• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.345-358
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• 1982

1980.8-1982.8월까지 일광, 주문진, 돌산, 어청도 및 성산포에서 채집한 1,663미의 보라성게의 성장 및 산란에 관한 조사이다. 1세부터 5세까지의 평균각경은 가각 19, 32, 43, 51, 58mm로 추정됐으며 $l_\infty=84.4 mm,\;k=0.223,\;t_o=-0.187$의 성장식을 보였다. 가경에 대한 각고, 보대, 간보대, 위홍문부경 및 극 길이의 상관관계는 매우 높았다. 연령에 따른 가부분의 상대성장은차이가 없으나 극의 성장에서는 3세까지는 각경에 비례하여 성장하나 그 이후의 연령부터는 반비례하고 있다. 일광해역에서의 산란은 6-10월에 일어나며 주 산란은 8월로 사료한다. 연령에 따른 주 산란시기는 다르며 고연령군은 저연령군 보다 일찍 산란하고 있다. 제주산 보라성게는 8월 이전에 산란을 이미 마친 상태이며 여수산, 일광산은 주로 8월에, 주문진산, 어청도산은 8월 이후에 산란하는 것으로 판단된다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.535-544
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• 2015

Yield per recruit model is the most popular method for fisheries stock assessment. However, stock assessment using yield per recruit model can lead to recruitment overfishing as this model only considers the maximum yield per recruit without spawning biomass for reproduction. For this reason, spawning biomass per recruit model which reveals variations of spawning stock biomass per fishing mortality (F) and age at first capture ($t_c$) is considered as more proper method for stock assessment. There are mainly two methods for spawning biomass per recruit model known as age specific selectivity method and knife-edged selectivity method. In the knife-edged selectivity method, the spawning biomass per recruit has been often calculated using biomass per recruit value by multiplying the maturity ratio of the recruited age. But the maturity ratio in the previous method was not considered properly in previous studies. Therefore, a new method of the knife-edged selectivity model was suggested in this study using a weighted average of the maturity ratio for ages from the first capture to the lifespan. The optimum fishing mortality in terms of $F_{35%}$ which was obtained from the new method was compared to the old method for small yellow croaker stock in Korea. The value of $F_{35%}$ using the new knife-edged selectivity model was 0.302/year and the value using the old model was 0.349/year. However, the value of $F_{35%}$ using the age specific selectivity model was estimated as 0.320/year which was closer to the value from the new knife-edged selectivity model.

• Korean Journal of Poultry Science
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• v.47 no.4
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• pp.237-245
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• 2020

This study investigated the effects of breed, laying age, and egg storage period on hatching performance. Eggs were collected from early laying period (27 to 29 weeks old) and late laying period (50 to 52 weeks old) in Hwanggalsaek Jaeraejong, Korean Rhode Island Red, and Korean White Leghorn chicken breeds. Eggs laid for each period were stored for 3, 7 and 14 days and then hatched. Fertility, hatchability, and embryonic mortality were observed to determine the hatching performance. The results showed that hatching performance was affected by breed, laying age, and egg storage period with independently or interactively. The Korean Rhode Island Red breed had the lowest hatching performance. Hatchability and early embryonic mortality rate increased in early laying period eggs compared to the late laying period, but the late embryonic mortality rate increased in late laying period eggs. Additionally, hatching performance decreased as the egg storage period increased. Using breed-specific hatching management techniques, avoiding late laying period eggs, and shortening the egg storage period to seven days after laying may improve the hatching performance.

• Korean Journal of Poultry Science
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• v.43 no.4
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• pp.253-261
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• 2016

Egg quality is a very important factor for both consumers and producers. Factors affecting egg quality include strain and age of hens; egg storage temperature, time, and humidity; laying season; and feeding. This study aimed to determine the effect of hen age and egg storage time on egg quality. A total of 700 eggs obtained from Hyline Brown commercial layers were used for this experiment, and they were separated into two hen age groups (30 vs. 60 weeks) with eight treatments and four storage times (day 0, 10, 20, and 30). The egg weight; shell color, thickness, and density; albumen height; Haugh unit (HU); yolk color; and the yolk and albumen pH and viscosity were measured for the egg quality assessment. The results showed that the age of the hen and egg storage time significantly affected almost all parameters of the internal and external egg quality. The shell thickness, albumen height, HU, yolk color, pH of yolk and albumen, and yolk viscosity significantly decreased with increasing hen age. The egg shell color was significantly lighter in eggs from 60-week-old hens than in those from 30 weeks-old hens. The egg weight; shell weight, thickness, and density; albumen height, HU; and albumen viscosity significantly decreased, but the yolk color and pH of the yolk and albumen increased with increasing egg storage time. The interaction effects between the storage time and hen age were significant in shell thickness, albumen height, yolk color, and yolk and albumen pH and viscosity. The eggs obtained from 60-week-old hens showed significantly lower shell thickness, albumen height, and HU values, which are considered typical egg quality measurements, than values of eggs from 30-week-old hens. Therefore, increasing hen age and egg storage time caused the deterioration of egg quality. In conclusion, this study demonstrated that hen age is the major factor affecting the quality of fresh eggs, whereas the storage time is the determinant factor affecting the quality of stored eggs.

• Korean journal of applied entomology
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• v.34 no.1
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• pp.70-74
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• 1995

A study on seasonal changes in age structure and fecundity of Gryllotalpa africana Palisot de Beauvois was conducted in Suwon from 1991 through 194. It seemed that most of newly hatched nymphs emerge to adults in September and October, so have a life cycle a year, and some overwinter as nymphs and emerge to adults from August, so have a life cycle tow years. The mean number of eggs per cell was $36.00\pm$2.84 for egg cells laid in the laboratory, and $47.68\pm$4.35 for egg cells collected in the field. Mean and range of the numbers of egg cells produced per female were $1.17\pm$0.19 and 0~3.

• KOREAN POULTRY JOURNAL
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• s.94
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• pp.90-94
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• 1977

양계경영에 있어서 점등관리는 닭의 발육, 성 성숙, 산란성과 밀접한 관계를 갖고 있으며 육성기와 산란기의 적절한 점등관리는 닭의 품종, 계통, 연령 및 능력에 못지 않게 중요하다. 광선이 닭에 주어지면 시신경을 통하여 뇌하수체 전엽에 자극이 주어져서 성선자극호르몬이 분비되며 그 호르몬의 작용에 의하여 배란이 일어나게 된다. 이러한 닭의 감광성을 이용하여 산란을 촉진하게 하는 것이 점등관리인 것이다.

• Korean Journal of Poultry Science
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• v.48 no.1
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• pp.1-12
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• 2021

We investigated the effects of breed, laying age, and egg storage period on the vitality of chicks using the Hwanggalsaek Jaeraejong, Korean Rhode Island Red, and Korean White Leghorn chicken breeds. Their eggs were collected during the early laying period (27~29 weeks) and late laying period (50~52 weeks) and were stored for 3 days, 7 days and 14 days. After the eggs hatched, the hatching time, production performance, and organ weight of chicks were investigated. IL-6 gene expression level and relative length of telomeres were analyzed to determine the physiological activity of the chicks. HSP gene expression level and heterophil to lymphocytes ratio were also analyzed to examine the degree of stress response in the chicks. The results showed that breed and laying age influenced the vitality of chicks, but the egg storage period did not. Korean Leghorn chicks were considered the weakest breed in terms of vitality owing to their low survival rate, small heart size, low physiological activity, and high stress response level. Although the survival rate of chicks produced in the early laying period was low, their high physiological activity and low stress response indicated that they had a high vitality than the chicks produced in the late laying period. In conclusion, to obtain chicks with high vitality, it would be desirable to select a high vitality breed and avoid the use of chicks produced in the late laying period.

• Korean Journal of Ichthyology
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• v.28 no.2
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• pp.72-78
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• 2016

The age and spawning characteristics of Iksookimia pacifica were investigated in this study to provide baseline data for its ecological characteristics in the Bukcheon (stream), Goseong-gun, Gangwon-do, Korea from January to December, 2013. Age groups of I. pacifica (female) estimated by the frequency distribution of total length in the spawning season indicated that the 30~49 mm group is 1 year old, the 50~74 mm group is 2 years old, the 75~99 mm group is 3 years old, the 100~124 mm group is 4 years old, and the 130~160 mm group is $5{\leq}$years old. The sex ratio (♂/♀) was 0.63, and females were 30~60 mm larger than males. The lamina circularis at the base of pectoral fins in males as a secondary sexual character was created at the 13th month after hatching. The spawning season according to the gonadosomatic index (GSI) was July to August (main spawning season in July) with water temperatures of $20{\sim}25^{\circ}C$. The average number of eggs was $2,503{\pm}1,337$ with a diameter of $1.11{\pm}0.04mm$ in mature eggs.

• Korean Journal of Poultry Science
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• v.36 no.4
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• pp.293-300
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• 2009

The rate of fetus with abnormal chromosomes increase with maternal age. Nondisjunction of aging oocyte chromosome is a major reason for the increased rate of abnormalities. Telomeres are the ends of eukaryotic chromosome, which are essential for chromosome stability and are related in cell senescence. This study was carried out to analyze the chromosome aberration rate and amount of telomeric DNA in chick embryo along with maternal age. Fertilized eggs and blood were sampled from White Leghorn layers starting at 20 weeks through to 70 weeks age at 10 weeks interval. Chromosome aberration rate was analyzed by karyotyping. The amounts of telomeric DNA in embryonic cells and lymphocytes were quantified by Quantitative Fluorescence in situ Hybridization method. The chromosome aberration rate in chick embryos significantly differed with maternal age. The chromosome aberration rate increased at early laying period and beyond 70 weeks of maternal age. Therefore, chromosome aberration rate was affected by maternal age due to ovulated oocytes state. However, the amount of telomeric DNA on embryonic cells did not differ significantly with maternal age. Thus, maternal age does not affects telomere quantity in their embryos due to cellular reprograming at early embryonic stage after fertilization.

• 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.