• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.595-603
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• 2014

This study is aimed to analyze the hydrodynamic characteristics of the cage net in the circulating water channel. It visualized wake flows using a PIV (paricle imaging velocimetry) and analyzed the flow velocity distribution. In addition, the vorticity and turbulence intensity were analyzed from the wake flow distribution and compared changes by flow velocity. Results showed that the average turbulence intensity in the circulating water channel was very stable showing less than 1% in the range between 0.2 and 0.8 m/s. The drag coefficient affecting to the netting was estimated to be 1.35. The flow decreasing rate of the wake in the middle of the netting was 2.1% at the range of 0.2 m/s and it was constant at 6.6-6.9% over the range of 0.4 m/s irrespective of velocity increases. Finally, the change of turbulence intensity by netting and knot mesh could be confirmed. These results can be utilized as a basic information for the future research of flow characteristics by fishing nets and meshes.

• Development and Reproduction
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• v.24 no.2
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• pp.79-88
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• 2020

This study was carried out to obtain information on the developmental biology and the management of biological resources of the abalone Haliotis gigantea in Korea. The sex ratio (female:male) in the present study was 1:1.7 and the proportion of females was 36.6% (n=106/290). Their gonadal structures displayed definitive seasonal changes which were similar in pattern to the changes in the gonad index (GI). The GI showed a pattern of definitive seasonal changes in both males and females it was high in the fall and low in the spring. The reproductive cycle could be categorized into the following six stages: inactive, early active, late active, ripe, spent, and degenerative stage. Based on the monthly changes in GI and stages of gonadal development, October to November was determined to be the main spawning period for H. gigantea on Jeju Island, Korea.

• Fisheries and Aquatic Sciences
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• v.21 no.3
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• pp.12.1-12.15
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• 2018

A preliminary investigation of length-weight relationship, condition factor and reproductive ecology of African pike fish, Hepsetus odoe, was conducted between June to August 2010 in Lake Eleiyele. A total of 90 samples of the fish species were caught by fishermen using gill nets. The results obtained showed that fish species had isometric growth pattern (contrary to negative allometry expected) with the growth exponent, b value of 2.64, that is not statistically different from 3 and with high statistical power of 0.866 when tested. The mean condition factor, K, was found to be 2.6, indicating that the fish species were in good condition in the study area. For reproductive biology, mean fecundity and gonadosomatic index were found to be 1349 eggs and 3.53% respectively. This study was necessary to fill the knowledge gap and provide information for management and conservation of the investigated species in the lake system. This study recommended that further research needs to be conducted because the sampling was carried out in the rainy season period and within a quarter of a year.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.596-616
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• 2021

A global increase in fish consumption has led to a rapid expansion of aquaculture production, which has been linked to enhancing the spread of infectious diseases. Viral diseases can cause high mortality in many cultured fish species, posing a serious threat to the aquaculture industry. Infectious hematopoietic necrosis virus (IHNV) is one of the primary threats to aquacultured salmonid species, causing huge economic losses. Since the first report in cultured sockeye salmon Oncorhynchus nerka during the 1950s in North America, IHNV has spread to other regions, including Europe, Asia, South America, and Africa by transportation of infected fish and eggs, causing disease and increasing mortality in a wide variety of salmonid species. Here, we review existing information relevant to IHNV: its phylogenetic characteristics, origin, infection history, virulence determinants, susceptible hosts, vectors, and vaccine development. This review also addresses a possible cross-species transmission of IHNV to a new host, olive flounder Paralichthys olivaceus, a cultured fish of economic importance in East Asian countries.

• Journal of fish pathology
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• v.34 no.1
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• pp.9-15
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• 2021

Rock bream (Oplegnathus fasciatus) is a highly valued aquaculture species in Korea. However, the aquaculture industry suffers huge economic losses due to rock bream iridovirus (RBIV) infection in summer. The objective of this study was to determine genetic diversity and relationships of DNAs isolated from two groups of rock bream after RBIV infection using five microsatellite (MS) markers. The first group of fish died early and the second group of fish died later after RBIV infection. In this experiment, 90 fish (5.1±1.0 cm and 4.1±1.3 g) were injected with 50 μl of RBIV (10⁴ TCID⁵⁰/ml) and maintained at 26℃ for 15 days. Genomic DNAs were extracted from fins of 20 fish that died earlier or later after RBIV infection. These DNAs were subjected to genotyping using five MS markers (CA-03, CA3-05, CA3-06, CA-10, and CA3-36). Of these markers, CA3-05 (early death group), CA3-06 (late death group), and CA3-36 (both early and late death groups) showed different alleles distribution rates. In-depth studies are needed to provide valuable information for selecting RBIV-resistant fish. In conclusion, microsatellite marker distribution pattern differences between early- and late- death groups of rock bream after RBIV infection showing different RBIV susceptibilities were determined using MS markers and genotyping. Results of this study suggest that MS markers could be used to facilitate the selection of RBIV resistant rock bream.

• Journal of Aquaculture
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• v.20 no.1
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• pp.26-30
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• 2007

Resources of the sea cucumber, Stichopus japonicus in the west coast of Korea are decreasing sharply due to overfishing and severe marine pollutions. Artificial seed production and release of this species need to be conducted to maintain sea cucumber stock in the region. In this study, to provide basic information for such works, reproductive cycle of sea cucumber collected from Anmyondo in the region was histologically studied for a year from October 2004 to September 2005. This species was dioecious, and its gonads was composed of a number of gametogenic follicles. The gonadosomatic index (GSI) was reached the maximum in June (7.91), and the minimum in October (0.42). The main spawning occurs between June and August. The reproductive cycle of the sea cucumber could be divided into five stages: multiplicative stage (January to March), growing stage (March to April), mature stage (April to July), spawning.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.562-563
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• 2004

Environmental management system has been constructed using by marine GIS, which is applied latest scientific algorithm, and fisheries related data for the citizens of the Jinhae Bay and executive officers. Through this system, we will get more easily marine environmental data, and production features of aquaculture farming areas.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.257-258
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• 2001

The freshwater snail genus Semisulcospora is widespread in Korea, Japan, Taiwan and China (Davis, 1969). Semisulcospira gottschei is becoming a candidate shellfish species for aquaculture in Korea. Although amino and fatty acids composition of S. gottschei has been reported by Sim et al. (1994), no information on nutrient requirements for this species is available. (omitted)

• The Journal of Fisheries Business Administration
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• v.37 no.1 s.70
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• pp.45-71
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• 2006

The main objective of this study is to analyze problems of the Country of Origin Labeling(COOL) in small live fish(SLF) trade by applying the asymmetric information theory which is called ${\ulcorner}$Lemon Market Theory${\lrcorner}$. The purpose of importing SLF is to enhance fishing household income and import substitution effect as well. SLF importation is quite different in its nature from importing general fish and fish products for final/direct consumption. SLF are imported for the purpose of domestic aquaculture and naturalization where domestic production/supply of SLF is less than domestic demand for or such species are not native to Korean waters. Information asymmetric problems arise even in SLF trade as the same way in general goods and services. However, the information asymmetry issues in SLF trade are much more complex than non-living goods because SLF are traded in the live state. To alleviate such problems the Korean government initiated the general COOL scheme to imported SLF. However, many experts argues that such policy on SLF would not be appropriate because of SLF's very nature. Applying the lemon market theory, we can analyze how information discovery schemes are able to signal correct information to SLF trading parties and to result in more symmetric information in SLF trade markets. This research carried out a case study about small live eel(SLF) trade and its farming. The results showed that applying the COOL to small live eels just right upon coming into fish farms tends to increase substantially fish farmer's income and at the same time to lower unnecessary transaction costs. In particular, such transaction costs by imposing simply the general COOL on SLF may easily outweigh its benefits. For instance, to resolve the problems, the Korean ministry of agriculture and forestry(KMAF) has developed a quite different COOL rules from the general ones and has applied them to imported live cattle and medium/small livestocks. The KMAF's differentiated COOL policy on some imported livestocks may be a good case which can be applied to imported SLF. In addition to the differentiated COOL on SLF, Sanitary and Phytosanitary (SPS) and traceability system would play crucial complementary roles in alleviating information asymmetry problems in SLF trade. Advanced fisheries tend to strengthen their SPS system rather than to adopt the general comprehensive COOL schemes into imported SLF trades and domestic market exchanges.

• Korean Journal of Ichthyology
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• v.24 no.3
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• pp.220-226
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• 2012

The aim of this study is to observe the reproductive behavior of the marine medaka, Oryzias dancena, and determine the factors of reproductive behavior to provide useful information for improving their artificial reproduction techniques. The reproductive behavior of the marine medaka was observed in laboratory aquaria. Once the experiment began, all of the males chased the females. The males attempted to stimulate the urogenital openings of the females. While chasing a female, a large male would bite a relatively small male's anus. Larger males expelled smaller males with biting, and the defeated males were barred from the female. After the other males were expelled, the remaining male approached and drew alongside the female. The male's dorsal and anal fins covered the female's body. Spawning began after complete covering took place. Spawning of males and females occurred simultaneously. The loadings for 2 factors were calculated. The calculation was restricted to 2 factors because these 2 factors explained about 81% of the total common variance (P<0.05) and the following factors possessed no practical significance. Two movements (biting, expelling) had high positive values for factor one. This factor related a male's defensive behavior to courtship behavior and spawning, and explained 23.1% of the total common variance (P<0.05). The second factor had high positive values for chasing, rejection, covering, and parallel swimming. This factor related a male's courtship behavior and female's defensive behavior to spawning, and explained 59.7% of the total common variance (P<0.05). This research provided basic biological data for the conservation of this species and useful information for improving their artificial reproduction techniques.