• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.1
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• pp.9-16
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• 2004

Parapenaeopsis tenella occurs widely on the south and west coasts of Korea. Sex ratio showed seasonal variations, with a mean value of 48.6% for the females. The species produces one cohort a year, with the ovaries ripening from July to August. Insemination took place from July to August, as more than half of the females sampled in the study over 14 mm CL were inseminated. Gonadosomatic index (GSI) reached the maximum between July and August. The smallest mature female was 11 mm CL. Size at 50% sexual maturity ($CL_{50}$), determined from both mature females and inseminated females, was 12.53 mm and 12.28 mm CL, respectively. The life span of females appeared to be 14-15 months according to size frequency distributions, while that of the male was 13-14 months. Population growth was estimated by the modified von Bertalanffy growth function incorporating seasonal variation in growth. Based on the growth parameters (K = 1.22 $yr^{-1}$ and $L_{\infty}$ = 21.99 mm CL for females, and K = 2.00 $yr^{-1}$ and $L_{\infty}$ = 15.00 mm CL for males) growth curves showed that females grew faster and reached a larger size at age than males.

• Korean Journal of Ichthyology
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• v.10 no.2
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• pp.191-199
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• 1998

The ovary of the spotted flounder Verasper variegatus is a conical bag in shape and is bilateral structure develops lengthily from the posterior of the abdomen to the end of the anal fin. The testis also is bilateral in structure, usually located in small size in the abdomen. In females, the gonadosomatic index (GSI) showed very low from March to July, and then began to increase from August, thereafter reached the maximum in January through out the year. In males, the GSI reached the maximum (1.7) in January through out the year, as seen in females. Compared with the male GSI in other fishes, the maximum GSI of this species were very lower than those of other fishes. According to the distributions of egg diameter in the spawning season, it is assumed that the spotted flounder spawn four times or more in the spawning season. The total length of female and male reached 50% first sexual maturity were 42.0~44.0 and 28.0~30.0cm, respectively and total length of female and male reached 100% maturity were 44.0 and 32.0cm, respectively. The reproductive cycle could be classified into four successive developmental stages: growing stage (August~October), mature stage (November~December), ripe and spent stage (December~February), degenerative and resting stage (March~July).

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.101-106
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• 2007

We investigated the maturity and spawning of black edged sculpin, Gymnocanthus herzensteini caught by gillnet in the East Sea from March 2003 to February, 2004. We analyzed monthly changes in maturity stages, gonadosomatic index (GSI), gonad weight (GW), egg diameter, fecundity, total length at 50% group maturity and sex ratio. The spawning period was December to February. The fecundity ranged form 8,814 eggs at 14.7 cm (TL) to 25,560 eggs at 24.4 cm (TL). The relationship between total length (TL) and fecundity (F) was $F=285.11TL^{1.4092}$ ($R^2$ =0.571) and fecundity increased with total length. The total length at 50% group maturity was estimated to be 15.25 cm. The sex ratio was 60 for female and 40 for male, where the female population was seen to be slightly predominant. For sex ratio by length class, male was a little predominant in small size, but female was 90% more than 24 cm.

• Korean Journal of Ichthyology
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• v.22 no.3
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• pp.154-161
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• 2010

The reproductive ecology of the cardinalfish Apogon lineatus was examined using 4,300 specimens collected monthly from January to December 2006 in the coastal waters of Gori, Korea. Specimens ranged in standard length (SL) from 2.1 to 8.6 cm. They were distributed more in surface areas during summer and autumn and more on bottom areas during spring and winter. The gonadosomatic index (GSI) of females was highest in September and decreased until December, with the spawning season lasting from August to October. The monthly ratio of female to male did not significantly differ (${\chi}^2$-test, p>0.05). The size of 50% maturity was estimated at 5.43 cm SL and all females more than 7.0 cm SL were sexually mature. A. lineatus is a multiple spawner, spawning on more than one occasion in a single spawning season. The maximum egg diameter was 0.65 mm. Fecundity (F) ranged from 8,555 to 20,084 eggs, with a mean of 15,038 eggs. The relationship between fecundity and standard length was estimated as F=$334,851\;SL^{1.9876}$ ($R^2$=0.53). The relationship between fecundity and body weight(BW) was estimated as F=7,167.6 Ln (BW)-2,198.1 ($R^2$=0.33).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.57-66
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• 2020

The purpose of this study was to provide information about annual variations in catch size and changes in reproductive biology in the common octopus Octopus vulgaris, a commercially important species. Samples were collected from coastal waters off Gyeongnam, Korea, by coastal trap and coastal complex fishery from February to December 2018. Octopus vulgaris have been decreasing in this region since 2007 and catch prices have been increasing. The mantle length (ML) of O. vulgaris ranged from 1.2 to 21.2 cm and body weight ranged from 42.6 to 5,537 g. The sex ratio differed significantly from what was expected, at 0.45:0.55 (P<0.05). Mature females were found from February to December, except in October and November, and males occurred from February to December, except in October. The gonadosomatic index value was higher from May to September than in other months. The total number of eggs in fecund individuals ranged from 40,280 in 578.1 g of body weight to 138,994 in 1,666.5 g of body weight. The relationship between body weight and fecundity was F=76.486BW^1.0087 (r²=0.7897). At 50% group maturity, average weight was estimated to be 636.35 g, while it was 969.30 g at 75% maturity and 1736.55 g at 97.5% maturity. This study highlights changes in catch size and reproductive biology between 2007 and 2018. These results provide basic evidence that may be used to establish regulatory policy for O. vulgaris fisheries.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.4
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• pp.463-470
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• 2011

Gonadotropin-releasing hormone receptor (GnRHR) gene is expressed at the anterior pituitary gland and plays a key role in gonad development. This study aimed to investigate molecular genetic characteristics of the GnRHR gene and elucidate the effects of single nucleotide polymorphisms (SNPs) of GnRHR gene on sex steroid level in Japanese flounder (Paralichthys olivaceus). We used polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and sequencing of the GnRHR gene in 75 individuals. We identified three SNPs in the GnRHR gene: P1 locus (C759A and C830T) in the coding region of exon2 which were both linked together and P2 locus (G984T) in the coding region of exon3, which added a new transcript factor (ADR1) and a new methylation site (CG). Only C830T of P1 leads to amino acid changes Thr266Ile. Statistical analysis showed that P1 was significantly associated with $17{\beta}$-estradiol ($E_2$) level (p<0.01) and gonadosomatic index (GSI) (p<0.05). Individuals with genotype BB of P1 had significantly higher serum $E_2$ levels (p<0.01) and GSI (p<0.05) than those of genotype AA or AB. Another SNP, P2, synonymous mutation, was significantly associated with GSI (p<0.05). Individuals with genotype AB of P2 had significantly higher GSI (p<0.05) than that of genotype AA. In addition, there was a significant association between one diplotype based on three SNPs and reproductive traits. The genetic effects for both serum $E_2$ level and GSI of diplotype D4 were super diplotypes (p<0.05). These results suggest that the SNPs in Japanese Flounder GnRHR are associated with $E_2$ level and GSI.

• Development and Reproduction
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• v.13 no.4
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• pp.341-351
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• 2009

The effects of serotonin (5-hydroxytryptamine, 5-HT), ecdysone (20-hydroxyecdysone, 20-E) and HCG (human chorionic gonadotropin) on the ovarian maturation of the fleshy shrimp, Fenneropenaeus chinensis were investigated. Adult female fleshy shrimps were injected with 5-HT ($5{\mu}g$/g body weight (BW) or $20{\mu}g$/g BW), 20-E ($5{\mu}g$/g BW, $10{\mu}g$/g BW or $20{\mu}g$/g BW) or HCG (5 IU/g BW or 10 IU/g BW) three times at 5-day intervals and were sacrificed 10 days after the last injection. The effects were compared against an intact control group and sham control group which received the injection of sterile saline solution as a vehicle. 20-E and HCG showed no effectiveness on ovarian maturation in fleshy shrimps. However flesh shrimp given 5-HT of $20{\mu}g$/g BW showed significant increase in gonadosomatic index (GSI) in early spring. The results suggest that treatment of 5-HT of $20{\mu}g$/g BW or more is useful approach for the nursery production of the fleshy shrimp, Fenneropenaeus chinensis aquaculture.

• Journal of Life Science
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• v.27 no.10
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• pp.1097-1103
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• 2017

For the artificial induction of the sexual maturation of Anguilla japonica, salmon pituitary extract (SPE) is continuously injected into females, and the eggs obtained from artificial sexual maturation are artificially fertilized with sperms and hatched. However, repeated injection of SPE in the abdominal cavity causes tremendous stress in females, which may prevent their complete sexual maturation and reduce the immune system function, ultimately resulting in death. In addition, the poor quality of the ovulated eggs can reduce the hatching and survival rate of larvae. In the present study, sexual maturation of females was induced by inserting an osmotic (OS) pump containing hormone analogs known to effectively induce sexual maturation into the abdominal cavity of female eels, and the effect of the OS pump on the induced sexual maturation was investigated. Our study results showed that the gonadosomatic index (GSI) was significantly higher in the fish subjected to SPE injection than those subjected to human chorionic gonadotropin (hCG), gonadotropin-releasing hormone analog (GnRHa), and methyl testosterone (MT) injections, either separately or in combination. In addition, a histological analysis showed that the oocytes in the SPE OS pump groups were more mature (entered the nuclear shift stage) than those in the other groups. These results suggest that an osmotic pump containing hormone analogs can be used to induce sexual maturation in female A. japonica artificially.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.5
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• pp.404-409
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• 2006

This study investigated the reproductive cycle of the female hairychin goby, Sagamia geneionema, histologically. The fecundity of female hairychin goby ranged from 1,002 to 1,240 eggs when they reached a total length of 9.1-10.0 cm. Fecundity is related to total length. The gonadosomatic index (GSI) increased from December (1.87$\pm$0.46) and reached a maximum in April (11.57$\pm$1.92). The histological changes in the ovary were correlated with the GSI. Oocytes at the chromatin-nucleolus and peri-nucleolus stages were observed in the ovary year-round. In December, oocytes containing yolk appeared in the ovaries of a few fish. Most oocytes appearing in January were at the yolk globule stage. The frequency of oocytes appearing at the yolk globule stage from January to March was higher than in other months. Subsequently, empty follicles and atretic oocytes were observed in the ovaries in May. Based on the histological observations of gonad development and the monthly change in the GSI, the reproductive cycle was classified into the following successive stages: growing (October to November), mature (December to January), ripe and spawning (February to April), and degenerative and resting (May to September) stages. The histological observations of ovaries during the spawning period indicate that this species is a multiple spawner with abbreviated iteroparity based on the developmental pattern of oocytes.

• Journal of Aquaculture
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• v.16 no.3
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• pp.129-134
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• 2003

Spawning induction and early growth of the sea urchin, Strongylocentrotus intermedius were studied with the purpose of artificial seedling production. Gonadosomatic index(GSI) of the sea urchin showed the highest value in October, and rapidly decreased in December. It means that October and November is the peak of spawning season of the sea urchin in the latitude. Spawning induction by injection of potassium chloride solution in October has showed 44.0~100.0% reaction rate, and were produced 6,300$\times$10$^4$ eggs. Spawned eggs have shown the fertilization rate of 92.3~98.2% and the hatching rate of 78.2~87.0%. The metamorphosis of larvae after hatching in the seawater temperature of 13.7~17.1$^{\circ}C$ resulted in early eight-armed larvae in 13 days and late eight-armed larvae in 20 days. The collection of progenies was possible in 24~25 days after hatching and collection rate was 18.5~26.1% (mean 22.3%). Test diameter immediately after collection had a mean 350 ${\mu}{\textrm}{m}$. Survival rate and test diameter of juvenile sea urchin after collection were 58.5%, 1.32 mm in 30 days, 27.7%, 3.82 mm in 92 days and 15.6%, 11.70 mm in 181 days, respectively.