• Korean Journal of Ichthyology
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• v.31 no.1
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• pp.23-29
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• 2019

The embryonic development and hatchability of the artificially fertilized eggs of convict grouper (Hyporthodus septemfasciatus) ♀${\times}$giant grouper (Epinephelus lanceolatus) ♂ (CGGG) were compared to those of the maternal pure species (convict grouper ♀${\times}$♂, CG) to establish a novel grouper hybrid for aquaculture industry. The fertilized eggs were divided into nine 5-L beakers (3,000~5,000 eggs/beaker) filled with UV sterilized seawater and incubated at a temperature range of $23.5{\sim}24.8^{\circ}C$ (32.1~32.8 psu). The percentages of fertilization and hatching of CGGG were $69.4{\pm}1.5%$ and $59.0{\pm}5.1%$, respectively and were significantly lower than those of CG (p<0.05). The CGGG proceeded normal embryonic development similar to that of CG, but showed an irregular cleavage, immature embryonic body and spinal deformity in hatched larvae. The incubation time from fertilization to hatching of CGGG was 31 hrs, which was approximately 2 hrs slower than that of CG. Our study provided the possibility of mass production of grouper hybrid CGGG larvae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.31-37
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• 2021

The mass production of fertilized eggs of the convict grouper Hyporthodus septemfasciatus was studied from 2013 to 2020 for industrial aquaculture. The experiment was divided into two groups. Group 1 broodstock was raised from wild-caught fry and used from 2013 to 2020. Group 2 broodstock was raised from artificially propagated fry and used from 2019 to 2020. Males used to collect sperm for artificial insemination weighed more than 7 kg. The effects of various hormones on artificial ovulation were investigated from 2013 onward. Among these, luteinizing hormone-releasing hormone analogue (LHRHa) at 100 ㎍/kg body weight showed the most effective results and was used for artificial egg collection from 2014 onward. In Group 1, the average total egg production per year, average egg production per individual, fertilization rate, and hatching rate were 26,143 mL, 609.7 mL, 93.3%, and 91.8%, respectively, and in Group 2, were 2,750 mL, 316.5 mL, 92.1%, and 90.4%, respectively. Based on these results, we showed that a large number of fertilized eggs for artificial seeding could be produced consistently. Moreover, the mass production of fertilized eggs in Group 2 establishes a foundation for the complete aquaculture cycle of H. septemfasciatus.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.479-485
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• 2020

We evaluated the hatchability of fertilized eggs from six hybrid combinations of highly valued grouper species inhabiting temperate and warm waters, with the goal of establishing a novel hybrid with enhanced growth and viability during the culturing period in the temperate waters of Korea. Hybrid combinations with red-spotted grouper females exhibited high hatchability with high a fertilization and hatching rate of fertilized eggs and a low deformity rate of hatched larvae. Conversely, hybrid combinations with kelp grouper females had very low hatching rates and very high deformity rates; commercial production of seed from such crosses would be difficult without improving hatchability. The hatchabilities of convict grouper ♀×giant grouper ♂ and kelp grouper ♀×red-spotted grouper ♂ were lower than those of maternal purebreds, but these two hybrid combinations were expected to produce potentially large quantities of hatched larvae. In the above evaluation, promising hybrid combinations were identified for commercial production of seed. For these hybrids to contribute to the development of Korea's mariculture industry, mass production of fertilized eggs and seeds is necessary, along with the development of advanced rearing techniques, such as the identification of a suitable rearing temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.6
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• pp.864-875
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• 2015

This study investigated the sanitary characteristics of commercial salted semi-dried convict grouper Epinephelus septemfasciatus (SSD-CG) and longneck croaker Pseudotolithus typus (SSD-LC) and suggested standards for salted semi-dried fish (SSD-F), based on the domestic standards for salted mackerel (Scomber japonicus or kwamegi) and salted dried yellow corvenia (Pseudosciaena manchurica), and sanitary characteristics of commercial SSD-F. For the commercial SSD-CG and SSD-LC, respectively, the moisture content ranged from 64.6-76.1 and 65.7-77.5%, salinity from 2.7-8.2 and 1.5-4.9%, volatile basic nitrogen (VBN) from 22.1-88.2 and 13.5-87.4 mg/100 g, peroxide value (POV) from 17.2-195.0 and 28.5-190.2 mEq/kg, and viable cell counts from 6.1-8.4 and 5.4-7.2 log (CFU/g). No Escherichia coli was detected in six kinds of SSD-CG or three kinds of SSD-LC. The standard for controlling the quality of SSD-F is the moisture content (>68%), salinity (>3%), VBN content (>50 mg/100 g), POV (>60 mEq/kg), viable cell counts (>$10^6$ CFU/g), E. coli (>MPN/100 g), and others. Using the established standards, no commercial SSD-F passed. The chemical, microbial, and other results for commercial SSD-F suggest that provisions for controlling the quality of high-quality SSD-F should be established.