• 한국수산과학회지
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• 제53권1호
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• pp.50-56
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• 2020

Determination of the precise size at sexual maturity is very important for science-based stock assessment and fisheries resource management. In this study, two different models, (1) a visual method and (2) a gonadosomatic index (GSI) method, were employed to estimate length at sexual maturity of the small yellow croaker Larimichthys polyactis in the Yellow Sea of Korea. The visual method is a common qualitative method using visual gonadal identification. Conversely, the GSI method is a quantitative method using the GSI, which can be easily and precisely collected. We compared results from these methods to determine the best approach, and to examine the practicality of the GSI method. Logistic regression of the maturity ogive was conducted using a general linear model (GLM) with the R statistics program. Also, the bootstrapped 95% confidence intervals of all estimates were calculated. The best-fit model was the visual method (R_Mc²=0.805, AUC=0.989, L₅₀=15.1). Among models using the GSI method, the model computing GSI_ref=0.94 was the best-fit model (R_Mc²=0.792, AUC=0.989, L₅₀=15.2). There was no significant difference between the two models, evidencing the effectiveness and accuracy of the GSI method.

• 대한수의학회지
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• 제33권2호
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• pp.277-283
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• 1993

In the present study, observations were made on the life-history of Lymnaea viridis under laboratory conditions, involving incubation period of the eggs and their hatching rate, shell length of the newly hatched snails, sexual maturity, size of the snails when the snail produced the first egg-mass, the number of eggs in each egg-mass, egg-laying, ovipostion, growth rate of the snails, and longevity of the snail. At temperatures between $19.8^{\circ}C$ to $22.5^{\circ}C$, incubation period of the eggs occupied 10~12 days, and after beginning of hatching, all young snails emerged completely from the egg-mass within 5 days. The hatching rate was 88%. The average shell length of the newly hatched snails was about 0.064cm. The rate of growth was extraordinarily rapid under good laboratory conditions. When two snails were reared in one culture vessel($20{\times}15{\times}5cm$) with blue-green algae at about $22^{\circ}C$, snail growth was optimal, taking 37 days to reach 1.2cm in shell length. Sexual maturity reached in about 19 days. The size of the snails at sexual maturity was $0.78{\pm}0.05cm$ in length and $0.47{\pm}0.04cm$ in width. The first egg-masses produced were $0.59{\pm}0.22cm$ in length and $0.34{\pm}0.08cm$ in width, and contained 7~38 eggs. The eggs are usually laid in water. The egg-laying was affected by food and temperature. Snails fed with blue-green algae at about $22^{\circ}C$ produced larger egg-masses than the snails fed with fish food at about $26^{\circ}C$. Under conditions of continuous activity and growth, the maximum expectation of life appears to be 109~350(mean 230) days. And the shell length of snails at death were 1.39~1.64cm.

• 한국어류학회지
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• 제19권2호
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• pp.101-106
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• 2007

본 연구는 2003년 3월부터 2004년 4월까지 강원도 연안에서 유자망어업에서 어획된 대구횟대를 매월 채집하여 성숙과 산란에 관하여 조사한 것이다. 대구횟대의 산란기는 생식소성숙도지수, 난경 등의 월별 변화에 의한 결과 12월에서 이듬해 2월로 추정되어졌다. 체장과 포란수와의 관계는 $F=285.11TL^{1.4092}$ ($R^2$=0.571)이었으며 체중과 포란수와의 관계는 $F=1.449.8BW^{0.5514}$ ($R^2$=0.577)이었으며, 포란수는 어체가 커질수록 증가하였다. 최소포란수로 8.814립 (TL: 14.7 cm), 최대포란수는 28,560립 (TL: 24.4 cm)이었다. 최소성숙체장은 15 cm였으며, 이때의 나이는 약 2세였다. 체장계급별 성비는 소형어에서는 수컷이 약간 우세하였으나 24 cm 이상에서는 암컷이 90%로 높게 나타났다.

• 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.

• 한국어류학회지
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• 제22권2호
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• pp.83-89
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• 2010

본 연구는 우리나라 남해안에 서식하는 문치가자미(pleuronectes yokohamae)의 성숙과 산란에 관한 연구로, 2006년 5월부터 2007년 4월까지 경남 남해군 연안 호망어업과 연안자망에서 어획된 것을 무작위로 채집하여 조사하였다. 암컷의 생식소 발달과정 및 생식소 중량지수의 월 변화로부터 문치가자미의 산란기는 11~2월, 주 산란기는 12~1월로 추정된다. 전장(TL)과 포란수(F)간의 관계식은 $F=3.656TL^{3.518}$ ($R^2$=0.872)이며, 체장이 커질수록 포란수도 증가하는 경향을 보였다. 산란에 참여하는 50% 성숙체장은 전장 19.8 cm이었다. 전 조사기간에 대한 성비(암 수)는 55.2:44.8로 암컷이 우세하였고, 체급별 성비는 전장 25 cm 이하에서는 수컷의 비율이 높았으나 체장이 커질수록 암컷의 비율이 증가하여 32 cm 이상에서는 전 출현개체수가 암컷이었다.

• 한국수산과학회지
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• 제47권3호
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• pp.255-263
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• 2014

We investigated the reproductive characteristics of Lycodes tanakae in the coastal waters of the middle East Sea to elucidate the species' population structure. We investigated Lycodes tanakae maturation and spawning based on samples collected by Danish seine and gill nets from January 2012 to December 2013. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), egg diameter, fecundity, and total length at 50% group maturity. The spawning period was December to February, while fecundity ranged from 1,677 eggs at 57.3 cm (total length;TL) to 6,445 eggs at 75.7 cm. The relationship between TL and fecundity (F) was $F_e=6E-05TL^{3.127}$ ($R^2$ = 0.516), and F increased with increasing TL. We estimated the TL at 50% group maturity as 60.4 cm for females and 59.8 cm for males. This study is the first report of Lycodes tanakae reproductive characteristics in the coastal waters of the middle East Sea.

• Fisheries and Aquatic Sciences
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• 제23권6호
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• pp.16.1-16.10
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• 2020

This study was conducted in Lake Hayq between January and December 2018. The objectives of this study were to determine the growth, condition, sex ratio, fecundity, length at first sexual maturity (L₅₀), and spawning seasons of common carp (Cyprinus carpio). Monthly fish samples of C. carpio were collected using gillnets of stretched mesh sizes of 4, 6, 7, 8, 10, and 13 cm and beach seines of mesh size of 6 cm. Immediately after the fish were captured, total length (TL) and total weight (TW) for each individual were measured in centimeters and grams, respectively, and their relationship was determined using power function. Length at first maturity (L₅₀) was determined for both males and females using the logistic regression model. The spawning season was determined from the frequency of mature gonads and variation of gonadosomatic index (GSI) values of both males and females. Fecundity was analyzed from 67 mature female specimens. The length and weight relationship of C. carpio was TW = 0.015TL^2.93 for females and TW = 0.018TL^2.87 for males that indicate negative allometric growth in both cases. The mean Fulton condition factor (C_F) was 1.23 ± 0.013 for females and 1.21 ± 0.011 for males. The value of C_F in both cases was > 1 that shows both sexes are in good condition. Among the total 1055 C. carpio collected from Lake Hayq, 459 (43.5%) were females and 596 (56.5%) were males. The chi-square test showed that there was a significant deviation between male and female numbers from 1:1 ratio (χ²= 22, df = 11, P > 0.05) within sampling months. The length at first sexual maturity (L₅₀) for females and males were 21.5 and 17.5 cm, respectively. Males mature at smaller sizes than females. The spawning season of C. carpio was extended from February to April, and the peak spawning season for both sexes was in April. The average absolute fecundity was 28,100 ± 17,462. C. carpio is currently the commercially important fish while Nile tilapia fishery has declined in Lake Hayq. Therefore, this baseline data on growth, condition, and reproductive biology of common carp will be essential to understand the status of the population of carp and design appropriate management systems for the fish stock of Lake Hayq, Ethiopia, and adjacent countries.

• 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.

• 한국수산과학회지
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• 제53권1호
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• pp.98-102
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• 2020

We examined the comparative spawning ecology of daggertooth pike conger Mureanesox cinereus and common pike conger M. bagio in the South Sea of Korea from May 2018 to December 2019. In the South Sea of Korea, the mean total length (TL) of M. cinereus was significantly smaller than that of M. bagio. The sex ratios of both species were skewed toward females. The spawning period of M. cinereus was from June to October, while the spawning period of M. bagio was from August to October. The lengths at 50%, 75%, and 97.5% sexual maturity of M. cinereus females were estimated as 54.6 cm, 60.4 cm, and 74.1 cm TL, respectively. It was not possible to estimate lengths at sexual maturity for M. bagio in the South Sea of Korea due to the absence of immature stages.

• 한국양식학회지
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• 제22권1호
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• pp.92-99
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• 2009

대하새우 양식장에 서식하는 곤쟁이 Neomysis japonica (Ishikawa and Oshima, 1951)의 개체군 역학과 성 성숙에 관한 전반적인 생물학적 정보를 밝히기 위해 2002년 10월부터 2003년 9월까지 12개월 동안 매월 1회씩 충남 태안군 남면 당암리에 소재한 순천향대학교 해양수산연구소의 대하새우 양식장에서 표본을 채집하였다. 개체군의 특성을 알기 위해 성비, 성 성숙도, 포란수 그리고 성장계수 등을 조사하였다. 암컷이 수컷에 비해 월별 성비가 높았고, 평균 갑각장은 수컷($2.42\;mm{\pm}0.52$)이 암컷($2.31\;mm{\pm}0.48$)보다 높았으나 모두 오차 범위내에서 차이를 보여 갑각장의 크기는 통계학적으로 유의하지는 않았다. 암컷은 성체의 크기가 큰 개체가 많은 난을 포란하였으며, 암컷의 50%가 포란하는 체장은 4.48 mm였다. von Bertalanffy, 성장 매개변수를 바탕으로 한 계절별 성장 속도는 암컷이 수컷보다 빨랐으며, 양식장내에 서식하는 개체군은 일년 중 2회의 가입을 하는 것으로 나타났다. 암컷과 숫컷의 상대성장을 회귀직선 방식으로 비교한 결과수컷의 성장속도가 암컷보다 조금 빨랐다.