• Journal of Aquaculture
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• v.8 no.4
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• pp.307-316
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• 1995

Jicon scallop (Chlamys farreri), as one of new culture species, has been taken a growing interest in Korea recently. Artificial seeds are needed since seeds in natural waters are absolutely short. To develop the better methods for the artificial spawning and the rearing larvae on a large scale, experiments were carried out from July 1993 to May 1994. Mother shells were collected from the area near Tong-yeong and Geoje-do, the southern part of the Korean Penninsula. It was estimated that a period of 2-years was needed to be mother shells after the fertilization. Generally, spawning occourred intermittently from March to August and the maximum occurred in July. A best way for the artificial spawning was a chemical incentive, a 'serotonin injection' in parallel with the exposure and the temperature stimulation. Densities of the fertilized eggs for the normal development was from 30 to 40 per mililiter. It took 27-days from the fertilization to the settling larva averaging $155{\mu}m$ in size with water temperature 11.5\~13.0^{\circ}C$. Isochrysis galvana and Chaetoceros calcitrans with a density of $1,500\times10^4$ cells per ililiter were supplied for rearing the larvae. A proper density of larvae was 10 individuals per mililiter, and the survival rate of larvae from the flowing water system was much better than that of larvae from the still water.

• Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.82-93
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• 1998

Monthly changes of the gonad follicle index (GFI), reproductive cycle, egg-diameter composition, first sexual maturity of the Pacific oyster, Crassostrea gigas, were studied based on the samples which have been collected from the intertidal zone of Poryong west coast of Korea, from January to December, 1996. C. gigas, is dioecious, while a few individuals are alternatively hermaphroditic. Monthly variation of gonad follicle index (GFI) used for determination of spawning period, coincided with the reproductive cycle. GFI increased from April when seawater temperatures gradually increased and reached the maximum in May. And then, GFI sharply decreased from June to September due to spawning. Reproductive cycle of this species can be divided into five successive stages: in females, early active stage (March to April), late active stage (April to May), ripe stage (May to August), partially spawned stage (June to September) and spent/inactive stage (September to February); in males, early active stage (February to March), late active stage (April to May), ripe stage (May to September), partially spawned stage (June to September) and spent/ inactive stage (September to February). The diameter of fully mature eggs are approximately 50um. Spawning occurred from June to September, and two spawning peaks were observed in June and August when the seawater temperature was above $20^{\circ}C$. Percentages of the first sexual maturity of males of 20.1-25.0 mm in shell height were over $50\%$, while those of females of 25.1-30.0 mm in shell height were over $50\%$. All the males of > 30.1 mm and all the females of ^gt; 35.1 mm completed their first sexual maturity. The results suggest that C. gigas has a protandry phenomenon. Sex ratios of 919 oysters observed were 453 females $(49.29\%)$, 429 males $(46.68\%)$, 16 hermaphrodites $(1.74\%)$, and 21 indeterminate individuals $(2.29\%)$. In age class I, sex ratio of males were $64.00\%$, thus, a higher percentage than that of females. It was noted that $64.00\%$ of the young males (age class I) were more functional than females in age class I, but 2-3 year-old oysters showed higher percentage of females. Percentages of hemaphrodites in 2-3 year classes were relatively higher than those in other year classes. Histological pattern of hermaphrodites can be divided into two types: Type I (hermaphrodite having a number of newly formed developing oocytes on the oogenic tissues within a degenerating spermatogenic follicle after discharge of numerous spermatozoa) and Type II (hermaphrodite having two separate follicles in the same gonad).

• The Korean Journal of Malacology
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• v.19 no.1
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• pp.19-24
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• 2003

Artificial spawning, larval and spat developments of the bay scallop, Argopecten irradians, which was transplanted from China on 16 August 1996, were investigated monthly until August 1997 in the Deukyang Bay, Jangheung-gun, Jeollanam-do, Korea. Sufficient amount of cultured microalgae supplemented seawater were supplied as food (6 kinds of phytoplankton) for fully grown adult individuals at 17.1-23.2$^{\circ}C$ for 44 days. A total of 45,320,000 eggs were spawned by way of 2 times of artificial spawning inductions such as exposure stimulus to the air and thermal shock (with water temperature) on 29 January and 31 January in 1997. Artificially fertilized eggs were developed to D-shaped larvae (77.5 ${\times}\;63.8\;{\mu}m)$ and metamorphosed to larvae (191.8 ${\times}\;181.2\;{\mu}m)$ 181.2 m) in the attached larval stage on the collectors. A total of 110,000 spats (average 3.04 mm in shell length) were produced at 22.8-26.3$^{\circ}C$ and 31.0-34.4 psu in the indoor rearing tank from 14 February through 7 May in 1997. In case of Argopecten irradians, if the attached larvae in the attachment stage are detached from the collector, they could not live. Accordingly, it is assumed that survival (%) of the attached larvae of A. irridians showed very low because of weak power attached to the collector due to the small number of the byssuses of the attached larva, not the short attachment period by the byssus as seen in other scallops such as Argopecten balloti.

• The Korean Journal of Malacology
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• v.31 no.3
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• pp.171-178
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• 2015

The reproductive ecology of freshwater bivalve, Unio douglasiae in Lake Uiam were examined from March 2014 to February 2015. The gonads distributed in reticular connective tissue, the dioecious clams take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The gonad index (GI) began to increase in April, reached the maximum value in July and to decrease in August. The reproductive cycle of U. douglasiae can be divided into five successive stages: multiplicative stage (November to January), growing stage (February to March), mature stage (February to May), spawning stage (April to September), recovery stage (August to December). The spawning periods were from April to September, and the main spawning occurred between April and July. The shell length at 50% group maturity was estimated to be 29.4 mm.

• Journal of Aquaculture
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• v.12 no.3
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• pp.197-204
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• 1999

Successful produciton of seedlings for marine fish species are highly influenced by the aquisiton of sufficient number of good-quality eggs on required time. human chorionic gonadotropin has been used to induce successful ovulation for the purpose. Rabbitfish, siganus canaliculatus, is inhabited along the coast of Cheju Province and treated valuably for raw fish and fish roasted with seasoning. Female wild-captured rabbitfish (314 to 279 g in body weigth) were injected into intraperitoneal space with human chorionic gonadotropin (HCG) of 5,00,1,000, and 1,500 IU/kg body weight during spawning season of July 14 (trial 1), and July 27 (trial 2). Test fish in trial 1 were injected two times, first on July 14 and second on July 21 with one weekinterval because of no ovulation symptoms, but just one time in trial 2. All females injected both 1,000 and 1,500 IU/kg body weight ovulated in all trials. Among 500 IU/kg injection treatments, just one female ovulated in trial 1 showing 25% of ovulation rate, but none ovulated in trial 2. Ovulation was not occurred in control goups during test period. Time to reach ovulation after injection was 172 to 270 hours in trial 1 and 77 to 132 hours in trial 2, showing shorter as spawning season approached. Generally, ovulation of smaller females were late than that of larger ones. Gonadosomatic index (GSI) and pseudo-gonadosomatic index (Pseudo-GSI) were ranged 22 to 33% and 19 to 28%, respectively. One female spawned 406,200 to 1,032,000 eggs, and obtainable eggs per 100g of body weight were calculated by 130,000 to 190,000. Spawning rates were comparatively high by 96.0 to 98.4%. Rates to reach embryo-formation and hatching were higher in 500 high by 96.0 to 98.4%. Rates to reach embryo-formation and hatching were higher in 500 and 1,000 IU/kg treatments than in 1,500 IU/kg treatment. The result of present study demontrates that HCG treatment during spawning season could become very useful for ovulation of rabbitfish and the suitable dosage was suggested as 1,000 IU/kg of body weight.

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.101-106
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• 2007

We investigated the maturity and spawning of black edged sculpin, Gymnocanthus herzensteini caught by gillnet in the East Sea from March 2003 to February, 2004. We analyzed monthly changes in maturity stages, gonadosomatic index (GSI), gonad weight (GW), egg diameter, fecundity, total length at 50% group maturity and sex ratio. The spawning period was December to February. The fecundity ranged form 8,814 eggs at 14.7 cm (TL) to 25,560 eggs at 24.4 cm (TL). The relationship between total length (TL) and fecundity (F) was $F=285.11TL^{1.4092}$ ($R^2$ =0.571) and fecundity increased with total length. The total length at 50% group maturity was estimated to be 15.25 cm. The sex ratio was 60 for female and 40 for male, where the female population was seen to be slightly predominant. For sex ratio by length class, male was a little predominant in small size, but female was 90% more than 24 cm.

• Journal of Aquaculture
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• v.20 no.4
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• pp.239-247
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• 2007

We studied spawning, hatching and larval growth of Amphiprion melanopus under laboratory conditions. Each time a fish spawned about 440 to 650 eggs. The eggs were hatched 9 days later. Nest colour of the eggs changed from clear yellow orange to greyish violet with processing of embryogenesis. With regard to spawning according to the substrates, the fish prefered red clay pot and ceramic pot to volcanic scoria and live rock. Hatching rate (%) of the eggs on the former substrates was significantly higher than that on the latter. The number of eggs varied with the food stuff supplied to the fish. The fish fed Tetra bits (commercial diet), meat of short necked clams and mussels, and astaxanthin showed significantly higher fecundity with 638 eggs than that fed only Tetra bits (477 eggs) or Tetra bits with meat of shellfish without astaxanthin ($549{\sim}553\;eggs$). Higher temperature ranging from 24 to $30^{\circ}C$ induced shorter incubation period and smaller total length, but higher hatching rate. The optimum salinity and L:D cycle with $60\;{\mu}mol$ photon $m^{-2}s^{-1}$ for hatching were 33 psu and 16:8, respectively. The newly hatched larvae about 4.6 mm in total length grew to 7.5 mm in one week, 18.8 mm in a month and 37.9 mm in 70 days after hatching.

• Journal of Aquaculture
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• v.16 no.3
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• pp.179-186
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• 2003

Reproductive cycle, gonadal development and the spawning period of the Korean anchovy Coilia nasus were investigated by histologhical observations. Samples were collected at the coastal area of Geumgang dyke which is connected to Gunsan and Janghang, Korea, from February 2002 to January 2003. C. nasus is dioecious; the ovary consists of a pair of saccular structure with many ovarian lobules, and the testis consists of a pair of lobular structure with many testicular lobules and connected to the posterior seminal vesicle. Monthly changes in the gonadosomatic index (GSI) began to increase in April when seawater temperature increased and reached the maximum in June when the ovary was getting mature, the summer season of longer day length with higher water temperature. The reproductive cycle can be classified into five successive stage in females: 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 (July to January): in males, the cycle can be divided into four successive stages; growing stage (February to April), mature stage (May to July), ripe and spent (June to July), and recovery and resting stages (July to January). According to the frequency distributions of egg diameters in the spawning season. C. nasus is presumed to be summer spawning species and polycyclic species to spawn 2 times or more during the spawning season.

• Korean Journal of Ichthyology
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• v.25 no.4
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• pp.208-215
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• 2013

Host species preference of Acheilognathus signifer for spawning in freshwater mussels was investigated at the part of the Dalcheon Stream (site 1) and the Gaedaecheon Stream (site 2) in Chungcheongbuk-do, Korea from April to June (spawning period) 2011. The spawned mussel rate of A. signifer at the study site 1 (wild condition) was 63.6% in Lamprotula leai and 2.1% in Unio douglasiae sinuolatus. It was not found in Anodnta arcaeformis flavotincta and Lanceolaria grayana. The number of eggs, larvae, or both of A. signifer at the study site 1 (wild condition) was 1~41 ($12.0{\pm}9.21$) in L. leai and 6 in U. d. sinuolatus. As a result of experiment 1, A. signifer was only spawned in L. leai with 60% of spawned mussel rate and the number of eggs, larvae, or both was 1~19 ($6.8{\pm}5.44$). According to experiment 2, A. signifer was spawned in all mussels. Spawned mussel rate of A. signifer was 75.0% in L. leai, 42.9% in U. d. sinuolatus and 21.4% in A. a. flavotincta and the number of eggs, larvae, or both was 1~35 ($13.0{\pm}8.80$) in L. leai, 1~26 ($5.2{\pm}6.92$) in U. d. sinuolatus and 2~19 ($8.6{\pm}5.64$) in A. a. flavotincta. Experiment 3 showed A. signifer was solely spawned in L. leai and the number of egg was from 2 to 10 ($6.7{\pm}4.16$). This study confirmed A. singifer is not so much generalist as specialist. We found the most preference species for spawning in the mussels by A. signifer was L. leai.

• Korean Journal of Environment and Ecology
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• v.35 no.2
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• pp.115-125
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• 2021

This study surveyed the population ecology of Acheilognathus chankaensis (Pisces: Acheilognathinae) in the vicinity of the Churyeongcheon (Stream) and Seomjingang (River) in Jeonbuk, Korea, from February 2006 to May 2007. The survey found the habits mainly in the slow-flowing waters having sand, mud, and gravel bottoms. Age groups estimated by the standard length-frequency distribution of the population indicated that the one-year-olds were 30-46 mm long, the two-year-olds were 47-58 mm long, the three-year-olds were 59-68 mm long, and the four-year-olds were longer than 69 mm. The gonadosomatic index (GSI) and the ratio of ovipositor length/standard length were the highest in March (♀: 12.9%, ♂: 5.0%) and in April (46.3%), respectively. The ratio of mature egg diameters that were 1.6 mm was highest in May (13.2%). The comprehensive analysis of spawning characteristics showed that the spawning season was from March to June with water temperatures in 11.5-22.5℃, and the sex ratio of female:male was 1:1.13. The fecundity in the ovaries and the number of mature eggs were 318±174.5 (50~583) and 220±139.2 (50~406), respectively. The size of the mature eggs was 2.04±0.110 mm on the long axis and 1.55±0.100 mm on the short axis for the study period. Gut contents of A. chankaensis were mainly phytoplankton such as the genera Fragilaria, Synedra, Navicular, Cymbella (Bacillariophyceae), and Cosmarium (Chlorophyceae).