Konstanz, Univ., Diplomarb., 1998.

Techn. University, Diss., 2001--Dresden.

Techn. Universiẗat, Diss., 2002--Dresden.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-11-08T12:00:17Z No. of bitstreams: 1 texto completo.pdf: 1951546 bytes, checksum: a3752f2e42b9e32d30012099fab32d59 (MD5) / Made available in DSpace on 2017-11-08T12:00:17Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1951546 bytes, checksum: a3752f2e42b9e32d30012099fab32d59 (MD5) Previous issue date: 2017-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Antilophia galeata é uma espécie endêmica do Cerrado, uma província biogeográfica altamente ameaçada pela ação antrópica. A história natural da espécie é ainda mal conhecida, especialmente no tocante à sua biologia reprodutiva e comportamento de corte, com informações superficiais e baseadas em uma baixa amostragem. O presente estudo visa descrever de forma detalhada a biologia reprodutiva da espécie, seu comportamento de corte e determinar a área de vida no período reprodutivo. Os estudos foram conduzidos na Universidade Federal de Viçosa - Campus Florestal (CAF), em um fragmento florestal de aproximadamente 180 ha localizado em uma área de transição entre Mata Atlântica e Cerrado. Indivíduos machos e fêmeas foram capturados em rede de neblina e anilhados com anilhas metálicas e uma sequência única de anilhas coloridas. Um total de 38 indivíduos foram anilhados, sendo encontrados 11 ninhos, seis dos quais puderam ser monitorados em atividade. Os ninhos encontrados são similares aos descritos para a família Pipridae, sendo do tipo cesto baixo/forquilha, com uma camada decorativa externa. O tamanho da ninhada foi de dois ovos por ninho, com período de incubação de aproximadamente 20 dias e período de ninhegos de até 18 dias. Todo o processo de construção, incubação e cuidados com a prole foram exclusivamente executados pelas fêmeas. A espécie nesse estudo não se mostrou territorialista no período reprodutivo como descrito na literatura, demonstrando ser uma espécie promíscua com comportamento de corte em leks, onde os machos se exibem para as fêmeas em forma de perseguições, ocupando extensas áreas para tal exibição. Foram mensuradas áreas de vida de 12 indivíduos, com média de 9 ha calculado pelo método Kernel e 5,8 ha pelo Mínimo Polígono Convexo. Algumas áreas de vida se estenderam por mais de 20 ha, com extrema sobreposição entre elas. O presente estudo contribui de forma significativa para a história natural da espécie, pois até então essa era considerada como apresentando um comportamento reprodutivo monogâmico e territorialista, com áreas de vida inferiores a 3 ha. / Antilophia galeata is an endemic species of the Cerrado, a biogeographic province highly threatened by anthropic action. The natural history of the species is still poorly known, especially in terms of its reproductive biology and courtship behavior, and the available information is scarce and based on small samples. This study aims to describe in detail the reproductive biology of the species, its courtship behavior and determine its home range during the reproductive period. The studies were conducted at the Universidade Federal de Viçosa - Campus Florestal (CAF), in a forest fragment of about 180 ha located in a transitional area between the Atlantic Forest and the Cerrado. Males and females were mist-netted and banded with metal band and a unique sequence of colored bands. A total of 38 individuals were banded and 11 nests were found, six of which could be monitored in activity. The nests found are similar to those described for the Pipridae family, being of the low cup/fork type, with an external decorative layer. The clutch size is two eggs, with an incubation period of approximately 20 days and nestling period of up to 18 days. The whole process of building, incubating and caring for the nestlings are exclusively performed by the females. The species did not show territorial behavior during the reproductive period as described in the literature, proving to be a promiscuous species with courtship behavior in leks, whit the males exhibit themselves to the females in the form of chasings across extensive areas. Home ranges of 12 individuals were estimated, with a mean of 9 ha calculated by the Kernel and 5.8 ha by the Minimum Convex Polygon. Some home ranges extended over 20 ha, with large overlap between them. The present study contributes significantly to the natural history of the species, which was until now considered monogamous, territorialist, and with home range areas smaller than 3 ha.

Made available in DSpace on 2016-06-02T19:32:10Z (GMT). No. of bitstreams: 1 6176.pdf: 1190025 bytes, checksum: 0119abc6ca8354633f6913759cdd7868 (MD5) Previous issue date: 2014-06-30 / Financiadora de Estudos e Projetos / The present study aimed to analyze and discuss the results of the analysis of the landscape at different scales and levels of details of its structure interfere in predicting the presence and population size of a species and environmental quality of a unit of study. For this, executest were three main steps: 1) The choice of the species of study; 2) Review the unit of study with different models for the species of study; and 3) Propositions for the unit of study. The choice of the species of study was based on a questionnaire to various ornithologists, where we tried to select the most suitable species for the study. For the analyzes of the study unit was used , on the conception of Landscape Ecology , tools such as scanning a satellite image obtained by Google Earth ® and landscape analysis by MapInfow ® program. Propositions for the unit of study was based on analysis of the model considered more real and critical to the species of study aiming at establishing minimum viable conditions for the establishment and maintenance of the species studied. This specie of study was chosen Antilophia galeata, the unit of study is located in the municipality of São Carlos (SP), and the whole basin of Ribeirao das Araras. This study showed that one must have a very great care in analyzing the most appropriate model for a given species, because the way that the landscape can be analyzed can generate completely different results and sometimes lagged the actual situation, as evidenced by this paper. / O presente estudo objetivou discutir como os resultados da análise da paisagem em diferentes escalas e níveis de detalhamento da sua estrutura interferem na previsão da presença e tamanho populacional de uma espécie e na qualidade ambiental de uma unidade de estudo. Para isto, três etapas principais foram executas: 1) A escolha da espécie de estudo; 2) Análise da unidade de estudo com diferentes modelos para a espécie de estudo; e 3) Proposições para a unidade de estudo. A escolha da espécie de estudo foi baseada na aplicação de um questionário para vários ornitólogos, onde procurou-se selecionar a espécie mais apropriada para o estudo. Para as análises da unidade de estudo utilizou-se a abordagem de Ecologia da paisagem, ferramentas, como digitalização em tela de uma imagem de satélite obtida pelo Google Earth® e análise da paisagem pelo programa MapInfow®. As proposições para a unidade de estudo foram baseadas na análise do modelo considerado mais real e crítico para a espécie de estudo, objetivando o estabelecimento de condições mínimas viáveis para o estabelecimento e manutenção da espécie de estudo. A espécie de estudo escolhida foi Antilophia galeata e a unidade de estudo é localizada no município de São Carlos (SP), sendo toda a bacia do Ribeirão das Araras. Este estudo mostrou que se deve ter um cuidado muito grande em se analisar qual o modelo mais apropriado para uma determinada espécie, pois a maneira com que a paisagem pode ser analisada pode gerar resultados completamente distintos e por vezes defasados de uma situação mais realística, como evidenciou este trabalho.

Ziel der Arbeit war eine möglichst umfassende Analyse der Nahrungsbedingungen von D. galeata unter Berücksichtigung der damit verbundenen Strategien der Daphnien zur Optimierung des Nahrungserwerbs, um den Einfluß dieser Faktoren bezüglich des Auftretens einer Sommerdepression der Daphnien zu beurteilen. Aufbauend auf den bereits vorhandenen Kenntnissen aus der Literatur sollte dazu im Rahmen der Arbeit festgestellt werden, ob morphologische Veränderungen des Filtrationsapparates der Daphnien (Ausbildung großer, hydrodynamisch dichter Filter), die als Reaktion auf die geringen Nahrungsmengen im Klarwasserstadium auftreten, bei einer drastischen Erhöhung der Nahrungskonzentration zu einer "Überlastung" der Filterbeine der Daphnien, zu hohen Energieausgaben und schließlich zu erhöhter Mortalität (Sommerdepression) führen können. Hauptziel war dabei die Klärung der Frage, ob bottom-up gesteuerte schnelle Veränderungen im Nahrungsangebot, wie sie für geringe bottom-up Limitation (Hypertrophie) typisch sind, eine erhöhte Mortalität bei Daphnien hervorrufen können. Die Beantwortung dieser Fragestellung ist wichtig, um die Effizienz der top-down Steuerung (Biomanipulation) als ökotechnologische Maßnahme zur Gewässersanierung zu erhöhen. Dazu wurden in der biomanipulierten Talsperre Bautzen in drei Untersuchungsjahren (1997 - 1999) wichtige bottom-up wirkende Steuerfaktoren der Daphnienentwicklung sowie morphologische Charakteristika der Filterkämme und physiologische Leistungskriterien von D. galeata vor und während der Zeit des potentiellen Auftretens einer Sommerdepression untersucht. Aus den Ergebnissen ließ sich ableiten, daß das Zusammenspiel der vielfältigen Anpassungsmöglichkeiten der Daphnien in einem bestimmten Variationsbereich der Steuerfaktoren eine erfolgreiche Strategie zur Optimierung der Nahrungsaufnahme darstellen kann. Werden jedoch bestimmte Schwellenwerte über- oder unterschritten, ist eine Kompensation durch die Anpassungsstrategien nicht oder nur bedingt möglich. Dabei kann durch verschiedene Ursachen der gleiche Effekt (Mortalität adulter Daphnien) auftreten, was die Interpretation erschwert. Dieser Effekt wird besonders bei adulten Daphnien durch die gegenüber juvenilen Daphnien höheren Filterwiderstände und die damit verringerte effektive Energieaufnahme begünstigt. Erst wenn ungünstige Nahrungsbedingungen und die am Ende der Klarwasserphase beobachteten ungünstigen Konstellationen der Filterkämme zusammentreffen (timing), tritt die erhöhte Mortalität adulter Daphnien auf. Die Ergebnisse der Untersuchungen unterstreichen damit die Bedeutung von Ganzsee-Experimenten und die möglichst simultane Erfassung verschiedener Zustandsgrößen, um eine umfassende Kausalanalyse der Sommerdepression der Daphnien zu ermöglichen, zu der die vorliegende Arbeit einen Beitrag liefert. Für den Erfolg der Biomanipulation konnte daher geschlußfolgert werden, daß eine nachhaltige Wirkung nur dann erreicht werden kann, wenn zusätzlich zur top-down Steuerung des Nahrungsnetzes gleichzeitig eine erfolgreiche Kontrolle der bottom-up Prozesse im Gewässer realisiert wird, indem starke Schwankungen von bottom-up Faktoren vermieden werden und damit das System insgesamt stabilisiert wird. / The occurrence of midsummer declines of daphnids is often related to poor food conditions or fish predation. In this three-year-study on the midsummer decline of Daphnia galeata field investigations in the highly eutrophic biomanipulated Bautzen reservoir were combined with flow-through experiments in the laboratory. The following hypothesis was tested: The inability of adult Daphnia to reduce the filtering area of their feeding appendages in response to fast increasing food levels after a clear-water phase enhances adult mortality. During the clear-water phase daphnids develop large and dense filtercombs to optimise their filter feeding. When food concentrations increase, however, this adaptation to low-food situation may be inappropriate due to too high energy consumtion. As adult daphnids cannot reduce the size of their feeding appendages, the filtration process may be hindered when seston concentrations rise, resulting in reduced fitness and increasing adult mortality. Indeed, adult survival in the laboratory (predation excluded) drastically decreased exactly at that time when the Daphnia galeata population in Bautzen reservoir declined. However, enhanced mortality was found irrespective of different food conditions offered during the experiments. It is concluded that increased mortality of adult daphnids is not an direct effect of their inability to adapt the morphology of their filtercombs to high seston concentrations. Furthermore daphnids are able to compensate unfavorable food conditions within a certain range by different kinds of adaptation mechanisms. Therefore the timing of the changes of food conditions and the adaptations of daphnids is most important to the efficiency of energy gain of the daphnids. Concerning the success of biomanipulation it is concluded that in addition to the regulation of top-down mechanisms there is an urgent need for control of bottom-up processes in order to stabilize the ecosystem.

The population dynamics and demography of Daphnia galeata was analysed in a five year study in the biomanipulated Bautzen Reservoir. Samples were taken two times a week during the period May-July in the pelagic zone of this highly eutrophic water. Major bottom-up and top-down factors were determined during the study period and analysed with regard to their influence on Daphnia dynamics and life history. Field data on fecundity and population structure of D. galeata were combined with results from life table and growth experiments performed under approximately in situ conditions to gain insight into the mechanisms leading to a midsummer decline of this cladoceran species which dominates the zooplankton community in Bautzen Reservoir. Two main patterns of Daphnia dynamics emerged: In years without a midsummer decline the population increased slowly in spring, starting from low densities. High water transparency was observed already during the build-up of the population of D. galeata. Despite considerable fluctuations, Daphnia abundance remained on a high level throughout summer. In years with a midsummer decline the population started from relatively high densities in early May and more than doubled during one week. Peak densities were reached before the clear-water stage emerged. At the end of this period the population declined to low values which lasted for the rest of the summer. Fecundity of the Population of D. galeata declined, whereas the mean egg volume increased at the beginning of the clear-water stage as a result of declining food levels. The size at maturity (SAM) remained high during this period. Additionally, juvenile growth was reduced and the age at maturity was retarded. Survival probability was low for those daphnids born shortly before or during the clear-water stage compared to those born later. It can be concluded from these results that recruitment to adult stages is strongly reduced during the clear-water stage. The end of this period is marked by an alternation in generations. Only at that time can SAM be reduced because the new generation of adults matures at a smaller size, carrying small eggs. A high impact of non-predatory adult mortality can be expected when the population is dominated by a strong peak-cohort during the clear-water stage according to recruitment patterns during the build-up of the population. The most drastic decline both of Daphnia abundance and SAM was observed in those years when the biomass of juvenile fish exceeded 20 kg ha-1 at the end of the clear-water stage. Due to gape-size limitation juvenile fish mainly feed on juvenile daphnids during this period and thus, they reinforce bottom-up effects on the Daphnia population. When fish change their size selection towards adult daphnids at the time when the new generation takes over, this seems to represent the worst case for the Daphnia population. Consequently, the timing between bottom-up effects and the feeding pressure of juvenile fish determines the extent of the decline. - (This manuscript is also available - in the form of a book - from Shaker Verlag GmbH, Postfach 101818, 52018 Aachen, Germany world-wide web address: http://www.shaker.de, electronic-mail address: info@shaker.de. It has been posted on the web sites of Dresden University of Technology with the permission of the publisher)

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-05-23T17:10:40Z No. of bitstreams: 1 LUCIANO CAMPOS TARGINO - DISSERTAÇÃO PPGSA PROFISSIONAL 2015..pdf: 553406 bytes, checksum: 2610d8596de919df9e7821e442749625 (MD5) / Made available in DSpace on 2018-05-23T17:10:40Z (GMT). No. of bitstreams: 1 LUCIANO CAMPOS TARGINO - DISSERTAÇÃO PPGSA PROFISSIONAL 2015..pdf: 553406 bytes, checksum: 2610d8596de919df9e7821e442749625 (MD5) Previous issue date: 2015 / A exploração racional de Galinhas da Angola (Numida melagris galeata) pode ser um negócio rentável e sua viabilidade econômica está intimamente ligada ao manejo adequado e capacidade empreendedora do produtor, já que é uma ave extremamente apreciada pelo sabor característico e peculiar de sua carne. Objetivou-se com este estudo avaliar a viabilidade e oportunidade de mercado na criação de Galinhas da Angola como parte do setor avícola. A coleta de dados ocorreu ao longo do ano de 2014 e meados de 2015 em dois municípios do estado do Ceará (Maracanaú e Cascavel), que se destacam no cenário nacional, na exploração comercial e industrial dessas aves. Verificou-se que ao atingirem 100 (cem) dias de idade quando apresentam no mínimo, 1,5kg/ave, são abatidas, atingindo uma média de abates de 3.000 galinhas angolas/mês, da linhagem Francesa, sendo o Kg comercializado (em setembro/2014) pelo valor de RS 16,00. O público consumidor que mais aprecia a carne é a classe média. Toda a produção é escoada na Grande Fortaleza e municípios vizinhos, tendo como público alvo, os restaurantes (70%), frigoríficos (28%) e pessoas que adquirem individualmente as aves já abatidas, direto com os produtores (2%). Observou-se que o pequeno produtor que recebe 160 pintos, no final da produção de cada lote, poderá lucrar até R$ 400,00/ciclo de criação, com valor recebido de R$ 2,50/ave, onde poderá lucrar até R$ 800,00/mês quando são entregues dois lotes sem nenhum custo já que toda a despesa com manejo alimentar e sanitário é custeado pelo produtor distribuidor. A exploração de Galinhas da Angola caracteriza-se por ser uma atividade economicamente viável, devido à rusticidade dos animais, minimizando os custos com manejo sanitário e uso de medicamentos. O sistema semi-intensivo de produção é o mais indicado para a criação comercial, por permitir uma maior qualidade vida às aves, pré- requisito que permite um sabor característico a carne, fugindo assim dos padrões dos frangos e galinhas criadas em total confinamento. A criação de Galinhas da Angola mostra-se viável, devido sua boa aceitação pelo mercado consumidor que busca cada vez mais alimentos alternativos e de qualidade, e por garantir uma diversificação e renda extra aos sistemas de produção dos municípios de Maracanaú e Cascavel. / The rational exploitation of chickens Angola (Numida melagris galeata) can be a profitable business and their economic viability is closely linked to adequate management and entrepreneurial capacity of the producer, as is a bird greatly appreciated by the characteristic and peculiar flavor of their meat. The objective of this study was to evaluate the feasibility and market opportunity in creating chickens Angola as part of the poultry sector. Data collection took place during the year 2014 and mid-2015 in two cities in the state of Ceara (Maracanau and Cascavel), which stand out on the national scene, in the commercial and industrial exploitation of these birds. It was found that on reaching one hundred (100) days of age when they present at least 1.5 kg / bird is slaughtered, reaching an average of 3,000 Angolans slaughter chickens / month, the French lineage, being marketed Kg (in September / 2014) in the amount of RS 16.00. The consumer audience that appreciates more the flesh is the middle class. The entire production is sold in the Fortaleza Grande and neighboring municipalities, with the target audience, restaurants (70%), refrigerators (28%) and people who individually have already slaughtered birds, direct with producers (2%). It was observed that the small producer who receives 160 chicks at the end of each production batch, it may profit to R $ 400.00 / creation cycle with value received from R $ 2.50 / bird where you can earn up to R $ 800.00 / month when they are delivered two lots at no cost since all spending on food and health management is funded by the distributor producer. The exploitation of chickens Angola is characterized for being an economically viable activity, due to the rusticity of animals, minimizing the costs of health management and use of medications. The semi-intensive production system is the most suitable for business creation by enabling a higher quality life to the birds, prerequisite that allows a characteristic meat flavor, thus escaping the standards of chickens and hens in virtual confinement. The creation of chickens Angola proves feasible, due to its good acceptance by the market seeking more and more alternative and quality food, and ensuring diversification and extra income to production systems in the municipalities of Maracanau and Cascavel.

Ziel der Arbeit war eine möglichst umfassende Analyse der Nahrungsbedingungen von D. galeata unter Berücksichtigung der damit verbundenen Strategien der Daphnien zur Optimierung des Nahrungserwerbs, um den Einfluß dieser Faktoren bezüglich des Auftretens einer Sommerdepression der Daphnien zu beurteilen. Aufbauend auf den bereits vorhandenen Kenntnissen aus der Literatur sollte dazu im Rahmen der Arbeit festgestellt werden, ob morphologische Veränderungen des Filtrationsapparates der Daphnien (Ausbildung großer, hydrodynamisch dichter Filter), die als Reaktion auf die geringen Nahrungsmengen im Klarwasserstadium auftreten, bei einer drastischen Erhöhung der Nahrungskonzentration zu einer "Überlastung" der Filterbeine der Daphnien, zu hohen Energieausgaben und schließlich zu erhöhter Mortalität (Sommerdepression) führen können. Hauptziel war dabei die Klärung der Frage, ob bottom-up gesteuerte schnelle Veränderungen im Nahrungsangebot, wie sie für geringe bottom-up Limitation (Hypertrophie) typisch sind, eine erhöhte Mortalität bei Daphnien hervorrufen können. Die Beantwortung dieser Fragestellung ist wichtig, um die Effizienz der top-down Steuerung (Biomanipulation) als ökotechnologische Maßnahme zur Gewässersanierung zu erhöhen. Dazu wurden in der biomanipulierten Talsperre Bautzen in drei Untersuchungsjahren (1997 - 1999) wichtige bottom-up wirkende Steuerfaktoren der Daphnienentwicklung sowie morphologische Charakteristika der Filterkämme und physiologische Leistungskriterien von D. galeata vor und während der Zeit des potentiellen Auftretens einer Sommerdepression untersucht. Aus den Ergebnissen ließ sich ableiten, daß das Zusammenspiel der vielfältigen Anpassungsmöglichkeiten der Daphnien in einem bestimmten Variationsbereich der Steuerfaktoren eine erfolgreiche Strategie zur Optimierung der Nahrungsaufnahme darstellen kann. Werden jedoch bestimmte Schwellenwerte über- oder unterschritten, ist eine Kompensation durch die Anpassungsstrategien nicht oder nur bedingt möglich. Dabei kann durch verschiedene Ursachen der gleiche Effekt (Mortalität adulter Daphnien) auftreten, was die Interpretation erschwert. Dieser Effekt wird besonders bei adulten Daphnien durch die gegenüber juvenilen Daphnien höheren Filterwiderstände und die damit verringerte effektive Energieaufnahme begünstigt. Erst wenn ungünstige Nahrungsbedingungen und die am Ende der Klarwasserphase beobachteten ungünstigen Konstellationen der Filterkämme zusammentreffen (timing), tritt die erhöhte Mortalität adulter Daphnien auf. Die Ergebnisse der Untersuchungen unterstreichen damit die Bedeutung von Ganzsee-Experimenten und die möglichst simultane Erfassung verschiedener Zustandsgrößen, um eine umfassende Kausalanalyse der Sommerdepression der Daphnien zu ermöglichen, zu der die vorliegende Arbeit einen Beitrag liefert. Für den Erfolg der Biomanipulation konnte daher geschlußfolgert werden, daß eine nachhaltige Wirkung nur dann erreicht werden kann, wenn zusätzlich zur top-down Steuerung des Nahrungsnetzes gleichzeitig eine erfolgreiche Kontrolle der bottom-up Prozesse im Gewässer realisiert wird, indem starke Schwankungen von bottom-up Faktoren vermieden werden und damit das System insgesamt stabilisiert wird. / The occurrence of midsummer declines of daphnids is often related to poor food conditions or fish predation. In this three-year-study on the midsummer decline of Daphnia galeata field investigations in the highly eutrophic biomanipulated Bautzen reservoir were combined with flow-through experiments in the laboratory. The following hypothesis was tested: The inability of adult Daphnia to reduce the filtering area of their feeding appendages in response to fast increasing food levels after a clear-water phase enhances adult mortality. During the clear-water phase daphnids develop large and dense filtercombs to optimise their filter feeding. When food concentrations increase, however, this adaptation to low-food situation may be inappropriate due to too high energy consumtion. As adult daphnids cannot reduce the size of their feeding appendages, the filtration process may be hindered when seston concentrations rise, resulting in reduced fitness and increasing adult mortality. Indeed, adult survival in the laboratory (predation excluded) drastically decreased exactly at that time when the Daphnia galeata population in Bautzen reservoir declined. However, enhanced mortality was found irrespective of different food conditions offered during the experiments. It is concluded that increased mortality of adult daphnids is not an direct effect of their inability to adapt the morphology of their filtercombs to high seston concentrations. Furthermore daphnids are able to compensate unfavorable food conditions within a certain range by different kinds of adaptation mechanisms. Therefore the timing of the changes of food conditions and the adaptations of daphnids is most important to the efficiency of energy gain of the daphnids. Concerning the success of biomanipulation it is concluded that in addition to the regulation of top-down mechanisms there is an urgent need for control of bottom-up processes in order to stabilize the ecosystem.

The population dynamics and demography of Daphnia galeata was analysed in a five year study in the biomanipulated Bautzen Reservoir. Samples were taken two times a week during the period May-July in the pelagic zone of this highly eutrophic water. Major bottom-up and top-down factors were determined during the study period and analysed with regard to their influence on Daphnia dynamics and life history. Field data on fecundity and population structure of D. galeata were combined with results from life table and growth experiments performed under approximately in situ conditions to gain insight into the mechanisms leading to a midsummer decline of this cladoceran species which dominates the zooplankton community in Bautzen Reservoir. Two main patterns of Daphnia dynamics emerged: In years without a midsummer decline the population increased slowly in spring, starting from low densities. High water transparency was observed already during the build-up of the population of D. galeata. Despite considerable fluctuations, Daphnia abundance remained on a high level throughout summer. In years with a midsummer decline the population started from relatively high densities in early May and more than doubled during one week. Peak densities were reached before the clear-water stage emerged. At the end of this period the population declined to low values which lasted for the rest of the summer. Fecundity of the Population of D. galeata declined, whereas the mean egg volume increased at the beginning of the clear-water stage as a result of declining food levels. The size at maturity (SAM) remained high during this period. Additionally, juvenile growth was reduced and the age at maturity was retarded. Survival probability was low for those daphnids born shortly before or during the clear-water stage compared to those born later. It can be concluded from these results that recruitment to adult stages is strongly reduced during the clear-water stage. The end of this period is marked by an alternation in generations. Only at that time can SAM be reduced because the new generation of adults matures at a smaller size, carrying small eggs. A high impact of non-predatory adult mortality can be expected when the population is dominated by a strong peak-cohort during the clear-water stage according to recruitment patterns during the build-up of the population. The most drastic decline both of Daphnia abundance and SAM was observed in those years when the biomass of juvenile fish exceeded 20 kg ha-1 at the end of the clear-water stage. Due to gape-size limitation juvenile fish mainly feed on juvenile daphnids during this period and thus, they reinforce bottom-up effects on the Daphnia population. When fish change their size selection towards adult daphnids at the time when the new generation takes over, this seems to represent the worst case for the Daphnia population. Consequently, the timing between bottom-up effects and the feeding pressure of juvenile fish determines the extent of the decline. - (This manuscript is also available - in the form of a book - from Shaker Verlag GmbH, Postfach 101818, 52018 Aachen, Germany world-wide web address: http://www.shaker.de, electronic-mail address: info@shaker.de. It has been posted on the web sites of Dresden University of Technology with the permission of the publisher)