• 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 Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.9-18
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• 1968

A series of experiments since 1963 ha sbeen made on the artificial propagation of Penaeus oriental is for the purpose of improving breeding of the prawn. The results are as follows: 1. Spawning takes place in the evening, and almost completes before 10 o'clock p. m.. Number of spawns deposited by a prawn is 30,000 to 150,000. 2. Deposited spawns become nauplius stage after approximately 18 hours (about 13 hours in hatching tanks) at water temperature of $23\~25^{\circ}C$, and grow to first nauplius stage in subsequent 28 hours. 3. It takes about five days from first nauplius stage to zoea stage, and additional four or five days from first zoea stage to first mysis stage. 4. It takes approximately 2 to 3 weeks from spawning to post larva. 5. Hatching rate ranged from $1.4\%$ to $14.9\%$, with the average of $6\%$ in 1966 and $10\%$ to $35\%$ averaging $20\%$ in 1967.

• Korean Journal of Ichthyology
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• v.22 no.2
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• pp.83-89
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• 2010

We studied the maturity and spawning of Marbled sole Pleuronectes yokohamae from May 2006 to April 2007 in the Southern Sea of Korea. We analyzed monthly changes in maturity stages, gonadosomatic index (GSI), egg diameters, fecundity (F), total length (TL) at 50% group maturity, and sex ratio. The spawning period was November to February, and the main spawning period was December to January. The fecundity ranged from 75,155 eggs at 17.8 cm(TL) to 1,307,195 eggs at 36 cm (TL), and the relationship between TL and F was $F=3.656TL^{3.518}$ ($R^2$=0.872). The TL at first maturity was 17.8 cm and at 100% maturity, 32 cm. Thus, TL at 50% group maturity was estimated to be 19.8 cm. For sex ratio by length class, males were slightly predominant at sizes under 25 cm TL, but females were 100% at greater than 32 cm TL.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.6
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• pp.529-535
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• 1984

This study aims at obtaining the basic data for the development of pen shell culture at Yoja Bay, the southwest coast of Korea. The authors dealt with the annual gonadal changes of the pen shell, Atrina pectinata japonica, to find out the gametogenesis, reproductive cycle and spawning season, and to investigate the fluctuation in the larval occurence in Yoja Bay. From July 1983 to June 1984, an average of 20 individuals as specimens were monthly collected by commercial fishing dredge near Manwol island located at the mouth of Yoja Bay. The degree of gonadal development was determined by the histological observations as resting spent stage, early developmental stage, after developmental stage, early spawning stage, after spawning stage and degenerative stage. According to these degrees of gonadal development, annual reproductive cycle of the pen shell population was determined. From July to August, the gonads were changed through degenerative into resting stage and, in September and October, they became entirely empty gonads. From November they showed the first sign of gametogenesis developing very slowly. Nevertheless, the developing gametes did not increase in number probably owing to a phagocytic phenomenon by phagocytes which appeared in the gonad during this stage. Some individuals started spawning in April and in May majarity of individuals were in spawning stage. In June, majority of the individuals showed signs of degenerative stage. Therefore, the authors came to a conclusion that the pen shells in Yoja Bay spawn chiefly in May. And this is also supported by the result of the survey on the planktonic occurrences of the pen shell larvae. Namely, there were no larvae at all in April, only a few in May and many in June by vertical water sampling.

• Korean Journal of Ichthyology
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• v.18 no.4
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• pp.363-367
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• 2006

The maturity and spawning of brown sole, Pleuronectes herzensteini were investigated using samples randomly collected in the East Sea of Korea from April, 2003 to March, 2004. We analyzed monthly changes in maturity stages, gonadosomatic index (GSI), egg diameter, fecundity (F), total length (TL) at 50% group maturity, and sex ratio. The spawning period was February to May, and the main spawning period was March to April. The fecundity was 38,702 eggs at 22 cm (TL) to 133,085 eggs at 37 cm (TL), and the relationship between TL and F was $F=11.307TL^{2.628}$. The TL at first maturity was 15 cm and at 100% maturity, 21 cm. Thus, TL at 50% group maturity was estimated to be 17.8 cm, which corrensponded to the age of 3 years. The sex ratio was 60.2 for female and 39.8 for male, where the female population was seen to be slightly predominant.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.206-218
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• 1984

The gonadal development and gametogenesis of shad, Konosirus, punctatus (TEMMINCK et SCHLEGEL) were studied by comparing with various quantitative indices, such as seasonal changes of gonadosomatic index, fatness, egg-diameter composition, first maturing size, and by comparing with histological changes of gonad and gonadotrophs(GTH) in pituitary. The materials were monthly sampled from Dadaepo at the estuary of the Nakdong river in Korea from September, 1982 to October, 1983. The ovary of shad is a pair of sac-shaped organs revered with a fibromuscular capsule and consisting of numerous sacs. The type of testicular structure is lobular type with development of germ cells, mesenchymal tissue on the lobuli. The gonadosomatic index (GSI) is rather low till March, but increases in April and reaches to peak in June in females and May in males. And it suddenly falls in July. The gonads become active on the increase of water temperature and spawning season ends before high water temperature. After spawning, the small oocytes continue to remain as they are untill the growing period next year. The reproductive cycle includes the successive stages of growing from March to April, mature from April to May, ripe and spawning in June, and recovery and resting from July to February next year. In egg-diameter composition of an ovary taken in the spawning season, 2-3 modes were recognized with some batches shown in an ovary. An individual shad spawns twice or more in a month-spawning season. The individual spawning interval is estimated to be ten days or less. Changes of fatness are corelated with those of water temperature that affect on the condition of feeding, but less corelated with spawning. The percentage of mature of female and male fish, are $50\%$ in 17.0-18.0 cm and $100\%$ in 18.0-19.0 cm. GTH cells are activated from growing period and decrease their activity at pre-spawning season with peak activity for mature period.

• The Korean Journal of Malacology
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• v.16 no.1_2
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• pp.35-41
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• 2000

We investigated the gonad index (GI), gonadal development, the reprodutive cycle and first sexual maturity of the venus clam, Cyclina sinensis by histological observation. Samples were collected from the intertidal zone of Komso Bay, Chollabuk-do, west coast of Korea, from April 1998 to March 1999. This clam is dioecious and oviparous. Monthly changes in the gonad index (GI) showed a similar pattern to the reproductive cycle. Ripe oocytes are about 90-100 ㎛ in diameter. The spawning period was between early July to September, and the main spawning occurred between July and August when the sea water temperature was over 20$\^{C}$ The reproductive cycle of this species can be divided into five successive stages: early active stage (February to April), late active stage (March to June), ripe stage (April to August), partially spawned stage (July to October), and spent / inactive stage (September to February). Percentages of first sexual maturity of female and male clams measuring 26.1-30.0 ㎜ in shell length were 53.3% and 62.5%, respectively, and 100% for the clams > 41.0 ㎜. It is assumed that both sexes begin reproduction at about two years age.

• Journal of Animal Reproduction and Biotechnology
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• v.39 no.1
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• pp.31-39
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• 2024

Background: The biological information of fish, which include reproduction, is the prerequisite and the basis for the assessment of fisheries. Methods: The aim of this work was to know the reproductive biology with the first sexual maturity (TL₅₀) and the spawning period for 58 mainly fish species in the waters around La Réunion Island (Western Indian Ocean). Twenty families belonging to the Actinopterygii were represented (acanthuridae, berycidae, bramidae, carangidae, cirrhitidae, gempylidae, holocentridae, kyphosidae, labridae, lethrinidae, lutjanidae, malacanthidae, monacanthidae, mullidae, polymixiidae, pomacentridae, scaridae, scorpaenidae, serranidae, sparidae; 56 species; n = 9,751) and two families belonging to the Elasmobranchii (squalidae, centrophoridae; 2 species; n = 781) were sampled. Between 2014 and 2022, 10,532 individuals were sampled covering the maximum months number to follow the reproduction periods of these species. Results: TL₅₀ for the males and the females, respectively, ranged from 103.9 cm (Acanthurus triostegus) to 1,119.3 cm (Thyrsitoides marleyi) and from 111.7 cm (A. triostegus) to 613.1 cm (Centrophorus moluccensis). The reproduction period could be very different between the species from the very tight peak to a large peak covered all months. Conclusions: Most species breed between October and March but it was not the trend for all species around La Réunion Island.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.2 no.1
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• pp.87-91
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• 1969

Experiments on the rearing of larvae of the prawn, Penaeus japonicus Bate, have been con-ducted by using a large tank A ($3.4\times1.9\times1.0m$) and two small tanks B and C ($1.45\times0.85\times1.0$). 1) Between spawning and the first zoeal stages, no significant elapsed time difference was noticed among the rearing tanks. At about $23^{\circ}C$ of water temperature nearly all of the larvae in the tanks metamorphosed into the first zoeal stage in about 36-48 hours. However the period of time which elapsed between the spawning and post-larval stage showed some differences bet-ween the tanks, i.e., 19-20 days in tank A and 15-17 days in tanks B and C, respectively 2) No difference in body length of the larvae has been observed among the three tanks. 3) The post-larva passed through several molts, one every four or five days, before reaching the young prawn about 36-40 days after spawning. 4) Throughout the zoeal stages the highest mortality was found at the time of molting between the first and second zoeal stages showing about $51.39\%$ in tank A, $50.70\%\;and\;31.91\%$ in tanks B and C, respectively. 5) Total mortality during the duration of the larval stages was around $75\%$ in all the rearing tanks.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.6
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• pp.563-574
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• 1986

The structure of gonads, gametogenesis and reproductive cycle of the jackknife clams, Solen strictus and Solen gordonis were investigated mainly by histological observation. The first species used were monthly sampled at the coastal area of Dadaepo, Pusan, Korea and Naechodo, Kunsan, Korea for one year from February 1982 to January 1983. The second species were monthly sampled at the sand beach of Dadaepo, Pusan, Korea, from February 1982 to January 1983. Sexualities of Solen strictus and Solen gordonis are dioecious, and these species are oviparous. The gonads are irregularly arranged from the subregion of mid-intestinal gland in visceral cavity to reticular connective tissue of foot. The ovary was composed of a number of small ovarian sacs and the testis was composed of several testicular lobuli which from the tubular structure. Early multiplicating oogonium was about $10{\mu}m$ in diamater. Nucleus and nucleolus, at that time, were distinct in appearance. Each of the early growing oocytes made an egg-stalk, connected to the germinal epithelium of the ovarian sac. A great number of undifferentiated mesenchymal tissue and eosinophilic granular cells are abundantly distributed in the ovarian sacs in the early development stages. With the further development of gonad, these tissue and cells gradually disappeared. Then the undifferentiated mesenchymal tissue and eosinophilic granular cells function as nutritive cells in the formation and development of the early stage germ cells. Mature oocytes were free in the lumen of ovarian sacs and gradually become round or oval. Ripe oocyte was about 80 to $90{\mu}m$ in diameter. With the further development of testis, each of the testicular lobuli formed stratified layers composed of spermatogonia, spermatocytes, spermatids and spermatozoa in groups on the germinal epithelium. After spawning, the gonad gradually degenerated, and disorganized completely. Then new differentiated tissues were rearranged next year. The annual reproductive cycle of those species could be classified into five stages; multiplicative, growing, mature, spent, degenerative and resting stage. It seems that the spawning season is closely related to the water temperature, and the spawning of Solen strictus occurs from June to July at above $20^{\circ}C$ in water temperature. The peak spawning season appeared in June at Dadaepo and in July at Kunsan, The spawning of Solen gordonis occurs from May to June with the peak spawning season in June. Percentages of the first maturity in female of Solen strictus ranging from 5.1-6.0 cm and 7.1-8.0 cm in shell length were $50\%$ and $100\%$, respectively.