• The Korean Journal of Malacology
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• v.27 no.3
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• pp.261-271
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• 2011

The gametogenic cycle, the spawning season and the biological minimum sizes in female and male Protothaca (Notochione) jedoensis were investigated by quantitative statistical analysis. In females, monthly changes in the percents of the follicle areas to the ovarian tissue areas and the percents of the oocyte areas to the ovarian tissue areas increased in February and reached the maximum in April, and then gradually decreased from May to July, with the spawning peak between June and July. In males, monthly changes in the percents of the testicular tissue areas to total tissue areas and the percents of the spermatogenic stage areas to the testicular tissue areas increased in February and reached the maximum in April, and then showed a rapid decrease from May to July. From these data, it is apparent that the number of spawning seasons in female and male P. (N.) jedoensis occurred once a year, from May to July. Therefore, P. (N.) jedoensis in both sexes showed a unimodal gametogenic cycle during the year. Compared the gametogenic cycle by quantitative statistical analysis in 2007 with the previous qualitative results of this species, the results of the gametogenic cycle calculated by quantitative statistical analysis showed some differentiations in the spawning seasons evaluated by the gonad index by qualitative histological analysis. The intervals of the beginning of two spawning seasons showed one month between the results of quantitative and qualitative analyses. The biological minimum sizes (considering to 50% of group sexual maturity) in female and male clams by quantitative analysis of this species are 32.01 mm in shell length in females and 30.58 mm in males, respectively. According to the mean shell length fitted to von Bertalanffy's equation, 30.58 and 32.01 mm in shell length were considered to be two years old. Therefore, we assume that both sexes of this population begin reproduction from two years of age.

• Journal of Aquaculture
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• v.11 no.2
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• pp.141-149
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• 1998

Spawning inducement of striped knife-jaw, Oplegnathus fasciathus, was attempted by two experiments. In experiment I (Exp. I), water temperature was gradually increased from 14.5$^{\circ}C$ in December 15, 1996 to $21.0^{\circ}C.$ in February 22, `997 and then maintained at this level. Photo-period was also gradually increased from 10.5L/13.5D in December 15, 1996 to 15.5L/8.5D in February 17, 1997, and then maintained at this level. In experiment II (Exp. II), water temperature was increased in the same way from Exp. I. Photoperiod was natural conditions from December 1996 to March 9, 1997, and then suddenly increased to 15.5L/8.5D until the end of experimental period. Spawning of the fish was occurred from February 22 through April 2, 1997 (for 40 days) in Exp. I. Number of total spawned eggs was 30.04 million and fertilization rate was 77.2%. The fish began to spawn at $21.0^{\circ}C.$ and 15.5L/8.5D. It requied 65 days to spawn since the water temperature had increased from $14.5^{\circ}C.$ to $21.0^{\circ}C.$. Spawning of the fish was not occurred until March 9, 1997 in Exp. II. After 7 days, photo-period was suddenly incresed to 15.5L/8.5D and fish were spawned from March 17 through April 4, 1997 (for 20 days). Number of total spawned eggs was 21.28 million and fertilization rate was 72.1%. The fish began to spawn at $21.0^{\circ}C$ and 15.5L/8.5D. It required 65 days to spawning since the water temperature had increased from $14.5^{\circ}C$ to $21.0^{\circ}C$.

• Korean Journal of Ichthyology
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• v.7 no.2
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• pp.195-202
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• 1995

The seasonal changes in the muscle components of hibernant fish, amphibious mudskipper (Boleopthalmus pectinirostris), caught during the period between June 1993 and April 1994 were studied. The distributional changes of its major components in each muscle tissues was also observed before and after spawning and hibernation. Moisture content was the lowest after spawnig season and the highest just after hibernation, but crude protein was the highest after spawning sea-son. Crude lipid in female was the highest before spawning season, while in male it was the highest after spawning season, but both of female and male the lowest just after hibernation. Carbohydrate content in female and male showed the highest value just before hibernation and tended to decrease thereafter. In case of mudskipper, dyeing distribution was more or less spread in almost all of the tissues after spawning season but showed nearly no difference just after hibernation with the exception of small increase in dyeing degree of muco layer and epidermis layer. Investigation of mudskipper muscle tissue through the method of sudan black B dyeing yielded the results as follows ; lipid component in mudskipper in seasons before and after spawning season was percieved as mainly distributed in muco layer, epidermis and hypodermis layer respectively and also percieved a little between hypodermis subscutoneus cells. In season just before hibernation, it prevailed in almost all of the tissues, contrary to the weakness in its distribution degree just after hibernation.

• Korean Journal of Ichthyology
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• v.20 no.4
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• pp.263-271
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• 2008

The maturity and spawning of Korean flounder Glyptocephalus stelleri were investigated using samples randomly collected in the East Sea of Korea from May 2005 to September 2008. Gonadosomatic index began to increase in December and reached a maximum between March and May. After spawning it began to decrease from June. The spawning period was March to June, and the main spawning period was April to May. Annual reproductive cycles of this species can be divided into four successive stages; immature stage (July~November), maturing stage (December~February), mature stage (March~April) and spent stage (May~June). The fecundity ranged from 15,146 eggs at 24.1 cm (TL) to 101,491 eggs at 38.1 cm (TL). The relationship between total length (TL) and fecundity (F) can be expressed as $F=0.0004TL^{3.449}$ ($R^2=0.663$), with F increasing with TL. The TL at 50% group maturity ($TL_{50%}$) was estimated to be 25.6 cm.

• Korean Journal of Ichthyology
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• v.27 no.4
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• pp.300-305
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• 2015

The characteristics of 11 spawning sites in the natural environment of the Korean endemic species, Liobagrus somjinensis were investigated in the Yocheon (stream) of Seomjingang (river), located in Sikjeong-dong, Namwon-si, Jeollabuk-do, Korea from May to June 2015. The spawning sites had largely two parts, the upper region close to the surface of the waters and under region at bottom: the upper part was covered with a large and flat boulder over about 256 mm in size, whereas the under part consisted mainly of pebbles and sand. The large boulder put on the upper region may be seen as a bulwark for guarding eggs laid at the under (bottom) region. All the sites under the boulder showed a similar structure having a small hollow filled with an egg mass and an individual (male). The spawning bottoms left clean having no any benthic invertebrates and detritus. The egg shape was spherical, yellow and covered with a transparent membrane and the egg size was $3.31{\pm}0.15mm$ (n=30) in diameter. The development stage of each egg mass under the boulder was almost same from morula stage to formation stage of eye lens. The average number of eggs in 11 spawning sites was $121{\pm}35.5$ (84~176) and the average number of female fecundity in ovary was $143{\pm}31.3$ (110~232).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.45 no.4
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• pp.243-250
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• 2009

Maturation and spawning of the jack mackerel, Trachurus japonicus was investigated based on the samples captured in the coastal waters around Jeju Island from January 2007 to December 2008. Gonadosomatic index began to increase in March, and reached a maximum between April to June. After spawning it began to decrease from August. Reproductive season was estimated to March-July, with peak in April. Fecundity was proportional to the size of the female, with the clutch size varying from 33,493 eggs in the smallest female(FL=27.0cm) to 627,061 eggs in the largest(FL=40.6cm). Size at 50% sexual maturity(FL50), determined from mature females, was 26.6cm FL. Annual reproductive cycles of this species could be divided into six successive stages; immature stage(September-December), nucleolus stage(January-February), yolk vesicle stage(February-March), vitellogenic stage(March-April), ripe stage(April-July) and spent stage(July-September).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.3
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• pp.255-263
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• 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
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• v.29 no.2
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• pp.191-196
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• 1996

Age growth and spawning period of Enedrias nebulosus were estimated based on otoliths taken from a total of 255 fish samples of E. nebulosus, which were caught in the costal waters of $Kod\v{o}kto$ near Pusan from November 1990 to October 1991. Marginal increment analysis indicates that annuli in E. nebulosus are formed in December. Spawning period was estimated to be November to January, with a peak in December. The von Bertalanffy growth equations were expressed as follows: $L_t=33.64(1-e^{-0.1357(t+2.6853)})$ and $W_t=414.11(1-e^{-0.1357(t+2.6853)})^{3.9745}$, Where $L_t$, is total length in cm, $W_t$, is total weight in g and t is age in year.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.329-332
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• 1982

A Series of trials for the spawning induction of the Israeli strain of common carp were carried out at the fish culture research station of National Fisheries University of Pusan from 1978 to 1981. 1, During 3 years up to the first periods in 1980 carp pituitaries and/or commercial gonadotropic hormone was used to induce the brood fish to spawn without success. In the trials in the later periods in 1980 and in 1981, water temperature increase method was used with success in 40 females of 16 trials leaving a single failure with 2 females. 2. Brood fish had been kept in a small circular tank ($7\;m^2$) continuously supplied with cool well water enough to keep the water temperature in the tank relatively cool, ranging from 16.9 to $20.2^{\circ}C$, and the water in the spawning tank ($15\;m^2$) was 3.0 to $6.5^{\circ}C$ higher than in the brood fish holding tank. 3. It could be said that the spawning of Israeli strain of common carp in Korea hardly occur without water temperature increase even though treated with hormone.

• Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.276-285
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• 2009

Despite great commercial interest, relatively little has been described about molecular mechanism of bivalve reproduction. We investigated genes involved in ovarian maturation of the Yesso scallop, Patinopecten yessoensis. GSI index and histological analysis revealed that maturation of ovary begin in February and spawning period is from April to June which is similar to the previous study in the East Sea. As result of combination analysis of differential display RTPCR (DDRT-PCR) and histological examination, vitellogenin (Vg), ferritin (Ft) and ADT/ATP carrier protein (ACC) were identified as differently expressed genes in maturating ovary. Endpoint RT-PCR results showed that Vg is ovary-specific genes whereas Ft and ACC are expressed ubiquitously suggesting that Vg can be good molecular markers for ovarian development and sex determination in bivalves. Quantitative PCR results revealed that Vg were expressed highest during growth stage and appears to play a major role in oocyte maturation. On the contrary, expression of Ft was highest after spawning stage, which suggests that up-regulation may be involved in spawning and inactive stages in which the scallops recover from spawning. In addition, high level of the mitochondrial gene, ACC, may play a role in energy metabolism in maturating oocytes. Isolation and molecular studies of these key genes will expand our knowledge of the physiological changes from various exogenous factors including temperature, salinity, pH, even or numerous endocrine disrupting chemicals (EDCs) during reproductive cycle. In addition, further study of these genes implicates various industrial applications including the stable seed production, increased food quality, or economic aquaculture system.