• 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.

• Journal of Aquaculture
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• v.16 no.3
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• pp.179-186
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• 2003

Reproductive cycle, gonadal development and the spawning period of the Korean anchovy Coilia nasus were investigated by histologhical observations. Samples were collected at the coastal area of Geumgang dyke which is connected to Gunsan and Janghang, Korea, from February 2002 to January 2003. C. nasus is dioecious; the ovary consists of a pair of saccular structure with many ovarian lobules, and the testis consists of a pair of lobular structure with many testicular lobules and connected to the posterior seminal vesicle. Monthly changes in the gonadosomatic index (GSI) began to increase in April when seawater temperature increased and reached the maximum in June when the ovary was getting mature, the summer season of longer day length with higher water temperature. The reproductive cycle can be classified into five successive stage in females: early growing stage (February to March), late growing stage (March to April), mature stage (May to June), ripe and spent stage (June to July), and recovery and resting stage (July to January): in males, the cycle can be divided into four successive stages; growing stage (February to April), mature stage (May to July), ripe and spent (June to July), and recovery and resting stages (July to January). According to the frequency distributions of egg diameters in the spawning season. C. nasus is presumed to be summer spawning species and polycyclic species to spawn 2 times or more during the spawning season.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.1
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• pp.8-16
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• 1998

Sexual maturation and reproductive cycle of the goldeye rockfish, Sebastes thompsoni were investigated under photomicroscopy. Samples were collected monthly in the coastal water of Samcheonpo ($34^{\circ}55'N$ ), Korea from November 1995 to October 1996, The ovary consists of several ovarian lamellae originated from ovarian outer membrane. Oogonia which are originated from the inner surface of the ovarian lamella protrude to the ovarian cavity in oocyte stage, and they ave suspended by the egg stalk. The testis is seminiferous tubule type in internal structure. Seminiferous tubule consists of many testicular cysts which contain numerous germ cells in same developmental stage. Biological minimum size of female and male were 19.5 cm and 21.5 cm in total length, respectively. Gonadosomatic index (GSI) of female was the highest (9.56) in March and the lowest (0.15) in August. GSI of male was the highest (0.25) in February and the lowest (0.04) in July. Reproductive cycle was classified into the following successive stages: in female, growing (October and November), maturation ( $December\~February$), gestation (March), parturition and recovery ($April\~June$) and resting ($July\~September$), and in male, growing ($September\~November$), maturation ( December and January), ripe and copulation ( February and March) and degeneration and resting ($April\~August$).

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.672-681
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• 2019

The ecological characteristics of Sargassum macrocarpum, an ecologically and commercially valuable brown alga, were investigated from May 2018 to June 2019 in Jeju Island, Korea. The S. macrocarpum population formed patches at depths of 3-5 m. Growth in the length of the alga reached a maximum of 135.3±20.0 cm in June. The weight of the alga reached a maximum of 3.6±2.1 kg·wet-wt in May. The mean density and biomass of S. macrocarpum was 4.5 individuals·m^-2 and 4.6 kg·wet-wt.·m^-2 in their habitat. Receptacles were observed from April to August and egg release was detected from June to July when the seawater temperatures were 19.3-22.9℃. The developmental initiation of thalli occurred at temperatures above 14.1℃ and maturation required approximately 726.3 degree-days. The reproductive allocation of this alga, calculated from the reproductive frond length(RFL) and reproductive frond weight(RFW) indices to the whole length and weight, reached a maximum of 69.3% in June. The growth and maturation patterns of S. macrocarpum could be divided into vegetative growth (October-January), maturity preparation (February-April), maturation (May-June), egg release (June-July), and resting period (August-September). This was the first study to examine an S. macrocarpum population throughout the entire year in a natural habitat in Jeju Island, Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.167-176
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• 1991

Sexual maturation of the bluespotted mud hopper, Boleophthalmus Pectinirostris(Linnaeus) was investigated histologically on the gonadal development, and studied by gonadosomatic index(GSI), egg diameter composition. Samples were collected in the intertidal zone of Wolyon-ri, Hoihyon-myon, Okku-gun, Chollabuk-do, Korea, from April to October in 1988 and from June to August in 1989. The ovary is a pair of sac-shaped organ. The testis is a pair of tubule-shaped organ and it is connected to the seminal vesicle which is located at the posterior end of the testis. In male and female, GSI began to increase from late May when the water temperature began to increase and reached the maximum value in June and July, respectively. It began to decrease from August, the highest water temperature season. Thereafter, maintained relatively low values until October. The annual reproductive cycle of this species could be classified into four sucessive developmental stages: growing stage$(April{\~}May)$, mature stage$(June{\~}early\;July)$, ripe and spent stage(late lune-early August), degenerative and resting stage$(late\;August{\~}March:\;the wintering\;period)$. According to the frequency distributions of egg diameters in the spawning season, Boleophthalmus Pectinirostris was species to spawn twice or more in the spawning season.

• Journal of Aquaculture
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• v.8 no.1
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• pp.1-19
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• 1995

In red seabream, Pagrus major the female specific protein in the vitellogenic female serum was identified by Ouchterlony's immunodiffusion test and immunoelectrophoresis. The female specific serum protein might be vitellogenin based on the results of the immunological analysis for the male and vitellogenic female sera and crude egg extracts. Also, it was identified by the immunodiffusion test that the purified yolk protein from ovarian egg extracts has antigenic identities shared with the female specific serum protein. To study the relationship between the maturational stages of gonad and plasma levels of vitellogenin, these were measured from the late resting period (January) to the vitellogenic preiod (April) by the modified enzymeimmunoassay (EIA) using antiserum against yolk protein. The level of plasma vitellogenin began to increase in February (previtellogenesis stage) and continuously increased with the ovarian growth during the vitellogenesis period (March to April). The plasma vitellogenin levels were significantly different between the females and the males in February. Validation for the modified EIA system. was tested .The absorbance curve of serial dilutions of serum from the vitellogenic female was paralleled to the standard curve of yolk protein; $109\pm5.6\%$ recovery was achieved by the modified EIA. And the intraassay coefficients of variation were less than 10% within the concentration ranging from 31.3 ng/ml to 1,000 ng/ml. These findings suggest that the sex determination in adult red seabreams could be possible by using the modified EIA as early as in February.

• Development and Reproduction
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• v.21 no.3
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• pp.297-305
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• 2017

An experiment was conducted to investigate the annual reproductive cycle of a Korean endemic species, Acheilognathus majusculus, from Jeokseong-myeon located in Seomjin River. The reproductive cycle is examined histologically regarding water temperature and day length of the habitat, the gonadosomatic index (GSI), the female ovipositor length index (OLI), monthly variation in egg diameter distribution, and developmental characteristics of female and male gonads. The maximum GSI was found in $19.21{\pm}2.32$ and $6.90{\pm}0.53$ for female and male respectively when water temperature ($14^{\circ}C$) and day length (11.1hr) began to rise. On the other hand, the minimum level was reached during August ($1.87{\pm}0.67$ for female and $0.88{\pm}0.50$ for male). No samples represent with measurable ovipositor between September and November, while the longest ovipositor length index was in April ($79.68{\pm}4.69%$). We compared and calculated the stages of testis and ovary development process in order to determine the germ cell development characteristics and the reproductive cycle. According to the result, we classified the female Acheilognathus majusculus reproductive cycle into four stages: Ripe (April) and spawning phase (May to June), degenerative phase (July), growing phase (August to December), and mature phase (January to March). The annual reproductive cycle of male Acheilognathus majusculus was categorized into five stages viz. Ripe and spawning phase (May to June), degenerative phase (July to August), resting phase (September to November), growing phase (December to February), and mature phase (March to April).

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.395-404
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• 2000

The gonadosomatic index (GSI), hepatosomatic Index (HSI), egg size distribution, gonad development and reproductive characteristics of venus fish, Aphyocypris chinensis, were examined during March 1997- March 1998 in agricultural waterways of the Sedo-myun, Puyo county, Chungnam Province, Korea. Annual reproductive cycle was classified into the following five successive phases by monthly changes in GSI and the characteristics of ovary: quiescent phase (January- February), secondary growing and mature phase (March-May), ripe and spawning phase (June-July), degenerating and resting phase (August-September) and primary growing phase (October-December). The hepatosomatic index (HSI) showed clear seasonal pattern with two separate peaks. However, it exhibited a negative correlation to changes of GSI values. The regression analysis suggested that fecundity showed a strong positive linear relationship ($r^2\;=\;0.91$, n = 34) with body weight. The sex ratio of female to male was 1.4 : 1 in the natural population during the study. The minimum reproductive size of female and male venus fish was 38 mm and 33 mm in fork length, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.27-35
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• 2020

Filefish Thamnaconus modestus has seen a sharp decline in their catch, we must strive for continuous resource management. We investigated the maturation and spawning of T. modestus by trawl net and set net from January 2018 to November 2019, off Jeju Is. and in coastal waters of North Gyeongsang Province's Korea. We analyzed monthly change total length (cm), gonadosomatic index (GSI) and maturity stages, egg diameter (mm), the relations fecundity and total length. GSI for Jeju Is. was the highest in April (3.17, 2.43), and decreased from July to 1.73 in August and GyeongBuk's GSI was the highest in Apri l (1.86, 2.58), followed by the high in May and the sharp decline in September, which is 0.23. Using a histological method, the annual reproductive cycle of T. modestus can be divided into 5stage in females; the early growing stage (Jan.-Mar.), late growing stage (Apr.-May), Mature stage, spent stage (Oct.), Recover and resting stage (Nov.-Jan.).We estimate the TL at 50% maturity as 24.1cm for female, fecundity ranged from 560,044 eggs at 23.4cm total length to 1,580,387 eggs at 36.6.cm TL.

• Ocean and Polar Research
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• v.44 no.4
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• pp.319-329
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• 2022

The paramyxean parasite Marteilioides chungmuensis infects the cytoplasm of the eggs of Pacific oysters Crassostrea gigas , resulting in spawning failure of the infected females. Such infected eggs appear as bump-like nodules on the body in late fall when most of the uninfected females complete spawning. In this study, we estimated the quantity of the infected eggs using an enzyme-linked immunosorbent assay (ELISA), which is destroyed by M. chungmuensis parasitism. In December, the infected oysters collected from Tongyoung on the south coast exhibited numerous yellowish bump-like nodules as signs of infection. In histology, the infected oysters exhibited mature eggs in the follicle, which were heavily infiltrated by hemocytes. ELISA indicated that the infected egg mass accounted for 7.52±5.50 percent of the body weight, suggesting the ovarian parasite causes substantial reproductive loss. Histology also indicated that the infected oysters are in a poor nutritional condition, as the digestive gland atrophy (DGA) level is comparatively higher than the uninfected oyster. The total carbohydrate contents in the infected oysters (108.68±44.41 mg/g dry wt) were significantly lower than in uninfected oysters (269.76±50.97 mg/g dry wt), suggesting that M. chungmuensis parasitism also affected the energy storage capacity of the host during the resting stage.