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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Capteur colorimétrique à base d’oxydes mixtes pour la détection du chloroforme dans l’air des piscines couvertes / Mixed Oxides Colorimetric Sensors applied to Indoor Swimming-pool Chloroform Level Measurement

Landreau, Nina 12 December 2016 (has links)
Depuis une vingtaine d’années, des campagnes de mesures de la qualité de l’air intérieur des piscines couvertes ont révélé la présence de composés toxiques, notamment de chloroforme (cancérigène probable pour l’homme) à des concentrations très supérieures à la valeur toxicologique de référence recommandée par l’Anses. Ainsi, la garantie de la santé des baigneurs nécessite de pouvoir détecter facilement le dépassement de cette valeur limite.Pour pallier à l’absence d’appareil répondant à ce besoin, l’objectif de cette thèse est donc d’élaborer un capteur colorimétrique, fait d’une matrice nanoporeuse dopée en molécules-sondes capables de réagir de façon sélective et sensible avec le chloroforme pour former un produit coloré.La réaction de Fujiwara a été sélectionnée pour notre capteur et son optimisation a permis de dégager les conditions optimales qui devront être reproduites dans les pores de la matrice sol-gel pour assurer un fonctionnement optimal du capteur. En raison des contraintes imposées par la réaction de Fujiwara, un nouveau type de matrices mixtes silice-zircone a été développé pour héberger cette réaction en phase gaz.La maîtrise fine de la différence de réactivité entre les précurseurs de silice (peu réactifs) et les précurseurs de zircone (très réactifs) nous a permis de moduler à la fois l’homogénéité, l’absorbance et la porosité de ces matrices de façon à obtenir des matrices présentant les caractéristiques requises de transparence, porosité, tenue mécanique, absorbance et compatibilité avec la réaction colorimétrique choisie.Le dopage de cette matrice avec les réactifs de Fujiwara finalement été réalisé avec succès et la fonctionnalité du capteur a été démontrée. / During the last twenty year, indoor swimming-pool air quality measurement campaigns confirmed the presence of toxic compounds such as chloroform (carcinogenic) at higher level than those advised by French authorities. Hence, the ability to easily perform direct detection of chloroform at concentration above the advised threshold is crucial to ensure the safety of swimmers.At the moment, no devices seems to meet such a need. This PhD work aims at preparing a colorimetric sensor suited to this application, thanks to a nanoporous material incorporating probe-molecules to specifically react with chloroform and yield a coloured product.The optimization of the Fujiwara colorimetric reaction was carried out and the best mode to be used within the nanopores in the gas phase was identified. A new type of silica-zirconia materials had to be specifically developed to resist to the harsh chemical conditions of the Fujiwara reaction.Fine-tuning of the differential reactivity of silica (slow) and zirconia (fast) precursors led to a good control of the homogeneity, absorbance and porosity of the materials which was absolutely essential to meet the specifications of transparency, porosity, mechanical stability, absorbance and ability to host the Fujiwara reaction.Such materials were successfully doped with Fujiwara reagents, and the functional material obtained was validated as a chloroform sensor.
142

Hydrologic Structure and Function of Vernal Pools in South Deerfield, Massachusetts

Axthelm, Charlotte 29 October 2019 (has links)
Vernal pools are small, ephemeral wetlands lacking an inlet or outlet. These wetlands, also known as seasonal pools, are found in a wide range of biomes, and their characteristics vary based on location. While the vegetation of western U.S. pools, and amphibians of eastern U.S. pools have been extensively studied, many aspects of vernal pools have not been fully characterized. In particular, although the general seasonal wetting and drying cycle is understood qualitatively, few studies have attempted to quantify the hydrological regime of vernal pools in New England. As water level variation drives many, if not all, of the characteristics unique to these systems, more research on this aspect of vernal pool functioning is needed. The primary objective of this study was to gain a better understanding of vernal pool hydrology through the study of a complex of three pools in South Deerfield, MA. The water level in the South Deerfield pools has been monitored since 2009. For this study, the most recently recorded water year (1 October 2017 to 30 September 2018) was used to characterize the water level fluctuations in the Middle Pool. Water level was monitored manually (weekly intervals) and with pressure transducers (4-hour intervals) in permanently installed wells. The effects of precipitation and evapotranspiration on water level were quantified with a water balance analysis. This analysis also estimated changes in storage by estimated inflow from the uplands and outflow via deep seepage. Water level changes in the Middle Pool were consistent with qualitative descriptions and trends described in earlier studies in the region. We found that the countervailing effects of precipitation and evapotranspiration were the primary drivers of water level fluctuations throughout the year. However, the estimate of storage derived as a water balance residual was not representative of water level in the vernal pools. The storage estimate derived for the Middle Pool was more successful at estimating the water level during spring transition, the high water period most important to amphibian breeding.
143

Bezpečnost provozu chladicích technologií na zimních stadionech / Ammonia Refrigeration Safe Operation on Ice Pools

Puskeilerová, Lenka January 2011 (has links)
he thesis deals with safe operation of ammonia refrigeration technologies on ice pools in the Czech Republic. This thesis focuses on the possibility of evaluation and risk operation management. The thesis starts with a summary of basic factors affecting safe operation on ice pools. This includes also possible ways how to realize the ammonia refrigeration technology including week and strong part of different access. The ice pool are splitted into tree groups based on a precondition for a safe operation. Next, there is done analysis of current legal and directive frame for safe operation of ice pools in the Czech Republic. There are also included a methods for evaluation and simulation of risk for ihabittants. There is named a metod STADION_01 dedicated to evaluate a capability of tested companies to manage operations risk. Practical experience with evaluation are included. The metod stress, that is important to keep long-lasting and pernament safe operation of ammonia refrigeration.
144

Sportovní plavání v Československu 1918-1938 / Sports swimming in Czechoslovakia 1918-1938

Tomšová, Petra January 2021 (has links)
The dissertation deals with sport swimming in the Czech lands and in Czechoslovakia in the interwar period, specifically in the period of the so-called First Republic. However, the work dates back to the beginning of the 19th century, when the first, especially river, swimming pools began to be established in our territory, which were first used for swimming training of soldiers, and only at the end of the 19th century did the general public learn to swim and there are also the first swimming competitions. The greatest development of sport swimming in our territory occurred only after the First World War, when the Czechoslovak Amateur Swimming Association was founded and it sought maximum organizational, financial and material support for swimming. Our swimmers achieved the best swimming performances in the 1920s, when they were able to compete with the European swimming powers. However, they did not have the world's top swimming, which was also seen at the Olympic Games in 1920, 1924, 1928 and 1936. In the early 1930s, the performance of our swimmers began to stagnate, which could be attributed to the fact that in other countries swimming was supported in all respects, but this was not the case in the Czechoslovak Republic, from the very beginning of sport swimming in our territory. Keywords:...
145

Pedaling towards a sustainable future: lessons Learned from Cargo Bike Pool Operators in Sweden

Brandon David, Kvist January 2023 (has links)
This study examines the impact and potential of cargo bikes as socio-economically and ecologically beneficial modes of transportation. It focuses on the perspectives of cargo bike pool members and the challenges faced by pool operators. Three interviews were conducted with cargo bike pool operators in Sweden to understand the challenges and considerations involved in establishing and operating a pooling service, as well as their opinions on its financial future. Additionally, a user survey targeting pool members from one of the interviewed operators was conducted in 2020. The survey investigated user barriers, motivations, opinions towards the pooling service, and its effect on user mobility habits before and after joining. Although the acceptance and utilization of these services depend on factors such as proximity, pricing, availability, quality, and convenience of the service. The findings show that pooling services increase member interest in owning and using cargo bikes as a replacement for cars. However, concerns regarding the marketability of cargo-bike pools alone are raised in this study, thus, to enhance the attractiveness of cargo-bike pools, this study suggests incorporating additional modes of transportation, offering supplementary value propositions, and ensuring a user-friendly experience. On the operator side, this study highlights the importance of stakeholder collaboration in maximizing the potential of cargo bike pools for sustainable transportation enabling resource sharing, and marketing efforts, and improving the overall service by leveraging financial, spatial, and logistical benefits. Finally, this study finds that the current state of cargo bike pools necessitates collaboration and subsidies from municipalities and stakeholders. Suggesting innovations in business models and increased marketing strategies that capture a broader demographic through an enhanced value proposition that includes other forms of modality and benefits in their services, are vital for the growth of cargo biking through pooling systems.  The research provides insights for prospective operators in establishing and operating cargo bike pools, emphasizing considerations related to the physical layout, financial aspects, marketing, and value proposition of the service and has broader implications in how to encourage more sustainable mobility practices.
146

Koupání dětí v krytých bazénech / Bathing of children in indoor swimming pools.

OHEROVÁ, Martina January 2016 (has links)
This diploma thesis deals with bathing children, especially infants and toddlers, in indoor swimming pools. It focuses primarily on the potential health and hygiene risks of this activity. It is divided into theoretical and practical part. The theoretical part provides a deeper insight into the field of artificial swimming pools, is dedicated to current as well as first ever legislation, in more detail is dedicated to the hygienic requirements for swimming pools according to Decree no. 238/2011, as amended; describes the process of pool water treatment, provides an overview of possible types of disinfecting pool water treatment and comparison within the advantages and disadvantages, describes indicators of water quality and their importance, and mostly focuses on hygienic and health risks in connection with the visit of indoor pools. Gives examples from practice (epidemic), mentions the most common sources of pollution including the most common violations of visitors. The theme of hygienic and health risks is then divided according to the origin of risk to the microbiological part (dedicated to infectious agents), to chemical part (disinfection by products) and to the part of accident risks and risks associated with the water temperature. The thesis is also keenly interested in the views of experts for bathing children, especially infants and toddlers, in indoor artificial pools. Research in the practical part was made by a qualitative method using secondary data analysis (operational and guest regulations, operational logbooks for 2015, the results of laboratory analysis of pool water for the 2015, laws and decrees), participant observation and interviews. The research was conducted in indoor swimming pools in towns Jihlava and Prachatice, which run swimming courses for infants and toddlers as well as for older children. For research, I set the following goals: C1: To monitor the microbiological and the physical-chemical indicators of the pool water quality in relation to Decree no. 238/2011 Coll., as amended, in pre-selected artificial indoor pools during annual operation. C2: To focus on the health status of children (infants and toddlers) in swimming classes. C3: To find out the knowledge and attitudes of visitors (parents) and trainers in the field of hygiene principles for swimming in artificial pools and risks arising from them. Based on the targets I have set the following research questions: V1: Are the monitored microbiological and physico-chemical water quality limits exceeded, and if so, which and under what circumstances? V2: What health problems, if they occured, did infants and toddlers after regular visits of indoor pools have ? V3: Are these children suffering from allergic diseases, and if so, from what type? V4: What knowledge and attitudes do visitors (parents) and lecturers in the field of hygienic principles for swimming in artificial pools and potential risks have? This thesis may serve the general public to extend the knowledge in the field of bathing (not only the children) in artificial pools and to give a view on this subject from different perspectives, as well as operators of swimming pools as an information material.
147

Development of a project plan to enhance the import process for Clear Blue International

Peters, Marc 12 1900 (has links)
Thesis (MBA)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Clear Blue International (pty) Ltd (CBI) is a swimming pool construction company that is in need of a high performance swimming pool pump in order to offer a competitive tender for the construction of an intricate swimming pool at a prestigious resort. There is one supplier of this particular pump in South Africa and due to their sole distributorship and the pump's technical specifications, it is sold at a very expensive price. The result being that CBI can't offer a competitive tender by this means, instead they need to source the pump from another source at a lower price. It was decided to develop a project plan to facilitate the importation process, which is the outcome of this study. A thorough analysis of project management is conducted and incorporated into the importation process. The study takes into consideration the intricacy of the importation process and how this can be facilitated by project management that will lead to success for CBI. CBI recognises that in order to stand out in a highly competitive industry they need to re-invent themselves by new and innovative means in order to stand out from the rest. Project management has proven to be the means by which they can add value to their corporate image. This study provides a useful template that can be of benefit to other importers that wish to use project management and it can be adjusted accordingly to a particular commodity and importers requirements. / AFRIKAANSE OPSOMMING: Clear Blue International (Edms) Bpk (CBI) is 'n swembad konstruksie-maatskappy. Hulle benodig 'n hoe verrigting pomp met die oog op 'n mededingende tender vir die bou van 'n ingewikkelde swembad-konstruksie by 'n toonaangewende oord. Daar is huidiglik net een verskaffer van hierdie spesifieke pomp in Suid-Afrika en vanwee hulle alleen-verspreiding, plus die pomp se spesifieke tegniese spesifikasies, word dit teen 'n baie hoe prys verkoop. CBI kan tans nie 'n mededingende tender verskaf nie en wil daarom die pomp eers teen 'n laer prys vanuit 'n ander oord bekom. Die besluit was dus om 'n projek-plan te inisieer om die invoer-proses te vergemaklik, wat die resultaat van hierdie studie is. 'n Deeglike analise van projek bestuur is aangevoer en by die invoer-proses geinkorporeer. Hierdie studie neem ook die ingewikkeldheid van die invoer-proses in ag en hoe projek bestuur dit kan vergemaklik en sodoende kan bydra tot die sukses vir CBI. CBI besef dat, om uit te staan in 'n hoogs mededingende industrie, hulle hulself moet vernuwe op 'n innoverende wyse. Projek bestuur is bewys as die metode waarby hulle hul korporatiewe beeld kan verhoog. Die studie verskaf 'n waardevolle profielvorm waarby ander invoerders wat projek bestuur wil implementeer, ook kan baat vind. Dit kan aangepas word volgens spesifieke handelsartikels en invoer-voorskrifte.
148

Faktory ovlivňující druhové složení vážek v nově vytvořených tůních a efekt bezobratlých predátorů na zooplankton v tůních / Factors affecting dragonfly species composition in newly created pools and assessment of invertebrate predation on pools zooplankton

Dobiáš, Jakub January 2012 (has links)
To identify and quantify the influence of physico-chemical, biotic and geographic factors on the population of dragonflies (Odonata) is an essential tool for research of their ecology. The aim of this study was to 1) assess how these factors influence species richness, diversity and spatial distribution of dragonflies in 42 newly constructed or renewed pools located in the Kokořínsko Protected Landscape Area, which is characterized by two valleys of Liběchovka and Pšovka creeks, low human impact, and a great diversity of small water bodies and 2) use laboratory experiments in order to estimate the relationship between large predatory invertebrates of these pools (Aeshna cyanea, Coenagrion puella, Chaoborus crystallinus and Notonecta glauca) and their common prey (Daphnia curvirostris) in an artificial environment with or without aquatic macrophytes. The pools were monitored and sampled between years 2005 and 2006. In total, 23 dragonflies species were found inhabiting these lentic habitats, comprising 11 species belonging to the suborder Zygoptera and 12 species belonging to the suborder Anisoptera, including a rare species Sympetrum depressiusculum (larvae). Most variability in the dragonfly species richness was explained by the size of the water surface area, followed by the location of the pools (inside...
149

Advantages and limitations of distributed optical-frequency-domain-reflectometry for optical fiber-based sensors in harsh environments / Avantages et limites des capteurs à fibre optique distribuée basés sur la réflectométrie optique dans le domaine fréquentiel en milieux radiatifs / Vantaggi e limiti dei sensori a fibra ottica distribuiti basati sulla riflettometria ottica nel dominio delle frequenze in ambienti radiativi

Rizzolo, Serena 04 April 2016 (has links)
L’accident de Fukushima-Daiichi du 11 Mars 2011 a fortement marqué l'industrie nucléaire en mettant en évidence plusieurs faiblesses dans le contrôle des systèmes critiques qui assurent la sécurité des centrales nucléaires, en particulier, lors de conditions accidentelles. Cette thèse a été réalisée en collaboration avec AREVA, groupe industriel français actif dans le domaine de l'énergie, avec l’objectif de réaliser des capteurs à fibres optiques résistants aux contraintes sévères d'une centrale nucléaire et, en particulier, de surveiller la température et le niveau de l'eau à l'intérieur d’une piscine de stockage de combustible. La thèse est composée de deux parties organisées en 7 chapitres. Dans la première partie, le chapitre 1 traite des phénomènes contribuant à l'atténuation de la lumière au cours de sa propagation dans la fibre et donne un aperçu des effets des radiations sur les fibres optiques. Pour identifier la technique la plus prometteuse adaptée aux applications visées par AREVA, le chapitre 2 propose un état de l’art sur les capteurs distribués à fibres optiques existants avec une attention particulière à leur emploi dans des environnements radiatifs. La dernière partie de ce chapitre est consacrée à la description détaillée de l’OFDR qui est la technique retenue pour cette application. La deuxième partie est consacrée à la présentation des résultats obtenus et leur analyse. Le chapitre 3 présente le détail des irradiations et des traitements thermiques, les échantillons retenus et les bancs de mesure utilisés. Afin de déterminer la meilleure combinaison fibre/technique par rapport à l’application visée, une étude systématique des capteurs distribués de température et de contrainte a été réalisée. Les effets permanents des rayonnements (niveaux de dose du MGy) sont étudiés dans le chapitre 4. Le chapitre 5 illustre des mesures in situ sur les fibres résistantes aux radiations pour comprendre les effets combinés de la température et des radiations (rayons X), effets représentatifs des conditions nominales et accidentelles des piscines de stockage. Enfin, nous avons développé un prototype de capteur de niveau d’eau pour les piscines de combustible qui est décrit dans le chapitre 6. Ensuite, les principales conclusions et les perspectives de ce travail de thèse sont discutées / Fukushima-Daiichi event on March 11th, 2011, signed a turning point in nuclear industry by highlighting several weaknesses in the control of critical systems that ensure the safety in nuclear power plant (NPP) operating, particularly, in accidentals conditions. This PhD thesis has been carried out in collaboration with AREVA, the French industrial group active in the energy domain, with the aim of realizing optical fiber sensors resistant to the harsh environment constraints of a NPP and, in particular, to monitor temperature and water level several parameters inside the spent fuel pools (SFPs). It consists of two parts organized in 7 chapters. In the first part, chapter 1 deals with the phenomena contributing to the light attenuation during its propagation along the fiber and gives an overview on the radiation effects on optical fibers. To identify the most promising technique suitable for AREVA needs, in chapter 2 is reported the state-of-the-art on the distributed OFSs with particular attention to their employment in radiation environments. The last part of this chapter is devoted to the detailed description of the OFDR that is the selected sensor technique for this application. The second part is devoted to present and discuss the obtained results. Chapter 3 gives the experimental details on radiation and thermal treatments, investigated samples and used setups. In order to determine the best fiber/setup combination, a systematic study on temperature and strain distributed sensors was carried out in relation to the harsh constraints demanded from the application. The permanent radiation (MGy dose levels) effects on different fiber classes are investigated in Chapter 4. Chapter 5 illustrates in situ measurements on radiation resistant fibers to understand the combined temperature and radiation (X-rays) effects representative of the SFP nominal and accidental conditions. Simultaneously, we have developed the OFS design for its integration at SFP facility. The prototype is described and its performance is evaluated in chapter 6. Then, the main conclusion and perspective are discussed / L'incidente di Fukushima-Daiichi dell’11 marzo 2011 ha segnato un punto di svolta per l’industria nucleare, mettendo in evidenza diversi punti deboli nel controllo di sistemi critici che garantiscono la sicurezza nelle centrali, in particolare in condizioni di incidente. Questa tesi è stata condotta in collaborazione con AREVA, il gruppo industriale francese attivo nel settore dell'energia, con l'obiettivo di produrre sensori a fibra ottica resistenti alle condizioni estreme di una centrale nucleare e, in particolare, per controllare diversi parametri all'interno di una piscina di stoccaggio di combustibile nucleare, quali la temperatura e il livello dell'acqua. La tesi si compone di due parti organizzate in 7 capitoli. Nella prima parte, il capitolo 1 riguarda i fenomeni che contribuiscono all'attenuazione della luce durante la sua propagazione nella fibra e permette di comprendere gli effetti della radiazione sulle fibre ottiche. Per identificare la tecnologia più promettente per le esigenze di AREVA, nel capitolo 2 é discusso lo stato dell’arte sui sensori distribuiti con particolare attenzione alle loro performance in ambienti radiativi. L'ultima parte di questo capitolo è dedicato ad una descrizione dettagliata della tecnica OFDR che è la tecnologia scelta per questa applicazione. La seconda parte è dedicata a presentare e discutere i risultati. Il capitolo 3 fornisce i dettagli sui campioni studiati e i trattamenti effettuati su di essi e descrive il setup utilizzato. Per determinare la migliore combinazione fibra/tecnica per l’applicazione prevista, è stato eseguito uno studio sistematico sulla risposta alla radiazione dei sensori distribuiti di temperatura e strain. Glieffetti permanenti della radiazione (dosi dell’ordine del MGy) su diverse classi di fibre, resistenti e sensibili alle radiazioni, sono discussi nel capitolo 4. Il capitolo 5 riporta le misure in situ sulle fibre resistenti alla radiazione per investigare gli effetti combinati di temperatura e radiazioni (raggi X) rappresentativi delle condizioni operative e accidentali nelle piscine di stoccaggio. Infine, abbiamo sviluppato un prototipo di sensore del livello dell’acqua nelle piscine di stoccaggio che è descritto nel capitolo 6. In seguito, le principali conclusioni e le prospettive sono discusse
150

Especialização individual em três espécies de peixes em um rio intermitente do semiárido brasileiro

Duarte, Maria Rita Nascimento 02 February 2016 (has links)
Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-05-17T12:56:17Z No. of bitstreams: 1 PDF - Maria Rita Nascimento Duarte.pdf: 2708130 bytes, checksum: 83ff7c3f4dd9638f2a12090069b8a8e8 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-07-21T20:42:27Z (GMT) No. of bitstreams: 1 PDF - Maria Rita Nascimento Duarte.pdf: 2708130 bytes, checksum: 83ff7c3f4dd9638f2a12090069b8a8e8 (MD5) / Made available in DSpace on 2016-07-21T20:42:27Z (GMT). No. of bitstreams: 1 PDF - Maria Rita Nascimento Duarte.pdf: 2708130 bytes, checksum: 83ff7c3f4dd9638f2a12090069b8a8e8 (MD5) Previous issue date: 2016-02-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In the Neotropical zone the generalist habit is common among fish populations, especially in semi-arid rivers. In these systems, where the availability of food items varies spatially and temporally, it is expected that a more generalist strategy dominates. However, populations classified as generalist may actually be composed of relatively specialist individuals. This study aims at quantifying the use of food resources and understanding the individual contribution to population niche of Hoplias malabaricus, Geophagus brasiliensis and Prochilodus brevis. Four collections were performed at four sites along the Ipanema (PE) River, in April and July 2007 (wet season) and October 2007 and January 2008 (dry season). Sampling was performed at daylight, using gillnets, manual trawls and cast nets. The specimens collected were fixed in 4% formalin and preserved in 70% ethanol. The diet was quantified using the indirect volumetric method, frequency of occurrence and numeric frequency. Spatial patterns of variation in food items between species were evaluated using the Nonmetric Multidimensional Scaling (NMS). The Multi-Response Permutation Procedure (MRPP) was used to test the significance of differences in diet composition between species, sites and sampling periods. The degree of specialization of each individual was calculated using a proportional similarity index. The amplitude and niche overlap ratios were calculated using the Levins and Bolnick indexes. The graphical analysis of Amundsen was performed in order to correlate the diet composition with the selection of specific prey. The species showed a pattern of distribution and segregation in diet between the sampling sites. The MRPP showed that there were significant differences in the diet composition between species (MRPP, A= 0, 61; p= 0, 00). Geophagus brasiliensis specie showed significant differences between site 1 and site 4 (MRPP, A = 0.14; p = 0.03) and site 2 and site 4 (MRPP, A = 0.16 p = 0, 03), the Prochilodus brevis specie between site 1 and site 3 (MRPP, A = 0.28 p = 0.02) and site 1 and site 4 (MRPP, A = 0.11; p = 0.04). The three species present individual specialization in all sampling sites and in both periods of the hydrological cycle. The species Hoplias malabaricus has a population with most experts individuals, with rest of fish as the dominant item, however, with other individuals in the population consuming a high abundance of specific prey. However Geophagus brasiliensis presented a generalist population, with individuals of the population consuming a variety of items, displaying a relatively high component within phenotype. Prochilodus brevis showed a population with varied feeding strategy, presenting degrees of specialization with the contribution of Cyclotela item and generalization, where food items were consumed by more than half of the population. It was observed that individual specialization is highly correlated with niche overlap, indicating that the smaller the overlap the larger the degree of individual specialization. It is important to emphasize that the greatest degree of individual specialization was observed where there was a greater availability of food resources consumed by the populations. / Na região neotropical o hábito generalista é comum em populações de peixes, especialmente em rios do semiárido. Nesses sistemas onde a distribuição dos itens alimentares varia espacial e temporalmente, espera-se que a estratégia generalista predomine entre as espécies. Este estudo objetiva quantificar a utilização de recursos alimentares e compreender a contribuição individual para o nicho populacional em três espécies de peixes, Hoplias malabaricus, Geophagus brasiliensis e Prochilodus brevis. Foram realizadas coletas em quatro pontos ao longo do rio Ipanema (PE) nos meses de abril e julho de 2007 (período chuvoso) e outubro de 2007 e janeiro de 2008 (período seco). As amostragens foram feitas durante o dia, usando redes de arrasto, espera e tarrafa. Os espécimes coletados foram fixados em formol 4% e preservados em álcool 70%. A dieta foi quantificada usando o método volumétrico indireto, frequência de ocorrência e a frequência numérica. Padrões espaciais de variação de itens alimentares para as espécies foram avaliados por meio Escalonamento Multidimensional Não- Métrico (NMS). O Procedimento de Permutações Múltiplas (MRPP) foi utilizado para testar diferenças na composição da dieta entre as espécies, pontos e períodos de amostragem. O grau de especialização de cada indivíduo foi calculado utilizando um índice de similaridade proporcional. A amplitude e sobreposição de nicho foram calculadas utilizando os índices de Levins e Bolnick. Foi realizada a análise gráfica de Amundsen a fim de relacionar a composição da dieta com a seleção de presas específicas. O MRPP mostrou que houve diferenças significativas na composição da dieta entre as espécies (A = 0,61; p = 0,005). Entre os pontos de coleta a espécie Geophagus brasiliensis apresentou diferenças significativas entre o ponto 1 e ponto 4 (MRPP, A = 0,14 e p = 0,03) e ponto 2 e ponto 4 (MRPP, A = 0,16 e p = 0,03), a espécie Prochilodus brevis entre o ponto 1 e ponto 3 (MRPP, A = 0,28 e p = 0,02) e ponto1 e ponto 4 (MRPP, A = 0,11 e p = 0,04). As três espécies apresentaram especialização individual em todos os pontos de coletas e em ambos os períodos de regime hidrológico. A espécie Hoplias malabaricus apresentou uma população com a maioria dos indivíduos especialistas, apresentando resto de peixe como item dominante, porém, com outros indivíduos da população consumindo uma alta abundância de presas especificas. Geophagus brasiliensis apresentou uma população generalista, com indivíduos da população consumindo uma variedade de itens, exibindo um componente relativamente elevado dentre- fenótipo. Prochilodus. brevis mostrou uma população com estratégia de alimentação variada, apresentando graus de especialização com a contribuição do item alimentar Cyclotela e generalização, onde os itens alimentares tinham sido consumidos por mais da metade da população. Observou-se que a especialização individual está correlacionada com a sobreposição de nicho, indicando que, quanto menor sobreposição maior é o grau de especialização individual. É importante ressaltar que o maior grau de especialização individual foi observado onde houve uma maior riqueza de recursos alimentares consumidos pelas populações.

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