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Landscape dynamics are widely thought to govern the tempo and mode of continental radiations, yet the effects of river network rearrangements on dispersal and lineage diversification remain poorly understood. We integrated an unprecedented occurrence dataset of 4,967 species with a newly compiled, time-calibrated phylogeny of South American freshwater fishes—the most species-rich continental vertebrate fauna on Earth—to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Five abrupt shifts in net diversification rates occurred during the Paleogene and Miocene (between 30 and 7 Ma) in association with major landscape evolution events. Net diversification accelerated from the Miocene to the Recent (c. 20 to 0 Ma), with Western Amazonia having the highest rates of in situ diversification, which led to it being an important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including the Early Miocene (c. 23 to 16 Ma) uplift of the Serra do Mar and Serra da Mantiqueira and the Late Miocene (c. 10 Ma) uplift of the Northern Andes and associated formation of the modern transcontinental Amazon River. The combination of high diversification rates and extensive biotic interchange associated with Western Amazonia yielded its extraordinary contemporary richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics, which shaped the history of drainage basin connections, strongly affected the assembly and diversification of basin-wide fish faunas.

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

Estudos em Macroecologia lidam com padroes e processos em amplas escalas (espacial, temporal e taxonomica) que sao muito abrangentes para serem estudados com experimentos replicados, manipulativos e controlados como e feito tradicionalmente na ecologia. Estudos macroecologicos tem sido primordialmente realizados com foco em vertebrados e plantas terrestres, enquanto os sistemas marinhos e principalmente os de agua doce permanecem ainda pouco explorados. O objetivo deste trabalho e destacar alguns avancos dos campos de estudo da macroecologia no tocante a padroes espaciais de peixes em riachos brasileiros (padroes de diversidade alfa e beta). Por meio da coleta de informacoes de ocorrencia de especies de riacho em larga escala, nos encontramos maiores valores de riqueza total na Amazonia, no Cerrado e na Mata Atlântica e uma riqueza media geral de sete especies por sub-bacia. Alem disso, a composicao de especies foi diferente entre biomas, sendo evidenciados tambem elevados valores de substituicao de especies dentro deles. Em adicao aos resultados obtidos, apresentaremos uma discussao que guiara o leitor a compreensao das possiveis causas e mecanismos subjacentes aos padroes encontrados em um contexto macroecologico. MACROECOLOGY OF BRAZILIAN STREAM FISHES: Studies in Macroecology deal with patterns and processes on large scale (spatial, temporal and taxonomic) and that by definition are too comprehensive to be studied with replicated, manipulative and controlled experiments as it has been traditionally performed in Ecology. Macroecological studies are still conducted with a focus on terrestrial vertebrates and plants, while marine systems and especially freshwater systems remain little explored. The objective of this study is to highlight some advances in the fields of study of aquatic macroecology (spatial patterns of alpha and beta diversity), using fish from Brazilian streams as the object of analysis. By gathering stream fish occurrence information from large scale data sets, we found high total richness in Amazonia, Cerrado and Atlantic Forest, and found on average seven species per sampling unit, with small variation related to the identity of the analyzed biomes. Yet, species composition is distinct between biomes and we found high turnover levels within them. We will guide the reader through possible causes and mechanisms of the identified patterns.

The invasion of non-native species is one of the major factors influencing the loss of biodiversity. The rotifer Kellicottia bostoniensis, which is native to North America, has been registered in several other countries and on other continents. We investigated the main climatic-environmental variables suitable for the potential distribution of K. bostoniensis and, hence, the areas of non-native regions where it could spread. We used different statistical niche models within an ensemble forecasting approach to estimate environmental suitability and the potential global distribution area of K. bostoniensis. Precipitation in the driest month and temperature in the coldest month were the most important variables in predicting the distribution of the species. Our predictions indicated that countries with high invasive potential included Argentina and Brazil (South America), Croatia, France, and Germany (Europe). The results also revealed that many areas with high invasive potential, such as East Asia, have no recorded occurrences yet. Our study provides important information for implement management measures to deal with the problems of the spread of K. bostoniensis through ballast water and aquaculture in countries and regions highly susceptible to invasion (mainly areas that the species has not yet reached), thus providing useful information for decision making.

Ecological niche modelling (ENM) has been used to quantify the potential occurrence of species, by identifying the main environmental factors that determine the presence of species across geographical space. We provide a large-scale survey of the distribution of ostracod species in South America, by using the domains of 25 river basins. From 221 known ostracod species, we estimate the potential distribution of 61 species, using ENM. Ten clusters of potential distribution patterns were found. Clusters 8 and 9 grouped most of the species, which presented high similarity of niche between them. Heterocypris paningi Brehm, 1934 (group 1) obtained higher niche variability. The minimum temperatures of the coldest month and the mean elevation of the river basin were most important to predict the potential distribution of ostracods of most groups. South America has a complex pattern of elevation, which affects species distributions indirectly through changes in local factors. For instance, the Andes mountains might impose a barrier for ostracod distribution in the southern part of South America because of the low temperatures and precipitation. The ENM indicated that some regions and/or basins of South America might be susceptible to the entry of several ostracod species, presently absent, including non-native species.

Made available in DSpace on 2019-10-06T15:47:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Reptiles are highly susceptible to climate change, responding negatively to thermal and rainfall alterations mainly in relation to their reproductive processes. Based on that, we evaluated the effects of climate change on climatically suitable areas for the occurrence of snakes in the Atlantic Forest hotspot, considering the responses of distinct reproductive groups (oviparous and viviparous). We assessed the species richness and turnover patterns affected by climate change and projected the threat status of each snake species at the end of the century. We also evaluated the effectiveness of the protected areas in safeguarding the species by estimating the mean percentage overlap between snake species distribution and protected areas (PAs) network and by assessing whether such areas will gain or lose species under climate change. Our results showed greater species richness in the eastern-central portion of the Atlantic Forest at present. In general, we evidenced a drastic range contraction of the snake species under climate change. Temporal turnover tends to be high in the western and north-eastern edges of the biome, particularly for oviparous species. Our predictions indicate that 73.6% of oviparous species and 67.6% of viviparous species could lose at least half of their original range by 2080. We also found that existing protected areas of the Atlantic Forest Hotspot have a very limited capacity to safeguard snakes at the current time, maintaining the precarious protection in the future, with the majority of them predicted to lose species at the end of this century. Although oviparous and viviparous snakes have been designated to be dramatically impacted, our study suggests a greater fragility of the former in the face of climate change. We advocated that the creation of new protected areas and/or the redesign of the existing network to harbour regions that maximize the snake species occupancy in the face of future warming scenarios are crucial measures for the conservation of this group. Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais (PEA) Universidade Estadual de Maringá Maringá Laboratório de Herpetologia e Comportamento Animal Universidade Federal de Goiás Programa de Pós-Graduação em Biologia Comparada (PGB) Universidade Estadual de Maringá Laboratório de Macroecologia Universidade Federal de Goiás Regional de Jataí Departamento de Zoologia Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) Departamento de Ecologia Instituto de Ciências Biológicas Universidade Federal de Goiás Departamento de Zoologia Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP)

Climate change is now recognized as a reality and along with human pressures such as river fragmentation by dams, amplifies the threats to freshwater ecosystems and their biodiversity. In the Brazilian portion of the Upper Paraguay River Basin (UPRB) that encompasses the Pantanal, one of the largest tropical wetlands in the world, in addition to the high biodiversity found there, fisheries are an important ecosystem service mostly supported by migratory fishes. We estimated the current range of migratory fish of commercial interest, also assessing the climate change effects predicted on the distribution patterns. Then, we assessed the effects of future climate on fish richness, and combining species ranges with routes blocked by artificial dams investigated possible impacts on fishery and food security in the UPRB. Climate change will induce range contraction between 47% and 100% for the species analyzed, and only four migratory fish may have suitable habitat until the end-of-century. The local richness will reduce about 85% in the basin. River fragmentation by dams acting together with climate change will prevent upstream shifts for most fish species. About 4% of present range and up to 45% of future range of migratory fish should be blocked by dams in UPRB. Consequently, this will also negatively affect fishery yield and food security in the future.

The Cichlidae is one of the most diverse fish families in Neotropical and Afrotropical regions. It includes many species that are valued for aquaculture, the aquarium trade, and sport fishing, which has resulted in their introduction into different ecosystems worldwide. In the Americas, non-native cichlids have been recorded from southernmost Canada to northern Argentina, and North America has received the largest number of non-native cichlids followed by South and Central America. This group has a set of life history traits (e.g., parental care, multiple spawning, and piscivorous or omnivorous diets) that favors its occupation of new environments. This review provides information about non-native cichlids in the watersheds of the American continents including their distribution, predominant introduction vectors, reasons for success, and impacts on local ecosystems.

Made available in DSpace on 2019-10-06T16:17:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-06-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Climate change threatens freshwater fish by severely modifying water quality and hydrological dynamics, hence altering the species distribution. We assessed the climate change effects on the geographical distribution of Salminus brasiliensis, a keystone species of economic interest in the La Plata River basin. Using ecological niche models, we estimated the species range in the present time and assessed the range shift phenomena through climatically suitable areas in the future. We also quantified the predictive uncertainty from niche models, atmosphere–ocean general circulation models, and carbon emission scenarios. Our predictions indicated a great range contraction of S. brasiliensis in the future. The south-central portion of the basin should retain the climate refuge function for the species at 2050. Nonetheless, the segregation of this climate refuge in two smaller parts was predicted at the end of the century. Our study also revealed that the greatest source of uncertainty in forecasts of species range shifts arises from using alternative niche algorithms in modeling process. Our results contribute to more effective measures for conservation of S. brasiliensis, thus helping to ensure the ecosystem processes and socioeconomic activities in the basin dependent on this species. Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais. Núcleo de Pesquisas em Limnologia Ictiologia e Aquicultura - Nupelia Universidade Estadual de Maringá (UEM), Av. Colombo 5790 Programa de Pós-graduação em Ecologia – Universidade Federal de Juiz de Fora Instituto de Ciências Biológicas- ICB, Campus Universitário, Bairro São Pedro Departamento de Zoologia Instituto de Biociências de Rio Claro Universidade Estadual Júlio Mesquita Filho – UNESP Programa de Pós-Graduação em Ecologia e Evolução Universidade Federal de Goiás Universidade Estadual de Mato Grosso do Sul – UEMS Departamento de Zoologia Instituto de Biociências de Rio Claro Universidade Estadual Júlio Mesquita Filho – UNESP CNPq: 141371/2016-1

Brazilian biodiversity is undergoing numerous attacks and misguided policies that aim to reduce protected areas (PAs) with the main argument of expanding agribusiness to improve the country's economic performance. An example is the draft law (DL) 527/2016, which aimed to reduce approximately 70% of the Devonian Escarpment Environmental Protection Area (DEEPA), a large PA in southern Brazil, hosts two biodiversity hotspot biomes. This study shows the possible downsizing damages to biodiversity and landscape by quantifying the size and connectivity of the vegetation remnants in the surrounding landscape concerning the degree of threat to the species that occur in both the Atlantic Forest and Brazilian Savanna domains. The DEEPA downsizing can affect natural savanna and Atlantic Forest vegetation area proposed by DL 527/2016 would fail in protecting 383 (56.82%) of the threatened species. Only three species evaluated as critically endangered, 13 classified as endangered, and 13 classified as vulnerable would be preserved; the reduction would also negatively affect essential ecosystem services and the quality of life in human populations. Furthermore, man-made fragmentation and habitat loss would jeopardize several biological and ecological aspects fundamental to biomes' maintenance and ecosystem services. In addition to reducing this environmental protection area, it would cut taxes from the current PA and could affect its surrounding municipalities in southern Brazil.

The invasion of tilapia can result in substantial impacts on native communities. Thus, understanding the spatial dynamics of invasions may help prevent future introductions and mitigate impacts. This study estimated the environmentally suitable areas for occurrence of eight tilapia species (genera Coptodon, Oreochromis, Pelmatolapia, and Sarotherodon) in the Americas and their invasive potential using Ecological Niche Models (ENMs). The United States is the most invaded country, receiving all tilapia species. In South America, the southeast and south regions of Brazil are highlighted as the areas where two species are concentrated. The ENMs predicted that all tilapia species have high invasive potential in the Americas, and despite having more tilapias in North America, South and Central Americas are more susceptible to tilapia invasion. All South American basins were predicted to harbor tilapia species that have not yet arrived on the subcontinent. Our study evidences the need to implement management measures and governmental policies in the Americas to deal with problems caused by tilapia introductions. In North America, the focus is on the control of tilapia populations and in Central and South America priority should be given to contention of introduction processes.

AIM: Contemporary patterns of species diversity are the result of a hierarchy of natural processes and modern anthropogenic influences. However, studies of these patterns in human‐modified systems from a macroecological perspective are lacking. Considering that fish assemblages in reservoirs reflect both long‐term evolutionary responses of species and shorter term responses to anthropogenic stressors, we employed a multi‐hypothesis approach using different magnitudes of predictors to analyse the processes that drive fish diversity in reservoirs at a broad spatial scale. LOCATION: Brazil. METHODS: We derived species richness from an extensive database of fish inhabiting Neotropical reservoirs, and using multiple regression analysis, we tested seven hypotheses that link species richness to continuous variables associated with regional, local and population components. We analysed the spatial structure using Moran's I autocorrelation coefficients and used spatial eigenvector mapping to explicitly account for the spatial component when testing the hypotheses by multiple regressions. Partial regressions were performed to map the relative contributions of the different components in explaining species richness. RESULTS: Predictors related to six hypotheses were retained in the best‐fit models, and our data supported the species–energy, metabolic, species–area, species–distance from the source and time of habitat alteration hypotheses. However, the predictions of the population abundance hypothesis (PAH) were not supported by the data. The shared effects of the different components explained the greatest proportion of the variation in species richness, indicating that distinct mechanisms related to these alternative hypotheses interact or are not spatially independent. MAIN CONCLUSIONS: Our findings indicate that the latitudinal diversity gradient typically displayed by freshwater fish is maintained in human‐modified habitats, such as reservoirs, and that multiple mechanisms drive fish diversity in reservoirs over large spatial scales. The lack of support for the PAH implies that mechanisms structuring diversity patterns can be influenced by anthropogenic stressors.

Considerando a necessidade de monitoramento das águas subterrâneas utilizadas para o consumo humano, este estudo avaliou a qualidade da água de poços artesianos rurais, localizados no Assentamento Pedro Ramalho, Mundo Novo, Mato Grosso do Sul. Amostras de água foram obtidas em janeiro/2012 e setembro/2013, em dois poços artesianos. Foram determinados parâmetros físico-químicos (alumínio, cobre, cor, cloreto, cromo total, ferro, fluoreto, manganês, nitrito, pH, sólidos dissolvidos totais, sulfato e zinco) e microbiológico (NMP de coliformes totais e de coliformes termotolerantes, bactérias heterotróficas e Escherichia coli) para os dois poços. Os valores registrados para cada parâmetro foram confrontados com os limites estabelecidos pela legislação brasileira. Apenas a água do Poço 1 apresentou valores de pH inferiores ao estabelecido pela Portaria no 2914/2011 e valores de manganês acima do valor máximo permitido pela Resolução CONAMA nº 396. Os demais parâmetros atenderam os valores limites preconizados pelas legislações. Os resultados apresentados evidenciam a necessidade de monitoramento continuo da água dos poços artesianos do Assentamento Pedro Ramalho, uma vez que foram registradas irregularidades que inspiram preocupações à saúde pública dos moradores.

This study uses species distribution modeling and physiological and functional traits to predict the impacts of climate change on native freshwater fish in the Murray-Darling Basin, Australia. We modelled future changes in taxonomic and functional diversity in 2050 and 2080 for two scenarios of carbon emissions, identifying areas of great interest for conservation. Climatic-environmental variables were used to model the range of 23 species of native fish under each scenario. The consensus model, followed by the physiological filter of lethal temperature was retained for interpretation. Our study predicts a severe negative impact of climate change on both taxonomic and functional components of ichthyofauna of the Murray-Darling Basin. There was a predicted marked contraction of species ranges under both scenarios. The predictions showed loss of climatically suitable areas, species and functional characters. There was a decrease in areas with high values of functional richness, dispersion and uniqueness. Some traits are predicted to be extirpated, especially in the most pessimistic scenario. The climatic refuges for fish fauna are predicted to be in the southern portion of the basin, in the upper Murray catchment. Incorporating future predictions about the distribution of ichthyofauna in conservation management planning will enhance resilience to climate change.

Summary This study reports the length-weight relationship estimatives (LWRs) for 55 fish species caught in the Iguatemi River drainage, Upper Parana River Basin, Mato Grosso do Sul State, Brazil. The LWRs of 15 of the species are provided for the first time.

The genus Astyanax is relatively common and encompasses various similar taxa forming a highly complex group that is difficult to precisely delimit. The present study aims to analyze cytogenetically and morphologically specimens of A. altiparanae belonging to distinct populations of the Iguatemi River Basin, Mato Grosso do Sul State, Brazil, for a better understanding of the evolutionary processes in this fish group. This study analysed 32 specimens of Astyanax altiparanae from Iguatemi River basin, MS, Brazil: 24 from the Agua Boa stream and 8 from the Santa Maria stream. All specimens showed a diploid number equal to 50 chromosomes with differences in the karyotypic formula and types of chromosomes bearing the NOR between the two localities. The constitutive heterochromatin showed interstitial markings evident in the region of some chromosomes in both populations. In the morphometric analysis, the first three axes were retained for interpretation which together explained 81% of variance, showing morphometric distinction between populations. Chromosomal and morphometric data obtained may be useful for taxonomic and phylogenetic studies in this group of fish.

In the context of diversity gradients, the metabolic theory of ecology (MTE) posits that the logarithm of species richness should decrease linearly with the inverse of temperature, resulting in a specific slope. However, the empirical validity of this model depends on whether the data do not violate certain assumptions. Here, we test the predictions of MTE evaluating all of its assumptions simultaneously. We used Neotropical freshwater fish and tested whether the logarithm of species richness varied negatively and linearly with temperature, resulting in the slope value specified by the MTE. As we observed that the assumption of the energetic equivalence of populations was not achieved, we also analyzed whether the energetic nonequivalence of populations could be responsible for the possible lack of fit to the MTE predictions. Our results showed that the relationship between richness and the inverse of temperature was linear, negative and significant and included the slope value predicted by the MTE. With respect to the assumptions, we observed that there was no spatial variation in the average energy flux of populations or in the body size and abundance of species. However, the energetic equivalence of populations was not achieved and the violation of this assumption did not affect the predictive power of the model. We conclude that the validity of the assumptions (spatial invariance in the average flux energy of populations and spatial invariance in the body size and abundance, especially) is required for the correct interpretation of richness patterns. Furthermore, we conclude that MTE is robust in its explanation of diversity gradients for freshwater fish, proving to be a valuable tool in describing ecological complexity from individuals to ecosystems.

We described the spatial distribution of fish trophic groups in the Água Boa Stream, MS, Brazil. Specimens were caught using electrofishing in the upper, intermediate and lower stretches of the stream, between March and November 2008. We analyzed 415 stomach contents of 24 species. Detritus/sediment and aquatic invertebrates were the main exploited resources. Ordination analysis categorized the species in six trophic groups. Aquatic invertivores showed the highest richness (10 species), followed by detritivores (08 species), omnivores (03 species), terrestrial invertivores (03 species), algivores (02 species) and herbivore (01 species). Three trophic groups occurred in the upper stretch, six in the intermediate and five in the lower. Detritivores, omnivores and algivores showed the highest density, while detritivores and aquatic invertivores presented the highest biomass. Autochthonous resources were particularly important to the studied fish fauna, especially aquatic invertebrates, so, conservation actions reducing the simplification of the habitat by silting and recovering the riparian forest are essential to maintain the ichthyofauna of the Água Boa Stream.

ABTRACT Hypoptopomatinae is a monophyletic subfamily that includes 147 species, distributed in 20 genera. Otothyropsis is a genus of Hypoptopomatinae, recently described. Here, we provided the first cytogenetic information of Otothyropsis . The specimens were collected from córrego Dourado, a small tributary of rio Iguatemi, which flows into rio Paraná. The specimens of Otothyropsis cf. polyodon were analyzed with respect to diploid number, C-Band and Ag-NOR patterns. The diploid number was 54 chromosomes, distributed in 18 metacentric, 28 submetacentric, and 8 subtelocentric chromosomes, with single Ag-NOR and conspicuous heterochromatic blocks on the short and long arms of the 24th pair of chromosomes. Our study highlights the conservation trend of the diploid number (2n=54) and fundamental number (FN = 108) among the species of Hypoptopomatinae. However, the karyotype formula (18m+28sm+8st) seems to be specific to O. cf. polyodon , considering the other Hypoptopomatinae species already analyzed. RESUMO Hypoptopomatinae é uma subfamília monofilética que inclui 147 espécies distribuídas em 20 gêneros, sendo Otothyropsis um gênero recentemente descrito. Aqui, fornecemos a primeira informação citogenética do gênero Otothyropsis . Espécimes foram coletados no córrego Dourado, um pequeno tributário do rio Iguatemi, o qual deságua no rio Paraná. Espécimes de Otothyropsis cf. polyodon foram analisados em relação ao número diploide e padrões de Banda-C e Ag-NOR. O número diploide foi de 54 cromossomos, distribuídos em 18 metacêntricos, 28 submetacêntricos e 8 subtelocêntricos, com Ag-NOR simples e blocos heterocromáticos evidentes no braços curto e longo do par de cromossomos 24. Nosso estudo destaca a tendência de conservação do número diploide (2n=54) e número fundamental (NF=108) entre as espécies de Hypoptopomatinae. Entretanto, a fórmula cariotípica (18m+28sm+8st) parece ser específica para O. cf. polyodon, considerando as outras espécies de Hypoptopomatinae já analisadas.

AIM: We evaluated the composition and community attributes of invertebrates associated to Eichhornia azurea at Cascalho Lagoon, Upper Paraná River, Mato Grosso do Sul State, Brazil, over a hydrological cycle, as well the possible influence of abiotic factors upon these attributes. METHODS: The samplings were conducted during 2010 in the rainy and dry periods at stands of E. azurea. The attributes evaluated were abundance, richness, diversity, evenness and dominance. The abiotic factors, temperature, dissolved oxygen, pH and turbidity were summarized by a Principal Component Analysis (PCA). In order to verify possible differences between the mean values of the community attributes and the scores of the PCA axis in different periods, we employed null models analysis of variance. The influence of abiotic factors on each attribute was evaluated through Pearson correlations. RESULTS: We captured 3,052 individuals, distributed into 32 taxa, belonging to the phyllum Mollusca, Annelida, Nematoda and Arthropoda. Among the assessed attributes, only abundance and richness varied significantly between periods, with higher values during the rainy period. Chironomidade was dominant in both periods, whereas Notonectidae and Cyclopoida were rare in the rainy, and Bivalve, Decapoda, Haliplidae, Trichoptera and Pyralidae, in the dry period. A temporal distinction was evident only for the PCA axis 1, which represented gradients in temperature, dissolved oxygen and pH. Among the community attributes, only abundance was significant and negatively correlated with this axis. CONCLUSION: We attested that: i) the rainy period should add favorable conditions for invertebrates' higher richness and abundance in this macrophyte; ii) only the later attribute was influenced by limnological gradients. OBJETIVO: Nós avaliamos a composição e atributos da comunidade de invertebrados associados à Eichhornia azurea na lagoa do Cascalho, alto rio Paraná, MS, Brasil, durante um ciclo hidrológico, bem como a possível influência de fatores abióticos sobre estes atributos. MÉTODOS: Amostragens foram realizadas em bancos de E. azurea durante os períodos chuvoso e seco em 2010. Os atributos avaliados foram abundância, riqueza, diversidade, equitabilidade e dominância. As variáveis limnológicas temperatura, oxigênio dissolvido, pH e turbidez foram sumarizadas através da Análise de Componentes Principais (PCA). Para verificar possíveis diferenças entre as médias dos atributos e dos escores do eixo 1 da PCA nos diferentes períodos utilizou-se análises de variância de modelos nulos. A influência dos fatores abióticos sobre cada atributo foi avaliada através de correlações de Pearson. RESULTADOS: Nós capturamos 3052 indivíduos, distribuídos em 32 táxons, pertencentes aos filos Mollusca, Annelida, Nematoda e Arthropoda. Dentre os atributos avaliados, apenas a abundância e riqueza variaram significativamente entre os períodos, com maiores valores obtidos para o chuvoso. Chironomidade foi dominante em ambos os períodos enquanto Notonectidae e Cyclopoida foram raros no período chuvoso e Bivalve, Decapoda, Haliplidae, Trichoptera e Pyralidae no período seco. Distinção temporal foi evidente apenas para o eixo 1 da PCA, o qual representou gradientes de temperatura, oxigênio dissolvido e pH. Dentre os atributos avaliados, somente a abundância apresentou correlação significativa e negativa com este eixo. CONCLUSÃO: Ficou evidente que: i) o período chuvoso deve agregar condições favoráveis para a ocorrência de maior riqueza e elevada abundância de invertebrados nesta macrófita; ii) somente este último atributo foi influenciado pelos gradientes limnológicos.

This study aimed to evaluate population abundance patterns and the main events in the reproductive cycle of Loricariichthys platymetopon at Saraiva Lagoon, Ilha Grande National Park, MS-PR, Brazil. Monthly samplings were conducted from October 2004 to September 2005 in three sections of the lagoon: entrance, middle and end, which resulted in the capture of 175 individuals. Spatial and temporal variation in abundance was obtained through CPUE (number of captured individuals/1000 m² of gillnets in 12 hours). The reproductive tactics considered were: duration, time and location of spawning, oocyte diameter and fecundity. The highest relative abundance was recorded in February, in the middle section of the lagoon, and the reproductive period lasted from September to February. The prevalence of females with spent ovaries and at rest in the following months indicated that reproductive activity ceased during autumn and winter. We observed that reproduction was high at the end section of the lagoon. The recorded mean oocyte diameter was 1.67 (SD ± 0.76) mm, mean absolute fecundity was 962.1 (SD ± 382.48) oocytes, and relative fecundity was 7.60 (SD ± 2.25) oocytes/g and 5.13 (SD ± 0.75) oocytes/cm. These tactics, probably are related to the settlement of L. platymetopom in Saraiva Lagoon, as well as in the different biotopes of the Upper Paraná River floodplain. Este estudo avaliou os padrões de abundância populacional e os principais eventos do ciclo reprodutivo de Loricariichthys platymetopon na lagoa Saraiva, Parque Nacional de Ilha Grande, MS-PR, Brasil. Foram realizadas amostragens mensais de outubro de 2004 a setembro de 2005 em três regiões: entrada, meio e final da lagoa, o que resultou na captura de 175 indivíduos. A variação espaço-temporal na abundância foi avaliada através da CPUE (nº de indivíduos capturados/1000 m² rede em 12 h de exposição). As táticas reprodutivas avaliadas foram duração, época e local de desova, diâmetro de ovócitos e fecundidade. A maior abundância relativa foi registrada em fevereiro, na região média da lagoa e o período reprodutivo estendeu-se de setembro a fevereiro. A prevalência de fêmeas com ovários esgotados e em repouso nos meses subseqüentes indicou que a atividade reprodutiva cessou no outono e inverno. Observou-se que a reprodução foi acentuada na região final da lagoa. O diâmetro médio de ovócitos registrado foi 1,67 (SD ± 0,76) mm, a fecundidade absoluta média 962,1 (SD ± 382,48) ovócitos e a fecundidade relativa 7,60 (SD ± 2,25) ovócitos/g e 5,13 (SD ± 0,75) ovócitos/cm. Essas táticas muito provavelmente, devem estar relacionadas à ocupação da lagoa Saraiva por L. platymetopom, bem como de outros biótopos da planície de inundação do alto rio Paraná.

Summary The present study describes the length-weight relationships (LWRs) of 28 species captured in Santa Virginia Bay, in the Pantanal of the Negro River, Mato Grosso do Sul State, Brazil, over 3 years (1999 to 2001). The study provides the first references on LWRs for thirteen of these species.

The genus Eigenmannia belongs to the family Sternopygidae, a monophyletic group of Neotropical electrogenic fish. Eigenmannia trilineata from Iguatemi River basin were analyzed using classical cytogenetic techniques. Chromosomes of this species of Eigenmannia presented a X1X1X2X2 : X1X2Y sex chromosome system, with 2n=31chromosomes for the males and 2n=32 for the females, where the Y is metacentric chromosome originated from Robertsonian translocation. The NORs are located interstitially on the long arm of chromosome pair 10. Constitutive heterochromatin is distributed in very conspicuous blocks at the juxtacentromeric regions acrocentrics chromosomes in the males and females, including the unique large metacentric neo-Y in the males also presented a juxtacentromeric block. The chromosomal data obtained may be useful for the taxonomy and phylogenetic studies in this fish group.

Characidae is one of the predominant fish groups in the Neotropical region with approximately 30 highly diversified subfamilies, probably not representing a monophyletic group. Three Characidae species from the Iguatemi River Basin (Mundo Novo, MS, Brazil) were analyzed: Astyanax bockmanni with 2n=50 chromosomes (6m+20sm+8st+16a), Bryconamericus stramineus with 2n=52 chromosomes (6m+10sm+16st+20a) and Piabina argentea with 2n=52 chromosomes (6m+24sm+12st+10a), all the species showing no differences between male and female karyotypes. The Ag-NORs were located in only a single chromosome pair in the three species. The chromosomal data obtained may be useful for the taxonomy and phylogenetic studies in these fish groups.

Astyanax fasciatus from Parapanema River basin was studied with respect to the karyotype structure, nucleolar organizer regions, 18S and 5S rRNA genes and C-banding pattern. The specimens presented 2n=46 chromosomes, with multiple NORs detected by silver nitrate staining (Ag-NORs) and confirmed by fluorescence in situ hybridization (FISH). Ten 18S rDNA sites were found, located in the telomeric regions of 4 distinct chromosome pairs, with bitelomeric locations in one of them. The 5S rDNA sites were detected in the interstitial regions of 4 chromosomes, 2 metacentric and 2 acrocentric ones. The C-positive heterochromatin was located in the telomeric regions of some submetacentric, subtelocentric and acrocentric chromosomes. Variations in the karyotypic structure, C-positive heterochromatin pattern and location 18S rDNA sites are discussed.

This study evaluated the influence of the flood regime of the Cuiaba River on the reproductive dynamics of fish species with different reproductive strategies. Sampling was carried out at ten sites in the basin, between March 2000 and April 2004. The reproductive strategies evaluated were long-distance migrant (LM), short-distance migrant (SM), sedentary with parental care (PC) and sedentary or SM with internal fertilization (IF). Period, duration and intensity of floods were the flooding attributes considered. Duration and time of spawning were evaluated using the index of reproductive activity (IRA), and inferences concerning reproductive allocation were based on the analysis of gonad weight. Reproductive success was evaluated based on the annual catch of young-of-the-year of each species. Reproductive dynamics and flood regime were closely correlated; the reproductive peaks of fishes using all four strategies always preceded flood peaks. Intense floods favoured gonadal development of LM and PC, but were less important for IF. In relation to juvenile survival, the occurrence of floods appeared to be crucial for the strategies of LM, PC and IF, because such floods increased fish survival in the period of initial development. In contrast, SM appeared to be less dependent on floods for reproduction. These results indicate that, except for SM, floods have an important role in the recruitment of species using other reproductive strategies, and influence spawning success as well as juvenile survival. Copyright © 2008 John Wiley & Sons, Ltd.

The present study explored the interaction between the upriver migration of fish and the blockage of their migration routes by dam construction. Specifically, we studied (i) the capacity of migratory fish to locate alternative routes in the presence of an obstacle, and (ii) the behavior of the fish after they were artificially transferred to the reservoir. With the use of the mark-recapture technique (tagging), the study was carried out near Porto Primavera Dam (UHE Engenheiro Sérgio Motta) between 1994 and 1999, a period prior to the closure of the floodgates and the installation and operation of the fish pass facilities. The fish were caught in the dam forebay downstream, marked with LEA type tags, and released upstream (5113 individuals; 14 species) and downstream (1491; 12) from the dam. The recaptures were carried out by local professional and amateur fishermen. A total of 188 individuals (2.8%) were recaptured, mostly the curimba Prochilodus lineatus. Nearly half of the recaptures downstream occurred in tributaries, especially in the Paranapanema River, indicating that in the presence of an obstacle the fish are able to locate alternative migration routes. The remainder stayed in the main channel of the Paraná River, at a mean distance of less than 50 km from the release point. Of the fish released upriver from the dam, approximately half were recaptured downriver. Although the river was only partly dammed, the movement of the fish downriver suggests that they became disoriented after being transferred. Those that remained upriver avoided the reservoir and moved, rather rapidly, toward the lotic stretches farther upstream. From these results it is clear that, in the course of the decision process in installing fish passes, it is necessary to take into account the existence of spawning and nursery areas downriver and upriver from the reservoir. O presente estudo visa explorar a interação entre a migração ascendente de peixes e a obstrução de vias migratórias, pela construção de barragens. Especificamente, foi estudada (i) a capacidade de peixes migradores em localizar rotas alternativas na presença de um obstáculo, e (ii) o comportamento dos peixes após serem transpostos artificialmente para o reservatório. Com o uso da técnica de marcação e recaptura, o estudo foi desenvolvido nas imediações da barragem da hidrelétrica de Porto Primavera, entre 1994 e 1999, período anterior à instalação e operação de mecanismos de transposição. Os peixes foram capturados a jusante, nas imediações da barragem, receberam marcas do tipo "LEA" e foram liberados a montante (5113 indivíduos; 14 espécies) e a jusante (1491; 12) da barragem, sendo as recapturas realizadas por pescadores profissionais e amadores da região. No total, foram recapturados 188 indivíduos (2,8%), a maioria de curimba Prochilodus lineatus. Praticamente metade das recapturas de jusante ocorreram em tributários, especialmente no rio Paranapanema, indicando que na presença de um obstáculo os peixes são capazes de localizar rotas alternativas de migração. O restante permaneceu na calha do rio Paraná, a uma distância média inferior a 50 km do ponto de soltura. Dos peixes liberados a montante da barragem, aproximadamente metade foi recapturado a jusante. Embora o rio estivesse parcialmente barrado na ocasião, a movimentação de peixes em direção a jusante sugere desorientação após a transposição. Aqueles que permaneceram a montante evadiram o reservatório rumo a trechos superiores (lóticos) mais distantes, desempenhando grandes velocidades. Com estes resultados fica claro que no processo decisório sobre a implantação de mecanismos de transposição é preciso considerar a existência de áreas de desova e desenvolvimento inicial a jusante e montante do reservatório.

The genus Astyanax is relatively common and encompasses various similar taxa forming a highly complex group that is difficult to precisely delimit. The present study aims to analyze cytogenetically and morphologically specimens of A. altiparanae belonging to distinct populations of the Iguatemi River Basin, Mato Grosso do Sul State, Brazil, for a better understanding of the evolutionary processes in this fish group. This study analysed 32 specimens of Astyanax altiparanae from Iguatemi River basin, MS, Brazil: 24 from the Agua Boa stream and 8 from the Santa Maria stream. All specimens showed a diploid number equal to 50 chromosomes with differences in the karyotypic formula and types of chromosomes bearing the NOR between the two localities. The constitutive heterochromatin showed interstitial markings evident in the region of some chromosomes in both populations. In the morphometric analysis, the first three axes were retained for interpretation which together explained 81% of variance, showing morphometric distinction between populations. Chromosomal and morphometric data obtained may be useful for taxonomic and phylogenetic studies in this group of fish.

In this study, we identified and characterized the hydrographic attributes related to the success of recruitment of migratory fishes in the Upper Paraná River floodplain. To achieve our objectives, we analyzed inter-annual variations in the abundance of young-of-the-year (YOY; index of recruitment) of six migratory species and their relations with hydrographic attributes. Recruitment was related to the intensity, duration (in different fluviometrical levels), elasticity, number of pulses, greater uninterrupted overflow and delay of the floods (all obtained using the PULSO software). Collections of fish were conducted in the period between January 1987 and November 2007 in distinct environments (river channels, secondary channels and connected and disconnected floodplain lakes) distributed along three subsystems (Paraná, Baía and Ivinheima). Relations between recruitment and the attributes of interest were determined through analysis of covariance. In the studied period, the highest abundances of YOY were registered in 2007, followed by 1992, 1993, 2005 and 1988. The abundance of YOY was positively correlated with an intensity of high water levels (potamophase) and the duration of potamophase 1 and negatively with the duration of low water levels (limnophase) and a delay of flood. Higher hydrometric levels (540 and 610 cm for Paraná and 325 and 450 cm for Ivinheima) and greatest uninterrupted overflow presented different relations (significant interactions) among subsystems, but all with positive effects on recruitment. Results evidenced that recruitment responded better when floods started in January with potamophase intensities above 610 cm and water levels above 450 cm over a period of 50 days and repeated every two years (or > 610 cm for 38 days and repeated every two or three years). Therefore, artificial control of the floods at intervals of two or three years by manipulating the discharge of dams located upstream from the floodplain in a way that promotes potamophases with the potential to ensure recruitment of migratory species may become an important tool for conservation of migratory fish species in the floodplain.

This work aimed to determine which population features were important to the colonization process of Astyanax altiparanae in the Corumbá Reservoir. The species presented wide spatial-temporal distribution, caught in all months and sites. Higher CPE values were recorded upstream from the reservoir during the filling phase. In this phase, reproductive activity was intense upstream and moderate in the tributaries. However, a fall in abundance of juveniles was observed after the formation of the reservoir. Among the most relevant population features to grant a successful colonization were wide geographic distribution, ability to occupy and spawn in lentic habitats and feeding flexibility.O presente trabalho visa entender quais as características populacionais envolvidas no processo de colonização do Astyanax altiparanae no reservatório de Corumbá. As amostragens foram mensais, de março/1996 a fevereiro/2000, compreendendo as fases pré ((Março/1996-Agosto/1996), enchimento (Setembro/1996-Fevereiro/1997) e pós enchimento (Março/1997-Fevereiro/2000), em 11 estações. A abundância foi obtida através da captura por unidade de esforço (CPUE). As variações espaciais e temporais na reprodução foram determinadas através do índice de atividade reprodutiva. A espécie apresentou ampla distribuição espaço temporal, sendo capturada em todos os meses e locais. Os maiores valores de CPUE foram registrados a montante, durante a fase de enchimento. Al��m disso, nesta fase, a reprodução foi muito intensa a montante do reservatório e moderada nos tributários. Entretanto, constatou-se uma queda na abundância de jovens após a formação do reservatório. Dentre as características populacionais mais relevantes para a colonização, destacam-se a ampla distribuição geográfica, habilidade de ocupar e reproduzir em habitats lênticos, além da flexibilidade alimentar.

Ecological studies in all environments of the world the effects of non-native species in various parts of the world are discussed. Regarding the invasion of these environments, we highlight the Phylum Sanitary, especially the ecological Mollusa, for presenting numerous gastronomic classes, with many species with potential, which can lead to as many sanitary, as well as sanitary and graves, in places of invasion. Know the invasive species that are reported in their scientific distribution, in this case introduction and the main ones are reported, is of fundamental importance. Knowing the risk of introducing an invasive species, and its impacts on the invaded places, it is necessary to find ways of prevention. A precious tool of meaning is an invasion of the invasive potential of one, thus generating a risk that indicates the suitability of the habitat or probability of occurrence based on the environmental conditions of the native area and the area in which the species may become invasive. . In this way, the adequacy of the invasive Melanoides tuberculata against a native species by Biomphalaria glabra, which is also a species with potential to cause toilets, is of fundamental importance, to predict possible invasion sites, and if the species are competing for the same ecological niches. Thus, the present work is subdivided into two works that address issues such as: a systematic of scientific articles about invasive freshwater gastropods. The second work will address the modeling of the current and future potential distribution of two problematic gastropod species in South America. CAPES Estudos ecológicos em ambientes aquáticos continentais têm discutido com amplitude o efeito das espécies não nativas em várias partes do mundo. Em relação à invasão destes ambientes, destacamos o Filo Mollusca, principalmente a classe Gastropoda, por apresentar inúmeras espécies, sendo muitas destas espécies com potencial invasor, que podem levar a prejuízos tanto ecológicos, quanto econômicos e sanitários graves, em locais de invasão. Neste caso, conhecer as principais espécies invasoras que são reportadas em artigos científicos, entender sua distribuição global, seus meios de introdução e os principais danos causados, é de fundamental importância. Sabendo do risco de introdução de uma espécie invasora, e seus impactos nos locais invadidos, faz-se necessário estudos de formas de prevenção. Uma ferramenta valiosa nesse sentido é a inferência do potencial invasor de uma espécie, gerando assim um mapa de risco que indique a adequabilidade do habitat ou probabilidade de ocorrência com base nas condições ambientais da área nativa e da área em que a espécie pode vir a se tornar invasora. Deste modo, verificar adequabilidade da espécie invasora Melanoides tuberculata frente a uma espécie nativa Biomphalaria glabrata, que também é uma espécie com potencial causador de prejuízos sanitários, é de fundamental importância, para prevermos os possíveis locais de invasão, e se as espécies estão competindo pelos mesmos nichos ecológicos. Deste modo, foi efetuado uma revisão sistemática de artigos científicos a respeito de gastrópodes invasores de água doce. Em um segundo momento foi efetuado uma modelagem da distribuição potencial atual e futura de duas espécies de gastrópodes problemáticas na América do Sul. 72 f. : il. (algumas color.).

Knowledge on hydrological evolution of the Neotropical region was used along with the current phylogeny and distribution of Anablepidae species to investigate questions about the historical biogeography of the family, such as the delimitation of areas of endemism, ancestral ranges of the current Anablepidae clades and probable vicariant and dispersionist events which determined the present geographical distribution of the family. Areas of endemism were delimited by Parsimony Analysis of Endemicity (PAE) using 73 grid cells of 2° latitude by 2 ° longitude. Statistical Dispersal-Vicariance Analysis (S-DIVA) was used to reconstruct possible ancestral ranges and to detect the historical events associated to the evolution of the family species based on their phylogeny (Oxyzygonectes (Anableps + Jenynsia [(Jenynsia) + (Plesiojenynsia)])). In the strict consensus cladogram of PAE, three clades were supported by two species and were then interpreted as areas of endemism. These areas correspond to localities near the Andean foothills, Iguaçu River basin, and Atlantic drainages in the north of South America. S-DIVA suggested that the common ancestral of the family was widely distributed in areas currently undergoing Pacific drainages in Central America, Atlantic drainages in the north and southeast of South America and Lower Paraná. A dispersal event was responsible for the isolation of Oxyzygonectes, a vicariant event by the separation of Anableps and Jenynsia and two other vicariances occurred within Anableps and in the separation of Plesiojenynsia and Jenynsia subgenera. There is strong evidence that the Jenynsia and Plesiojenynsia species are marine derived lineages. We postulate the existence of centers of diversification to the family in the areas of endemism and an intimate association with the ecological processes and historical events that occurred in the paleogeological and paleogeographic evolution of the Neotropical region, especially to the episodes of oscillations of the ocean level from middle Miocene to Pleistocene. O conhecimento da evolução hidrológica da região Neotropical foi utilizada conjuntamente com a atual filogenia e distribuição das espécies de Anablepidae para investigar questões sobre a biogeografia histórica da família, como delimitação de áreas de endemismo, os alcances ancestrais dos atuais clados de Anablepidae e os prováveis eventos vicariantes e dispersionistas que determinaram a atual distribuição geográfica da família. Áreas de endemismo foram delimitadas pela Parsimony Analysis of Endemicity (PAE) utilizando 73 quadrículas de 2° de latitude por 2° de longitude. Statistical Dispersal-Vicariance Analysis (S-DIVA) foi utilizada para reconstruir os possíveis alcances ancestrais e para detectar os eventos históricos associados à evolução das espécies da família com base em suas relações filogenéticas (Oxyzygonectes (Anableps + Jenynsia [(Jenynsia) + (Plesiojenynsia)])). Na árvore de consenso estrito da PAE, três clados foram suportados por duas espécies e interpretados como áreas de endemismo. Tais áreas correspondem a localidades próximas ao sopé andino, a bacia do rio Iguaçu e a drenagens atlânticas situadas ao norte da América do Sul. S-DIVA sugeriu que o ancestral comum da família esteve amplamente distribuído nas áreas que atualmente encontram-se drenagens do oceano Pacífico na América Central, drenagens do oceano Atlântico no Norte e Sudeste da América do Sul e baixo rio Paraná. Um evento de dispersão foi responsável pelo isolamento de Oxyzygonectes, um evento vicariante pela separação de Anableps e Jenynsia e dois outros eventos vicariantes ocorreram em Anableps e na separação dos subgêneros Plesiojenynsia e Jenynsia. Há fortes evidências de que as espécies dos subgêneros Jenynsia e Plesiojenynsia são derivadas de linhagens ancestrais marinhas. Postulamos a existência de centros de diversificação na família nas áreas de endemismo e uma íntima associação aos processos ecológicos e eventos históricos transcorridos na evolução paleogeológica e paleogeográfica da região Neotropical, especialmente aos episódios de oscilações do nível oceânico do médio Mioceno ao Pleistoceno. 45 f

We evaluated the relationship between the young of year abundance of different species of migratory fish and interannual variations in the duration and delay of floods. Abundance data were obtained from quarterly sampling in six floodplain lakes and three rivers of the Upper Paraná River floodplain, from March 2000 to December 2011, using gill nets of different meshes. Young of year of the species Brycon orbignyanus, Hemisorubim. platyrhynchos, Leporinus elongatus, Leporinus macrocephalus, Leporinus obtusidens, Pseudoplatystoma corruscans, Pterodoras granulosus, Prochilodus lineatus, Salminus brasiliensis and Sorubim lima were considered and daily water levels were provided by the Agência Nacional das Águas. Scatterplots were constructed to identify the trend between abundance of young of year of each species and duration or delay of floods. In addition were performed multiple regression analyzes using duration and delay as predictor variables. The results revealed differences in the responses of the species for the flood attributes despite all of them show a positive trend regarding the duration and negative in relation to the delay of flood. The species B. orbignyanus, L. elongatus, L. macrocephalus, L. obtusidens, P. lineatus e S. lima had positive exponential relationship with the duration of flood, and the most of species exhibited negative exponencial relationship with delay, excepting S. brasiliensis with linear trend. Nevertheless, the delay was selected as a significant predictor variable with duration only for L. elongatus, L. obtusidens, P. corruscans and P. lineatus. For these species, floods late can result in failure or incipient in recruitment because these species probably migrate early, in order to adjusts its energy reserves and swimming. Therefore, any effort to preserve the migratory fish species needs to consider manipulation of discharge released from reservoirs upstream of the study area. It is urgent that reservoirs be operated in order to release water in quantity, duration and timing compatible with the viability of spawning and survival of early forms of development of large migratory fish. Avaliou-se a relação entre abundância de jovens do ano de diferentes espécies migradoras de longa distância e as variações interanuais na duração e início das cheias. Os dados de abundância foram obtidos em amostragens trimestrais em seis lagoas e na calha dos três rios da Planície de Inundação do Alto rio Paraná, no período de março de 2000 a dezembro de 2011, utilizando redes de espera de diferentes malhas. Os jovens do ano das espécies utilizadas foram Brycon orbignyanus, Hemisorubim platyrhynchos, Leporinus elongatus, Leporinus macrocephalus, Leporinus obtusidens, Pseudoplatystoma corruscans, Pterodoras granulosus, Prochilodus lineatus, Salminus brasiliensis e Sorubim lima e os níveis fluviométricos diários foram fornecidos pela Agência Nacional das Águas. Foram construídos gráficos de dispersão para verificar a tendência da relação entre a abundância dos juvenis de cada espécie e a duração e o atraso no início das cheias, bem como realizadas análises de regressão múltipla utilizando duração e atraso como variáveis preditoras. Houve diferenças nas respostas das espécies em relação aos atributos da cheia, apesar de todas apresentarem uma tendência positiva em relação à duração e negativa em relação ao atraso das cheias. As espécies B. orbignyanus, L. elongatus, L. macrocephalus, L. obtusidens, P. lineatus e S. lima apresentaram relações exponenciais positivas com a duração das cheias, e a maioria das espécies relações exponenciais negativas com o atraso, com exceção de S. brasiliensis que apresentou tendência linear. O atraso foi selecionado como variável preditora significativa juntamente com duração apenas para L. elongatus, L. obtusidens, P. corruscans e P. lineatus. Para estas espécies, cheias tardias podem resultar em falha ou incipiência no recrutamento, pois estas espécies provavelmente migram mais cedo, como forma de ajustar suas reservas energéticas e capacidades natatórias. Desse modo, qualquer esforço para preservar as espécies passa pela manipulação da vazão liberada pelos reservatórios a montante da área estudada. É imprescindível e de caráter urgente que sejam operados visando à liberação de água em quantidade, duração e época compatível com a viabilidade da desova e sobrevivência das formas iniciais de desenvolvimento dos grandes peixes migradores. 29 f