.

• Journal of fish pathology
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• v.25 no.2
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• pp.111-116
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• 2012

Prevalence of viral nervous necrosis (VNN) in sevenband grouper Epinephelus septemfasciatus farms was investigated during the period of 2006-2008. The outbreak of the VNN was observed from August (water temperature: $24-26^{\circ}C$) to September or October ($20-25^{\circ}C$). The viral infection resulted in acute or chronic mortality of the host, where the mortality rate of juvenile fish was higher than that of the adult fish. Phylogenetic analysis based on partial RNA2 coat protein gene nucleotide sequences revealed that all the isolates from sevenband grouper were classified into the genotype redspotted grouper nervous necrosis virus (RGNNV). In conclusion, VNN of juvenile and adult sevenband groupers during the summer season (July to October, water temperature: about $24^{\circ}C$) was caused by virus belonging to the genotype RGNNV.

• Development and Reproduction
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• v.19 no.4
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• pp.209-215
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• 2015

Red spotted grouper, Epinephelus akaara is a popular aquaculture species in many Asian countries. This species is a protogynous hermaphrodite that first differentiates into female and changes to male later. Due to this reproductive characteristic, stable supply of male and female gametes is a key to the success of seed production in this species. Thus, understanding early gonadal differentiation is required to develop effective sex control techniques. Red spotted grouper were reared in indoor tanks and sampled every 5 days from 40 days post-hatch (DPH) to 130 DPH. Changes of gonadal tissues were examined and analyzed by means of histology. A pair of gonadal primordium has already existed underneath the kidney in the posterior part of the body cavity at 38 DPH when this study began. Gonadal primordia of 38, 40 DPH consisted of germ cells surrounded by a few somatic cells. The blood vessel was observed in the gonadal primordium at 45 DPH. The number of somatic cells and size of gonadal primordium increased age-dependently up to 60 DPH. Formation of ovarian cavity was obvious by two protuberant aggregations of somatic cells at 65 DPH. Completed ovarian cavity and oogonia were first observed in the gonad of one fish sample at 105 DPH. Based on these histological observations, it can be suggested that induction of primary male differentiation could be more successfully applied at around 60 DPH in this species.

• Animal cells and systems
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• v.16 no.1
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• pp.50-56
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• 2012

Kelp grouper ($Epinephelus$ $bruneus$ Bloch 1793) is a commercially important fish in Korea. In recent years, the catch of kelp grouper in the coastal waters of Korea has significantly declined. Despite its importance, little is known about its genetic diversity and conservation efforts are hampered. In this study, we isolated and characterized 12 microsatellite loci using an enrichment method based on magnetic/biotin capture of microsatellite sequences from a size-selected genomic library. All loci were readily amplified and contained TG/CA denucleotide repeats. To characterize each locus, 30 individuals from a natural E. bruneus population in the coastal waters of Jeju Island, Korea, were genotyped. All loci except three, KEm118, KEm154, and KEm219, were polymorphic, with an average of 8.1 alleles per locus (range 2-18). The mean observed and expected heterozygosities were 0.47 (range 0.19-1.00) and 0.61 (range 0.29-0.92), respectively. A significant deviation from Hardy-Weinberg equilibrium was observed at three loci (KEm134, KEm184, and KEm283). These findings will be useful for effective monitoring and management of genetic variation of kelp grouper as well as for the implementation of a fisheries conservation program.