• Animal cells and systems
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• 제11권2호
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• pp.227-234
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• 2007

Spermatogenesis, the reproductive cycle, and the size at first sexual maturity in male Mactra chinensis were investigated by cytological and histological observations. The spermatozoon exhibits a primitive type morphology and is similar to those of other bivalves in that it contains a short midpiece with four mitochondria surrounding the centrioles. The morphologies of the sperm nucleus type and the acrosome shape of this species are cylindrical and modified cap-like, respectively. The spermatozoon is approximately $40-45\;{\mu}m$ in length including the sperm nucleus (about $1.46\;{\mu}m$), acrosome (about $1.20\;{\mu}m$) and tail flagellum. The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure. The spawning period of this species lasts from June to September, and the main spawning occurs in July and August, when the seawater temperature is greater than $20^{\circ}C$. The percentage of individual male clams at first sexual maturity was 56.5% for those whose shell lengths were 35.1-40.0 mm, and 100% for over 45.1 mm. Accordingly, harvesting clams <35.1 mm in shell length could potentially cause a drastic reduction in recruitment, and a measure indicating a prohibitory fishing size should be taken for adequate fisheries management.

• 한국수산과학회지
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• 제56권5호
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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.

• 수산해양기술연구
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• 제54권4호
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• pp.353-359
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• 2018

Basic reproductive biology of the daggertooth pike conger, Muraenesox cinereus were investigated based on the samples from August 2015 to December 2017 in Korean waters. A total of 2,328 samples was collected (1,593 females and 735 males) during the study period. The mean anal lengths (AL) were $33.5{\pm}9.2cm$ in females and $26.2{\pm}7.3cm$ in males respectively. The females were larger than males in AL (p < 0.05). Sex ratio was 2.2:1 in female to male (p < 0.05). The gonadosomatic index (GSI) varied monthly. GSI of female reached the maximum in July 2016 and June 2017 and the minimum in October 2016 and September 2017 respectively. The spawning period was from June to October. The size at sexual maturity ($L_{50}$) of females was estimated at 24.9 cm in AL (63.5 cm in TL).

• 한국수산과학회지
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• 제55권6호
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• pp.927-937
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• 2022

The reproductive characteristics of Pacific anchovy, Engraulis japonicus were investigated using samples randomly collected from the southern waters of Korea between January and December 2021. We analyzed monthly changes in maturity stages, gonadosomatic index (GSI), egg diameter, fecundity, and fork length (FL) at sexual groups maturity of 50%, 75% and 97.5%, and sex ratio (female:male). GSI value showed two peaks in May and August; however, microscopic analysis of E. japonicus gonad tissue revealed that the spawning period was from March to October. The main spawning seasons for the entire populations were from April to June and August to September. The overall sex ratio was female-biased (1 females, 0.89 male). The fecundity (F) of female anchovies ranged from 429 eggs at an FL of 8.0 cm to 13,824 eggs at an FL of 14.9 cm and the relationship between FL and F was 0.0788FL^4.422. The FL at 50% group maturity was 8.26 cm for female anchovies. Based on the results, we suggest that the reproductive cycle in Pacific anchovies may be related to pulses in water temperature and the sexual cycle of the fish.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.421-424
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• 2005

Discusses the results of an investigation of the relationship between maturity in field-cured specimens and that from the thinner dimension structure to thick, particularly at cold weather concrete. Tests were carried out on two different concrete mixes with 28 day compressive strengths ranging approximately 30MPa. Ready-mixed concrete was used, and test specimens were the conventional field-cured 10$\times$20cm concrete cylinder with insulating materials and without them, and test structures were the thinner(width 20cm), the general(width 40cm), the thick dimension(width 60cm), respectively. Tests were performed at age of 3, 7, 14, 28 day. Analyses of test results show that the maturity of concrete for require compressive strength was suggested to be keep higher than $164D^{circ}D$ until at least from 8day to 10day

• 한국수산과학회지
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• 제53권1호
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• pp.36-42
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• 2020

The maturation and spawning of white crocker Pennahia argentatus were investigated using samples collected in the Southern Sea of Korea from January to December 2018. We analysed monthly changes in maturity stage, gonad-osomatic index (GSI), total length (TL) at 50% group maturity. The spawning period was May to July. Fecundity varied between 71,627 and 888,041 eggs. The relationship between the fecundity and TL of the fish was expressd in the fecundity equation as F=0.2198TL^4.2784 (r²=0.8423). The percentage of sexually mature females estimated from a logistic function was over 50% for the size group 19.33 cm (total length, TL).

• 한국수산과학회지
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• 제55권5호
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• pp.575-582
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• 2022

This study revealed the reproductive biology of pointhead flounder Cleisthenes pinetorum, in the middle of the West Sea of Korea. We collected samples using gill net and drag net fisheries in coastal waters from January to December 2019. Mmonthly gonodosomatic index and maturity stage results showed that the spawning period was October to December, and the females grew faster than the males. The fecundity ranged from 16,728 to 1,039,616 number of eggs, and the relationship between TL and fecundity (F) was 0.0000003TL^4.7434 (R²=0.4898). The size-frequency distribution of eggs suggested that C. pinetorum spawm once during a spawning period. The length at 50% maturity for females was estimated to be 18.9 cm.

• 한국어류학회지
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• 제35권4호
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• pp.333-339
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• 2023

이번 연구는 인천 연안에 서식하는 쥐노래미(Hexagrammos otakii)의 성비, 성숙체장, 산란기를 구하였다. 암수성비는 1 : 1.2 (n=739 : 906, 전체 개체군의 81.6% 차지)로 암수 출현비율은 통계적 차이를 보이지 않았다. 쥐노래미 암컷의 생식소숙도지수(GSI) 값은 11월에 가장 높았고, 수컷은 10월에 가장 높게 나타났고, 산란기는 10월에서 1월로 추정되었다. 쥐노래미 암컷의 50% 성숙체장은 23.1 cm로 분석되었다.

• 한국양식학회지
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• 제13권3호
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• pp.245-251
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• 2000

1997년 12월부터 1998년 3월까지 경상북도 영덕~울진 인근 해역의 수심 170~250 m에서 채집된 대게, Chionoecetes opilio의 크기조성에 따른 생태학적인 특징과 성숙에 대해 연구하였다. 갑폭 조성에서, 암컷과 수컷의 주 출현개체군은 각각 70~80 mm (60.1%), 80~90 mm (64.2%) 체급군이었다. 갑장 및 갑폭의 관계 (암컷 CL=0.951 CW+0.2033, 수컷 CL=0.9387 CW+2.0811)는 암수 모두 갑장에 비해 갑폭이 약간 끈 것으로 나타났으며, 갑폭과 체중의 관계 (암컷 BW=0.0123 CW$^{2.1693}$ , 숫컷 BW=0.0056 CW$^{2.3694}$)에서 체중의 변화는 동일 체급군에서 숫컷이 암컷보다 무겁게 나타났다. 또, 갑폭 64.9-96.0 mm에서 암컷의 평균 포란수(F=8.5285 CW$^{2.0498}$ )는 35,000~114,000개로 조사되었다. 갑폭에 대한 성숙개체 (암컷 외포란 및 난소 발달, 수컷 : vasa deferentia 관찰)의 비율은, 암컷의 경우 갑폭 54.2 mm 에서 약 50%, 갑폭 60.1 mm 이상에서는 100%였으며, 갑폭 42.3 mm 이하에서는 성숙개체가 관찰되지 않았다 수컷의 경우는 갑폭 58.8 mm, 72.0 mm 이상에서 각각 50%, 100%의 성숙개체 출현율을 나타냈으며, 갑폭 48.4 mm 이하에서는 성숙개체가 관찰되지 않았다.

• Ocean and Polar Research
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• 제39권4호
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• pp.279-292
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• 2017

We determined the maturity and growth of the Marbled sole, Pseudopleuronectes yokohamae based on monthly sampling in the West Sea of Korea from February 2009 to December 2010. Determination of sex of P. yokohamae was by gonadal inspection, and age and growth were determined by analyzing the otolith. The biological minimum size of P. yokohamae female was 24.5 cm. The seasonal changes in the ratio of a translucent zone to an opaque zone revealed that the end of the translucent zone of the otolith were annuli formed in May once a year. We compared 8 type growth equations with several length-at-age data. By using the length-at-monthly age data of these, the calculated von Bertalanffy growth equations were $L_t=41.7(1-e^{-0.47(t+0.24)})$ for females and $L_t=32.7(1-e^{-0.75(t+0.01)})$ for males. We estimated that 24.5 cm was the total length of 2 year old P. yokohamae spawns in the cold water season from January to April, and grows to 8 years old for females and 6 years old for males in the West Sea of Korea.