• The Journal of Fisheries Business Administration
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• v.51 no.4
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• pp.19-45
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• 2020

This study is to evaluate economic effect of the creation project of snow crab, Chionoecetes opilio, spawning and habitat ground in Uljin and Youngdeok county. The main results of this study are summarized as follows: first, 14,400 million won was invested in the creation project cost of Chionoecetes opilio spawning and habitat ground of Uljin and Youngdeok County from 2015 to 2020. Second, the creation project of Chionoecetes opilio spawning and habitat ground directly provides fishing benefits, festival benefits, research and development benefits and employment benefits. Third, on the basis of above benefits, the creation project of Chionoecetes opilio spawning and habitat ground has net present value of 29,900.53 million won, internal rate of return 16.9%, and benefit-cost of 2.91 under a 4.5% social discount rate. Also, the creation project creates 195 jobs. This indicates that the creation project of Chionoecetes opilio spawning and habitat ground not only contributes to the increase in the income of coastal fishery and fishing villages but also to the job making. The result of this study provides useful information to policy makers or project managers as it shows that the project to create spawning and habitat ground should be carried out in consideration of the resource and biological characteristics of individual fish and that economic assessment logic should also be developed based on this. Also, it proves that the project to create a snow crab spawning and habitat ground is a national and local infrastructure project that increases the actual fishing income in the region. At the same time, it maintains the reproducibility function of most fish species, along with enhancing the people's benefits such as fishing village tourism and marine product consumption. Moreover, it provides useful information on budgeting for the continuous development of snow crab spawning and habitat ground in the mid to long-term.

• Journal of Aquaculture
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• v.17 no.1
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• pp.30-38
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• 2004

To estimate the spawning period the annual change of gonadosomatic index (GSI) were examined from January 2000 to December 2001. Fecundity, spawning frequency and egg diameter were measured by ocular observation. Germ cell differentiation during gametogenesis, the reproductive cycle and the first sexual maturity of greenling Hexagrammos otakii were observed under light microscopy from January to December, 2000. GSI began to increase in August and reached the maximum in November when ovary was getting mature. The reproductive cycle of H. otakii can be divided into five successive stages in females: early growing stage (July), late growing stage (July to August), mature stage (September to October), ripe and spent stage (September to December), and recovery and resting stage (December to June). Males showed four successive stages : growing (June to August), mature (August to October), ripe and spent (September to December), and recovery and resting stage (December to May). According to the frequency distributions of egg diameter in spawning season, H. otakii could be one of polycyclic species spawning 2 times or more during one spawning season. Number of total eggs and mature eggs in the absolute fecundity were related to the standard length and body weight, respectively. Number of total eggs and mature eggs in relative fecundity were also proportional to the standard length, but rather these numbers decreased with body weight. Percentages of first sexual maturity of females and males in greenling were over 50% from 19.1 to 21.1cm in length, and 100% for fish over 25.1cm in length. Therefore, both sexes are ready to reproduce after one year old.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.3
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• pp.226-231
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• 2004

Maturation and spawning of Acentrogobius pflaumi were studied using samples collected from the Gwangyang Bay, Korea, from January to December, 1999. The gonadosomatic index (GSI) of the female was the highest in May. The spawning season lasted from May to June. There was a significant difference in the 1 : 0.59 sex ratio between males and females (p<0.01). The percentage of sexually mature females was over $50\%$ for the size group between 4.5 cm and 4.9 cm, and $100\%$ for the size group over 5.5 cm in body length. The size of eggs spawned was between 0.4 to 0.6 mm, and the spawning occured once a year. Fecundity varied between 3,600 and 9,700 eggs. The relationship between the fecundity and body length of the fish was expressed in the fecundity equation as; $F=0.294{\times}10^3\;BL^{1.899}.$ The first spawning length was 4 cm BL.

• Fisheries and Aquatic Sciences
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• v.25 no.12
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• pp.619-625
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• 2022

The study carried out a 15-day feeding trial of the fleshy shrimp broodstock that have just finished their first spawn using five different maturation feed types (three types of manufactured feed, fresh feed, and commercial feed) to induce multiple spawning in the shrimp and then analyzed and compared hemolymph levels of total protein, total lipid, hemocyanin, glucose, and cholesterol as well as ovary histology between the treatments to identify the potential of the experimental diets to be utilized as maturation feed. The study found that the manufactured diets of polychaetes + clam and polychaetes + clam + squid resulted in significantly higher levels of lipid and protein in shrimp hemolymph suggesting an indicator of multiple spawning in the fleshy shrimp. The other manufactured diet of polychaets + squid led to the highest 2nd spawning with significantly lower levels of lipid, protein, and cholesterol in shrimp hemolymph. The fresh feed treatment showed similar hematological as well as histological responses to the manufactured diet of polychaetes + squid, but with a significantly lower spawning volume compared to the other treatments. The study demonstrated that the manufactured diets could replace fresh feed as maturation feed and attain a higher shrimp maturation than the commercial feed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.650-655
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• 2020

Chilsan-do Island, South Korea, has previously been identified as one of the biggest spawning sites of the small yellow croaker Larimichthys polyactis in the Yellow Sea. To determine whether Chilsan-do still serves as a spawning site for L. polyactis, three to five stations around Chilsan-do Island were surveyed for eggs from April to June (the main spawning season of L. polyactis) in 2019, using an RN80 net. For the first time, three L. polyactis eggs were identified at two stations, located just in front of Chilsan-do Island and between Chilsan-do and the coastline, only in May. The diameter of L. polyactis eggs (1.26-1.34 mm) was very similar to those of Collichthys niveatus (1.30-1.37 mm) and Setipinna tenuifilis (1.34-1.35 mm). During the survey period, the sea surface salinity remained constant (32.0-32.1 psu), but the sea surface temperature (SST) rapidly rose from 13.6-13.7℃ in April to 22.1℃ in May. Our findings suggest that L. polyactis still spawns near Chilsan-do Island today, but on a very small scale, and that changes in SST promote spawning of L. polyactis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.4
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• pp.245-250
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• 2005

The maturity and spawning of Pacific cod, Gadus macrocephalus, was studied using samples caught by gillnets in the East Sea from January to December 2003. Monthly changes of maturity observed with the naked eyes for females showed that maturing Pacific cod appeared from August, and their numbers increased to $83\%\;and\;100\%$ in November and December, respectively. In January, mature and spawning Pacific cod were observed for the first time and composed over $40\%$ of the population. In February, the proportion of spawning individuals increased to over $50\%$, however, the mature individuals decreased to less than $10\%$. In March, mature fish were not found, and all were in an immature (spent) or spawning state. From April to July all fish remained in immature condition. The males maintained this trend with the females, whereas, mature males appeared from November to March. Monthly changes in the gonadosomatic index (GSI) of females and males showed higher values both in January and February and declined sharply in March. The lower value remained until October and then began to increase from November for the female population. For the males, however, this value remained lower until August, and then began to increase from September, and showed higher values in October through December than in January and February. These results indicated that the spawning season of Pacific cod was from December to March, and the main spawning season was from January to February, and the period of the spawning season was longer for males than the females. The diameter of the matured oocytes was 0.80-1.10 mm with a single mode of 0.95 mm. Fecundity was 1,300,000-9,400,000 in total length of 65-95 cm and the relationship between the total length (TL, cm) and fecundity (Fc) was Fc= $180,248\timesTL-10,883,638$. The total length at first maturity was observed at 57 cm for females and 47 cm for males. The size at $50\%$ group maturity was estimated to be 63.9 cm for females and 56.0 cm for males.

• Development and Reproduction
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• v.18 no.1
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• pp.25-31
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• 2014

This study was investigated spawning behavior, structure of egg masses and egg development in Aplysia kurodai inhabiting the coastal waters of Jeju Island, Korea. The mating and courtship behavior of A. kurodai occurred in the form of unilateral copulating with chain formation. In chain copulation, only the first animal acted as a female; the second and succeeding animals acted as males (sperm donors) to the animals in front and as females to the animals behind. The fertilized eggs were packaged in capsules that are embedded in jelly to form a cylindrical string called an egg masses. The number of capsule per cm of the egg masses was 55 to 60 capsules and each capsule within the egg masses held 15 to 25 eggs. After spawning, the egg masses were bright yellow or orange in color. This egg masses color not changed until embryos developed into trochophore stage. Thereafter, as embryo developed from trochophore stage to veliger stage the egg masses color became brownish. The fertilized eggs were spherical, with a diameter of approximately $80{\pm}1{\mu}m$ at spawning. At 5 to 6 days after spawning, the embryo developed into trochophore stage and began to rotate within the egg capsule. In the trochophore stage, the precursor of the velum, called the prototroch or prevelum, developed. At 10 days after spawning, the prevelum is transformed into the velum, and the trochophore developed into veliger stage. Between 10 to 15 days after spawning, the veligers broke out of the egg capsule, and hatched as free-swimming larvae.

• The Journal of Fisheries Business Administration
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• v.49 no.4
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• pp.109-129
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• 2018

This study is to evaluate economic effect of the creation project of Octopus Ochellatu spawning and habitat ground in Taean County. The main results of this study are summarized as follows: first, the creation project cost of Octopus Ochellatus spawning and habitat ground invested in Taean from 2015 to 2017 was 3,400 million won. Second, The creation project of Octopus Ochellatus spawning and habitat ground directly provides fishing benefits, recreational boat fishing benefits, festival benefits, research and development benefits, and employment benefits. Third, on the basis of above benefits, the creation project of Octopus Ochellatus spawning and habitat ground has a net present value of 14,478 million won, internal rate of return 60.8%, and benefit-cost of 5.03 under a 4.5% social discount rate. Also, the creation project creates 47 jobs. This indicates that the creation project of Octopus Ochellatus spawning and habitat ground contributes not only to the increase in the income of coastal fishery, recreational boat fishing business and fishing villages but also to the job making. In conclusion, with all these results, a project for making spawning grounds and habitats in the specified region gives species more numerically abundant and this gives more profits to fishermen in the coastal area. In addition, this project helps to make attractions to visitors or people who came to those specified regions to participate in events or have recreation, which means it improves profits to that fishing village and improve a settlement condition.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.4
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• pp.248-253
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• 2007

We studied the maturation and spawning of female Spanish mackerel (Scomberomorus niphonius) based on 445 specimens collected monthly from January to December 2004 in the coastal waters off Busan. The fork length (FL) of S. niphonius ranged from 26.1 to 105.4 cm, the gonadosomatic index (GSI) of the females was highest in May 2004, and the spawning season take place from April to July. A significant difference was detected in the sex ratio between females and males ($X^2$ test, p<0.01). The percentage of sexually mature females exceeded 50% in the 50-60 cm (FL) size group and reached 100% in the over 70 cm (FL) size group. Fecundity (F) varied between 201,156 and 836,426 egg per female. The relationship between F and FL of the fish was expressed as $F=5.8756FL^{3.8465}$. The relationship F and body weight (BW) was expressed as F=581.421 n (BW)-4108.5. The first spawning length was 41.8 cm (FL.)

• Animal cells and systems
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• v.5 no.1
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• pp.37-44
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• 2001

Gonadal development, reproductive cycle, gonad index, meat weight rate, and first sexual maturity of the top shell, Omphalius rusticus were Investigated monthly by histological observations. Specimens were collected from the west coast of Korea during the period from January to December in 1999. O. rusticus is dioecious and oviparous. The gonad is widely situated on the surface of the digestive g1and located in the posterior spiral meat part in the shell. The ovary and the testis were composed of a number of oogenic follicles and several spermatogenic follicles, respectively. Ripe oocytes were approximately 120-130 $\mu$m in diameter. The meat weight rate peaked in June (27.7%), and then rapidly decreased in September (19.5%). Monthly changes in the gonad index in both sexes reached the maximum in June, and then sharply decreased in September. Percentages of first sexual maturity of female and male snails ranging from 9.0 to 9.9 mm in shell heights were 58.3% and 54.5%, respectively, and 100% in those over 11.0 mm in both sexes participated in reproduction. Reproductive cycle of this species can be categorized into five successive stages: in females, early active (October to April), late active (December to June), ripe (April to September), spawning (July to September) and recovery (September to January): in males, early active (November to March), late active (December to June), ripe (April to September), spawning (July to September) and recovery (September to December). Gonadal development, gametogenesis, reproductive cycle, and spawning were closely related to the seawater temperature.