• The Korean Journal of Malacology
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• v.21 no.1
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• pp.1-11
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• 2005

Reproductive cycle, first sexual maturity, spawning amount related with the size and spawning interval in female Ruditapes philippinarum were investigated by histological observation and the analysis of morphometric data during artificial spawning induction. Ruditapes philippinarum is dioecious and oviparous. The reproductive cycle of this species can be subdivided into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (May to October), and spent/inactive stage (August to February). The spawning period was once a year between May and early October, and the main spawning occurred between July and August when seawater temperature was approximately $20^{\circ}C$. Percentages of first sexual maturity of female clam of 15.1-20.0 mm in shell length were 56.3%, and 100% for the clams > 25.1 mm. The mean number of the spawned eggs increased with the increase of size classes (shell length). In case of spawning induction by the same size class, the number of spawned eggs were gradually decreased with the increase of spawning frequencies (the first, second, and third spawnings). In the experiments of artificial spawning induction during the spawning season, the interval of each spawning was estimated to be 15-17 days (average 16.5 days).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.2
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• pp.97-108
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• 1997

Variation of the catches and fishing grounds, and spawning ecology of Lophius litulon caught by large staw net were investigated from following as ; L. litulon caught through the year, and the peak in catches showed on January in winter, and the lowest catches showed on August in summer. The fishing grounds of L. litulon were located in the Yellow Sea and the East China Sea. And the main fishing ground was formed in the adjacent waters of Ilhyang-cho, where catches and CPUE were more than 50 M/T, 5 kg/haul, respectively, and the range of coefficient of variation(C.V) was 0.6~0.7. The spawning season of L. litulon was on March and April, when spawning area was formed in waters between Ilhyang-Cho and Cheju-Do. The fishing grounds distribution of L. litulon was obviously different with seasonal variation. Namely, in winter, the fishing grounds were mainly formed in the western waters of Cheju-Do, and on March and April( in spawning season), the fishing grounds were densely formed in the adjacent waters of Ilhyang-Cho, and after May, the fishing grounds were widely dispersed towards in the Yellow Sea and the East China Sea with temperature upgrade.

• Korean Journal of Ichthyology
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• v.30 no.4
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• pp.217-223
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• 2018

The study on the spawning ecology of Sarcocheilichthys variegatus wakiyae at Jicheon stream, Korea was investigated from March 2016 to February, 2017. The sex ratio of male to female was 1 : 0.97 and there was no significant difference. The spawning season was from the end of April to the mid-July, and the peak of spawning period was from the beginning of May to the end of June. The average water temperature at this time was $18^{\circ}C$. According to frequency analysis of total length, it is presumed that the group with a total length of less than 51~70 mm was one year old, the 71~100 mm was two years old, and the group over 101 mm was three years old. They sexually matured when they were over two years. The average number of eggs in the ovaries was estimated as $428{\pm}194per$ matured female. The mature eggs were yellowish, oval, and had a mean diameter of $2.38{\pm}0.25mm$ and a short diameter of $1.98{\pm}0.20mm$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.3
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• pp.226-231
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• 2004

Maturation and spawning of Acentrogobius pflaumi were studied using samples collected from the Gwangyang Bay, Korea, from January to December, 1999. The gonadosomatic index (GSI) of the female was the highest in May. The spawning season lasted from May to June. There was a significant difference in the 1 : 0.59 sex ratio between males and females (p<0.01). The percentage of sexually mature females was over $50\%$ for the size group between 4.5 cm and 4.9 cm, and $100\%$ for the size group over 5.5 cm in body length. The size of eggs spawned was between 0.4 to 0.6 mm, and the spawning occured once a year. Fecundity varied between 3,600 and 9,700 eggs. The relationship between the fecundity and body length of the fish was expressed in the fecundity equation as; $F=0.294{\times}10^3\;BL^{1.899}.$ The first spawning length was 4 cm BL.

• 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.

• Korean Journal of Ichthyology
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• v.29 no.4
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• pp.261-266
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• 2017

Microphysogobio koreensis is an endemic Korean freshwater fish that is protected as an endangered fish by the Ministry of Environment in Korea. In this study, we attempted to investigate the spawning period and spawning characteristics of M. koreensis to obtain basic information for its conservation. Though natural and histological observation, the spawning season occurred between April and May, with peak spawning occurred in early May when the water temperature was $20{\sim}23^{\circ}C$. During the spawning season, males had a bright-orange body and a thick red horizontal line from the rear of the operculum to the caudal peduncle, along with a lateral line, while females had a dark brown body. Nuptial organ had not appeared. The number of eggs in the ovaries was 10,705~22,165 ($15,573{\pm}4,274$). The number and appearance ratio of mature eggs were 1,100~5,920 ($3,383{\pm}2,126$) and 10.3~44.8% ($22.4{\pm}15.6$), respectively. And the size of mature eggs was 0.60~1.00 mm ($0.74{\pm}0.06$).

• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.142-148
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• 1999

Monthly changes in the gonad index (GI), egg-diameter composition, gonadal development, reproductive cycle of the ark shell, Scapharca subcrenata, were investigated by histological method and morphometric data. This species is dioecious and oviparous. The gonad is located among the subregion of mid-intestinal gland, digestive diverticula and the outer fibromuscular layers compacted by the fibrous connective tissues and muscle fibers. The gonad index sharply increased in May, reached the maximum value in June, and then gradually decreased from July to December. The reproductive cycle of this species can be divided into six successive stages: early active stage (January to May), late active stage (June to July), ripe stage (June to August), partially spawned stage (July to September), degenerative stage (August to December), and resting stage (January to April). S. subcrenata spawns once a year between July and early September, and the main spawning occurred between July and August when the water temperatures were above $20^{\circ}C$. This evidence suggest that timings of maturation and spawning are closely related to water temperatures. Even though the spawning period was once a year, it is assumed that the number of spawning frequencies (broods) may occur more than twice during the spawning season.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.4
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• pp.248-253
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• 2007

We studied the maturation and spawning of female Spanish mackerel (Scomberomorus niphonius) based on 445 specimens collected monthly from January to December 2004 in the coastal waters off Busan. The fork length (FL) of S. niphonius ranged from 26.1 to 105.4 cm, the gonadosomatic index (GSI) of the females was highest in May 2004, and the spawning season take place from April to July. A significant difference was detected in the sex ratio between females and males ($X^2$ test, p<0.01). The percentage of sexually mature females exceeded 50% in the 50-60 cm (FL) size group and reached 100% in the over 70 cm (FL) size group. Fecundity (F) varied between 201,156 and 836,426 egg per female. The relationship between F and FL of the fish was expressed as $F=5.8756FL^{3.8465}$. The relationship F and body weight (BW) was expressed as F=581.421 n (BW)-4108.5. The first spawning length was 41.8 cm (FL.)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.3
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• pp.318-328
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• 2021

We investigated the maturity and spawning of the brown sole Pseudopleuronectes herzensteini, in the coastal waters of the East Sea off Gangwon and Gyeongbuk, South Korea, using samples collected by gill net and longline fishery from January 2018 to December 2019. We analyzed oocyte development, monthly maturity stage, gonadosomatic index (GSI) and total length at maturity. Histological analysis of ovarian development in P. herzensteini revealed that the development was group-synchronous. The spawning peak in Gangwon and Gyeongbuk occurred from April to May and from February to March, respectively. Thus, the spawning season in Gangwon was 1-2 months later than that in Gyeongbuk. The length at 50% maturity for females was estimated as 24.2 cm and 19.0 cm in Gangwon and Gyeongbuk, respectively. Similarly, the length at 50% maturity for males was estimated as 19.8 cm and 16.5 cm in Gangwon and Gyeongbuk, respectively.

• Korean Journal of Ichthyology
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• v.17 no.2
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• pp.112-122
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• 2005

Iksookimia longicorpa was investigated in the upper part of the Seomjin River in Korea from 2003 to 2004. It inhabited pebble and cobble bottoms with water-current velocities of 10~30 cm/sec and depths of 30~100 cm. This species is active during daylight hours from March to October but hibernated in the river bottoms in the winter season. The sex ratio of female to male was 1 : 0.65, and the female was 20~40 mm larger than the male. Female length frequencies in this population indicated that the 65~90 mm group is 1+years old, the 90~110 mm group is 2+ years old, and the 110~130 mm group is 3+ years old. The males developed a secondary sexual character, the lamina circularis at the base of their pectoral fin, after 13~14 months. The spawning season was from early to middle June with water temperatures of $20{\sim}24^{\circ}C$ individuals became sexually mature after the age of 2 years. The average number of eggs in the ovaries was $2,402{\pm}944$. Stomach contents were mainly Chironomidae, Ephemeroptera, Arcellidae and Algae. The feeding rate was highest in April and September; they did not fed in the winter.