The middle Brazos River, located in east central Texas, is a meandering lowland river that contains many oxbow lakes on its floodplain. Flood dynamics of the Brazos River are aseasonal, and faunal exchange during lateral connections of the main river channel and oxbows is pulse-like and only occurs during floods that may be months or years apart. Patterns of resource use among sympatric gar species (Lepisosteus oculatus, L. osseus, and Atractosteus spatula) associated with river-floodplain connectivity was studied for a period of two years (May 2003 to May 2005). The first year was relatively dry yielding few lateral connections, whereas the second year was relatively wet resulting in more frequent lateral connections. This study focused on habitat and diet partitioning among the three gar species in oxbow habitats with different connection frequencies and an active river channel site. Overall, 684 gars were collected with experimental gillnets: 19 A. spatula (alligator gar), 374 L. oculatus (spotted gar), and 291 L. osseus (longnose gar). There was strong partitioning of habitat between spotted and longnose gars, in which 98% of spotted gars were captured in oxbow habitats and 84% of longnose gars were captured in the river channel. Hydrology did not appear to affect habitat partitioning, although longnose gar abundance significantly increased in oxbows during the wet year. Diet overlap was high between spotted and longnose gars. Temporal variation in diet was significantly influenced by flood pulses that connected oxbows with the river channel, and which allowed predators and their prey to move between habitats.

Seasonally fluctuating water levels, known as flood pulses, influence the population dynamics and catches of fishes from river-floodplains. Although different measures of flood pulses, here called flood pulse variables, have been correlated to changes in catches of river-floodplain fishes, the flood pulse variables that have the strongest relationships to catches have not been identified. Furthermore, it is unclear if flood pulses influence catches of river-floodplain fishes with different life history strategies in different ways. Catches of 21 taxa from approximately 18,000 fishing trips were modeled as a function of fishing effort, gear type, seasonal flood pulse variables, and interannual flood pulse variables. These models were analyzed to understand which flood pulse variables had the strongest relationships to catches, and evaluate different flood pulse influences among taxa with different life history strategies. High water flood pulse variables generally had positive influences on catches in future years, while low water flood pulse variables generally had negative influences on catches in future years. Flood pulses generally had stronger influences on the catches of fishes with high fecundities and smaller eggs than on catches of fishes with low fecundities and larger eggs. Variation was observed in strengths and directions of flood pulse influences on catches of fishes with similar and different life history strategies. While my results were generally consistent with prevailing knowledge of how flood pulses influence catches of fishes, other biological factors of specific fish populations may further explain population responses to flood pulses. / Master of Science

The Tonle Sap is the largest and most important natural wetland in Southeast Asia. It covers an area of more than 15,000 km2 with a unique mosaic of natural and agricultural floodplain habitats that coexist with the largest fishery in the Mekong Basin. Accelerating hydropower development and climate change, however, are altering the Mekong’s hydrology, which could negatively affect downstream ecosystems. The Tonle Sap is facing a two-fold problem. First, the link between its hydrology and ecosystem properties is not well understood. Second, potential ecological changes caused by future hydrological disruptions related to hydropower and climate change are unknown. Thus, the main objective of this thesis was to quantify how alterations to the Mekong hydrology could affect the Tonle Sap ecosystem. The following studies were performed to addressed the objective: (1) an assessment of landscape patterns using geographical information and remote sensing tools; (2) an assessment of habitat patterns based on field surveys of water, vegetation, and soils; (3) ecosystem function modelling to simulate net primary production (NPP) as a function of water quantity, sediments, and habitat type; and (4) fauna habitat modelling linking the results from the assessment of landscape patterns to fauna species. The assessment of landscape patterns revealed a distinct relationship between inundation and vegetation. Habitats in the Tonle Sap were divided into five groups based on annual flood duration, as well as physiognomic factors and human activity: (1) open water, (2) gallery forest, (3) seasonally flooded habitats, (4) transitional habitats, and (5) rainfed habitats. Large habitat shifts could occur as a result of hydropower development scenarios by the 2030s; areas optimal for gallery forest could decrease by 82% from baseline conditions, whereas areas of rainfed habitats could increase by 10-13 % (813-1061 km2). The assessment of habitat patterns demonstrated that despite the complexity and intense human use of this ecosystem, the flood-pulse is the underlying driver of habitat characteristics by (1) determining inundation depth and duration; (2) creating the main soils gradient; (3) limiting the area cleared for agriculture; (4) influencing vegetation structure and water quality; and (5) shaping the composition of plant species. The ecosystem function model was used to estimate a reduction of 9-39% in annual NPP caused by different scenarios of hydropower development and/or climate change during 2032-2042. Cumulative impacts from hydropower would disrupt NPP to a greater extent than climate change. The fauna habitat model revealed that species richness was greatest in the gallery forests and seasonally flooded habitats. Animals that permanently reside in or that rely on these habitats to complete essential life-history stages would be the most affected by future changes. This thesis provides the first quantitative formulation that directly links fundamental components of the Tonle Sap ecosystem to its flood-pulse hydrology. It also provides a comprehensive assessment of the impacts of expected hydrological alterations. Hydropower is expected to bring more abrupt and distinct ecological alterations than climate change in future decades. Relative aerial changes to the gallery forests are expected to be greater than in other habitats. A decline of the Tonle Sap’s ecosystem services will occur if appropriate measures are not implemented. These measures include mitigating hydropower alterations, conserving natural habitats in areas that are likely to remain hydrologically undisturbed, restoring natural habitats in projected areas for optimal growth, and optimizing agricultural practices in the floodplain. Research findings from this thesis focused on the Tonle Sap, but given the fundamental commonalities between this system and other large floodplains, the information presented is highly informative to other large flood-pulse driven systems around the globe.

Orientador: Raoul Henry / Resumo: As lagoas marginais são habitats lênticos, laterais ao rio, que podem manter comunicação permanente ou não com o rio. Nesses ecossistemas é encontrada elevada biodiversidade aquática, inclusive de zooplâncton. O objetivo deste estudo foi verificar diferenças na estrutura da comunidade zooplanctônica em lagoas marginais com diferentes níveis de conectividade hidrológica, por meio dos atributos ecológicos (riqueza, abundância, diversidade beta e funcional). Foi analisada a influência da conectividade hidrológica na comunidade de Cladocera e Rotifera em seis lagoas marginais antes e após um pulso de inundação do rio Paranapanema. Os resultados mostram que a estrutura da comunidade de Cladocera e Rotifera tende a ser mais distinta após o pulso de inundação. A diversidade beta foi mais elevada nas lagoas isoladas e na lagoa conectada que possui alta compartimentalização. Outro tema abordado diz respeito à analise da distribuição de Rotifera em um gradiente longitudinal da zona litorânea e envolvendo também a zona pelágica de uma lagoa marginal colonizada por macrófitas, por meio da diversidade taxonômica e funcional. A diversidade taxonômica foi maior na região de ecótono (transição da zona pelágica e litorânea) enquanto a diversidade funcional foi mais elevada na zona litorânea da lagoa. Neste estudo, também foi descrito como os microcrustáceos estão distribuídos em um transecto horizontal da zona litorânea e pelágica de uma lagoa marginal. A comunidade de microcrustáceos foi div... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The marginal lakes are lentic habitats, lateral to the river, that can maintain permanent communication or not with the river. High aquatic biodiversity is found in these ecosystems, including zooplankton. The aim of this study was to o verify differences in the structure of the zooplankton community in marginal lakes with different levels of hydrological connectivity, through ecological attributes (richness, abundance, beta and functional diversity). The influence of hydrological connectivity in the community of Cladocera and Rotifera in six marginal lakes was analyzed before and after the Paranapanema River pulse flood. The beta diversity was higher in isolated lakes and in connected lakes, which has high compartmentalization. Another topic addressed concerns the analysis of the distribution of Rotifera in a longitudinal gradient of the littoral zone and also involving the pelagic zone of a marginal lake colonized by macrophytes, through taxonomic and functional diversity. Taxonomic diversity was greater in the ecotone region (transition from the pelagic and littoral zone) while the functional diversity was higher in the littoral zone of the lake. In this study, it was also described how microcrustaceans are distributed in a horizontal transect of the littoral and pelagic zone of a marginal lake. The microcrustacean community was divided into six functional groups, with a predominance of the G2 group (bosminids) in the lake. Macrophytes had a strong influence on variations ... (Complete abstract click electronic access below) / Doutor

Doctor of Philosophy / Department of Biology / Craig Paukert / River discharge influences fish and invertebrate communities and understanding how hydrologic variables contribute to fish and invertebrate composition can provide information for restoration and management. This study examines the relationship between several flow regime metrics that may influence fish and invertebrate community structure in large river systems such as the Kansas River. First, I examined how hydrology influences macroinvertebrate (drifting and benthic) density and fish communities before, during, and after flooding in both main and secondary channels. I found that drifting invertebrate density increased during flooding potentially providing increased prey opportunities for fishes. I also found that fluvial dependent and generalist fish species use inundated habitats more than fluvial specialists. My results suggest that the flux of water into inundated habitats supports a unique subset of invertebrate and fish communities of the main channel. Next, I examined the importance of lateral connectivity on fish and invertebrate composition by examining differences in seasonally and permanently inundated secondary channels in relation to main channel reaches. I found that drifting and benthic invertebrate assemblages and fish assemblages differed between seasonally inundated and permanently connected secondary channels. These results suggest that maintenance of diverse secondary channel connections is useful in preserving native biota in the Kansas River. Finally, I tested if hydrologic variables influenced recruitment of four native Kansas River fishes. I found that recruitment for two of the four fish species (flathead catfish, Pylodictis olivaris, and shovelnose sturgeon, Scaphirhynchus platorynchus) increased in high flow years. These results indicate that a natural and variable flow regime may be important for maintaining fish community structure in the Kansas River. The results of this study have implications for management strategies that include the use of high flows to provide a pulse of insect prey to the main channel for fishes, restoration of natural high and low flow variability as important to fish recruitment, and diversity in secondary channel connectivity (seasonal and permanently connected) that promotes unique fish and invertebrate communities.

This project focused on the relationship between instream flows and smallmouth buffalo (Ictiobus bubalus) recruitment in the Gulf Coastal Plain of Texas. The flow regime is the dominant factor in lotic systems and, consequently, the relationship between instream flows, including impacts to natural flow regimes, and life-history is a subject of growing interest. Smallmouth buffalo is a good model to investigate the relationship between river flows and variable interannual recruitment success of periodic life-history strategist fish species. Smallmouth buffalo were collected from the Brazos, Colorado, and Guadalupe Rivers of Texas, U.S.A., and otoliths were extracted from individuals in the field and sectioned and photographed in the lab. Photographs of sectioned otoliths were used to estimate age and thus the year in which the individual was spawned by counting back from the time of capture. Population age structure (i.e. a ‘state' or condition at a point in time) was used to infer effects of flow variation on a rates-based process (i.e. recruitment). After controlling for mortality using recruitment index values, interannual variation in recruitment was modeled using multiple components of the flow regime quantified as indicators of hydrologic alteration (IHA) variables based on daily discharge data from USGS gaging stations in each river system. Model selection followed a two-tier approach, first fitting models using only flow attributes associated with the spawning season then adding additional informative parameters from the pre-spawn and post-spawn periods. The primary finding from model selection was that duration of high flow pulses during the spawning season is a critical component of the flow regime associated with successful Smallmouth Buffalo recruitment. These findings have implications for river management and conservation of ecological integrity, in particular populations of periodic life-history strategist species.

Understanding energy fluxes within and between floodplain water bodies, and between rivers and their floodplains is essential for comprehending the dynamics of modern, altered river systems. Floodplain aquatic invertebrates may move between habitats deliberately (through emergence and dispersal) or through passive transport during flooding. This movement may represent a significant flux of energy and an essential food web subsidy. I assessed the usefulness of the stable isotopes of hydrogen and oxygen (D and 18O respectively) for identifying the origins and movements of macroinvertebrates in Mississippi River floodplain water bodies. I sampled water and invertebrates from the Mississippi River, intermittent and permanent floodplain wetlands, and tributaries during 2007 and 2008. Results showed consistent relationships between δD and δ18O signatures in invertebrate tissues and their home water bodies. I also investigated whether δD and δ18O could be used as a multivariate "fingerprint" to trace a captured invertebrate back to its environment of origin. Results showed that δD can be a useful tracer of the movement of floodplain invertebrates in some cases, although δ18O is likely not suitable for that purpose.

Submitted by Alisson Mota (alisson.davidbeckam@gmail.com) on 2015-07-17T18:25:11Z No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:02:10Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:02:12Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:00:05Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:08:17Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Made available in DSpace on 2015-07-17T19:08:17Z (GMT). No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) Previous issue date: 2014-09-02 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / To check the influence of the flood pulse of the Solimões River in the Lake Paru (Manacapuru, Amazonas) in this study were determined concentrations of total mercury (THg) and methylmercury (MeHg) in bottom sediments in two seasons. The samples were collected in April (flood) and October (dry) in 2013 at Solimões River Basin. The locations of collected were 10 points; four located under influence of the black waters of the stream that flow into the lake and others next to the Solimões River. To analyze HgT, the sediments samples < 200 mesh were extracted with HCl:HNO3 and filtered through a cellulose membrane (3,0 μm and 9 cm) by approximately two hours. To analyze MeHg the samples < 200 mesh and lyophilized were extracted with 25% KOH/MeOH at 68°C by approximately four hours. The concentrations of HgT were determinates by atomic absorption spectrometry coupled to cold vapor generator (CV-AAS) and MeHg by aqueous ethylation separated by chromatography and detection by atomic fluorescence gas (GC- AFS). The results indicated that the means concentrations of HgT were 89,19 μg kg -1 (flood) and 115,07 μg kg -1 (dry), while the MeHg were 0,78 μg kg -1 (flood) and 0,17 μg kg -1 (dry). In terms of distribution was observed that HgT and MeHg don´t occur in the same way in both periods studied. At dry predominantes the deposition and at flood the remobilization of HgT. The MeHg has increase in the flood. Finally the HgT and MeHg concentrations at bottom sediments show the seasonally effect under the flood pulse at Solimões River and consequently in mercury cycle at the Paru Lake. / A fim de verificar a influência do pulso de inundação do rio Solimões no lago Paru (Manacapuru, Amazonas), neste trabalho foram determinadas as concentrações de mercúrio total (HgT) e metilmercúrio (MeHg) nos sedimentos de fundo em dois períodos do ano. As amostras foram coletas em abril e outubro, correspondendo respectivamente ao período da enchente e ao período da vazante, do ano de 2013, na bacia do rio Solimões. Os locais de amostragens consistiram em dez pontos; quatro localizados sob influência das águas pretas dos igarapés que deságuam no lago e os demais em água branca, próximos ao rio Solimões. Para analisar o HgT, as amostras de sedimentos < 200 mesh foram extraídas com HCl:HNO3 e filtradas em membrana de celulose (3,0 μm e 9 cm) por aproximadamente duas horas. Para analisar o MeHg, as amostras < 200 mesh e liofilizadas foram extraídas com 25% KOH/MeOH a 68°C, por aproximadamente quatro horas. As concentrações de HgT foram determinadas por espectrometria de absorção atômica acoplada ao gerador de vapor frio (CV-AAS) e a de MeHg por etilação aquosa, separada por cromatografia gasosa e detecção por espectrometria de fluorescência atômica (CG-AFS). Os resultados indicaram a concentração média de HgT de 89,19 μg kg -1 (enchente) e de 115,07 μg kg -1, (vazante), enquanto o MeHg foi de 0,78 μg kg -1, (enchente) e de 0,17 μg kg -1, (vazante). Em termos de distribuição observou-se que o HgT e o MeHg não ocorrem da mesma forma nos períodos estudados. Na vazante predomina a deposição e na enchente a remobilização de HgT. Por outro lado, o MeHg tem maior incremento na enchente. Finalmente, as concentrações de HgT e a MeHg nos sedimentos de fundo mostram o efeito da sazonalidade sobre o pulso de inundação do rio Solimões, e consequentemente do ciclo do mercúrio no lago Paru.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T18:39:36Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_finalizada.pdf: 1987710 bytes, checksum: 46c6e0b1f07f99706e86684cdd0bd406 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T18:39:46Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_finalizada.pdf: 1987710 bytes, checksum: 46c6e0b1f07f99706e86684cdd0bd406 (MD5) / Made available in DSpace on 2018-06-20T18:39:47Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_finalizada.pdf: 1987710 bytes, checksum: 46c6e0b1f07f99706e86684cdd0bd406 (MD5) Previous issue date: 2018-04-23 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In the Central Amazon, the fisheries are artisanal in character, being practiced by fishermen in rivers and flooded areas. Thus, the main issue addressed in the study is to verify how the hydrological cycle influences the catches of species, considering that the landing is made up of species with different feeding strategies. Firstly, we carried out a previous characterization of the fisheries, in order to determine the main environments and species exploited, as well as, more productive and attractive periods for the fishing activity. We also list the fishing gear used by fishermen with the target species. The characterization indicated that the lake environments are more exploited by the fishermen, however, most of the catches come from the river channels. In relation to the composition of the landing, a total of 34 species were landed, being the jaraqui coarse scale (Semaprochilodus taenirus) and the jaraqui fine scale (Semaprochilodus insignis) the most exploited species. The period of flood presented a significant difference in the catch values per unit of effort (CPUE) when compared to the other hydrological periods. The fishing gear varied according to the environment where the fishing occurred and the species to be exploited. Later, we used generalized linear models (Covariance Analysis - ANCOVA) to determine the influence of the river level on the fisheries in the Lower Solimões River. The analysis of covariance for the flood period showed that all species were influenced by river level, and by fishing effort, there was still a positive interaction between fishing effort and detritus species. During the flood period, the fishing effort positively influenced all species, there was also a positive interaction between fishing effort, detritivorous and herbivorous species and a positive effort in river environments. In the ebb period, only the fishing effort was significant, with a negative interaction between the fishing environment and the effort. In the dry season, only the omnivorous species were influenced by the fishing effort and the level of the river, with negative interaction between fishing effort and omnivorous species. The results found may contribute to the generation of knowledge about fishing activities, providing information for the construction of public policies related to fisheries management in the state of Amazonas. / Na Amazônia Central as pescarias possuem caráter artesanal, sendo praticadas por pescadores em rios e áreas alagadas, sendo altamente influenciadas pela variação do nível do rio. Desse modo, a principal questão abordada no estudo é verificar como o ciclo hidrológico influencia nas capturas de espécies, considerando que o desembarque é constituído de espécies com diferentes estratégias alimentares. Primeiramente, realizamos uma caracterização prévia das pescarias, no intuito de determinar os principais ambientes e espécies explotados, bem como, períodos mais produtivos e atrativos para a atividade pesqueira. Também relacionamos os apetrechos de pesca utilizados pelos pescadores com as espécies alvo. A caracterização indicou que os ambientes de lago são mais explotados pelos pescadores, no entanto, a maior parte das capturas é oriunda dos canais de rios. Em relação à composição do desembarque, foram desembarcadas um total de 34 espécies, sendo o jaraqui escama grossa (Semaprochilodus taenirus) e o jaraqui escama fina (Semaprochilodus insignis) as espécies mais explotadas. O período de cheia apresentou valores positivos na captura por unidade de esforço (CPUE) quando comparado aos demais períodos hidrológicos. As artes de pesca variaram de acordo com o ambiente onde ocorreu a pesca e as espécies a serem explotadas. Posteriormente, utilizamos modelos lineares generalizados (Análise de covariância – ANCOVA) para determinar a influencia do nível do rio sobre as pescarias no Baixo Rio Solimões. A análise de covariância para o período de enchente mostrou que todas as espécies foram influenciadas pelo nível do rio, e pelo esforço de pesca, houve ainda uma interação positiva entre o esforço de pesca e espécies detritívoras. No período de cheia, o esforço de pesca influenciou positivamente todas as espécies, houve ainda uma interação positiva entre o esforço de pesca, espécies detritívoras e herbívoras e um esforço positivo nos ambientes de rio. No período de vazante, apenas o esforço de pesca foi significativo, com uma interação negativa entre o ambiente de pesca e o esforço. No período de seca, apenas as espécies onívoras foram influenciadas pelo esforço de pesca e o nível do rio, com interação negativa entre o esforço de pesca e espécies onívoras. Os resultados encontrados contribuem para a geração de conhecimento sobre atividades de pesca, fornecendo informações para a construção de políticas públicas relacionadas à gestão da pesca no estado do Amazonas.

Made available in DSpace on 2016-06-02T19:29:30Z (GMT). No. of bitstreams: 1 3341.pdf: 16436735 bytes, checksum: 044164b9bed4be2545951d0e4ebd02ce (MD5) Previous issue date: 2010-09-20 / Fundação de Amparo à Pesquisa do Estado de Mato Grosso / Most ecological studies of tropical fishes involve limnology related to reproductive behavior, feeding and migration. This work is an attempt to consider, in the area of fish ecology, a new approach that involves addition of limnological variables, environmental variables morphometric and morphologic environment and determine whether, beyond the flood pulse, these characteristics determine the community structure fish in the wetland. Were chosen ten ponds, regionally called "bays" on the banks of the rivers Paraguay, Paraguaizinho, and Sepotuba Cabaçal. Their morphology and physical and chemical variables of water were measured. A sampling of the ichthyofauna was done in three sampling points in each pond using trawl 3mm between us, 2.5 x25m long. Species richness was analysed using indices of Margalef and Minhinicke. We used multivariate analysis to determine the environmental variables that contributed in determining the structure of fish communities. Correspondence Analysis showed that the major groups of fishes related to species richness in two main groups: periods of low water, drought and flood, and the flood period. The abundance showed clustering contrast, the higher observed during periods of low water, drought and flood and the lowest found during the flood. Results of discriminant analysis demonstrated that the lakes are listed in four categories, depending on the degree of similarity of environmental characteristics. In each category groupings were more strongly related collection period than the limnological and morphometric analysis. However, the group found in the discriminant analysis, the lake VI (Ximbuva) shown by the rounded morphology and the morphometric values smaller lake VIII (the right bank of the river Cabaçal), show that the two are related to the structure of fish community wetland at the local level, while the flood pulse events determined the regional level. / A maior parte dos estudos de ecologia da ictiofauna tropical envolve a limnologia relacionada com o comportamento reprodutivo, alimentar e migratório. Este trabalho é uma tentativa de considerar, na área de ecologia de peixes, uma nova abordagem que envolva além das variáveis limnológicas, variáveis ambientais morfométricas e morfológicas do ambiente e verificar se, além do pulso de inundação, essas características determinam a estrutura de comunidade de peixes no pantanal. Foram escolhidas dez lagoas, regionalmente denominadas de baías , nas margens dos rios Paraguai, Paraguaizinho, Sepotuba e Cabaçal. As suas características morfométricas e variáveis físicas e químicas da água foram mensuradas. A amostragem da ictiofauna foi feita em três pontos amostrais em cada lagoa utilizando rede de arrasto de 3mm entre nós, de 2,5x25m de comprimento. A riqueza de espécies foi analisada através dos índices de Margalef e de Minhinick. Foram utilizadas análises multivariadas para determinar as variáveis ambientais que contribuíram na determinação da estrutura das comunidades de peixes. Análise de Correspondência mostrou que os grandes grupos da ictiofauna relacionaram a riqueza de espécies em dois grupos principais: períodos da vazante, seca e enchente; e período da cheia. A abundância mostrou um agrupamento contrário, a maior observada nos períodos da vazante, seca e enchente e a menor encontrada no período da cheia. Os resultados das Análises Discriminantes demonstraram que as lagoas estão relacionadas em quatro categorias, em função do grau de semelhança das características ambientais. Em cada categoria os agrupamentos estiveram mais fortemente relacionados com o período de coleta do que com as variáveis limnológicas e morfométricas analisadas. Porém, pelo agrupamento encontrado na análise discriminante, a lagoa VI (Baía da Ximbuva) demonstrado pela morfologia arredondada e pelos menores valores morfométricos da lagoa VIII (à margem direita do rio Cabaçal), demonstram que ambas possuem relação com a estrutura de comunidade de peixes do pantanal à nível local, enquanto que o pulso de inundação determinaram os eventos à nível regional.