• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.3
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• pp.246-252
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• 2012

The age and growth of the blackthroat seaperch Doederleinia berycoides was investigated based on samples captured in the southern seas of Korea from January to December, 2006. Age was estimated by analyzing otolith growth rings. The spawning period was extrapolated from August to November based on monthly changes in the gonad somatic index. The relationship between total length and otolith radius was analyzed separately for each sex with TL=-15.6174+10.3274R for females and TL=-4.4083+7.0749R for males. From the parameters calculated using average total length and weight when the year ring was formed, the growth of D. berycoides was expressed by von Bertalanffy growth equations as $L_t=34.71(1-e^{-0.2557(t+0.2078)})$, $W_t=713.85(1-e^{-0.2557(t+0.2078)})^{3.1972}$ for females, $L_t=27.37(1-e^{-0.3388(t+0.7362)})$, $W_t=353.91(1-e^{-0.3388(t+0.7362)})^{3.1647}$ for males, and $L_t=34.20(1-e^{-0.2530(t+0.2871)})$, $W_t=674.10(1-e^{-0.2530(t+0.2871)})^{3.1171}$ for pooled sexes, where L is total length at age t.

• 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.33 no.3
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• pp.184-191
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• 2000

Gametogenesis and the reproductive cycle of the marsh clam, Corbicula leana(Prime} were investigated monthly Hyongsan estuary, Korea from January to December 1998 by histological observation. C. leana had separate sexes, and oviparous. The gonads were located between the sub-region of mid-intestinal gland in visceral cavity and reticular cennective tissue. The ovary and testis were composed of a number of ovarian and testicular tubules, respectively, Mature oocytes were characterized by germinal vesicles with nucleoli and their sizes ranged $70\;to\;80{\mu}m$ in diameter. A number of mesenchymal tissues and pigment granular cells were distributed in the growing oocytes and spermatocytes during early developmental stages. With the further development of gonad, these tissuse and cells gradually disappeared. The monthly changes in the fatness index were closely related to reproductive cycle. Minimun size for sexual maturity was reached over 10.0 mm in shell length. The reproductive cycle could be classified into 6 stages : multiplicative (March to April): early growing and growing (May to June), mature (July to August), spent (September), degenerative (October) and recovery (November to February).

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.12
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• pp.1702-1709
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• 2016

The reproductive function of G-protein subunit Galphaq (GNAQ), a member of the G protein alpha subunit family, has been extensively studied in humans and rats. However, no data is available on its status in ruminants. The objectives of this study were to evaluate the expression pattern of the GNAQ in the testis and epididymis of sheep by polymerase chain reaction (PCR). The mRNA expression levels were detected by real-time fluorescent quantitative PCR, and cellular localization of GNAQ in the testis and epididymis was examined by immunohistochemistry. Additionally, GNAQ protein was qualitatively evaluated via western blot, with the results indicating that similarities between GNAQ mRNA levels from sheep was highly conserved with those observed in Bos taurus and Sus scrofa. Our results also indicated that GNAQ exists in the caput and cauda epididymis of sheep, while GNAQ in the testis and epididymis was localized to Leydig cells, spermatogonial stem cells, spermatocytes, Sertoli cells, spermatid, principal cells, and epididymis interstitial cells. The concentrations of GNAQ mRNA and protein in the caput and cauda epididymis were significantly greater than those observed in the corpus epididymis (p<0.01) and testis (p<0.05). Our results indicated that GNAQ exists at high concentrations in the caput and cauda epididymis of sheep, suggesting that GNAQ may play an important role in gonad development and sperm maturation.

• Development and Reproduction
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• v.20 no.4
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• pp.305-314
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• 2016

The marine medaka, Oryzias dancena is a suitable sample as a laboratory animal because it has a small size and clearly distinguishes between female and male. Data on the growth and maturity of the diploid and triploid sea cucurbit species suitable for laboratory animals are very useful for studying other species. Triploidy was induced in the marine medaka by cold shock treatment ($0^{\circ}C$) of fertilized eggs for 45 min, applied two minutes after fertilization. The diploid and triploid male fish were larger than their female counterparts (P<0.05), and the concentrations of thyroid stimulating hormone (TSH) and thyroxine (T4) were higher in the induced triploids over 1 year (P<0.05). In both the diploid and tri-ploid groups the concentrations of TSH and T4 were higher in the male fish than in the females (P<0.05), while the testo-sterone and estradiol-$17{\beta}$ concentrations in the induced triploids were lower than in the diploids (P<0.05). The gonadosomatic index (GSI) of the triploid fish was lower than that for the diploids, and the GSI for females in each ploidy group were higher than that for the males. For both groups the GSI was highest at 4 months of age, and decreased thereafter to 12 months. Analysis of the gonads of one-year-old triploid fish suggested that the induction of triploidy probably causes sterility in this species; this effect was more apparent in females than in males.

• Development and Reproduction
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• v.19 no.4
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• pp.209-215
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• 2015

Red spotted grouper, Epinephelus akaara is a popular aquaculture species in many Asian countries. This species is a protogynous hermaphrodite that first differentiates into female and changes to male later. Due to this reproductive characteristic, stable supply of male and female gametes is a key to the success of seed production in this species. Thus, understanding early gonadal differentiation is required to develop effective sex control techniques. Red spotted grouper were reared in indoor tanks and sampled every 5 days from 40 days post-hatch (DPH) to 130 DPH. Changes of gonadal tissues were examined and analyzed by means of histology. A pair of gonadal primordium has already existed underneath the kidney in the posterior part of the body cavity at 38 DPH when this study began. Gonadal primordia of 38, 40 DPH consisted of germ cells surrounded by a few somatic cells. The blood vessel was observed in the gonadal primordium at 45 DPH. The number of somatic cells and size of gonadal primordium increased age-dependently up to 60 DPH. Formation of ovarian cavity was obvious by two protuberant aggregations of somatic cells at 65 DPH. Completed ovarian cavity and oogonia were first observed in the gonad of one fish sample at 105 DPH. Based on these histological observations, it can be suggested that induction of primary male differentiation could be more successfully applied at around 60 DPH in this species.

• Journal of Aquaculture
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• v.18 no.2
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• pp.76-80
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• 2005

The early gonadal development and sex differentiation of the mandarin fish, Siniperca scherzeri was described from hatch to the 130th day post-hatch (DPH). Primordial germ cells were observed on the just hatched fry (5.10 mm in total length (TL)) and began to protrude into the peritoneal cavity between mesonephric duct and gut. The primordial gonad, with the formation of genital ridge, developed on the 8-10th DPH (10.77-12.47 mm TL). Ovarian differentiation was identified by the presence of ovarian cavity and meiotic oocytes from the 40th DPH (29.75 mm TL). Testicular differentiation was identified by the presence of spermatogonial cells with efferent duct also from the 40th DPH. Sex differentiation of the mandarin fish was identified as gonochoristic type.

• Journal of Ecology and Environment
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• v.30 no.2
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• pp.109-119
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• 2007

The effect of water flow on the growth of Gafrarium tumidum was studied in the field using open cages constructed with stainless steel net and perspex in which holes were drilled. Cages with different flows (25, 50 and 75% of the control) were made by varying the area of perspex being drilled. Reduction in flow rate was directly proportional to the undrilled area, and the mean flow rate of the different treatment groups varied from 3.12 cm/s for the 25% exposure to 12.48 cm/s for the control cages. At the end of the 3-month experiment, no significant differences in sediment characteristics were found among the treatments. Growth in shell length, shell weight and tissue dry weight was, however, positively correlated with flow rate. Percentage increases ranged from $3.0{\sim}8.3%$ for shell length, $9.9{\sim}23.1%$ for shell weight and $17.2{\sim}53.3%$ for tissue dry weight. Condition index of the clam was not significantly different among the treatments. Seston depletion effect could reduce growth in G. tumidum only when water flow was reduced to 25% of the control. G. tumidum also exhibited different responses in shell and tissue growth at low flow rates, in which shell growth continued to decrease as flow rate decreased whereas tissue growth was relatively independent of low flows at 25 and 50% of the control. It was suggested that when seston flux was reduced at slow flows, it would be a better strategy for G. tumidum to channel energy for gonad development instead of shell growth during the reproductive stage.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1000-1006
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• 2021

The maturity and spawning of the common octopus Octopus vulgaris were studied using 317 samples collected monthly from January to December of 2020 from the coastal waters of Yeosu, Korea. The mantle length (ML) of O. vulgaris ranged from 5.1 to 19.7 cm and body weight (BW) ranged from 117.6 to 3,645.4 g. We analyzed monthly changes in sex ratio, gonadosomatic index (GSI), histological maturity stage, and body weight at 50%, 75% and 97.5% group maturity. The sex ratio was 1:1.02, which was not significantly different from the value that expected. Based on histological observation of the gonad development and gonadosomatic index, the spawning periods lasted throughout the year, with peak spawning periods estimated from March to April and July to August. The percentages of sexually mature females estimated using a logistic equation were over 50% at 554.46 g BW, 75% at 1,134.38 g BW and 97.5% at 2,474.22 g BW respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.667-675
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• 2023

The Spanish mackerel Scomberomorus niphonius is an economically important fish species in the southwestern waters of Korea. This study aimed to provide insights into the reproductive biology of this species in the southwestern waters of Korea. We analyzed monthly changes in fork length (FL), maturity stages, and gonadosomatic index (GSI). Moreover, we measured the in FL at sexual group maturity of 50%, 75%, 97.5%, and sex ratio (female vs. male). The overall sex ratio of female and male was 1:0.8. GSI value showed the highest peak in May; however, the spawning period revealed by the microscopic analysis of gonad tissue of S. niphonius was from April to August 2020. The main spawning seasons for the entire populations was from May to June. The fork length at 50% group maturity was 53.3 cm for females and 53.1 cm for males. These results of spawning period of Spanish mackerel highlight the influences of water temperatures that were higher than those in the past, an increase in resource levels, and the level of Pacific anchovy resources flowing into the spawning ground.