• Korean Journal of Environment and Ecology
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• 제35권3호
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• pp.285-293
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• 2021

This study was conducted to elucidate spawning period characteristics and early life development of eight barbel loach, Lefua costata (Balitoridae) at the Jusucheon stream, Okgye-myeon, Gangneung-si, Gangwon-do, Korea between January and December in 2018. The spawning period was estimated to be from May to August, considering the change in the gonad-somatic index, the appearance of young fry, and frequency distribution in egg diameter. It was a multi-spawning type. The gender ratio was 1:0.79 with 1,117 females and 879 males collected. The egg size was 0.24-0.93 mm, with mature and immature eggs found during the spawning period. The size of mature eggs was 0.71±0.02 mm, and the average number of fecundity was 1,786±818 (n=31). Observation of the egg development showed that the fertilized eggs were the sticky, gray, segregated, and demersal type with 0.76±0.03 mm in diameter. The hatching of the embryos began at about 34 hours (hatching rate 50%) after fertilization underwater temperature of 25℃. The average length of the newly hatched pre-larvae was 2.7±0.11 mm. The average length of pre-larvae at 4 days after hatching was 4.5±0.16 mm, and the yolk sac was completely absorbed and entered the post-larvae stage. At 20 days after hatching, the average length of post-larvae was 11.5±0.67 mm, and their fin rays were formed before they transitioned to the juvenile stage. At 100 days after hatching, the average length reached 49.8±2.60 mm, and the appearance and the lateral sideband patterns were similar to those of the adult fish.

• Korean Journal of Ichthyology
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• 제29권3호
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• pp.197-204
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• 2017

Life history of the Siberian stone loach, Orthrias toni, were investigated using samples collected from Buk Stream, Goseong-gun, Gangwon-do, Korea. Growth was rapid between April and October when water temperature exceeded $10^{\circ}C$, but growth almost stopped from November-March when water temperature was below $10^{\circ}C$. Age groups for O. toni estimated by frequency distribution of total length in spawning season (May) indicated the 60~81 mm is 1-year old, the 82~99 mm group is 2-years old, the 100~119 mm is 3-years old, and the 120~140 mm is more than 4-years old. Total length range by sex was similar, and sex ratio (♂/♀) was 0.73. Spawning season according to the gonadosomatic index (GSI) was May with water temperature $14{\sim}17^{\circ}C$, and almost all fish were mature after one year old. Fecundity increased rapidly with age with an average of $4,460{\pm}3,302$ ($mean{\pm}SD$). Size of mature eggs was $0.87{\pm}0.03mm$ in diameter irrespective of age.

• Korean Journal of Ichthyology
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• 제12권3호
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• pp.186-191
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• 2000

Population ecology of Abbottina springeri has been investigated from March to November, 1995 at Musimchon stream of Kadok-myon, Chongwon-gun, Chungchongbug-do. The favorite habitat was a sluggish area with muddy bottom, but larger individuals more than 60 mm in total length were also collected at rapids of low velosity. Judging from the total length frequency in this population on June, total length 30~50 mm group is one year old, 50~65 mm group is two years old, and longer than 65 mm is regarded over three years old. Sexual dimorphism was revealed conspicuously in genital papilla, nuptial tuberles and nuptial pigmentation in the males at spawning season. Peak season of spawning was June when the water temperature reaches $20\sim25^{\circ}C$ and they start spawning at the age of two. The sex ratio of female to male was 1:0.93. The mean of egg number and egg size in ovary were 652 and 0.43~0.06 mm respectively. According to the contents of stomach, this species feeds mainly on botton algae at all ages and some aquatic insects in adult.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 한국어업기술학회 2000년도 추계수산관련학회 공동학술대회발표요지집
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• pp.244-245
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• 2000

The top shell, Omphalius rusticus (Gastropoda: Trochidae), is marine mollusk inhabiting underneath a rock in the intertidal zone of the coasts of Korea and Japan, and it is one of the edible gastropods. This species is a herbivorous animal. Up to now, there have been some reports on the Trochidae: aspects of classification, spawning periodicity, production, growth and size-frequency distribution of living populations, feeding, reproductive cycle, and induction of larval metamorphosis. (omitted)

• Korean Journal of Fisheries and Aquatic Sciences
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• 제52권5호
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• pp.496-510
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• 2019

We investigated the reproductive characteristics of the sweetfish Plecoglossus altivelis, including changes in the gonadosomatic index (GSI), frequency of gonad developmental stages, and abundance of drifting larvae, in three streams (Gangjeong, Yeonoi, and Ongpo) on Jeju Island from May 2004 to December 2005. The GSI values of female P. altivelis in all Jeju streams began to increase in September and reached a maximum in October and November. Peak GSI values in males occurred in Gangjeong from October to November, in Yeonoi from November to January, and in Ongpo from September to October. The gonadal development of P. altivelis was classified into four stages: growth (March to October), maturity (September to December in females; July to December in males), spawning (September to January), and degeneration (October to March in females; after November in males). Drifting larvae were collected from October to January. These results suggest that the main spawning activity of P. altivelis in Jeju streams occurs from October to November. The information about the reproductive characteristics of P. altivelis obtained in this study is critical to fishery management for this species.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제42권1호
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• pp.41-47
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• 2009

The seasonal reproductive cycle of Gomphina melanaegis collected in the coastal area of Jumunjin, between April 2006 and March 2007, was analyzed. Maturation cycle parameters such as the gonad index (GI), ovarian egg diameter, frequency of developmental stages, protein content, and RNA/DNA variation in the gonads were analyzed monthly for the 40 samples. According to the indices from histological sections, the frequency of gonad developmental stages, and the oocyte diameter, this clam has a long-term partial spawning pattern from March to October. However, GI and nucleic acid values showed that the mature stage is from March to July and that the main spawning season is August. The peak RNA and DNA contents were good indicators of sexual maturation in females and males, respectively. The variation in protein content corresponded with the RNA/DNA ratios.

• Korean Journal of Ichthyology
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• 제7권1호
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• pp.33-42
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• 1995

The reproductive cycle of the bitterling, Rhodeus uyekii was studied to observe the annual variations of gonadosomatic index(GSI), size frequency distribution of egg, ovipositor length and histological changes of gonad. GSI began to increase from February when the water temperature started to increase, and reached the maximum value in May, whereas it began to decrease from July and reached the minimum value in August which in the highest water temperature season. It began to incerase again but showed low value from September to November. The GSI remained stable thereafter. Monthly changes in GSI, ovipositor length, frequency of egg diameter and gonadal histology showed that the annual reproductive cycle was classified into the following successive phases : primary growing phase from September to November, quiescent phase in December, secondary growing and mature phase from January to February, ripe and spawning phase from March to June, and recovery and resting phase from July to August.

• Korean Journal of Ichthyology
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• 제29권3호
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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.

• Development and Reproduction
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• 제15권2호
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• pp.133-141
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• 2011

The marine ornamental industry has become a multi-billion dollar industry these days. As developing, however, this industry has been criticized for the indiscriminate captures and the destruction of the surrounding environment. To circumvent these problems, it is suggested to breed the organisms artificially. While clownfishes Amphiprion sp. and Premnas sp. are the most famous ornamental organisms in the trade, few studies are yet available on the culture and commercial production of these fishes. These studies were performed to investigate the spawning periodicity, behavior and the habits during egg incubation, and to provide the information on the mass hatching system. The spawning periodicity and frequency were different in 4 pairs under the constant condition, temperature, salinity and photoperiod. On the contrary, the male's behaviors for egg incubation are almost same in the all. The egg-fanning activity of the male increased as the developing eggs reaching to the hatching day. Based on the above results, we designed a new artificial hatching system, the rotating type (RT), and compared it with the aeration type (AT) and spray type (ST) that were previously described. RT showed higher hatching rate of 87.3% than AT (74.4%) and ST (60.5%). Also, there were no significant differences in the hatching rate regardless of the number (2, 3, 5) of hatching plates. We suggest RT may accommodate various number of hatching plates and constitute a better hatching system for clownfishes.

• Korean Journal of Ichthyology
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• 제22권1호
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• pp.25-33
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• 2010

Effects of different salinity levels on spawning performance, embryonic development and early viability of a euryhaline medaka species, Oryzias dancena, were examined. O. dancena were able to spawn eggs in a wide range of salinity from 0 to 70$^{\circ}/_{\circ\circ}$, however, the spawning frequency was lowered in complete freshwater (0$^{\circ}/_{\circ\circ}$) and in highly salted water (70$^{\circ}/_{\circ\circ}$). Fertilization success was negatively affected when the environmental salinity was higher than the salt concentration found in normal seawater. Embryonic viability and hatching success were also inversely related with the salinity levels. Typical abnormality was observed in developing embryos incubated at high salinities (30, 45 and 60$^{\circ}/_{\circ\circ}$). In addition, the time to hatch was significantly delayed with increasing salinities: peak hatching occurred at 12~14 days post fertilization (dpf) in freshwater and at least at 17 to 18 dpf in 60$^{\circ}/_{\circ\circ}$. Mean survival rates of the hatched larvae up to 7 days post hatching (dph) were at least 97% in salinity levels ranging from 0 to 30$^{\circ}/_{\circ\circ}$. However, larvae reared in 45 and 60$^{\circ}/_{\circ\circ}$ experienced significant mortality, especially in the early phase, resulting in only 75% and 64% survival rates up to 7 dph, respectively.