• Development and Reproduction
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• v.21 no.3
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• pp.275-286
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• 2017

The purpose of this study is to investigate the differences fatty acids and hormonal parameters in the spawning and non-spawning season between the diploid and induced triploid Far Eastern catfish, Silurus asotus. The measured triploids were produced by cold shock for 50 min at $4^{\circ}C$ in May 2014, the spawning season of diploid was in May, and the non-spawning season was designated in January. Estradiol and testosterone and gonadosomatic index of diploid were higher than those of induced triploid in spawning season (P<0.05), and those of diploid in spawning season were higher than non-spawning season. On the other hand, thyroid stimulating hormone and thyroxine of induced triploid were higher than those of diploid in spawning season (P<0.05). Erythrocyte count of diploid was higher than that of induced triploid in spawning season and non-spawning seasons. Mean corpuscular volume and mean corpuscular hemoglobin of induced triploid were higher than those of diploid in both seasons (P<0.05). Percentages of total saturated fatty acids and n-3 polyunsaturated fatty acids of induced triploid were higher than those of diploid in spawning season, but those of diploid were higher in non-spawning season (P<0.05). Percentages of total mono unsaturated fatty acids and total n-6 polyunsaturated fatty acids of diploid were higher than those of induced triploids in spawning season, while those of induced triploid in non-spawning season were higher (P<0.05). Therefore, induced triploids in the spawning season tend to concentrate on growth and lipid-synthesization, whereas, diploids concentrate on reproduction and gonadal maturation rather than on growth. In non-spawning season, growth and lipid-synthesization were not significantly different between diploid and induced triploid.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.207-216
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• 2005

Spawning behaviors of Squalidus gracilis majimae (Cyprinidae) were observed in the laboratory whose environmental factors such as light (D/L = 16 : 8), temperature ($20\;{\sim}\;24\;＾{\circ}C$), and dissolved oxygen (>8 mg $L^{-1}$) were quite regularly controlled. The behavioral patterns were categorized into three stages ofpre-spawning, spawning, and Post-spawning behaviors. In Particular, the pre-spawning stage was specified by 11 specific behavioral patterns of aggressive mating behaviors. During the spawning stage, the male and female performed four distinct spawning behaviors including sexual temptation, stimulation, egg spawning, and the separation, and randomly laid about 200 ${\sim}$ 300 eggs on the bottom substrates through the night. After finishing spawning, two adults separated toward their refuges and showed 3 types of post-spawning behaviors such as the resting, occasional eggs protecting, and the egg eating. The fish was identified as a partial-parental care species after the spawning.

• Development and Reproduction
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• v.16 no.3
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• pp.205-217
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• 2012

The ovarian cycle, the biological minimum size, and artificial spawning frequency by artificial spawning induction of the female hard clam, Meretrix petechialis, were investigated by histological observations and morphometric data. The ovarian cycle of this species can be classified into five successive stages: early active stage, late active stage, ripe stage, partially spawned stage, and spent/inactive stage. The spawning period was from June to September, and the main spawning occurred between July and August when the seawater temperature exceeds over $20^{\circ}C$. The biological minimum size (shell length at 50% of first sexual maturity) in females were 40.39 mm in shell length (considered to be two years of age), and all clams over 50.1 mm in shell length sexually matured. In this study, the mean number of the spawned eggs by spawning induction increased with the increase of size (shell length) classes. In case of artificial spawning induction for the clams > 40.39 mm, the number of spawned eggs from the clams of a sized class was gradually decreased with the increase of the number of the spawning frequencies (the first, second, and third spawning). In the experiments of artificial spawning induction during the spawning season, the interval of each spawning of this species was estimated to be 15-18 days (approximately 17 days).

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.81-93
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• 2005

Reproductive cycle with the gonadal phases, first sexual maturity, artificial spawning amount by the size and spawning interval of the hard clam, Meretrix lusoria were investigated by histological observations and morphometric data by artificial spawning induction. Meretrix lusoria is dioecious and oviparous. The reproductive cycle of this species can be classified into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (June to September), and spent/inactive stage (September to February). The spawning period was from June to September, and the main spawning occurred between July and August when the seawater temperature exceeds over $20^{\circ}C$. Percentage of first sexual maturity of female and male clams ranging from 40.0 to 45.0 mm in shell length was over 50%, and all clams over 50.0 mm in shell length sexually matured. Female and male clams ranging from 40.0 to 45.0 mm in shell length are considered to be two years old. Therefore, we assume that the hard clams of both sexes begin reproduction from two years of age. The mean number of the spawned eggs increased with the increase of size (shell length) classes. In case of artificial spawning induction, the number of spawned eggs from the clams of a sized class was gradually decreased with the increase of the number of the 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 15-18 days (average 17 days).

• Korean Journal of Ichthyology
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• v.33 no.1
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• pp.15-21
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• 2021

The Nakdong nose loach, Koreocobitis naktongensis is an endangered freshwater fish endemic to Korea. The spawning behaviour of the K. naktongensis was observed after treating Ovaprim in laboratory aquarium from 20~27 April 2010. The behavioral patterns were categorized into three stages of pre-spawning, spawning and post-spawning behaviors. Before spawning K. naktongensis usually repeated taking a rest and swimming. On average, initial spawning activity started 11 to 12 hours later after injection with Ovaprim. During the spawning period, the number of spawning acts ranged from 1 to 18. The spawning ratio of female to male was 1 : 1. The male embraced the back of the female's dorsal fin with his lamina circularis. It looked like a complete circle at that time. After spawning, parental care was not observed. Individuals not participating in spawning have been observed to feed on some of the fertilized eggs.

• Fisheries and Aquatic Sciences
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• v.18 no.4
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• pp.395-399
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• 2015

We observed seasonality and other characteristics of spawning in the greenling Hexagrammos agrammus off the coast of Tongyeong. Eleven spawning grounds were identified between November, 2013 and January, 2014. The fertilized eggs of H. agrammus were assigned to developmental stages I, II, III, and IV. Based on this classification, we showed that the spawning season extended from the end of October to mid-January. H. agrammus used diverse seaweed species attached to shallow bedrock as spawning substrata that provided good camouflage. Two to seven egg masses were fertilized around the holdfasts of individual seaweeds at depths of 1.2-4.0 m. We identified species-specific reproductive traits of H. agrammus during the spawning season, including strong parental care of the fertilized eggs.

• 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).

• Korean Journal of Ichthyology
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• v.33 no.1
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• pp.8-14
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• 2021

Spawning behavior of the endangered Korean fish, Microphysogobio koreensis, was investigated in the Seomjingang (river), Imsil-gun, South Korea, during the spawning season, April to May 2012. The mating system of M. koreensis, a broadcast spawner, was a primitive spawning mode, and involved one male and one female, unlike group spawning fishes. Spawning behavior of M. koreensis in the wild were observed in eight patterns as resting, male chase, body beating, parallel swim, female withdrawal, male competition, spawning and not guard while spawning behavior in the glass tank were verified in six patterns as resting, male chase, body beating, parallel swim, spawning and not guard. In particular, a behavioral attempt of the pre-spawning stage showed more frequently in the wild than in the glass tank. We assume that difference of spawning behavior might be implication on behavioral restrictions in small and narrow indoor glass tank.

• Fisheries and Aquatic Sciences
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• v.4 no.4
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• pp.208-218
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• 2001

We have investigated the gonad index (GI), gonadal development, reproductive cycle, first sexual maturity, sex ratio, the number of spawned eggs and spawning frequency of the Manila clam, Ruditapes philippinarum. Samples were collected from the intertidal zone of Komso Bay, Korea from January to December in 1999. Monthly changes in the gonad index (GI) and condition index showed a similar pattern in the reproductive cycle. The spawning period was once a year between early June and early October, there was a spawning peak between July and August when seawater temperature was over $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages; early active (February to March), late active (April to May), ripe (April to August), partially spawned (June to October), and spent/inactive stage (August to March). Percentages of first sexual maturity of female and male clams of l5.1-20.0mm in shell length were $56.3\%$ and $60.0\%$, respectively, and $100\%$ for the clams >25. mm. The sex ratio of individuals >15.1 mm in shell length was about 1:1 $(\chi^2= 0.02,\;p>0.05)$. Number of the eggs released from each clam by the induction increased as the size of clam in terms of shell length increased. Mean number of the eggs from the second induction of the spawning was $75.35-84.30\%$ $(average\;79.81\%)$ of the number of the eggs released in the first spawning. Our data indicated that R. philippinarum in Komso Bay has one major spawning peak with over two minor spawning, and the interval of each spawning was estimated to be approximately 15-17 (average 16.5) days.

• Ocean and Polar Research
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• v.40 no.3
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• pp.127-143
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• 2018

This study analyzed the influence of climate change on the spawning ground area of the common squid, Todarodes pacificus. To estimate long term changes in the area of the spawning ground of the common squid, water temperature at 50 m deep that can be inferred from sea surface temperature (SST) based on both NOAA/AVHRR (1981.07-2002.12) and MODIS/AQUA (2003.01-2009.12) ocean color data was analyzed. In addition, five climate indices, Arctic Oscillation Index (AO), Siberian High Index (SH), Aleutian Low Pressure Index (ALP), East Asia Winter Monsoon Index (EAWM) and Pacific Decadal Oscillation (PDO) which are the main indicators of climate changes in the northwestern Pacific were used to study the relationship between the magnitude of the estimated spawning ground and climate indices. The area of the estimated spawning ground was highly correlated with the total catch of common squid throughout four decades. The area of the estimated spawning ground was negatively correlated with SH and EAWM. Especially, PDO was negatively correlated with the area of the spawning ground in the northwestern Pacific (r = -0.39) and in the southern part of the East Sea (r = -0.38). There was a positive relationship between the AO and the area of the spawning ground in the northwestern Pacific (r = 0.46) as well as in the southern part of the East Sea (r = 0.32). Temporally, the area of the winter spawning ground in the southern part of the East Sea in the 1980s was smaller than those areas in the 1990s and 2000s, because the area was disconnected with the western coastal spawning ground of Japan in the 1980s, while the area had been made wider and more continuous from the Korea strait to the western coastal water of Honshu in the 1990s and 2000s.