• Korean Journal of Ichthyology
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• v.30 no.1
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• pp.9-17
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• 2018

This study investigated how the larvae of three winter-spawning fishes are adapted in a cold water environment by examining the morphology, digestive system, and swimming ability of larvae from three winter-spawning species (Gadus macrocephalus, Liparis tanakae, Hexagrammos agrammus). Data were collected at hatching and first feeding. The results were compared with repored data on several non-winter-spawning species. Mean total lengths at hatching (${\pm}SD$) were $4.35{\pm}0.11mm$, $5.26{\pm}0.08mm$, and $7.48{\pm}0.35mm$ for G. macrocephalus, L. tanakae, and H. agrammus, respectively. Three winter-spawning fishes had well-developed digestive tracts after hatching than those of non-winter-spawning fish larvae. Yolks were intact until 5 days post-hatching in all three species, indicating that they had longer mixed-feeding periods compared with fishes spawned during other seasons. G. macrocephalus, L. tanakae, and H. agrammus larvae had superior cruise and burst speeds (measures of swimming ability) than non-winter-spawning larvae. We conclude that the unique characteristics of these three winter-spawning species are naturally selected adaptations under lower water temperature in winter.

• Journal of Aquaculture
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• v.5 no.2
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• pp.109-115
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• 1992

Effects of intraperitonial injections of human chorionic gonadotropin (HCG) on ovulation and spawning of the loach, Misgurnus mizolepts, were investigated. Matured females spawned successfully by a single dose of 6 IU (HCG) per gram body weight. Spawning usually occured 13 to 25 hours after hormone injection. Most of the eggs were fertilized and hatched normally. Fertilization rate, hatching percentage and Pseudo-gonadosomatic index were not correlated with increasing HCG doses. For the study of multiple spawning of this species, fatness, hepatosomatic and gonadosomatic indices of artificially spawned females were checked for 42 days after first spawning. According to this result, females could spawn again 40 days after first spawning.

• Development and Reproduction
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• v.14 no.1
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• pp.21-25
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• 2010

Nile tilapia (Oreochromis niloticus) are mouth-brooders so that the females holding eggs in their mouth sacrifice their somatic growth for reproduction. For this reason, artificial control of reproduction for the culture of this species has been of interest. Manipulation of photoperiod is an emerging technique for such purpose, but little information is available to establish appropriate photoperiod regime. To obtain necessary basic information, sexually mature females were individually accommodated to glass aquarium, and the spawning activity of these females were monitored for two years under natural photoperiod regime. Female tilapia spawned most frequently on March, April and May when the day length gradually increased from 11 hours to 14 hours and least frequently on September, October, November and December when the day length gradually decreased from 13 hours to less than 10 hours in the first year. The decrease of spawning frequency as day length decreased was also observed in the second year, although the increase of spawning frequency as day length increased was less clear. Spawning of female tilapia was less active when the night was dark due to the disappearance of moonlight (Dark Phase), compared to the Phase of Getting Lighter, Light Phase and Phase of Getting Darker. Results from this study suggest that long day length, particularly increasing phase, is favoured for active spawning of Nile tilapia, and that this species, as a tropical fish species, may utilize changing lunar phases as a secondary environmental cue for reproduction.

• Fisheries and Aquatic Sciences
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• v.23 no.6
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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.

• Animal cells and systems
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• v.3 no.4
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• pp.375-383
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• 1999

Gonadal development, gametogenesis, reproductive cycle, and first sexual maturity of Reishia clavigera were investigated monthly from July 1998 to June 1999 through cytological and histological observations. R. clavigera had separate sexes, and was an internal fertilizer. The ma1e penis was located near the two tentacles. The ovary and testis were composed of a great number of oogenic lobules and spermatogenic tubules, respectively. The size of ripe oocyte ranged from 130 to 140 ${\mu}$m in diameter. The peripheral cytoplasm of the germinal vesicle of the ripe oocyte in many cases were surrounded by smaller yolk granules, while the eccentric cytoplasm was occupied with larger ones. The reproductive cycle of R. clavigera could be classified into five successive stages: early active, late active, ripe, spawning, and recovery. Spawning of females occurred from early July to August when the seawater reached above 24.8$^{\circ}C$. Spawning of males occurred from early June to August in the water above 22.8$^{\circ}C$. Minimum size for sexual maturity of both sexes was above 10.0 mm in shell height. Each egg capsule was a cylinder or spindle in shape, 4-6 mm in length and 1-2 mm in width. Colors of newly spawned egg capsules showed yellowish white or pale yellow, while those with veliger larvae showed pale black, and released larvae or dead egg capsules showed black violet. The fecundity in an egg capsule ranged from 70 to 91 eggs (mean＝80.28 eggs).

• Korean Journal of Environmental Biology
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• v.20 no.3
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• pp.268-275
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• 2002

Seasonal variation in reproductive condition of the Pacific oyster Crassostrea gigas was investigated from a suspended cultured oyster population in Gosung Bay, South Korea using histological techniques, Gametogenesis of oysters initiated in February when water temperature reached 11 to $13^\circ{C}$. Increase in oocyte size and the number resulting in follicle expansion was observed from March to May First spawning of oysters observed in mid Jun when the surface water temperature reached 22 to $25^\circ{C}$. Spawning activity of oysters extended from mid June to late September with two marked spawning peaks in June and August. Most oysters collected from October to December exhibited few residual eggs in packed follicles exhibiting a typical spent condition. No gametes were observed from December to February from oysters collected in the Bay. Gonadal development of oysters in the Bay seemed to follow a seasonal fluctuation in environmental conditions such as water temperature and food availability in the water column. Spawning of oysters in late June was in part associated with sudden drop in salinity due to vast amount of freshwater input in the Bay after the summer flooding. Sex ratio of oysters was 59.5% male and 39.8% female. Less than 1 percent (0.6%) of the oysters examined were hermaphrodite; few eggs were observed in testis.

• Korean Journal of Ichthyology
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• v.22 no.2
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• pp.90-95
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• 2010

Blue devil (Pomacentrus caeruleus, also called Chrysiptera cyanea) is widespread in the Indo-Pacific Ocean and very popular all over the world as an aquarium fish because it is so easy to keep in a marine aquarium. However, tank-breeding techniques are not completely known. In this study, we reared blue devil and investigated its spawning ecology, as a necessary precursor for successful artificial-tank breeding. We investigated the spawning volume according to time with two types of calendars: solar and lunar. Rearing conditions were set at 30 ppt salinity, $27^{\circ}C$ water temperature, in two aquariums with water volumes of 80 and 125 L. We successfully bred P. caeruleus in this artificial-tank system. The aquarium fish formed a spawning harem with one male and more than two females. We harvested about 113,580 eggs in 44 spawning episodes by two spawning harems during the 11-month period from December to October. They showed a peak season of spawning volume and time in May and June. We confirmed the two peak points in spawning volumes and times, which coincided with the first quarter and last (third) quarter of the lunar phases of the moon.

• Ocean and Polar Research
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• v.38 no.1
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• pp.21-33
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• 2016

Gametogenesis of the comb pen shell, Atrina pectinata (Linnaeus, 1767) (Bivalvia: Pinnidae) on the southern coast of Ulleungdo Island, Korea was assessed monthly (November 2013 to October 2014) using histology. Gametogenesis commenced in January when the surface water temperature was $12.6^{\circ}C$ and pen shells evidenced an early development phase with small oogonia from January to April, although few females exhibited ripe eggs in their follicular epithelium. In April, the oocyte diameter increased rapidly, and fully mature eggs appeared in May. First spawning males and females were observed in June as the surface water temperature reached $19.3^{\circ}C$ and July ($23.2^{\circ}C$) respectively. The spawning activity continued until the end of September. Histology indicated that the spawning peak of the females in Ulleungdo Island was July to August. During October to January, most of the pen shells were in spent and resting stages. Our data suggested that A. pectinata is a summer spawner, and their annual gametogenesis is closely associated with the seasonal variation in the surface water temperature. The present study is the first provided fundamental information on the life history of A. pectinata in Ulleungdo Island, and this can be put to good use in the management of this pen shell in the study area.

• Development and Reproduction
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• v.13 no.2
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• pp.123-132
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• 2009

The gonadosomatic index (GSI), fatness, ovarian development, first sexual maturity, and fecundity of the Korean anchovy Coilia nasus were investigated by histological observations and morphometric analysis from January to December, 2007. The GSI and fatness began to increase in February, and reached the maximum in June when the ovary was getting mature and spawning occurred. Thereafter these parametes rapidly decreased in July when spawning occurred. Therefore, monthly changes in the GSI and fatness were closely related to ovarian maturation and spawning. The duration of ovarian development in females can be classified into five successive stages: early growing stage (February to March), late growing stage (March to April), mature stage (May to June), ripe and spent stage (June to July), and recovery and resting stage (December to January). Maturation and spawning of this species occurred between June and July during the period of high seawater temperature-long day length. Percentages of first sexual maturity in female individuals were over 50% for fish ranging 24.1 to 27.0 cm in total length, and 100% for fish over 30.1 cm in total length. The number of total eggs and mature eggs in the absolute fecundity were increased with the increase of total length and body weight, respectively. The number of total eggs and mature eggs in relative fecundity were also proportional to total length, but rather these numbers decreased in the maximum body weight (126.0${\sim}$150.0 g).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.261-263
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• 1976

In 1975, a trial for channel catfish spawning was made for the first time in Korea, by stocking 11 pairs of brood fish in a $470m^2$ earthen pond provided with 5 cans of 35 cm in diameter with depths of about 60 cm as spawning nests. The same trial and another pen cage method combined with pituitary injection were practiced in 1976. All these trials failed without any spawning. On the other hand 4 females and 1 male were put in a recycling water system indoor aquarium for exhibition purpose it late spring of 1976. After removing 3 females which were injured from being bitten by the male, remaining one pair of the catfish spawned successfully in July and the most eggs developed normally. The water in the recycling system showed the pH range of 7.2 to 7.4,and mean water temperature of every 10 day period of a month gradually increased from 19.3 to 23.6C until spawning. The outdoor .ponds where the spawning was failed received water from the same origin as the indoor recycling system, and the mean temperature of every ten day period ranged Iron 17.2 to $29.8^{\circ}C$ in 1975 and 19.7 to $28.4^{\circ}C$ in 1976 these being considered well falling in the optimum range for catfish spawning, but pH ranged from 7.3 to 9.5 under the influence of photosynthesis of algae and weeds in the ponds. The high pH value may suppress the spawning of catfish as pointed out by Nelson in 1957.