• Fisheries and Aquatic Sciences
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• v.10 no.3
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• pp.159-169
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• 2007

The complex 2-dimensional movements of fish during an annual migration circuit were generated and simulated by a chaotic model of fish movement, which was expanded from a small-scale movement model. Fish migration was modeled as a neural network including stimuli, central decision-making, and output responses as variables. The input stimuli included physical stimuli (temperature, salinity, turbidity, flow), biotic factors (prey, predators, life cycle) and landmarks or navigational aids (sun, moon, weather), values of which were all normalized as ratios. By varying the amplitude and period coefficients of the klinokinesis index using chaotic equations, model results (i.e., spatial orientation patterns of migration through time) were represented as fish feeding, spawning, overwintering, and sheltering. Simulations using this model generated 2-dimesional annual movements of sea bream migration in the southern and western seas of the Korean Peninsula. This model of object-oriented and large-scale fish migration produced complicated and sensitive migratory movements by varying both the klinokinesis coefficients (e.g., the amplitude and period of the physiological month) and the angular variables within chaotic equations.

• 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.

• Journal of fish pathology
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• v.36 no.2
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• pp.229-238
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• 2023

In this study, the correlation between clinical changes and RSIV genome copy number was investigated to determine the quantitative criteria for the characteristics of RSIV infection. The rock bream (Oplegnathus fasciatus) was intraperitoneally injected with three different doses (1.0×10¹, 1.0×10³ and 1.0×10⁵ viral genome copies/fish) as low, medium, and high doses, respectively. The clinical signs (spleen enlargement, death) observation and real-time PCR were conducted at 5, 10 and 14 days post-injection. During the experiment, spleen index as a quantitative indicator for spleen enlargement was continuously increased in the medium- (up to 2.26) and high-dose (up to 4.99) challenge groups, respectively. Notably, when the spleen index was over 1.5, 2.0, 2.5 and 3.0, a positive correlation was revealed with average viral genome copy numbers of 2.51, 3.37, 4.97 and 5.43×10⁷ viral genome copies/mg, respectively. Moreover, the threshold of spleen index over 1.5 was 1.0×10⁶ viral genome copies/mg, while the thresholds of spleen index over 2.0 and dead was 2.51×10⁷ viral genome copies/mg and the thresholds of spleen index over 2.5 and 3 was 3.98×10⁷ viral genome copies/mg. These findings suggest the possibility of quantitatively analyzing the characteristics and development process of RSIV infection.

• The Journal of Fisheries Business Administration
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• v.46 no.1
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• pp.15-28
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• 2015

This research examined a task to foster into the export industry, through analyzing the competitiveness of the ornamental fish industry and identifying the position of Korea's ornamental industry in the world. Ornamental fish in Korea holds the world's leading aquaculture technology, but products are limited to a few species, lacking competitive products. In the case of aquarium supplies, the Korean technology level is receiving relatively positive marks in the global market, but ornamental fish products are lagging behind the global trend. In other words, Korea's ornamental fish industry has the overall technical foundation, but lacks differentiation in the global market. Meanwhile, Korea's market share of world trade market in fishery products is minimal. Growth was also analyzed not high compared to other countries. Various trade competitiveness index results rated very low in competitiveness, but it is hard to compare Korea with other countries which have already built a strong foundation in the ornamental fish industry. Therefore, for the mid to long term Korea should adapt a "Choice and concentration" strategy and focus on the production of ornamental fish and aquarium supplies, which will enable Korea to become differentiated in the global market and capture the world exports.

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.172-182
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• 2009

This study was to analyze characteristics based on tolerance and trophic guilds and to determine the level of total mercury in tissues of sentinel species, Zacco platypus at 3 sampling sites of the Mangyeong River in 2007. Total sampled fishes were 26 species and the most dominant species was Zacco temminckii (47%). Fish community analysis was resulted that eveness index and diversity index showed low value at S1. However, diversity index and richness index at other sites showed high. According to various guilds analysis, relative abundance of sensitive species was 70% and 42% at S1 and S2, respectively. While sensitive species were decreased (1%) and tolerant species were increased (60%) at S3. It was mainly carried to the impacts of wastewater treatment plants near the location. Relative abundance of insectivore species was decreased from up (S1) to midstream area (S3). In addition, chemical water quality, based on analyses of BOD, COD, TP, TN, EC, MPN and SS concentration showed similar trends. Qualitative Habitat Evaluation Index (QHEI) was averaged 164, judged as "good" habitat condition. Average concentrations of total [Hg] was 146.9 ${\mu}g$ $kg^{-1}$. In the muscles of total [Hg] was the highest, and then followed by kidney, vertebrae, liver, and gills. According to FDA standards (500 ${\mu}g$ $kg^{-1}$) of Korea, total [Hg] has not affected to the individual fish health.

• Parasites, Hosts and Diseases
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• v.56 no.1
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• pp.41-48
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• 2018

The infection status of Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fish from a highly prevalent site, Wicheon (a branch of Nakdong-gang), which is located in Gunwi-gun, Gyeongsangbuk-do, the Republic of Korea. Total 1,162 fish in 32 species were examined by the artificial digestion method through 6 years. CsMc were detected in 720 (67.5%) out of 1,067 fish (26 spp.) and their density was 610 per fish infected. In the susceptible gobioninid fish group, i.e., Pungtungia herzi, Squalidus gracilis majimae, Squalidus japonicus coreanus, Sarcocheilichthys variegatus wakiyae and Pseudorasbora parva, all of 323 fish were infected with an average of 1,310 CsMc. Total 23 (95.8%) gobioninid fish, i.e., Pseudogobio esocinus, Abbottina springeri, Hemibarbus longirostris, Microphysogobio koreensis, and Microphysogobio jeoni, were infected with 127 CsMc in average. In the acheilognathinid fish (bitterlings) group, the prevalence was 77.0%, and the density was 50 CsMc per fish infected. In the rasborinid fish (chubs) group, i.e., Zacco platypus, Zacco temminckii, Zacco koreanus, and Opsariichthys uncirostris amurensis, 147 (36.5%) out of 403 fish examined were infected with 15 CsMc in average. The susceptibility indices of CsMc were 412 in the overall positive fish group, 1,310 in the gobioninid group-1, 122 in the gobioninid group-2, 38.5 in the acheilognathinid group, and 5.5 in the rasborinid fish group. Conclusively, it was confirmed that CsMc are highly prevalent in fish from Wicheon, and their infection tendency varied according to the subfamily groups in Cyprinidae fish hosts.

• Journal of fish pathology
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• v.6 no.1
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• pp.11-20
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• 1993

To study the immune responses of the japanese eel. Anguilla japonica, fish were injected intraperitoneally with several types of Edwardsiella tarda antigen, i. e., FKC(formalin killed cells), HKC(heat killed cells) or LPS(lipopolysaccharide), and the changes of immunocytes numbers, phagocytosis and agglutination titre in the peripheral blood of the fish were investigated. The number of lymphocytes in the peripheral blood of eels were decreased until 6 hours after injection, and then were turn to normal levels after 24 hours of injection. However, the level were slightly increased and were remained after 24 hours. The number of neutrophils of FKC, HKC or LPS injected fish were the highest at 12 hours after injection and were decreased slowly after that. Three weeks after the injections, the agglutination of antibody titre of all immunized groups were reached at 128 and were remained this level thereafter. However 6 weeks after the injections, that in HKC injected fish were dropped the level up to 4. Fish were injected with LPS and the blood from the fish were bled after 12 hours. Then the blood were incubated with E. tarda. Six hours after incubation, the phagocytic index was reached the highest level, 28.3. One week after the LPS injection, the blood were again bled and incubated with E. tarda. The phagocytic index at this time was 3.9. The phagocytic indexes of the fish injected with FKC and HKC, treted as same LPS injected fish as above, were 18.8 and 10.7, respectively. The phagocytic index of the control fish was 1.2. The antibacterial activities of normal antiserum against E. tarda were shown for both FKC and LPS injected fish, but not for HKC injected fish. The RPS(relative percentage of survival) of HKC, FKC and LPS injected fish in the challenge test were 10%, 20% and 30%, respectively. These results suggest that the effect of protection of the eel which were injected with antigen were varied with the method of preparation of the antigen.

• Korean Journal of Environmental Biology
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• v.20 no.2
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• pp.152-157
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• 2002

The fauna of freshwater fish and the structure of fish community were investigated from March to October in 2001 at six stations in the middle reach of the Seomjin River, Gokseong-gun. The collected fishes (1,786 individuals) were identified into 30 species of 22 genera belonging to S families. Of them, cyprinid fish occupied 26 species, only one species (Rhinogobius brunneus) was secondary freshwater fish. Dominant species was Zacco platypus (dominance index: 24.2%) and subdominant species was Pungtungia herzi (10.7%). The endemic species of Korea were 11 species including Rhodeus uyekii (36.7%) about the ichthyofauna. In estimation of water quality by diversity indices, the general conditions of water quality of all survey times and all stations were relatively fine $(\beta$-mesosaprobic, diversity index: 2.70). But four survey sites except St. 2 and St. 3 showed severe water pollution with one or move times in total survey periods.

• Journal of Environmental Impact Assessment
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• v.18 no.3
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• pp.151-160
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• 2009

In order to use fundamental data for conservation of species diversity and stream health with dam development, fish investigation in up- and downstream of Pyeonglim Dam was seasonally conducted in 2007~2008. In addition, data of water qualities, investigated for environmental impact assessment, were used to determine a water quality standard level in Pyeonglim Stream, and it revealed that water environment condition was good in the stream. During the study period, a total number of fish caught from the 4 study sites was 5,449 representing 9 families 25 species, and there were 8 Korean endemic species (32.0%) including Rhodeus uyekii, Squalidus gracilis majimae, and Microphysogobio yaluensis. Two species of Zacco temminckii (37.5%) and Zacco platypus (26.3%) were dominant and subdominant in all sites. There were few individuals of the $2^{nd}$-class endangered species (Sand lamprey, Lampetra reissneri) and the introduced species (Bluegill, Lepomis macrochirus), found in the upstream of the dam. and further investigation for conservation of the endangered species and for prevention of the introduced species is needed in future. With fish fauna and multi-metric health assessment model in each sampling attempt, index of biotic integrity(IBI) was evaluated and it resulted mostly in good(26~35) and excellent(36~40) condition in all sites. The results indicate that it is very important to study not only environmental impact assessment with fish composition but also stream health assessment in order to conserve healthy aquatic ecosystem.

• Journal of Aquaculture
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• v.19 no.2
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• pp.133-139
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• 2006

The gossypol existed in cottonseed meal is a well known antispermatogenic agent which can impair reproductive performances of male fish as well as mammals. Two feeding experiments were conducted to examine a toxic effect of dietary supplementation of cottonseed meal on reproduction in juvenile olive flounder (the first experiment) for 19 weeks and growing olive flounder (the second experiment) for 26 weeks. After each feeding study, females and males were sampled for histological examination in gonads and liver to verify any negative effects by the dietary supplementation of cottonseed and soybean meal on reproduction. After two feeding trial, the gonad somatic index (GSI) of male and female (from the first feeding trial) were not significantly different among all the dietary treatments. The GSI values of female (from the second feeding trial) were not significantly different among all the dietary treatments. However, males fed cottonseed and soybean meal containing diets exhibited significantly lower GSI than that fed the control diet after the second feeding trial. Histological examination of gonads and liver of fish fed cottonseed and soybean meal did not show any negative effects compared to those of fish ffd the control diet. Hepatosomatic index of fish in the first and second feeding trials were not significantly different among all the dietary treatments. The findings in this study suggest that dietary supplementation of cottonseed and soybean meal up to 40% fish meal replacement might not deteriorate the gametogenesis of juvenile and growing olive flounder. However, the supplementation in diets over 30% fish meal replacement might reduce GSI of male in growing olive flounder.