• 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).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.4
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• pp.320-328
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• 2007

Maturation and spawning of the Pacific cod, Gadus macrocephalus was investigated based on the samples captured in East Sea of Korea from April 2006 to July 2007. Gonadosomatic index began to increase in November, and reached maximum between December and January. After spawning it began to decrease from March. Reproductive season was estimated to November-February, with peak in January. Fecundity was proportional to the size of the female, with the clutch size varying from 753,985 eggs in the smallest female(TL＝58.6cm) to 9,311,520 eggs in the largest(TL＝101.0cm). Size at 50% sexual maturity(TL50%) determined from mature females was 56.3cm of TL. Annual reproductive cycles of this species could be divided into six successive stages; immature stage(March-September), nucleolus stage(September-October), yolk vesicle stage(October-November), vitellogenic stage (November-December), ripe stage and spent stage(December-February).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.2
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• pp.119-124
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• 2008

Reproductive ecology of the snow crab Chionoecetes opilio was investigated in terms of the reproductive organs, abdominal flap, fecundity, and maturity. Specimens were collected with gill nets and trawls from June 2002 to May 2003 in the eastern waters of Korea. The female and male C. opilio are distinguished only by the shape of the abdominal flap, which is triangular in males and circular in females. The gonads of female and male crabs are generally X-shaped. The male gonad is white, while the female gonad appears milk-white after spawning and then turns from light orange to dark orange with maturation. The female gonads matured from June, and mature and immature groups could be distinguished from December to February or March. Brooding eggs changed from bright orange to dark brown with formation of the compound eye immediately before hatching. Accordingly, the main spawning season is February and March. The minimum maturity carapace width of female crabs was 61.1 mm, and the mean fecundity is about 108,300 eggs.

• Korean Journal of Ichthyology
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• v.23 no.2
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• pp.158-162
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• 2011

Growth and spawning ecology of Cobitis lutheri (Teleoste: Cobitidae) were investigated in the Samcheon Stream, Mangyeong River, Jeollabuk-do, Korea from 2005 to 2006. Age group of C. lutheri estimated from the total length indicated that the 40 ~ 60 mm group is 1 year old, the 60 ~ 80 mm group is 2 years old, and the 80 ~ 110mm group is 3 ${\leq}$ years old. The sex ratio (Male/Female) was 0.78, and the female was 20 ~ 30 mm larger than the male. Lamina circularis at the base of pectoral fins in the males as a secondary sexual character was created 12 months after hatching. A change of lateral coloration of males was observed from April to September. The spawning season was early to middle July with water temperatures of $24{\sim}26^{\circ}C$. The average number of eggs was $1,127{\pm}453$ with the egg diameter of $1.09{\pm}0.02$ mm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.1
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• pp.61-66
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• 2022

Amphioctopus fangsiao is a crucial fishery stock located off Korea's western and southern coasts. In this study, we present data on the spawning period and estimated recreational catch of A. fangsiao in the coastal waters of Jeollanam-do, South Korea. The overall sex ratio was estimated to be 1:1.13 (female: male); in females and males, the gonadosomatic index ranged from 1.22 to 12.14 and 0.17 to 3.44, respectively. The breeding season lasted from December to May, with spawning peaks observed between March and May. Furthermore, the estimated total annual recreational catch of A. fangsiao was 185,085 kg, with November recording the highest recreational catch. A. fangsiao catch per unit effort (CPUE) ranged from 3 to 302.4 kg per vessel d^-1. Therefore, these findings underscore the need for additional monitoring, as any further assessment of A. fangsiao stock necessitates an understanding of recreational catch assessment and fishing efforts in Jeollanam- do's coastal waters.

• Korean Journal of Environment and Ecology
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• v.38 no.2
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• pp.143-147
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• 2024

This study aimed to determine the egg-hatching period of boreal digging frogs, Kaloula borealis, and investigate whether the incubation temperature affects the hatching period. In this study, the egg hatching was recorded based on the appearance of the tadpole. The results of this study showed that all the eggs hatched within 48 hours after spawning, with 28.1% (±10.8, n=52) hatching within 24 hours and 99.9% (±0.23, n=49) within 48 hours after spawning. The mean hatching rate of tadpoles showed significant differences depending on the difference in water temperature. The mean hatching rate between 15 and 24 hours after spawning was higher at a water temperature of 21.1 (±0.2) ℃ than at 24.1 (±0.2) ℃. The results suggest rapid hatching occurs at relatively low water temperatures because the spawning habits that spawn eggs in temporary ponds or puddles in the rainy season require rapid hatching before the puddles dry out. The results of this study are helpful for understanding the most suitable temperature conditions for the incubation of eggs of the endangered species, boreal digging frog.

• Korean Journal of Ichthyology
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• v.29 no.3
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• pp.176-189
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• 2017

Age estimation and sexual dimorphism of Coreoleuciscus splendidus were estimated using otolith, length-frequency distribution and 23 morphological measurements, from 245 individuals collected from September 2016, February and April 2017 in the Gapyeong stream, Han River, Korea. Result of age estimation of C. splendidus, we most examined were 2, 3 and 4-age, and the maximum observed ages were 5-age. Nine out of twenty-three morphometric measurements were significantly different between the genders. Anal fin have showing major sexual dimorphism in particular between adult individuals. This sexual dimorphism was based on extension of anal fin soft rays of male individuals. Therefore anal fin of males is always longer and wider than females. During spawning season male individuals possess nuptial tubercles on anal fin rays. However, another measurements and morphological characters does not exhibit sexual dimorphism in the between male and female individuals. The sexual dimorphism was observed to only over 2-years old individuals with sexual maturity. But juvenile and 1-years old individuals do not have sexual dimorphism with sexual maturity. Peak season of spawning was April to May and they start first spawning at 2-age. The ages at major spawning groups were most 3-age, and they maximum GSI index was 14.91 (female), 8.96 (male) at 5-age, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.5
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• pp.477-483
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• 1985

This paper describes seasonal changes of total length, hepatosomatic index (HSI), fatness, egg-diameter composition, and fecundity of the longchin goby Chasmichthys dolichognathus(HILGENDORF). The specimens used were captured in the tide pool of Tongbaekseom, Pusan, Korea from February 1983 to January 1984. The age of longchin goby, tested by size frequency, was believed to be usually one year which grows to 8.0 cm in total length. The annual variations of HSI reached the maximum in the early spring when the gonad was actively growing and decreased during the spawning season from April to July. The coefficients of fatness were represented low values for the spawning periods. Frequency distribution of the egg diameter of mature ovary has three modes: one is the evident mode of the ripe eggs group, and the other two are modes of maturing and immature eggs groups. And an individual is considered as spawns one in the spawning season. Relationships between the fish size in total length (TL cm) and the number of ovarian eggs(F), the fish weight (BW g) and the number of ovarian eggs are indicated by the exponential equation respectively : F=42.585 $TL^{1.608}$, F= 524.589 $BW^{0.475}$.

• Korean Journal of Environment and Ecology
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• v.35 no.2
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• pp.115-125
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• 2021

This study surveyed the population ecology of Acheilognathus chankaensis (Pisces: Acheilognathinae) in the vicinity of the Churyeongcheon (Stream) and Seomjingang (River) in Jeonbuk, Korea, from February 2006 to May 2007. The survey found the habits mainly in the slow-flowing waters having sand, mud, and gravel bottoms. Age groups estimated by the standard length-frequency distribution of the population indicated that the one-year-olds were 30-46 mm long, the two-year-olds were 47-58 mm long, the three-year-olds were 59-68 mm long, and the four-year-olds were longer than 69 mm. The gonadosomatic index (GSI) and the ratio of ovipositor length/standard length were the highest in March (♀: 12.9%, ♂: 5.0%) and in April (46.3%), respectively. The ratio of mature egg diameters that were 1.6 mm was highest in May (13.2%). The comprehensive analysis of spawning characteristics showed that the spawning season was from March to June with water temperatures in 11.5-22.5℃, and the sex ratio of female:male was 1:1.13. The fecundity in the ovaries and the number of mature eggs were 318±174.5 (50~583) and 220±139.2 (50~406), respectively. The size of the mature eggs was 2.04±0.110 mm on the long axis and 1.55±0.100 mm on the short axis for the study period. Gut contents of A. chankaensis were mainly phytoplankton such as the genera Fragilaria, Synedra, Navicular, Cymbella (Bacillariophyceae), and Cosmarium (Chlorophyceae).

• Korean Journal of Environment and Ecology
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• v.36 no.6
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• pp.615-626
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• 2022

This study investigated the habitat characteristics and spawning ecology of Hippocampus haema (Syngnathidae) in Soando Island, Korea, from May 2015 to December 2016. The survey site where seahorses inhabit was mainly formed by seagrass of Zostera marina populations. Total density and biomass (Mean±SE) of Z. marina were the highest at 136±14.4 shoots/m² and 489.8g DW/m², respectively, in spring (May), while the total density was lowest at 93±7.0shoots/m²in autumn (October), and biomass was the lowest and at 122.3g DW/m² in winter (February). During the study period, 293 individuals were identified through a diving and kick net survey, and the total length of H. haema ranged from 10.1 to 87.0mm. Male individuals nurturing fertilized eggs or larvae appeared beginning in May and were collected until October in both 2015 and 2016. Juvenile individuals were captured beginning in July 2015 and June 2016. As a result of a comprehensive analysis of the spawning season characteristics, it was estimated that the spawning season of H. haema was from April to October. The number of fertilized egg or larvae inside the male brood pouch were 38.3±14.8 (20-76), and the number of fecundity identified from female were 47.2±8.6 (31-59). The male-to-female ratio of H. haema was 1:1.7, indicating the dominance of males.