• Korean Journal of Ichthyology
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• v.29 no.2
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• pp.109-116
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• 2017

We investigated maturation and spawning of Miichthys miiuy in the south-western water of Korea, based on samples collected by stow net from August 2015 to December 2016. We analysed monthly changes in maturity stage, gonadosomatic index (GSI), total length (TL) at 50% group maturity. The spawning period was August to October. We estimated the TL at 50% group maturity as 54.8 cm for females and 49.0 cm for males.

• The Korean Journal of Malacology
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• v.30 no.2
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• pp.107-116
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• 2014

Gonadal development and maturation mechanism were studied on the freshwater marsh clam Corbicula papyracea (Heude), which is the endangered species in Korea. The specimens were collected in the rearing ponds and waterway of NFRDI in Gapyeong-gun, Gyeonggi-do from January to December 2004, and then investigated by condition factor, relative growth, gonadal development phases and gonad histological characters based on 30-50 individuals every month. Comparing with the freshwater marsh clam, C. papyracea is small, light olive brown shell and violet interior. The hermaphrodite individuals of C. papyracea take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The average water temperature of inhabit area was in range of $1.8-27.0^{\circ}C$ and usually took great effects on the gonad maturation of C. papyracea. The condition factor ranged from 0.14 to 0.21 throughout the year, which was the lowest during winter season (December-February), and gradually increased to the highest value of 0.21 in May. The ratio of meat weight to total weight was 25.9-38.7%, indicating the similar trend with condition factor. The highest values of condition factor and the ratio of meat weight appeared 1-2 months later than gonadosomatic index reached the peak value, it was probably because that the ovoviviparous eggs would spend a long period before hatching from the foster-sack in the gills. To synthesize the characters of meat weight, condition factor and gonad development by histological study, reproductive cycle of C. papyracea could be divided into five successive stages: multiplicative stage (December to February), growing stage (February to May), mature stage (June to August), spawning stage (August to November), recovery stage (November to December). The smallest shell length of matured C. papyracea was 12.6 mm, and individuals, larger than 16 mm, was formed the nursery in the gills.

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

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

• Journal of Aquaculture
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• v.17 no.1
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• pp.30-38
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• 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
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• v.19 no.2
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• pp.153-153
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• 2003

Reproductive cycle with the ovarian developmental phases, first sexual maturity of the female venus clam, Cyclina sinensis, was investigated by a histological study, and the number of spawned eggs and spawning frequency by artificial spawning induction of the clams were estimated. Samples were collected from the intertidal zone of Simpo, Gimje city, Korea between January and December, 2001. The reproductive cycle of this species can be classified into five successive stages; early active (February to April), late active (March to June), ripe (May to August), spent (July to September), and spent and inactive (September to February). The spawning period was once a year between July and August, a spawning peak was seen in July and August. Percentages of first sexual maturity of female clams of 25.1-30.0 mm in shell length were 64.3%, and 100% for the clams > 40.1 mm. The number of the eggs released from each clam by spawning induction increased as the size of clam in terms of shell length increased. The mean number of the eggs released from the second induction of spawning was 76.87% of the number of the eggs released in the first spawning. Our data indicated that the interval of each spawning was estimated to be approximately 15-17 (average 16.5) days.

• Development and Reproduction
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• v.9 no.2
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• pp.123-134
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• 2005

Germ cell development during oogenesis, ovarian maturation and first sexual maturity in female Ruditapes philippinarum were investigated by cytological and histological observations. R. philippinarum is dioecious. During vitellogenesis, the Golgi complex, glycogen particles, and mitochondria were involved in the formation of lipid droplets and lipid granules in the cytoplasm of the early vitellogenic oocyte. In the late vitellogenic oocyte, cortical granules, the endoplasmic reticulum, and mitochondria were involved in the formation of proteid yolk granules in the cytoplasm. At this time, exogenous lipid granular substance and glycogen particles in the germinal epithelium passed into the oocyte through the microvilli of the vitelline envelope. The spawning period was once a year between early June and early October, and the main spawning occurred between July and August when seawater temperature was approximately $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages: early active stage(January to March), late active stage(Februaryto May), ripe stage(April to August), partially spawned stage(May to October), and spent/inactive stage (August to February). Percentages of female clams at first sexual maturity of $15.1{\sim}20.0mm$ in shell length were 52.6%(50% of the rate of group maturity was 17.83mm in length), and 100% for the clams >25.1mm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.1
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• pp.132-138
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• 1997

In order to obtain the basic information for seedling production of surf clam, Spisula sachalinensis, annual reproductive cycle was investigated from March 1994 to May 1995. S. sachalinensis was dioecious. The gonads are located between the digestive diverticula and muscle tissue of the foot. The condition factor was reached its maximum (0.19) in June, and then decreased to 0.16 in July. In November, the value was the lowest and then increased slowly. The age and minimum size for sexual maturation were 2 years old and about 50 mm in shell length, respectively. However, less than $10\%$ of sexually undifferentiated individuals were larger than 80 mm in shell length. On the other hand, the size of mature oocytes was ranged to $50\~60{\mu}m$ in diameter and testis-ova was observed in testis of the mature stage. Annual reproductive cycle could be classified into five successive stages : multiplicative (October to January), growing (February to April), mature (April to June), spawning (June and July) and degenerative and resting (August and September) stages.

• Journal of Aquaculture
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• v.17 no.1
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• pp.81-88
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• 2004

Annual gametogenic cycle of Manila clam Ruditapes philippinarum collected from Shi-Heung-Ri beach in Jeju was investigated for the 12 month period from May 2001 to April 2002. Water temperature varied from 10 to 27$^{\circ}C$ and salinity from 27 to 35 psu during the course of study. Most of the clams collected in March were in indifferent or in early developing indicating that clams initiated gametogenesis when water temperature becomes 14 to 15$^{\circ}C$. In early June, most of the clams were in developing, expanding follicles and exhibiting growing oocytes. Fully ripe gonads were observed in clams collected during late June to early August. Spawning clams were observed as early as in early June although the spawning activity reached its maximum in early August. Condition index (CI) was rapidly increased from July to early August and then dropped in late August, indicating that most of clams in Shi-Heung-Ri beach spawn in late summer when water temperature was within a range of 25 to 27$^{\circ}C$.

• Korean Journal of Ichthyology
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• v.30 no.2
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• pp.84-91
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• 2018

The study about maturity and spawning of Korean Mandarin fish, Siniperca scherzeri collected using the set net and gill net in Soyangho Lake from April to November 2014 was conducted. The number of individuals was 401 (female: 204, male: 197). The total length of females ranged from 113 mm to 365 mm and that of males was from 140 mm to 342 mm. The water temperature in May which is the start of spawning season indicated about $15^{\circ}C$ and gradually increased to July ($26^{\circ}C$). Gonadosomatic index (GSI) of females indicated 2.3%, 4.6% and 3.1%, respectively, in May to July. Males' value showed the similar pattern recording 8.0%, 6.6% and 4.5% in the same time. According to histological observations of gonadal tissue, the most of female in May had the gonadal tissue of maturing and mature stage. And the ovary of June was mostly in the stage of ripe and spawning and a number of individuals in July was recovery stage. In the case of male, a number of males in May showed in the stage of mature. The testis of June showed that mature sperm was releasing. And the testis of July was mostly in recovery stage. The total length at 50% group maturity was estimated 245.16 mm. As shown in the above, the main spawning period of S. scherzeri was May to June.