published_or_final_version / Real Estate and Construction / Doctoral / Doctor of Philosophy

Adult stonefly emergence, nymphal growth, drift and microdistribution were examined in Battle Branch, a secondorder, spring-fed stream, from November, 1982 to May, 1984. Adults of 22 species emerged successionally, with specific adults present every month. Searching emergent objects and the stream margin was best for collection of winter and early spring emerging species. Sweeping the streamside and light trapping were most efficient for late spring and summer emerging species. Nymphal growth for nine abundant species generally fit double log or semilog models. Drift was low, but did show a post-sunset pulse. Generally, leaf material was found to be significantly related (p<O.001) to density, diversity and biomass of stoneflies in Battle Branch.

Invertebrate spatial patterns were investigated in 36 and 12 spring and runoff-fed streams in New Zealand and in Northern Spain, respectively. Moss biomass and resource levels were more abundant in springbrooks than in runoff-fed streams. Invertebrate densities were greater in spring habitats, but invertebrate richness was higher and lower at more stable sites in New Zealand and Spain, respectively. These differences in invertebrate diversity may be related to the larger diversity of invertebrate predators in New Zealand springbrooks, and the lack of temperature mediated life history cues in the New Zealand invertebrate fauna. I carried out two experiments to look at the effect of local factors on the spatial distribution of invertebrate communities. The first experiment investigated the effect that algal biomass and habitat structure had on stream invertebrate communities. To do this I used artificial canopies to reduce algal growth and artificial substrates with different habitat complexities. Numbers of invertebrate taxa and individuals were both lower on bricks under the artificial canopies and on the simplest substrates. Algal productivity may enhance invertebrate richness by increasing the number of individuals in a given area, whereas habitat complexity may increase invertebrate richness by providing greater food and/or space resources. The second experiment examined the effects of primary productivity and physical disturbance on stream invertebrates by using artificial canopies and by kicking and raking patches of the stream bed (10 m2). We compared the effects of natural versus experimental disturbance on the benthic invertebrate fauna Invertebrate fauna in high productivity patches recovered quicker than in low productivity patches after both experimental and natural disturbance. The experimental disturbance reduced number of invertebrate taxa and individuals to a greater extent than the spate. Primary productivity limited the recovery of the invertebrate fauna after the disturbances. I also investigated temperature patterns in five runoff and seven spring-fed streams in the North and South Islands of New Zealand. The invertebrate fauna was sampled at 4 distances (0, 100, 500 and 1 km) from seven spring sources. Temperature variability was much larger for runoff-fed streams than for springs, and it increased with distance from the source. Flow, altitude, and the number and type (i.e., spring or runoff-fed) of tributaries joining the springbrook channel determined the degree of temperature variability downstream of the spring sources. Moving downstream, invertebrate communities progressively incorporated taxa with higher mobility and those more common to runoff-fed streams. Changes in substrate composition, stability and invertebrate drift are more likely explanations of the observed longitudinal patterns in the invertebrate communities than changes in temperature regimes.

Initially, components of an aquatic food web were examined to study impacts of recreational use on the aquatic ecology of Quartzville Creek, Oregon in 1995 and 1996. Measurements of the food web components consisted of observations of harlequin ducks (Histrionicus histrionicus), visual counts of the larval caddisfly Dicosmoecus gilvipes, benthic macroinvertebrate samples, and chlorophyll a biomass of epiphytic algae. In February 1996, a major flood forced closure of the study area to the general public throughout the 1996 season, providing a "natural experiment" situation. The difficulty was how to distinguish between effects of flood damage and effects of the presence/absence of humans. By accounting for various measured abiotic and biotic factors using multiple regression, distinctions between disturbance effects were made with regard to abundances of D. gilvipes and benthic invertebrates. Regression analysis also was used to account for annual site differences in average depth, habitat types and substrates. Generally, recreational impacts were apparent at more localized spatial and temporal scales than were effects from extensive flooding. However, scales at which these disturbances affected components of the food web varied. Impacts of the flood included an 81% reduction in overall D. gilvipes densities, a 37% decrease in benthic abundance, reduced chlorophyll a biomass, fewer numbers of ducks and changes in site substrates and habitats. These impacts occurred across all study sites and throughout the 1996 season, except for the recovery of benthic abundance to 1995 levels by July 1996. Recreational impacts were apparent at the site scale and appeared to be seasonal in duration. In 1995, sites without human use had significantly higher densities of D. gilvipes than those sites impacted by recreation. In 1996, no significant differences in D. gilvipes densities among sites were observed after accounting for flood effects and site differences. There were no direct significant relationships to human use among sites with regard to total benthic invertebrates, chlorophyll a biomass or H. histrionicus. Despite the lack of a direct spatial relationship between H. histrionicus and D. gilvipes at the local scale of this study, there were strong temporal correlations between harlequin brood development and D. gilvipes maturation. / Graduation date: 1997

Chemically mediated interactions have important ecological and evolutionary effects on populations and communities. Despite recognition that herbivory can significantly affect the biomass and composition of freshwater macrophyte communities, there are few investigations of chemical defenses among freshwater vascular plants and mosses and none of freshwater red algae. This study compares the palatability of five species of freshwater red algae (Batrachospermum helminthosum, Boldia erythrosiphon, Kumanoa sp., Paralemanea annulata, and Tuomeya americana) that occur in the southeastern United States relative to two co-occurring macrophytes (the chemically defended aquatic moss Fontinalis novae-angliae and the broadly palatable green alga Cladophora glomerata). We assessed the potential role of structural, nutritional, and chemical traits in reducing macrophyte susceptibility to generalist crayfish grazers. Both native and non-native crayfish significantly preferred the green alga C. glomerata over four of the five species of red algae. B. erythrosiphon was palatable, while the cartilaginous structure of P. annulata reduced its susceptibility to grazing, and chemical defenses of B. helminthosum, Kumanoa sp., and T. americana rendered these species as unpalatable as the moss F. novae-angliae. Extracts from these latter species reduced feeding by ~30-60% relative to solvent controls if tissues were crushed (simulating herbivore damage) prior to extraction in organic solvents. However, if algae were first soaked in organic solvents that inhibit enzymatic activity and then crushed, crude extracts stimulated or had no effect on herbivory. B. helminthosum, Kumanoa sp., and T. americana all exhibited "activated" chemical defenses in which anti-herbivore compounds are produced rapidly upon herbivore attack via enzymatic processes. In an additional accept/reject behavioral assay, B. helminthosum extracts reduced the number of crayfish willing to feed by >90%. Given that three of the five red algal taxa examined in this study yielded deterrent crude extracts, selection for defensive chemistry in freshwater rhodophytes appears to be substantial. Activated chemical defenses are thought to be an adaptation to reduce the resource allocation and ecological costs of defense. As such, activated chemical defenses may be favored in freshwater red algae, whose short-lived gametophytes must grow and reproduce rapidly. Roughly 20% of the known chemical defenses produced by marine algae are activated; further examination is needed to determine whether the frequency of activated chemistry is higher in freshwater red algae compared to their marine counterparts. Continued investigation of chemical defenses in freshwater red algae will contribute to among-system comparisons, providing new insights in the generality of plant-herbivore interactions and their evolution.

Biomanipulation im Sinne einer top-down Steuerung des Nahrungsnetzes wurde in Standgewässern intensiv erforscht und wird als Mittel zur Verbesserung der Wasserqualität bzw. Verringerung der Eutrophierungserscheinungen eingesetzt. Ebenso könnte die Idee der Biomanipulation genutzt werden, um die Eutrophierung in kleinen Fließgewässern zu verringern. Eine Förderung benthischer herbivorer Schlüsselorganismen (z.B. Eintagsfliegenlarven) durch die Reduzierung des Fischfraßdruckes könnte helfen, Algenmassenentwicklungen zu vermeiden. Studien zur Biomanipulation von Nahrungsnetzen in Standgewässern zeigten allerdings eine zunehmende Entwicklung von planktischen invertebraten Räubern bei Abwesenheit planktivorer Fische. Die Bedeutung des Fraßdruckes invertebrater Räuber in fischfreien Fließgewässernahrungsnetzen ist dagegen noch unbekannt. Aufgrund von letalen und subletalen Fischeffekten könnte die Konsumtion räuberischer Invertebraten bei Fischabwesenheit so stark gefördert werden, dass das Ziel der Biomanipulation verfehlt wird. Invertebrate Räuber haben insgesamt einen relativ hohen Anteil an der Biomasse der Benthosgemeinschaft in Fließgewässernahrungsnetzen. Sie könnten somit potentiell einen ähnlichen Fraßdruck wie vertebrate Räuber (z.B. benthivore Fische) auf die unteren trophischen Ebenen ausüben. Auch der Anteil der Omnivorie ist in Fließgewässernahrungsnetzen hoch. Ziel dieser Arbeit war es deshalb, die Bedeutung invertebrater Prädation im Nahrungsnetz eines kleinen Fließgewässers (Gauernitzbach) unter Berücksichtigung der obligaten Räuber sowie des räuberischen Potentials Omnivorer abzuschätzen. Außerdem wurde der Einfluss benthivorer Fische auf die Populationsentwicklung und das Ernährungsverhalten der wichtigsten invertebraten Räuber und Omnivoren untersucht. Dazu wurde ein Bachabschnitt, der mit benthivoren Fischen (Gobio gobio, Barbatula barbatula) besetzt war, mit einem fischfreien Abschnitt über zwei Jahre verglichen. Nach der Identifizierung wichtiger Räuber- und Omnivorenarten anhand ihrer Biomasse und ihrer trophischen Positionen mittels Isotopenanalyse wurde ihr Gesamtfraßdruck abgeschätzt. Invertebrate Prädatoren im Nahrungsnetz des Gauernitzbaches waren Rhyacophila fasciata und Plectrocnemia conspersa (Trichoptera), Isoperla grammatica (Plecoptera) sowie Dugesia gonocephala (Turbellaria). Wichtige Omnivore aufgrund ihrer hohen Biomassen waren Gammarus pulex (Amphipoda) und Hydropsyche spp. (Trichoptera). Anhand eines Mischungsmodells (ISOSOURCE), das auf der Basis der stabilen Isotopensignaturen d13C und d15N die einzelnen Ressourcenanteile einer gemischten Signatur berechnet, konnte das ausgeprägte räuberische Potential der Omnivoren gezeigt werden, da sie einen hohen tierischen Anteil in der Nahrung aufwiesen (20-90 %). Im Nahrungsnetz des Gauernitzbaches waren Omnivore als Räuber damit ebenso bedeutsam wie obligat räuberische Invertebrate. Der Gesamtfraßdruck der invertebraten Räuber und Omnivoren auf die Beuteorganismen (bis 16 g TM m-2 a-1) in der Fischstrecke war höher als der Fraßdruck der benthivoren Fische (~3 g TM m-2 a-1). Dieser Unterschied lag hauptsächlich in höheren täglichen Konsumtionsraten bei ähnlich hohen Biomassen der Invertebraten begründet. Durch die Analyse der stabilen Isotope von Kohlenstoff und Stickstoff konnten die trophischen Beziehungen im Nahrungsnetz des Gauernitzbaches identifiziert werden. Dabei stellten allochthone Kohlenstoffquellen im Frühjahr und Herbst die bedeutendste Ressource für die Primärkonsumenten dar, während autochthone Ressourcen nur im Frühjahr für wenige Herbivore relevant waren. Dies spiegelte sich ebenso in der Nahrung der Omnivoren wider, die neben Organismen hauptsächlich Detritus nutzten. Ebenso zeigten die invertebraten Räuber eine deutliche Abhängigkeit vom allochthonen Kohlenstoff über die Nutzung der Primärkonsumenten. Letale Effekte der Fische auf die räuberischen und omnivoren Populationen im Gauernitzbach fanden hauptsächlich in Abhängigkeit von den bewohnten Habitaten statt. Die Pool-Arten (P. conspersa, D. gonocephala, G. pulex) entwickelten geringere Biomassen in der Fischstrecke, während die Biomassen riffle-bewohnender Invertebraten (R. fasciata, I. grammatica, Hydropsyche spp.) nicht deutlich reduziert wurden. Dabei waren allerdings meist hohe Biomassen in der Fischstrecke weniger stark ausgeprägt als in der fischfreien Strecke. Die Adulten der untersuchten Arten wurden oft stärker letal beeinflusst als die Juvenilstadien. So war die Emergenzproduktion der räuberischen Köcherfliegen und die Abundanz großer und eiertragender Weibchen von G. pulex in der Fischstrecke deutlich verringert. Subletale Effekte der Fische traten im Gauernitzbach in Abhängigkeit von den Ernährungstypen auf. Während die adulten räuberischen Köcherfliegenarten R. fasciata und P. conspersa keine negative Beeinflussung der Fitness und Größe zeigten, emergierte die omnivore Köcherfliege H. instabilis in der Fischstrecke kleiner als in der fischfreien. Außerdem unterschieden sich die Antworten der omnivoren Arten vermutlich aufgrund ihrer unterschiedlichen Lebenszyklen. G. pulex zeigte als ausschließlich aquatisch lebende Art keine subletalen Kosten (unveränderte Fitness) bei Fischanwesenheit wie dies für die omnivore merolimnische Insektenart H. instabilis beobachtet wurde. Die mittlere Fitness der Populationen (gemessen an der Eiproduktion pro Zeit- und Flächeneinheit) war für alle untersuchten invertebraten Räuber und Omnivoren bei Fischanwesenheit deutlich geringer als in der fischfreien Strecke. Für die Räuber (R. fasciata, P. conspersa) und G. pulex waren vermutlich letale Fischeffekte für den geringen Reproduktionserfolg verantwortlich. Dagegen wurde die Fitness der Population von H. instabilis durch die Kombination aus der geringeren individuellen Körpergröße (subletal) und den schwachen letalen Effekten auf die Emergenz reduziert. Der Einfluss der Fische auf die räuberischen Larven von R. fasciata und P. conspersa resultierte in einem Wechsel der Beutezusammensetzung, nicht in der Reduzierung der täglichen Fraßaktivität. Dies war vermutlich auf eine Aktivitätsänderung des Räubers R. fasciata bzw. auf die veränderte Beuteverfügbarkeit für P. conspersa unter Fischeinfluss zurückzuführen. Eine grundsätzliche Verringerung der Fraßaktivität oder der tierischen Anteile in der Nahrung der omnivoren Arten unter dem Einfluss benthivorer Fische wurde nicht festgestellt. Dagegen änderten sich die Relationen der Ressourcen Omnivorer zueinander, so konnte in der fischfreien Strecke eine flexiblere Ressourcennutzung nachgewiesen werden. Die jährliche Gesamtkonsumtion der räuberischen und omnivoren Invertebraten wurde durch die Anwesenheit der benthivoren Fische um 20-50 % reduziert, wofür hauptsächlich fischinduzierte Biomasseänderungen verantwortlich waren. In der fischfreien Strecke konnte dagegen die erhöhte Konsumtion der Invertebraten den fehlenden Fischfraßdruck mehr als kompensieren. Allerdings änderte sich die beutespezifische Konsumtion der Räuber in der fischfreien Strecke durch den verhaltensinduzierten Wechsel in der Beutezusammensetzung. Damit fand ein erhöhter Fraßdruck auf detritusfressende Arten (z.B. Diptera) statt, während die vermuteten Schlüsselarten einer potentiellen Biomanipulation (grazende Eintagsfliegen) in der fischfreien Strecke relativ unbeeinflusst blieben. Da die invertebrate Prädation in Fließgewässern sehr bedeutend sein kann, ist Biomanipulation nur unter Berücksichtigung aller Populationen räuberischer Invertebraten möglich. Nur durch Einstellung einer optimalen (relativ hohen) Biomasse geeigneter benthivorer Fischarten kann eine ausreichende Hemmung der invertebraten Räuber erreicht werden, so dass grazende Arten indirekt profitieren. / Biomanipulation (top-down control of the food webs) in lakes was intensively studied and can today be regarded as an important tool for improvement of the water quality and eutrophication. Similarly, the idea of biomanipulation can be used to reduce eutrophication phenomena in streams. The enhancement of benthic herbivorous key species (e.g. mayflies) by reduction of fish predation pressure could prevent exploding benthic algae biomass. Studies dealing with trophic cascades in lakes suggested that biomass of planktic invertebrate predators is increasing in the absence of planktivorous fish. But until now the importance of invertebrate predation pressure in fishless stream food webs is hardly known. Due to lethal and sublethal fish effects the consumption of predatory invertebrates could be enhanced by the absence of fish to such an extent that biomanipulation could be off target. In general, the proportion of invertebrate predators to the biomass of the benthic community in stream food webs is relatively high. Therefore, invertebrate predation on benthic prey can be as important as vertebrate predation (e.g. by benthivorous fish). Furthermore, omnivory occurs frequently in streams. Therefore, the aim of this thesis was to assess the importance of invertebrate predation in a food web of a small stream (Gauernitzbach) including the obligatory predators as well as the predatory potential of omnivores. Furthermore, the impact of benthivorous fish on population dynamics and feeding behaviour of the most important predators and omnivores was studied. Therefore, a reach stocked with benthivorous fish (Gobio gobio, Barbatula barbatula) was compared with an upstream fishless reach over a two-year period. After identification of important predators and omnivores based on their biomass and trophic position by stable isotope analyses their total consumption was estimated. Rhyacophila fasciata and Plectrocnemia conspersa (Trichoptera), Isoperla grammatica (Plecoptera) as well as Dugesia gonocephala (Turbellaria) were the invertebrate predators in the food web of Gauernitzbach. Because of their high biomasses the most important omnivores were Gammarus pulex (Amphipoda) and Hydropsyche spp. (Trichoptera). Using a mixing model (ISOSOURCE) that estimates the proportions of single resources on a mixed signature on the basis of the stable 13C and 15N isotopes, the predatory potential of both omnivores was pronounced by a high animal food proportion (20-90%). In this stream food web the predation impact of omnivores was comparable to this of obligatory predacous invertebrates. The total invertebrate predation pressure (up to 16 g TM m-2 a-1) in the fish reach was higher than the vertebrate predation pressure (~3 g TM m-2 a-1) mainly caused by the higher daily consumption rates and similar biomass compared to fish. Using stable isotope analyses of carbon and nitrogen the trophic pathways in the food web of Gauernitzbach could be identified. The most important resources for primary consumers in spring and autumn were allochthonous carbon sources. Autochtnonous carbon sources were only utilized by a few herbivores in spring. This was also reflected in the food of omnivores which assimilated mainly detritus beside animal material. Similarly, the predators depended distinctly on the allochthonous pathway by feeding primary consumers. Lethal fish effects on the predatory and omnivorous invertebrate populations were mainly depended on their preferred habitats. Pool-dwelling species (P. conspersa, D. gonocephala, G. pulex) showed decreased biomass in the presence of fish. Contrary, the biomass of riffle-dwelling invertebrates (R. fasciata, I. grammatica, Hydropsyche spp.) was not significantly reduced in the fish reach. Thereby, the highest biomass values in the fish reach could not reach the same level as in the fishless reach. Adults of the investigated species were influenced more lethal than the young stages. Hence, the emergence production of the predatory caddisflies and the abundance of the biggest and gravid females of G. pulex were reduced in the fish reach. Sublethal fish effects existed in dependence on the feeding groups of the invertebrates in Gauernitzbach. Whereas the adult predatory caddisflies R. fasciata and P. conspersa did not show disadvantages in fitness and size, the omnivorous caddisfly H. instabilis emerged with smaller size in the fish reach than in the fishless reach. Different responses of both omnivorous species were observed because of their different life cycles. The exclusively aquatic living G. pulex was not influenced sublethal by fish as the merolimnic insect species H. instabilis. The average fitness of population (measured as egg production per unit time and space) of the studied invertebrate predators and omnivores was distinctly reduced in the fish reach compared to the fishless reach. Probably, lethal fish effects were mainly responsible for the low reproductive success of the predatory species (R. fasciata, P. conspersa) and G. pulex. In contrast, the reduction of population fitness of H. instabilis was caused by the reduced individual adult size (sublethal effect) in combination with the weak lethal effect on emergence. The impact of fish on the feeding behaviour of the predatory larvae of R. fasciata and P. conspersa resulted in a switched prey composition, whereas a reduction in the daily feeding activity was not observed. That was supposed because of changes in the activity pattern by the predator R. fasciata or the changed prey availability for P. conspersa in the fish reach. A general reduction in feeding activity or animal food proportion of the omnivores was not assessed in the presence of fish. In contrast, the relations between the resources switched to a more variable utilisation in the fishless reach. The annual total consumption of invertebrate predators and omnivores was decreased by 20-50% in the fish reach, mainly caused by fish induced biomass reduction. The missing fish consumption could be at least balanced by higher invertebrate consumption in the fishless reach. Contrary, the prey specific consumption of invertebrate predators changed by behavioural-induced switch in the prey composition between the stream reaches. Therefore, a higher predation pressure on detritus feeding species (e.g Diptera) was found in the fishless reach, but not on the supposed key species of the potential biomanipulation (e.g. grazing mayflies). Due to the high importance of invertebrate predation in stream food webs, the aim of biomanipulation can only be reached by considering the populations of predatory invertebrates. Controlling the biomass of suitable benthivorous fish to an optimum (relatively high) level could sufficiently reduce the impact of invertebrate predators leading to an indirect enhancement of grazing species.

published_or_final_version / Botany / Master / Master of Philosophy

Copies of author's previously published articles inserted. / Bibliography: leaves 317-359. / xxii, 360 leaves : ill. (some col.), maps (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the generality of the Flood Pulse Concept as a model for the role of flow in large floodplain rivers of all climatic zones and reviews the literature on hydrology-biology relations, with particular reference to the ecology of riverine fish. Using techniques of ordination, clustering and analysis of similarities (ANOSIM), examines the relations between flow variability, econology and climate in large rivers worldwide. Using a fie-year database for Cooper Creek in Central Australia, relates structures of fish, macroinvertebrate and zooplankton assemblages and indices of fish health and behaviour to hydrology at several spatial and temporal scales. These relations are established using multivariate techniques, univariate correlation and regression, and neural networks modelling. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1999

Copies of author's previously published articles inserted. / Bibliography: leaves 317-359. / xxii, 360 leaves : ill. (some col.), maps (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the generality of the Flood Pulse Concept as a model for the role of flow in large floodplain rivers of all climatic zones and reviews the literature on hydrology-biology relations, with particular reference to the ecology of riverine fish. Using techniques of ordination, clustering and analysis of similarities (ANOSIM), examines the relations between flow variability, econology and climate in large rivers worldwide. Using a fie-year database for Cooper Creek in Central Australia, relates structures of fish, macroinvertebrate and zooplankton assemblages and indices of fish health and behaviour to hydrology at several spatial and temporal scales. These relations are established using multivariate techniques, univariate correlation and regression, and neural networks modelling. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1999

Made available in DSpace on 2014-06-11T19:30:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-11Bitstream added on 2014-06-13T20:00:14Z : No. of bitstreams: 1 paula_fr_me_rcla.pdf: 4342789 bytes, checksum: 9634421fb04b3df8470ee1faea4a0d90 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os peixes apresentam uma grande diversidade de espécies, sendo na região Neotropical onde se encontra o maior número de espécies de água doce. Entretanto, esta grande diversidade encontra-se ameaçada devido à degradação dos ecossistemas lóticos, principalmente pela alteração do habitat devido à destruição das florestas e fragmentação da rede hidrográfica. As florestas, principalmente as florestas ripárias, possuem funções ecológicas importantes para a estruturação dos riachos e das comunidades aquáticas. Por muito tempo, as florestas têm sido extensamente destruídas, sendo substituídas principalmente pelos usos agrícolas, ocasionando a destruição dos ecossistemas e da biodiversidade aquática. Além das alterações nas florestas, a presença de represamentos e cruzamentos de estradas gera impactos adicionais para os peixes ao romper a conectividade existente na rede hidrográfica. Os peixes possuem ciclos de vida complexos que dependem da complexidade estrutural do riacho e da conectividade entre trechos montante e jusante da rede. Portanto, a conservação das florestas e a manutenção da conectividade hidrológica são fatores importantes para a conservação das comunidades de peixes. Neste trabalho, avaliou-se a diversidade das comunidades de peixes de riachos em função das alterações na estrutura da paisagem florestal (composição e configuração) e da conectividade da rede hidrográfica em paisagens agrícolas. O estudo foi realizado em microbacias de 1ª a 4ª ordem pertencentes à bacia do rio Corumbataí. Diferenças nos índices de diversidade das comunidades foram testadas a partir da Análise de Variância considerando a estrutura da paisagem florestal em diferentes escalas espaciais (microbacia, rede de drenagem e trecho de coleta) e a conectividade da rede hidrográfica. As relações entre as variáveis da paisagem (estrutura da paisagem... / Fish exhibit great species diversity, and the Neotropical region holds the largest number of freshwater fish species . However, this great diversity is threatened due to lotic ecosystems degradation, mainly through forest destruction and stream network fragmentation. Forests, mainly riparian forests, have important ecological functions for stream and aquatic communities structuring. For a long time, forests have been extensively destroyed and replaced mainly by agricultural uses, causing stream and aquatic biodiversity destruction. Besides the alterations in forests, the presence of dams and road crossings generates additional impacts to fish by disrupting existing connectivity to the stream network. Fish have complex life cycles that depend of the stream structural complexity and the connectivity between upstream and downstream sections of the stream network. Hence, forest conservation and maintenance of hydrological connectivity are important factors for the conservation of fish communities. In this study, we evaluated stream fish community diversity in relation to changes in forest landscape structure (composition and configuration) and the stream network connectivity in agricultural landscapes. The study was conducted in 1st and 4th order catchments belonging to the Corumbatai river basin. Differences in diversity indices were tested by Analyses of Variance considering forest landscape structure at different spatial scales (whole catchment, stream network and stream sampled reach) and stream network connectivity. The relationship between landscape variables (forest landscape structure, riparian forest landscape structure and physical and hydrological hierarchy variables) and aquatic environment variables (channel structure and limnology and fish diversity indices) were evaluated using Redundancy Analysis (RDA) and Multiple Regression Analysis. These relationships were also assessed... (Complete abstract click electronic access below)