• ALGAE
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• 제34권4호
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• pp.289-301
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• 2019

Mixotrophy in marine organisms is an important aspect of ecology and evolution. The discovery of mixotrophic abilities in phototrophic dinoflagellates alters our understanding of the dynamics of red tides. In the phototrophic dinoflagellate genus Alexandrium, some species are mixotrophic, but others are exclusively autotrophic. There are differences in the ecological roles of autotrophic and mixotrophic Alexandrium in marine food webs. However, of the 34 known Alexandrium species, the mixotrophic ability of >20 species has yet to be explored. In this study, the mixotrophic capabilities of Alexandrium insuetum CCMP2082, Alexandrium mediterraneum CCMP3433, Alexandrium pacificum CCMP3434, Alexandrium tamutum ATSH1609, and Alexandrium margalefii CAWD10 were investigated by providing each species with 22 diverse prey items including bacterium-sized microbeads (1 ㎛), the cyanobacterium Synechococcus sp., algal prey species, and the ciliate Mesodinium rubrum. None of the 5 Alexandrium species fed on any of the prey items. These results increase the number of Alexandrium species lacking mixotrophic abilities to 9, compared to the 7 known mixotrophic Alexandrium species. Furthermore, the Alexandrium phylogenetic tree based on the large subunit ribosomal DNA contained 3 large clades, each of which had species with and without mixotrophic abilities. Thus, the acquisition or loss of mixotrophic abilities in Alexandrium might readily occur.

• Journal of applied mathematics & informatics
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• 제38권1_2호
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• pp.13-36
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• 2020

In this paper, we have presented a multispecies prey-predator harvesting system based on Lotka-Voltera model with two competing species which are affected not only by harvesting but also by the presence of a predator, the third species. We also assume that the two competing fish species releases a toxic substance to each other. We derive the condition for global stability of the system using a suitable Lyapunov function. The possibility of existence of bionomic equilibrium is considered. The optimal harvest policy is studied and the solution is derived under imprecise inflation in fuzzy environment using Pontryagin's maximal principle. Finally some numerical examples are discussed to illustrate the model.

• Journal of Animal Science and Technology
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• 제56권5호
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• pp.16.1-16.9
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• 2014

Fatty acids (FA) have recently been used in several studies to infer the diet in a number of species. While these studies have been largely successful, most have dealt with predators that have a fairly specialized diet. In this paper, we used FA analysis as a tool to infer the diet of the nearctic river otter (Lontra canadensis). The river otter is an opportunistic predator known to subsist on a wide variety of prey including, fishes, crayfish, molluscs, reptiles and amphibians, among others. We analyzed the principle components of 60 FA from otters and 25 potential prey species in Illinois, USA. Prey species came from 4 major taxonomic divisions: fishes, crayfish, molluscs and amphibians. Within each division, most, but not all, species had significantly different profiles. Using quantitative FA signature analysis, our results suggest that, by mass, fish species are the most significant component of Illinois River otters' diet ($37.7{\pm}1.0%$). Molluscs ranked second ($32.0{\pm}0.8%$), followed by amphibians ($27.3{\pm}4.3%$), and finally, crayfish ($3.0{\pm}0.6%$). Our analysis indicates that molluscs make up a larger portion of the otter diet than previously reported. Throughout much of the Midwest there have been numerous otter reintroduction efforts, many of which appear to be successful. In regions where mollusc species are endangered, these data are essential for management agencies to better understand the potential impact of otters on these species. Our analysis further suggests that quantitative FA signature analysis can be used to infer diet even when prey species are diverse, to the extent that their FA profiles differ. Better understanding of the otter's metabolism of FA would improve inferences of diet from FA analysis.

• 한국수산과학회지
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• 제44권4호
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• pp.378-382
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• 2011

The feeding ecology of bluefin searobin Chelidonichthys spinosus around Jeju Island was examined. Specimens were caught every autumn from 2004 to 2007. The primary prey items of C. spinosus included fish, shrimp, and crabs. Chelidonichthys spinosus preyed upon a wide range of sub-pelagic crustacean groups(e.g., Leptochela gracilis, Leptochela sydniensis). This species was also an opportunistic feeder, exploiting the available prey groups in each area(i.e., L. gracilis in the South Sea and East China Sea groups and L. gracilis and L. sydniensis in the Yellow Sea group). The main prey group of this species changed from demersal shrimp to pelagic shrimp with prey environmental changes. Observed ontogenetic shifts in diet were relatively clear despite substantial overlap between the 10 cm and 20 cm C. spinosus groups.

• 한국수산과학회지
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• 제42권2호
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• pp.151-156
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• 2009

The stomach contents of Lumpenella longirostris, Malacocottus gibber and Bothrocara hollandi from the East Sea were examined to determine their feeding ecology. Specimens were caught seasonally from 2004 to 2006. The primary prey items of each species included crustaceans and mollusks. L. longirostris is a benthophage that primarily consumes bottom crustaceans and bivalves. M. gibber and B. hollandi are meso-pelagicphages that primarily consume amphipods and cephalopods. However, the species are opportunistic feeders that exploit the available prey in their habitat. The empty stomach ratio of the species is larger than that of offshore species (e.g. hairtail fish and yellow goose fish), and the prey diversity of the species evaluated in this study was much smaller than that of offshore species.

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1411-1427
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• 2009

We propose a model based on Lotka-Volterra dynamics with two competing spices which are affected not only by harvesting but also by the presence of a predator, the third species. Hyperbolic and linear response functions are considered. We derive the conditions for global stability of the system using Lyapunov function. The optimal harvest policy is studied and the solution is derived in the interior equilibrium case using Pontryagin's maximal principle. Finally, some numerical examples are discussed. The nature of variations in the two prey species and one predator species is studied extensively through graphical illustrations.

• Animal cells and systems
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• 제3권3호
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• pp.247-252
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• 1999

The aim of this study was to characterize antipredator tactics of anurans and to evaluate the effectiveness of these tactics for predator avoidance in real confrontations. Two types of experiments were conducted. In one experiment, one predator and one prey were placed together for one hour in a small confined space (one-to-one interaction). In another experiment, one predator and several prey were placed together for one day in a large enclosure in a field (field-based interaction). The prey consisted of three anuran species, Rana nigromaculata, R. rugosa, and Bombina orientalls: a snake species, Rhabdophis tigrinus tigrinus, was used as a predator. Results of both experiments demonstrated a range in antipredator responses of the frogs, from toxicity and warning coloration, coupled with slow responses in Bombina to little (or only slight) toxicity, crypsis, and fast take-off responses to the predator in the ranids. oth ranid species exhibited lower survival(57%) than Bombina (95%) in the field-based interaction, suggesting that motor responses of the palatable prey due to attacks of the predator ultimately limited their survival. The jumping of the ranids increased the activity of the predator, which became more likely to strike. Simple crouching(seen in R. rugosa and B. orientalis) and chemical defense (in Bombina) reduced predatory attacks.

• Fisheries and Aquatic Sciences
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• 제14권4호
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• pp.435-441
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• 2011

The feeding habits of yellow goosefish Lophius litulon and John Dory Zeus faber were studied by analyzing the stomach contents of specimens collected in the South Sea of Korea. In total, 132 hauls were taken during six experimental trawl survey (Tamgu 1) cruises conducted on a seasonal basis (March 2005-October 2007). The main prey items of the two species were similar. Fishes and crustaceans were the most important prey, with neither species showing ontogenetic changes in preferred species. Specifically, Pennahia argentata was the preferred prey item of L. litulon, whereas Trichiurus lepturus and Engraulis japonicus were preferred by Z. faber. Larger Z. faber (>24 cm) preferred bigger prey such as T. lepturus and Larimichthys polyactis, while smaller Z. faber preferred E. japonicus and Acropoma japonicum.

• 한국응용곤충학회지
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• 제36권3호
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• pp.237-242
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• 1997

폿트 재배한 강낭콩에서 점박이응애(Tetranychus urticae Koch)를 먹이로 제공하여 야외와 온실에서 3종 이리응애에 의한 점박이응애에 밀도 조절 작용에 대해 조사한 결과 다음과 같다. 6-7일 야외에서 A. fallacis는 점박이응애와 이리응애의 접종밀도 비율이 4:1, 10:1, 20:1 수준에서 접종 17일 후에 점박이응애의 밀도억제가 가능하였으나, A. womersleyi는 4:1에서만 밀도억제가 가능하였고, T. occidentallis는 4:1에서 접정 30일 후와 10:1, 20:1의 비율에서는 점박이응애 밀도억제가 전혀 불가능하f였다. 9월에 온실에서 점박이응애와 이리응애의 밀도를 10:1로 접종하였을 때 A. womersleyi는 초기 점박이응애 밀도억제가 가능하였으나 13일 이후에는 불가능하였고, A. womersleyi는 접종밀도보다 감소하였다. A. womersleyi는 초기부터 안정된 밀도가 유지되어 점박이응애 밀도억제 효과가 지속적이었다. T. occidentallis는 후기에 밀도가 증가하여 점박이응애 후기 밀도억제가 가능하였다.

• 수산해양교육연구
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• 제26권2호
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• pp.421-429
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• 2014

We investigated the feeding ecology of juvenile chum salmon (Oncorhynchus keta) during the critical early life stage prey selectivity of juvenile chum salmon during early marine migration in Korean waters at spring 2011. Salmon juveniles and zooplanktons were collected to draw with $20m{\times}5m$ gill net and $300{\mu}m$ mesh zooplankton net at each station on 11th-13th April n 2011. Collected zooplanktons were classified to 5 Phylum, 6 Class, 9 Order 17 Species in this study. Almost 76.4-100% species were classified to Phylum Arthropoda, dominant species was a species out of Hyperia galba of Order Amphipoda, Acartia spp and Paracalanus parvus of Order Calanoida. Collected salmon juveniles were grew up to average 4.7-5.4 cm fork length and average 1.0-1.5 g wet weight in whole station. Fish stomach content (mg/salmon) was heaver to 97.4, 82.4 and 63.2 mg wet weight/salmon in ST 2, 3, 4 than 20.4, 18.9 mg/salmon of ST 1, 5, because there are fish (sand eel, Hypoptychus dybowskii) and Krill (Euphausia) as prey in salmon stomach in ST 2, 3, 4. And ST 2, 3, 4 and 5 were dominated by Amphipoda as Hyperia galba, Themisto japonica and Gammarus sp., but ST 1 was dominated by copepod, because of absence of Amphipoda in the station. Therefore small Amphipoda as Hyperia galba was good prey for just released salmon juvenile in nature.