• Korean Journal of Microbiology
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• v.33 no.1
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• pp.66-71
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• 1997

호수 생태계내의 생물군집은 생산자로서의 식물플랑크톤과 소비자로서의 동물플랑크톤 및 어류가 주된 위치를 차지하고 세균은 분해자로서 기능한다는 것은 일반적으로 알려진 사실이다. 그러나 1970년대에 들어 세균군집이 생태계내에서 먹이사슬을 연계하는 2차 생산자로서도 기능한다는 사실이 제기되어, 오늘날에는 생태계내에서 세균군집의 역할이 보다 강조되고 있다(6,40,41,42,50). 먹이사슬에 대한 관심은 많은 연구결과들을 생산하였지만 복잡한 먹이사슬 구조는 아직까지 부분적인 이해만을 허락하고 있다. 특히, 어류, 동물 플랑크톤, 식물플랑크톤, 미생물의 각 분야가 서로 구분되어 발전해 왔기 때문에 이들간의 상호작용을 정확하게 밝히는 데에는 많은 한계가 있어 왔다. 1970년대 이래로 담수생태계의 부영양화를 해결하기 위한 방안으로서 생태계내의 먹이 사슬을 이용하는 생물조작의 개념이 대두되었으며, 각 분야의 통합적 연관성을 필요로 함으로써 생태계 이해에 많은 지식을 제공하였다. 이 글에서는 담수생태학의 한 분야로서 생물군집간의 상호작용인 먹이사슬의 연구동향을 생물조작 개념을 중심으로 기술하고자 한다.

• Proceedings of the Korean Aquaculture Society Conference
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• 2005.05a
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• pp.32-33
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• 2005

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.275-279
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• 1977

During the experimental rearing period of common carp in a small simple recirculating aquarium combined with frequent exchanges of water and cleanings, some observations were made on the conditions of fish growing which was directly and instantly affected by the cleaning frequency of strainer, changing rate of water, division and frequency of feed supply, prohibition of excess feeding and the amount of dissolved oxygen. The fish don't seem to be stressed by the manipulation for the change of rearing water, cleaning of detritus in the strainer and filter. It appeared that the most hazzardous matters to fish growth were : 1) supplying feed when fish do not show active response to feed supplied, and 2) giving ample amount of feed at one time. When especially the amount of the feed is within the range fish instantly can swallow, the water clarity is maintained even after feeding operation, but if any excess amount is given the fish intake into mouth much more feed than able to instantly swallow and try to swallow it resulting in much dissolving and suspension of feed materials in water, making the water quite cloudy. Consequently all the water as well as filter bed becomes significantly polluted.

• Journal of Marine Life Science
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• v.1 no.2
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• pp.121-125
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• 2016

This study examined the feeding response of the harpacticoid copepod, Tigriopus japonicus exposed to WAF or CEWAF to understand whether decreased feeding of the copepod by oil exposure is induced by food avoidance or medium toxicity. In the medium without WAF, there was no difference in the ingestion rate of the copepod among all polluted diets those were exposed to different concentrations of WAF. The present of WAF in the medium however caused a decrease in the ingestion rate at 100% WAF treatment. In the mixed diet treatment with adhesive diatoms and Tetraselmis suecica, T. japonicus had significantly lower ingestion rate on adhesive diatoms than on others in the medium with CEWAF. As a result, decreased ingestion of T. japonicus by oil exposure was caused by oil toxicity in medium, which may not have directly related with an avoidance of polluted food organisms.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.2 no.1
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• pp.47-62
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• 1969

A goby, Synechogobius hasta (Temminck et Schlegel) was studied to investigate the food consumed and the biological change of the food organisms, and the fish were sampled from the closed tributary and the lower Part of the Naktong River, near Pusan, during the period from November of 1967 to December of 1968. The fish were sampled from four stations (Fig. 1), the total number of fish being 1,295 and they were grouped and analysed monthly. The content of the alimentary canal was analysed in three categories according to modified Nilsson's method (Dahl 1962) with a slight alteration: 1) The number of each item of stomach contents was counted and the percentage of each item in proportion to the total number of food organisms is indicated by the letter 'N' representing numerical percentage in Table 2. 2) The percentage of fish which contained any items of food organisms in proportion to the total number of fish caught in a given season is indicated by the letter 'O' representing frequency of occurrence. 3) Dominant groups of food items were selected and the percentage of the number of each dominant item in proportion to the number of the food organisms belonging to the dominant groups is indicated by the letter 'D' representing dominance. All food organisms were classified in 50 food item categories and then they were grouped in 13 main groups (Fig. 2-1), and they were further divided into 1) obligatory bottom animals, 2) organic drifts and 3) actively swimming forms; according to the conditions of the animal communities within the habitat. Since the majority of its food was composed of the obligatory bottom animals ($94.6\%$), the fish appeard to be a typical bottom feeder. And the dominant food organisms of the fish is generally determined by the local composition of the benthic fauna within the fish habitat. And their seasonal rhythm occurs among the food organisms in the stomach by the biological interaction. Locality variation in the population of the same food organism occurs due to the difference of food organisms in the habitat of the fish at Seonam and Garak, and at Seongsan and Hadan the condition of the niche for the fish in the both regions seems to be the same since the composition and the seasonal variation of the organisms were the same. The results may be summarized as follows: 1) The goby mainly feed on the animals of bottom fauna, and the food organisms are deter-mined by the food compositions within the habitat. 2) Seasonal variation of the stomach content shows the seasonal rhythm due to the biological variation of the population and their interaction. 3) The goby shows no preference on specific food, and the food is composed of a variety of animals. 4) Major food items of the goby are Polychaeta, Palaemon modestus, Isopoda, Gammaridea, Insecta (nymphs and larvae), Ilyoplax deschampsi, and Paratye compressa. 5) Logitudinal succession oil the population of the food organisms is apparently recognized within the community of Seongsan, Garak and Seonam. 6) The goby begins to descend toward the estuary and sea around April when the water temperature reaches $20^{\circ}C$, and they begin to return to river waters in September.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5206-5210
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• 2012

We studied the effect of food concentration on grazing, growth and fecundity of cyclopoid copepod Paracyclopina nana. Marine phytoplankton Tetraselmis suecica was used as a livefood for the copepod. Six stage compositions were used and food concentrations for the experiment were 0.5, 1, 2, 5, 10, 20, 40, 60 and $80{\times}10^4$ cells/mL. Range of food concentrations with 0.2, 0.5, 1, 2, 3 and $4{\times}10^4$ cells/mL were used for nauplii production experiment. Grazing rates of P. nana in all developmental stages on the different concentrations were increased with increasing diet concentration. While the growth of nauplius was not affected by increase of food concentration, food concentration outside of $1{\times}10^4$ to $5{\times}10^4$ cells/mL range negatively affected that of copepodite. Daily nauplii production was increased with increasing food concentration but $3{\times}10^4$ and $4{\times}10^4$ cells/mL treatments were not significantly different with $2{\times}10^4$ cells/mL treatment. As a result, optimum concentration of T. suecica for mass culture of P. nana was considered to be 5,000 cells/mL for nauplius stage, 10,000 cells/mL for copepodite stage and adult male, 20,000 cells/mL for adult female, respectively.

• Korean Journal of Environment and Ecology
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• v.21 no.1
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• pp.30-37
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• 2007

Pellets and prey remains were analyzed to compare diets and foraging tactics of Eurasian eagle owls (Bubo bubo) in two different habitat types: forested areas and open fields. Overall 150 prey items of three taxa were identified from 66 pellets and 82 prey remains, and the birds were the most important prey in biomass (78.04%) and in frequency (56.67%). Eurasian eagle owls frequently used rats (Rattus spp.), ring-necked pheasants (Phasianus colchicus), and stripped field mice (Apodemus agrarius), but the ring-necked pheasant was most important in biomass in both habitat types. The owls generally foraged various prey in biomass but the mean mass of vertebrate prey used by the Eurasian eagle owls was 503.3g in central Korea. According to the comparison of diets in the two different habitat types, the owls used bigger and more diverse prey in forested areas than in open fields. In forested areas, the Eurasian eagle owls frequently foraged the pheasants and Mandarin ducks (Aix galericulata), but they preferred prey of particular sizes to prey of particular taxa. In open fields, however, the owls showed opportunistic foraging tactics by selecting many small mammals such as rodents or a few large birds.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.1
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• pp.50-56
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• 1988

In order to fine some proper bacterial food for Tigriopus japoncus, bacterial flora of the tide pool inhabited by the copepod has been isolated and tested as bacterial food. Food effect and optimum density of the bacteria in terms of survival rate of the copepod was measured in the larval and the adult stages. Among the 264 strains of isolated bacteria, Acinetobacter spp. Moraxella, spp., Flavobacterium spp. and Pseudomonas spp. were certified as effective food for the copepod. According to the experimental results, Acinetobacter spp. AG-3 was the most effective food for all the stages from nauplius to adult, while Moraxella spp. and Flavobacterium spp. were effective for copepodite stage, and Pseudomonas spp. for the adult stage only. The optimum density of bacteria for the food was about $10^6\;cell/ml$, which was the same average density of bacteria in the tide pool.

• Korean journal of applied entomology
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• v.34 no.2
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• pp.95-99
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• 1995

Acid phosphatase(AP) of he aphid, Megoura crassicauda and the major component of the lady beetle's artificial diet, fresh chicken liver, was adapted as a model protein to study the digestion of diet proteins in the midgut of Harmonia axyridis. The lady beetle did not secrete its own AP into the lumen of the midgut. The aphid and the live chicken liver had AP which was still alive in enzymatic activity from the extract of the lumen of the midgut of the lady beetle. The digestive ability of the lady beetle on proteins turned out to be different depending on food sources. In the lumen of the midgut of the lady beetle, though most of AP of live chicken liver lost its activity withtin 12 hours, that of M. cassicauda kept strong enzymatic activity up to 24 hours.

• Journal of Aquaculture
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• v.21 no.3
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• pp.184-189
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• 2008

Tryptic enzyme activities in the digestive glands (hepatopancreas) and digestive tracts of Pacific white shrimps Litopenaeus vannamei were assayed at three water temperature regimes. At $26^{\circ}C$, trypsin activity in the hepatopancreas was 200% higher than at $23^{\circ}C$ and 300% higher than at $20^{\circ}C$. The highest foregut trypsin activity levels showed no significant difference in the temperature regimes, but the time between peaks in foreguts and midguts shortened at higher temperature. In the midgut, the level of enzyme activity was highest at $26^{\circ}C$ regardless of the amount of ingested feed. The ratio of foregut and/or midgut dry weight to the body wet weight indicated feed movement through the digestive track directly and gave accurate account about the feeding mechanism. Maximum feed ingestion in the foregut was equivalent to 0.6% of the body weight (wet weight) at $23^{\circ}C$, 0.4% of the body weight at $20^{\circ}C$, and 0.5% of the body weight at $26^{\circ}C$. In view of the temperatures chosen for this study, although maximum ingestion was observed at $23^{\circ}C$, the shrimps showed highest enzyme activity, but lowest feed retention time at $26^{\circ}C$ and lowest enzyme activity, but highest retention time at $20^{\circ}C$.