• Fisheries and Aquatic Sciences
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• 제26권8호
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• pp.491-499
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• 2023

Lake Tinisu Abaya is home to some fish species. The lake's native fish species include Barbus and Tilapia zilli. Tilapia fish (Oreochromis niloticus L.) were stocked in Lake Tinishu Aabaya in 1997. This study aimed to investigate the feeding behaviors of O. niloticus in Lake Tinishu Abaya to develop an appropriate fisheries management approach in the lake. 428 O. niloticus fish samples (2.5 to 30.9 cm and 1.1 to 475 g) were collected to calculate the diet composition. Out of the total of 428 gut contents examined, 55 (12.85%) were found to be empty and 373 (87.15%) to be containing one or more food items. The diet behavior of the stocked fish in the study lake revealed that phytoplankton (39.5% by volume) and macrophytes (25.81% by volume) were the most noteworthy food items followed by detritus (14.39%) and zooplankton (12.95%). With increasing fish size, the importance of phytoplankton, macrophytes, and detritus increased while the contribution of zooplankton, insects, and other foods with an animal origin decreased. Seasonal variation in the diet composition of fish was evident (t-test; p < 0.05). Macrophytes, zooplankton, and detritus were the dominating food items during the wet season, while phytoplankton predominated during the dry season. This study demonstrated that O. niloticus had phytoplanktivores that primarily consumed phytoplankton and that the seasons and fish size had a significant impact on their feeding preferences. The diet of O. niloticus in Lake Tinishu Abaya comprised foods with both plant and animal origins. It concludes that the dietary habit of O. niloticus in the lake is, generally, the omnivorous type.

• 생태와환경
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• 제56권2호
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• pp.172-186
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• 2023

불안정한 천이양상을 보이는 소형 호소는 대형 호소에 비해 동물플랑크톤 군집 동태 연구가 미진한 상황이다. 최근 지역 생물다양성 보전의 측면에서 소형 호소의 존재 가치가 부각되면서 생물 군집 동태 대한 이해의 필요성이 강조되고 있다. 본 연구는 세 소형 호소의 출현 동물플랑크톤을 월별로 채집하여 계절별 군집 동태를 분석하였다. 소형 호소의 복잡한 동물플랑크톤 군집 동태를 파악하기 위해 종 출현 패턴을 기반, 4개의 그룹(LALF Group, Low Abundance Low Frequency; LAHF Group, Low Abundance High Frequency; HALF Group, High Abundance Low Frequency; HAHF Group, High Abundance High Frequency)으로 그룹화하였다. 그룹 간 계절적 패턴을 비교하였으며, 각 그룹의 시간적 베타 다양성 기여도를 기반으로 한 다양성을 산출했다. 분석 결과 같은 출현량 경향을 보이지만 상반된 출현 빈도를 보이는 그룹 간의 관계가 있는 것으로 나타났으며, Nauplius가 세 호소공통으로 높은 출현량과 빈도를 보이는 종으로 나타났다. 적은 개체수를 보이면서 출현 빈도 역시 드물게 나오는 종들이 포함된 그룹인 LALF 그룹에 속한 종이 월별 천이와 다양도에 핵심인 것으로 분석되었으며 해당 그룹에는 Anuraeopsis fissa, Hexarthra mira 및 Lecane luna가 포함되었다. 한편 연중 특정 시기에만 출현하여 수체를 우점하는 종들이 포함된 그룹인 HALF 그룹이 호소 공통적으로 시간적 다양성을 저해하는 것으로 분석되었다. 본 연구의 결과를 통해 종 특이적인 출현 패턴이 연내 군집의 생물다양성에 기여하는 종을 분석하는 데 있어서 핵심적으로 작용할 수 있음을 제안한다.

• 수산해양기술연구
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• 제22권4호
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• pp.1-20
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• 1986

Physical, chemical and biological surveys on Nakdong River estuary were made from October, 1985 to September, 1986. 1. For all the seasons except summer, the sea surface temperature in northwest area of the line which linked from Seo Island to Jisim Island was I-2$^{\circ}$C lower than in southeast area, but in summer the sea surface temperature in northwest area was I-2$^{\circ}$C higher than in southeast area. On the contrary, bottom temperature of coastal area was 1$^{\circ}$C higher than that of oceanic area except winter. 2. Surface salinity in summer and fall has minimum value of 1. 9%0 and maximum value of 32.9%0. This large variation was caused by the runoff of the Nakdong River. Effect of less saline Nakdong River water in northwest area of the line which linked from Seo Island to Jisim Island was greater than in southeast area. A strong current rip always formed near this line. 3. The yellowish-green colored zone was observed in the Nakdong River estuary throughout the year by influence of river discharge. The characteristics of the water quality in the zone have shown that the water color was grade 7 by the Forel water-color meter, transparency was less than 4 m, and concentration of suspended solids was more than 5 mg/1. This water body was in the state of eutrophication in terms of chlorophyll-a and inorganic nitrogen concentration during summer season. 4. During the study period, total 276 taxa were identified. Most of them were diatoms and dinoflagellates which consisted of 97.5%. The component ratio of the above two groups was 84.4% and 13.1 % respectively. Diatoms were plentiful in December and dinoflagellates in July. Dominant species were Nitzschia seriata in October, Thalassiosira rotula in December, Skeletoncma costatum in April, and Nitzschia longissima in July. 5. A total of 47 zooplankton taxa was identified from the samples collected. Copepods were numerically the most important components of zooplankton communities in the study area. The domir:ant copepod species were Paracalanus parvus, Acartia clausi and Temora turbinata. Noctiluca scintillans was the next important component. The other zooplankton with minor abundance were Cladocera. Sagitta spp., Cnidaria, Mysidacea, Lucifer spp. and Amphipoda. 6. During the study period, fishes from 47 families and 87 species were sampled in th~ study area. The four most abundant fish species were Rep~mucen//'s valencicnnei, Leiognathus n~cha!is, Amblychaeturicllthys hexanema and Sardirel/a zun:zsi. The fish species of the secondary importance in abundance were Cynoglossus joyneri, Sillago sihama, Engra~lis japonicus, Encdrias nebulos'l, Acanthogobius flavimanus, Trichiurus lepturus, LiParis tanai/ai, Cynagloss//'s interruptus, Aj)ogon line:z!us, Thrissz la 1l.'1la!ensis, and Limanda yokohamac.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.952-958
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• 2009

The International Maritime Organization (IMO) has adopted the ballast water management convention at a diplomatic conference in early 2004 that all ships should be equipped with a treatment system from 2010 gradually. In this paper, the disinfection characteristic of ultra-violet (UV) rays was studied and a ballast water treatment system (BWTS) which can treat $50m^3$/h sea water was manufactured. The system consists of a disinfection chamber with six 3.5 kW UV lamps which are operated by magnetic ballasts, a programmable logic controller (PLC) and set of pipe lines. The biological disinfection efficacy of the prototype BWTS was evaluated following the IMO rules using zooplankton such as Artemia and Rotifer species for the size over $50{\mu}m$, and phytoplankton such as Tetraselmis and Thalassiosira species for the size between 10 to $50{\mu}m$. From the experimental results, the disinfection efficacy was 99.99 % that meets the IMO requirement. However, more studies on an energy saving system are needed because the consumption power of the prototype system is as high as over 21 kWh for $50m^3$/h.

• 한국해양학회지:바다
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• 제9권1호
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• pp.13-19
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• 2004

망목 크기가 다른 네트를 사용하여 같은 지역에서 동시에 채집한 동물플랑크톤 자료를 비교하였다 작은 망목의 네트가 상대적으로 적은 종류의 분류군을 포함하였다. 그러나, 망목의 막힘 현상(clogging) 때문에 인양 거리가 짧아져 시료의 크기(sample size)가 작아진 점과 채집된 개체들이 대체로 작은 것이어서 분류상의 어려움으로 상위 분류군으로 검색된 점 때문에 망목 크기와 채집되는 분류군의 다양성 관계는 일반화하기 어려웠다. 개체수의 관점에서는 큰 망목의 네트가 크기가 큰 동물들을 보다 많이 채집하고, 작은 망목은 크기가 작은 동물을 보다 많이 채집하였으며, 작은 크기의 동물들이 한 order정도 더 많이 분포하는 것으로 판단되었다. 이러한 망목 차이에 기인한 선택적 채집 강도의 영향으로 인하여 주성분 분석을 통한 군집분석의 결과는 서로 달라짐을 확인하였다.

• 한국물환경학회지
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• 제29권5호
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• pp.641-647
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• 2013

We installed mesocosms including zooplankton, fishs, artificial marshy land and aquatic macrophytes in Kyoungan stream to study the reduction effects of algae from Sep. 16 to Oct. 28, 2011. The control tendency of phytoplankton taxa was compared by analyzing community structure and dominant species in each mesocosm. Under the condition where Bluegill was absent, Daphnia similoides showed good effect of algal control since it has large food area and has high grazing pressure. Bluegill selectively preys upon large zooplankton, Daphnia similoides, as it also preys on small zooplanktons that flow in. In condition that Bluegill was absent, Daphnia similoides preyed selectively large phytoplankton (Cryptomonas ovata). Due to the shading of light, removal of nutrients and providing refuge for small zooplanktons, aquatic macrophytes and artificial marshy land showed high level of algal control. In corrals with aquatic macrophytes and artificial marshy land, the dominancy of genus Coelastrum and Pediastrum, which are difficult for small zooplanktons to feed on, relatively increased. In conclusion, under conditions of small number of predators such as Bluegill, Daphnia similoides is thought to be useful in algal bloom; however, when lots of predators are present, using small sized zooplanktons along with artificial marshy land and aquatic macrophytes is thought to be more useful than using large zooplanktons.

• 환경생물
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• 제38권3호
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• pp.461-475
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• 2020

여수와 제주도 사이 해역에 출현한 수표성 동물플랑크톤의 군집 분포와 환경요인 간의 관계를 파악하기 위해 2017년 9월 총 14개 정점에서 뉴스톤 네트를 이용하여 선박 측면에서 예인 및 채집하였다. 동물플랑크톤은 총 81개 분류군으로 요각류가 최우점하였다. 동물플랑크톤 출현 개체수를 기반으로 연안수의 영향을 받는 해역, 연안수와 외해수가 만나는 해역, 외해수의 직접적 영향을 받는 해역으로 구분되었다. 본 연구에서 해역별 우점 요각류, 식성에 따른 요각류를 2개 그룹으로 구분하고 군집에 미치는 환경요인을 분석한 결과 수온과 염분, 식물플랑크톤, 부유플라스틱과 유의미하였다(p<0.05). 추가로 연구 해역에 출현한 치어 및 화살벌레류의 위 내용물 분석을 통해 미세플라스틱 섭식을 확인하였다. 낮은 영양단계에서 섭취한 플라스틱이 먹이사슬을 타고 올라가 높은 영양단계로 전달된 것으로 보인다. 결과적으로 우리나라 남해 서부 해역에 출현하는 동물플랑크톤 군집 특성을 볼 때 여름철 확장 범위를 달리하는 섬진강 수, 제주난류, 쓰시마난류의 영향을 받아 군집 분포가 달라지는 것으로 판단된다.

• Fisheries and Aquatic Sciences
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• 제25권1호
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• pp.20-30
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• 2022

The present study was carried out to investigate the food and feeding habits of Oreochromis niloticus in Lake Shala to manage this species in this high Soda Lake. Stomachs of 226 fish (65.9%) had different food items, while those of 117 fish (34.1%) were empty. Phytoplankton was the dominant food categories occurring in 90.3% of the stomachs estimated and contributed 75.5% of the total volume. Bacillariophyceae (Nitzschia, Anomoeoneis, Navicula and Melosira) were identified as the most desired phytoplankton item. The prey items of O. niloticus differed among size classes (ANOVA, p < 0.05). The main prey items were zooplankton by the smaller-size class, and phytoplankton in fish of the larger-size class. Seasonal variation in the diet composition was evident (t-test, p < 0.05) and zooplankton, chironomids, nematodes, fish scales and detritus were important during the wet season, while phytoplankton predominates during the dry season. This study concludes that O. niloticus had a phytoplanktivores feeding mainly on phytoplankton and their feeding habits influenced by season and fish size in Lake Shala.

• Ocean and Polar Research
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• 제28권1호
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• pp.57-65
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• 2006

Various marine plankton were observed in the ballast water of vessels entering Incheon and Busan harbors. The ballast water of which age ranged from 2 to 54 days originated from the coastal waters of New Zealand, Taiwan, Singapore, Japan, Hong Kong and Pakistan, and from the Pacific Ocean. The total number of marine plankton taxa in 9 ballast tanks of different ships was 170: 90 phytoplankton, 24 protozoa and 56 zooplankton. The most diverse taxonomic groups were diatoms in phytoplankton, ciliates in protozoa and copepods in zooplankton. Classifying the specimens by size, above 50% of the number species of phytoplankton belonged to the size range between 50 and 150 Un. Protozoa and metazooplankton were found frequently in the size range between 50 and $120{\mu}m$ and 500 and $1,000{\mu}m$, respectively. The relationship between the species number and the age of ballast water was not significant. This is because of difference of filtration amounts derived from discordance of collecting samples. Among plankton observed in ballast water, some harmful algae and non-indigenous aquatic species were identified. Therefore, we need to investigate whether these species can inhabit in Korean coastal waters in further study.

• 생태와환경
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• 제46권3호
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• pp.332-342
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• 2013

주변 토지 이용이 다른 소부당과 명동저수지의 수변부와 개방수역간에 동물플랑크톤 군집 분포와 먹이망을 파악하기 위해 2011년 5월부터 10월까지 조사를 수행하였다. 소부당과 명동저수지의 동물플랑크톤은 각각 51종, 65종이 출현하였으며, 수변부와 개방수역간에 뚜렷한 밀도 차이를 보였다(t-test, P<0.05). 지각류와 요각류는 수변부에서 높은 밀도를 보인 반면, 윤충류는 개방수역에서 더 높은 밀도를 나타냈다(t-test, P<0.05). 수변부에서 출현한 동물플랑크톤 종은 주로 부착성 성향을 가진 종이었다(Lecane, Monostyla, Alona 그리고 Chydorus). Chl.a의 농도가 높은 명동저수지에서는 부유성 윤충류(Brachionus, Keratella 그리고 Polyarthra)의 높은 밀도가 관찰 되었다. Two-way ANOVA 결과, 윤충류는 서식처의 특성과 토지 이용이 다른 두 저수지간에 뚜렷한 차이를 보인 반면, 지각류와 요각류는 서식처의 특성에만 의존하는 것으로 나타났다. 저수의 영양상태가 주변 토지 이용과 밀접하게 연관되는 점을 감안하면, 윤충류는 서식처의 특성 뿐만 아니라 저수지의 영양상태에 따른 먹이자원에도 밀접하게 연관되는 것으로 보인다. 그러나 지각류와 요각류는 먹이자원보다 서식처의 특성에 주로 영향받는다. 안정동위원소 분석 결과, 부유성 Chl.a의 높은 값에도 불구하고 동물플랑크톤은 주로 부착입자 유기물에 대해 의존하였다. 이것은 실잠자리 유충, 검정물방개 그리고 새뱅이 같은 무척추동물과의 먹이 경쟁을 피하기 위한 것으로 사료된다. 결과적으로 동물플랑크톤 군집 분포는 습지의 공간적 특성 및 먹이자원에 의해 결정되는 것으로 보인다. 흥미로운 점은 동물플랑크톤 군집 밀도를 결정하는 수생식물이나 식물플랑크톤 등은 수체 내의 영양염류의 농도에 영향받으며, 이는 습지 주변 토지 피복이 매우 중요하게 고려된다는 것이다.