• Journal of Aquaculture
• /
• v.1 no.1
• /
• pp.25-39
• /
• 1988

The flounder reared in captivity matured and spawned when the water temperature gradually increased to $14\~15^{\circ}C$ from $12^{\circ}C$ during winter and the diurnal photoperiod changed from 10L/14D in winter season to 14L/10D in spring. The eggs spawned naturally by reared spawners in captivity during the first half of a spawning period were superior in quality to those spawned during the later half. It would be better to use the eggs of the first half for the mass production of the seedlings.

• Ocean and Polar Research
• /
• v.27 no.3
• /
• pp.351-358
• /
• 2005

Reproductive condition of the tropical blacklip pearl oyster, Pinctada margaritifera collected during the period July through September 2003 from Chuuk Lagoon, Federated State of Micronesia was investigated using histology. The level of gonad development for each pearl oyster was determined with an average score of five microscopic fields, and the average score was used as the maturity index (ML). All wild pearl oysters collected in July did exhibit fully ripe eggs in their ovaries ($45{\sim}50{\mu}M$ in diameter), indicating that they were ready for spawning. In mid August most wild pearl oysters were in spawning and M1 dropped dramatically from mid- to late September, suggesting that the wild pearl oyster completed spawning during this period. In contrast, the cultivated pearl oysters collected in mid-September held ripe eggs in the ovaries and only a few of them spawned, indicating that gonad maturation of the cultivated pearl oyster was somewhat slower than that of the wild pearl oyster in Chuuk Lagoon during the summer period. Histological analysis also indicated that spawning of the pearl oyster is rather incomplete and they may spawn continuously during summer.

• Asian-Australasian Journal of Animal Sciences
• /
• v.14 no.2
• /
• pp.174-183
• /
• 2001

During the rapid phase of gonadal development of the freshwater teleost, the catfish (Silurus asotus), the influence of hCG upon the inducement of final oocyte maturation and spawning was investigated electrophoretically and ultrastructurally. The electrophoretic patterns obtained were different in the presence and absence of some of the major or minor zones, because of the hormone level in catfish. The vitellogenin of hormone-treated fish was stained more intensively than that of sham-treated fish. These proteins showed some minor or main bands of egg extracts which migrated at positions corresponding to molecular weights of approximately 90,000. However, the thickness of electrophoretic band in molecular weight for hCG-treated fish was slightly lower than that for saline control. It seemed the plasma protein with molecular weight of approximately 45,000 in hCG-treated fish disappeared. In contrast to the control fish, the ovaries in the catfish treated with hCG shows a marked ultrastructural change under the electron microscope. No dilated profiles were seen in the granulosa cells of the mature oocyte before ovulation. After germinal vesicle breakdown (GVBD), the zona radiata interna (ZRI) becomes more compact, and there is a loss of all the processes from the pore canals. There is a wide space between the vitelline membrane and zona radiata. Also, during final maturation, the microvillar processes from the oocyte are seen no longer to penetrate deeply into the extracellular spaces of the overlying granulosa cells, and the reticulate patterns of the zona radiata interna becomes occluded, giving the zona radiata a more solid appearance. It has been possible to initiate 100% oocyte maturation in yolk granules and follicles in vivo by treatment with hCG and a high water temperature ($27^{\circ}C$). In hCG-treated fish, the percentages of successful artificial fertilization and hatching were maximal at 15 h after a single injection. It seems clear that a long acting preparation containing hCG can be successfully used in prespawning fish to advance the final events of gonadal maturation and initiate spawning. Further studies are necessary to evaluate the potential of hCG to either stimulate or inhibit the reproductive development of fish at other stages of the seasonal reproductive cycle.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.53 no.1
• /
• pp.103-106
• /
• 2020

We investigated the biological maturation of blackthroat seaperch Doederleinia berycoides in southern Korea waters, based on samples collected from March 2018 to February 2019. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI) and total length (TL) at 50%, 75% and 97.5% group maturity. The spawning period was May to October in 2018. We estimated the TL at 50% group maturity as 27.0 cm for females in 2018. We estimated the TL of females at 75% and 97.5% group maturity as 28.7 cm and 32.7 cm, respectively, in 2018.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2000.10a
• /
• pp.244-245
• /
• 2000

The top shell, Omphalius rusticus (Gastropoda: Trochidae), is marine mollusk inhabiting underneath a rock in the intertidal zone of the coasts of Korea and Japan, and it is one of the edible gastropods. This species is a herbivorous animal. Up to now, there have been some reports on the Trochidae: aspects of classification, spawning periodicity, production, growth and size-frequency distribution of living populations, feeding, reproductive cycle, and induction of larval metamorphosis. (omitted)

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2000.05a
• /
• pp.282-283
• /
• 2000

The egg development of various fishes is studied by various methods including electron microscopy(Matsuyama et al, 1991) and hormone treatment(Schoonbee et al. 1980). In addition to attempt to induce final maturation and spawning, the present experiments were conducted to investigate the influence of hCG upon reproductive cycles in catfish(Silurus asotus) with developing gonads and to stimulate the reproductive system during the rapid phase of gonadal development. (omitted)

• Journal of Aquaculture
• /
• v.17 no.1
• /
• pp.30-38
• /
• 2004

To estimate the spawning period the annual change of gonadosomatic index (GSI) were examined from January 2000 to December 2001. Fecundity, spawning frequency and egg diameter were measured by ocular observation. Germ cell differentiation during gametogenesis, the reproductive cycle and the first sexual maturity of greenling Hexagrammos otakii were observed under light microscopy from January to December, 2000. GSI began to increase in August and reached the maximum in November when ovary was getting mature. The reproductive cycle of H. otakii can be divided into five successive stages in females: early growing stage (July), late growing stage (July to August), mature stage (September to October), ripe and spent stage (September to December), and recovery and resting stage (December to June). Males showed four successive stages : growing (June to August), mature (August to October), ripe and spent (September to December), and recovery and resting stage (December to May). According to the frequency distributions of egg diameter in spawning season, H. otakii could be one of polycyclic species spawning 2 times or more during one spawning season. Number of total eggs and mature eggs in the absolute fecundity were related to the standard length and body weight, respectively. Number of total eggs and mature eggs in relative fecundity were also proportional to the standard length, but rather these numbers decreased with body weight. Percentages of first sexual maturity of females and males in greenling were over 50% from 19.1 to 21.1cm in length, and 100% for fish over 25.1cm in length. Therefore, both sexes are ready to reproduce after one year old.

• The Korean Journal of Malacology
• /
• v.25 no.2
• /
• pp.127-133
• /
• 2009

The common octopus, Octopus vulgaris is commercially important species in Korea. Korean fishing vessels have actively caught it. However, the study of this species has been poorly known. Therefore, the purpose of this study is to provide information about maturation and spawning period of this species. Samplings have been monthly collected in Tongyoung and Sacheon of Gyeongsangnam-do, using traps. A total of 748 individuals were sampled from February 2007 to January 2008. We analyzed monthly changes in maturity stages, gonadosomatic index, total weight at 50% group maturity. The octopus total weight was between 128.6 and 3381.4 g. Females were distributed between 129.8 and 3381.4 g and males between 128.6 and 2378.4 g. The spawning periods were May to June and September. The total weight at 50% group maturity was estimated to be 919.6 g.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.47 no.3
• /
• pp.255-263
• /
• 2014

We investigated the reproductive characteristics of Lycodes tanakae in the coastal waters of the middle East Sea to elucidate the species' population structure. We investigated Lycodes tanakae maturation and spawning based on samples collected by Danish seine and gill nets from January 2012 to December 2013. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), egg diameter, fecundity, and total length at 50% group maturity. The spawning period was December to February, while fecundity ranged from 1,677 eggs at 57.3 cm (total length;TL) to 6,445 eggs at 75.7 cm. The relationship between TL and fecundity (F) was $F_e=6E-05TL^{3.127}$ ($R^2$ = 0.516), and F increased with increasing TL. We estimated the TL at 50% group maturity as 60.4 cm for females and 59.8 cm for males. This study is the first report of Lycodes tanakae reproductive characteristics in the coastal waters of the middle East Sea.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.34 no.5
• /
• pp.526-535
• /
• 2001

The gametogenesis, reproductive cycle, frequency distribution of egg diameter and fecundity of spotted sea bass Lateolabrax maculatus were investigated by histological observation. The samples were collected at Goheung, Jeonam from December 1996 to November 1997. Gonadosomatic index (CSI) was appeared less than 1.0 in female and male from December to July and began to increase from August and reached the maximum values of female 7.50 and male 2.98 in October. Hepatosomatic index (HSI) was appeared annual maximum value of female 1.97 and male 1.64 in March and then decreased from April. The annual reproductive cycle of this species can be divided into four successive stages: growing stage (July to August), maturation stage (September to October), ripe and spawning stage (October to November) and degeneration and resting stage (November to July). According to the frequency distribution of egg diameter, the development mode of egg was not seperated, formed one mode for the maturation and spawning season, The individual absolute fecundity ranges from $1,726,242\~17,822,576$ eggs, and individual relative fecundity ranges from $29,458\~214,730$ eggs in total length (cm) and $938\~3,363$ eggs in body weight (g). Female and male of L. maculatus were matured when total length were over 50.1 and 45.1 cm, respectively.