• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.203-213
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• 2011

Agriculture modern environments can vary due to factors such as land consolidation and ditch enhancement projects. But, these improvements projects can include cover-ing-up of irrigation ditches with concrete, increasing the drop between paddy field and drainage ditches, which might decrease the abundance and diversity of fish fauna around paddy fields. In this study, for the management of agrobiodiversity on fish in paddy fields, we installed a small-scale fishways between paddy fields and drainage ditches, and evaluated the effects on the eco-connection of the paddy fields, ditches and stream. Five fish species were recovered at the drainage ditches. The species exhibited characteristics spawning and growth based on the paddy field. The results indicate that the five fish species could ascend the paddy fields through the small-scale fishways. There are no difference of species numbers at ditches of environment-friendly agriculture paddy fields (A) and good agricultural practices (B) region, but individual numbers were higher at the B region. This result could be interpreted as indicating that ditch diversity was affected by positional properties rather than farming practices because the water flow and connection to adjacent stream of B region were better than A region. After ascertaining the fish species capable of ascending in a pre-survey of the drainage ditches, we set up small-scale fishways at the drop between paddy fields and drainage ditches. Three species of fish (Aphyocypris chinensis, Misgurnus anguillicaudatus, M. mizolepis) arrived at the paddy fields via small-scale fishways. The main movement time was from 18:00~24:00 and 00:00~06:00, indicating a preference for the night time period rather than the day period for migration. Concentrating the operation time from night to dawn seems prudent for effective management of small-scale fishways.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.57-69
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• 2023

The objectives of this study were to analyze the fish community structures and distribution characteristics of fisheries resources in the Osip Stream and Wangpi Stream, fishery resources protection areas. For the study, we conducted fish samplings four times in the two streams from April to October 2019. In Osip Stream and Wangpi Stream, we sampled 31 species and 29 species and the dominant species were Zacco platypus (28.6%) and Squalidus multimaculatus(41.7%), respectively. According to the life type of fish species, primary freshwater species were collected 18 species(58.1%) and 21 species(72.4%), and migration fishes were sampled 4 species (12.9%) and 6 species (20.7%) in Osip Stream and Wangpi Stream, respectively. Fisheries resources species showed high relative abundance in June, and the fish biomass was highest in October. As a results of comparing the previous studies with this study, both rivers showed high biodiversity and were found to maintain stable populations of fishes. According to analysis of tolerance guilds, the proportion of tolerant species, based on the number of individuals, was composed of 14.4% and 1.1% in Osip Stream and Wangpi Stream, respectively. This very low ratio of tolerant species confirmed that both streams have very good physiochemical environment conditions. From the above results, it was judged that the fishery resource protection areas of Osip Stream and Wangpi Stream have high ecological function and preservation value. For sustainable use and management of fishery resource protection areas of Osip Stream and Wangpi Stream, it is suggested that biological disturbance management, fish discharge projects considering environmental capacity, efforts to improve the habitat environment, and establishing a fishery resource protection areas management system were necessary as considerations.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.15-19
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• 2015

A fishway is a structure on or around artificial and natural barriers, such as dams, locks and waterfalls, to help fishes' natural migration. In this paper, a computational fluid dynamics (CFD) code, termed SNUFOAM is used to analyze vertical hydraulic characteristic of rollway of fishway. Volume-of-fluid (VOF) method was used to handle free-surface. It is important to determine the factors influencing flow characteristics in fishway because fish use directional information from the flow characteristics to navigate through fishway. Fishway was modeled in 2-D and the influence of the stream velocity, slope, and weir height of fishway was tested. In results, the transition Reynolds number was $2{\times}10^5{\sim}3{\times}10^5$.

• Journal of Environmental Science International
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• v.29 no.6
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• pp.633-641
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• 2020

Water temperature is one of the most important factors of fish survival, affecting the habitat, migration route, development, and reproduction. This experiment studied the induction level of heat shock protein (HSP70) mRNA and protein in a walleye pollock (Gadus chalcogrammus) primary hepatocyte culture based on different temperatures. Hepatocytes were attached at 7.5℃ for 24 hours. Hsp70 induction levels were then measured for 48 hours at 5, 8, 11, 14, and 17℃. The induction level was lowest at 5℃ and generally increased with temperature until 14℃. The induction level was reduced at 17℃, indicating that 14℃ is the highest tolerable temperature for hepatocytes. These data indicate that primary hepatocyte cell culture is under no stress at 5 and 8℃. Temperatures greater than 11℃ induce stress, showing similar induction patterns in both mRNA and protein in hepatocytes. The results suggest that 14℃ is the maximum internal defense temperature of walleye pollock survival.

• Journal of Biosystems Engineering
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• v.40 no.3
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• pp.261-270
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• 2015

Purpose: Cold storage is the most popular method used to preserve highly perishable foods such as beef and fish. However, at refrigeration temperatures, the shelf life of these foods is limited, and spoilage leads to massive food waste. Moreover, freezing significantly affects the food's properties. Ice crystallization and growth during freezing can cause irreversible textural damage to foods through volumetric expansion, moisture migration induced by osmotic pressure gradients, and concentration of solutes,which can lead to protein denaturation. Methods: Although freezing can preserve perishable foods for months, these disruptive changes decrease the consumer's perception of the food's quality. Therefore, the development and testing of new and improved cold storage technologies is a worthwhile pursuit. Results: The process of maintaining a food product in an unfrozen state below its equilibrium freezing temperature is known as supercooling. As supercooling has been shown to offer a considerable improvement over refrigeration for extending a perishable product's shelf life, implementation of supercooling in households and commercial refrigeration units would help diminish food waste. Conclusions: A commercially viable supercooling unit for all perishable food items is currently being developed and fabricated. Buildup of this technology will provide a meaningful improvement in the cold storage of perishable foods, and will have a significant impact on the refrigeration market as a whole.

• Journal of Environmental Science International
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• v.30 no.10
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• pp.811-820
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• 2021

The population variation of Spanish mackerel (Scomberomorus niphonius) according to its major prey abundance was analyzed using monthly catches of coastal set net fisheries in the southern waters off Gyeongsangnam-do and eastern waters off Gyeongsangbuk-do of Korea from 2006 to 2019. The abundance of Spanish mackerel and its prey species fluctuated almost simultaneously with time lags of +2 to -2 months between the set net fisheries in the southern and eastern waters. The generalized additive model revealed that the abundance of Spanish mackerel was influenced by its prey species such as hairtail and anchovy in southern waters, and common mackerel and horse mackerel in eastern waters. The model deviance explained 49% and 42% of Spanish mackerel abundance in southern and eastern waters respectively. These results suggest that the abundance of Spanish mackerel is affected by seasonal migratory prey fish species in the coastal areas and can be linked to their northerly migration.

• Korean Journal of Ichthyology
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• v.19 no.4
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• pp.318-323
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• 2007

The feeding habits of Pacific cod (Gadus macrocephalus) were studied based on the examination of stomach contents of 192 specimens collected from November, 2005 to January, 2006 in the coastal waters off Gadeok-do, Korea. The size of Pacific cod ranged from 35 to 82 cm in standard length (SL). Pacific cod mainly consumed shrimps such as Eualus spathulirostris, Crogon hakodatei and C. affinis and fishes. Its diet also included small quantities of cephalopods, amphipods, hermit crabs and crabs. Individuals between 35 cm and 45 cm SL mainly consumed shrimps. The portion of shrimps decreased with increasing fish size, and this decrease was paralleled with increased consumption of fishes and cephalopods. In this study we found Syngnathus schlegeli in the stomach contents of many Pacific cod specimens. S. schlegeli is a typical seagrass fish species which inhabits in seagrass beds, This fact means that Pacific cods stay in the seagrass beds during spawning period. Therefore migration of Pacific cod to coastal waters off Gadeok-do during spawning period seems to be a survival strategy for its larvae and small juveniles to stay in seagrass beds which provide with abundant foods and shelters to many commercial fish species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.4 no.1
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• pp.7-16
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• 1971

This paper deals with the numbers of vertebrae, gill rakers and relative growth of the Pacific saury, Cololabis saira along the eastern coast of Korea in May, July and December 1970. About 90 percent of the total fish population possessed 64-66 vertebrae with the mean of 64.80 and the mode of 65. The number of gill rakers varied from 33 to 44 in December with the mean of 37.08. With regard to the number of vertebrae and gill rakers of the medium (26.0-28.0 cm in fork length) and large (30.0-31.0 cm in fork length) sized groups, there are similarities between the northbound modium sized group and the southbound large sized one, and also between the southbound medium and southbound large sized groups. Although no correlation was found between the numbers of vertebrae and gill rakers, in December the number of vertebrae of the large sized group exceeded that of the medium sized group, and on the other hand the number of gill rakers of the large sized group was fewer than that of the meduim sized one. There was a tendency of decreasing in ratio of the head length to the fork length as the latter increased, The relationships between the fork length and the head length varied depending on the northbound and southbound migration of the fish. The same tendency was also seen in the relationship between the fork length and the body weight. The body weight increased from July to December (from medium to largo sized group) showed more than twice than that from December to the following July (from medium to large sized group). The coefficient of fatness remained constant in December, but a distinct variation was found between the medium and large sized groups in July, corresponding to the spawning sea-son of the fish. Relatively higher coefficient was found in December as compared to that found in July.

• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.423-432
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• 2008

The local migration or movement behavior of fishes in streams are related to feeding, spawning, growing, dispersing, and refuging. The pale chub (Zacco platypus) is a dominant species that migrates locally and inhabits in river and stream in Korea. However, dams, weirs, culverts and other regulatory structures are physical barriers that limit fish movement and fragment habits and populations. If main stream and off-channel habitats are connected with culverts, they would restrict the small fish as pale chub movement due to the high flow velocities and low depths. But in Korea, there is no experimental study to evaluate the swimming performance of species in Korea. Therefore, it is difficult to proposed that design guidelines for pass fishes through culverts. The purpose of this experimental study is to evaluate the swimming performance of pale chubs. A series of swimming performance test has been used in both of the fixed velocity and the incremental velocity methods in an experimental flume. As a result, the critical swimming speed for pale chub(body length 8.9 cm) was found to be about 0.7 m/s. Therefore, the flow velocity for culvert design in the low flow condition should not be exceed the its swimming ability, especially 0.7 m/s for pale chubs(body length 8.9 cm). And the minimum depth for culvert design in the low flow condition should not be lower than the fish body height add a dorsal fin height.

• The Journal of Fisheries Business Administration
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• v.18 no.1
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• pp.59-97
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• 1987

Tuna and tuna fishing extend over most of the tropical waters of the world oceans, especially, this study of the Indian Ocean and the fish and the fishing vessels are highly mobile. No country can deal in isolation with the problems of its tuna fishery and of any tuna fishery in its waters, without collaborating with other countries. This cooperation is often best established through some formal international mechanism. The essential requirements are for information-on the resources, the fishery, the trade-and to identify where management actions are needed to consore the resources or to maintain the economic or social function of the fishery. These will also usually require some form of international mechanism. With the changes in the Law of the Sea, the siuuation in respect of management of tuna-considered among the highly migratory species, requirng special treatment-has also changed. At present there are both uncertainty regarding tuna management and political arguments as to how such management can be best implemented. Bearing this in mind, together with the fact that only few tuna stocks have shown clear evidence of serious depletion through over-exploitation, present emphasis will be placed on information requirements. This study included compiling the data necessary to review the state of stoks in the Indian Ocean tuna fishing grounds. Information on the resources-where the fish are, their quantity, their movements, etc. is important, whether in planning development of new fisheries, or considering the need for collaboration with other countries (in ascertaining to what extent their catches may affect catches of the natoinal fleet) or for conservation measures. A major source of information is the statistics of for conservation measures. A major source of information is the statistics of catch and fishing effort from existing commercial vessels. These need to be assembled for all fisheries on the same stock on an oceanwide basis. The statistical data also need to be analysed and intepreted, and combined with biological data(e.g., on growth, mortality and migration rates) to provide information that is intelligible and useful for administrators and other decision-makers. This must also be undertaken on a resource-wide or ocean-wide basis. Finally, because of the world-wide similarities in the methods of datching, processing and marketing fish, there is a particular tut not exclusive need in those countries just beginning to develop their tuna fisheries-to have ready access to a syntheis of information on tuna, tuna biology and tuna fisheries and tuna fisheries economics and management on the Indian Ocean.