Navegando por Assunto "Peixe - Ecologia - Amazônia"

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Acesso aberto (Open Access)
Avaliação dos efeitos de monocultura de palma de dendê na estrutura do habitat e na diversidade de peixes de riachos amazônicos
(Universidade Federal do Pará, 2018-03-30) RUFFEIL, Tiago Octavio Begot; MONTAG, Luciano Fogaça de Assis; http://lattes.cnpq.br/4936237097107099
In the Amazon, oil palm plantation has been growing exponentially in recent years, altering the landscape natural characteristics and being a possible threat to biodiversity. This environmental impact extends to aquatic ecosystems, which because they are highly related to the adjacent vegetation, also suffer the impacts resulting from this agricultural action, such as habitat structure alterations, affecting the species distribution and ecosystem processes. Thus, studies to test the impact of this monoculture in the Amazon are important to support more efficient strategies for reducing impacts and maintaining biodiversity. Therefore, this thesis aims to answer the following questions: I) How the presence of oil palm cultivation around the streams affect their habitat structure and fish assemblage structure in relation to streams that drain through forested areas present along of this anthropogenic landscape? II) What are the effects of the substitution on landscape of primary forest on the oil palm in the habitat physical structure and on the taxonomic diversity of neotropical stream fish? III) How do the patterns of taxonomic and functional diversity of Amazon stream fish assemblages responds to the habitat and landscape changes caused by oil palm plantation? To answer these questions, we sampled and analyzed 39 streams in the Eastern Amazon. For the habitat characterization, an extensive protocol of the evaluation was applied, resulting in 238 habitat variables, besides that, was used landscape characteristics based on the percentage of land uses adjacent to the streams. For fish collection was used hand net for six hours in each stream. Morphological measures and ecological information of fish species were taken for later calculation of the functional attributes related to the third chapter. The results showed that oil palm plantation affect the stream habitat structure, modifying mainly the channel morphology, the substrate structure and shelter availability, such as woods and roots, for fish assemblage. Consequently, the fish species distribution was affected, resulting in changes in the assemblage structure. On the other hand, no changes were registered in the functional structure of these assemblies. Finally, we showed that the oil palm plantation modifies the stream habitat natural characteristics, as well as the distribution of the species, however the functional structure of the fish assemblages is maintained.
Acesso aberto (Open Access)
Impactos da pastagem na estrutura taxonômica e funcional de peixes de riachos amazônicos
(Universidade Federal do Pará, 2018-01-19) CANTANHÊDE, Lorrane Gabrielle; MONTAG, Luciano Fogaça de Assis; http://lattes.cnpq.br/4936237097107099
In recent years, increasing economic development has promoted high rates of deforestation and land use change that negatively impact terrestrial and aquatic ecosystems around the world. Therefore, this study aimed to assess how the taxonomic structure and functional diversity of the stream fish assemblages of eastern Amazonia respond to impacts caused by pasture. We sought to answer the following questions: (i) What is the effect of pasture on the environmental characteristics of streams?; (ii) How do they affect the taxonomic structure and functional diversity of the ichthyofauna?; (iii) What functional attributes will be related to the environmental variables that characterize the streams that drain pasture and forest areas? The sampling were carried out between the years of 2012 and 2015, in the dry season, with 13 streams in forested areas and 13 streams in pasture areas. Through a PCA the set of environmental variables related to forest and pasture areas were verified. The taxonomic structure was compared among the environments through the richness, composition and abundance of species. Functional diversity was measured through the components of richness, evenness and functional divergence. The significance of the results of the indices with Student's t-test was tested. RLQ ordering analysis and the fourth-corner component were used to determine the relationships between environmental variables of each treatment and functional attributes. A higher number of artificial shelters and a higher percentage of riffles were found in pastures and the higher canopy cover formed by large trees (DAP> 0.3 m) in forest areas. It was verified that the pasture negatively affects the taxonomic structure and the functional divergence of the ichthyofauna, favoring the presence of generalist species. The highest amount of canopy cover benefited benthic species. Although the Brazilian Forest Code provide for the maintenance of riparian vegetation around the streams, grazing generated negative effects on the physical habitat of streams, taxonomic structure and functional divergence of assemblages of fish from streams in the Eastern Amazon. To conserve the diversity of fish in Amazonian streams, there should be stricter laws and increased enforcement regarding the maintenance of riparian vegetation.
Acesso aberto (Open Access)
Influência de diferentes práticas de uso da terra sobre a fauna de riachos amazônicos
(Universidade Federal do Pará, 2019-02-27) SOUSA, Híngara Leão; MONTAG, Luciano Fogaça de Assis; http://lattes.cnpq.br/4936237097107099
Disturbances caused by land use practices lead to several negative effects on stream biodiversity. This dissertation was developed to contribute with information about the land use effects on Amazonian stream biodiversity. The dissertation was subdivided in three chapters. First, it was performed a review of articles that evaluated the land use effects on stream fauna in the Amazon in the last 25 years to show the scenario of scientific research for these ecosystems in the region. In the Chapter 2 the aim was to assess the effects of three land use practices (managed and convenctional logging, and pasture) on stream fish, considering the impacts on the community structure and niche characteristics of species. In the Chapter 3 the aim was to evaluate the ecological uniqueness of fish assemblages in these areas, in order to identify the land uses and species that more contribute to beta diversity in the region. As general results of the first Chapter, 42 articles evaluating the land use effects on stream fauna communities in the Amazon were found in the literature, mainly in areas of timber extraction. Recently, there has been an increase in studies, and only the last four years accounted for 74% of articles. However, we identified a lack of information about the land use history in the studied areas, a lack of studies using only the crustacean as a bioindicator taxon and a few multi-taxon studies. Chapter 2 showed that conventional logging and pasture had negative impacts on fish communities, and no effect was observed in managed logging areas. Additionally, pasture was mainly responsible for the separation of niche species, supporting species with higher marginality and smaller niche breadth. Finally, in the Chapter 3 was found higher contribution of pasture area to beta diversity, mainly due to the great variation in the disturbance levels associated to this land use practice. Besides that, both habitat specialist and generalists contributed to beta diversity in the area. In conclusion, the results of this dissertation have shown that different kinds of land use may result in particular effects on stream communities. Our findings also suggest that different approaches using information on stream biodiversity are useful in environmental impact assessment in these ecosystems.