Impactos e perturbações ambientais em peixes tropicais

Abstract

The tropical region is an extensive area that, in addition to having large rivers, is also home to a great diversity of freshwater fish. Despite the essential importance that this diversity presents, these organisms have been increasingly impacted as we enter the Holocene. Humanity's great challenges, such as energy generation, industrial production, agricultural production and potentially contaminating substances, directly affect the ichthyofauna. Therefore, the main objective of this thesis was to address some of these impacts and disturbances in the fauna of tropical fish, both adults and in their early stages of life. Therefore, the studies addressed in this thesis contemplated the effects of dam construction and reservoir formation on habitat fragmentation, abundance, richness and structure of the fish assemblage, in addition to experimentally evaluating the effects of contaminants on environmental concentrations during the phases early developmental fish. Thus, our information revealed that: (1) Studies involving the construction of dams are of paramount importance, especially when they can cover data from before and after damming. Thus, we were able to assess the impacts caused on the ichthyofauna, such as loss of diversity and species change. (two). Concomitantly with the direct changes in fish diversity, it is possible to know the secondary impacts such as habitat fragmentation on the ichthyofauna of migratory fish. Fish belonging to this specific breeding guild need long stretches of river free to spawn. However, the increase in dam construction alters the landscape, generating the lack of free stretches of rivers, compromising migration. Therefore, this thesis addresses how habitat fragmentation affects the migration of the genus Pseudoplatystoma and whether there is efficiency of fish transposition systems for this specific group. Thus, the study evidenced the low use of transposition systems by the genus Pseudoplatystoma, in addition to verifying the difficulty of descending transport of ichthyoplankton by these systems. (3). The impacts generated by dumping contaminants into water bodies is also a troubling issue. Therefore, environmental agencies generated values considered acceptable for several compounds and among them is nitrate. Nitrate is a natural compound that in recent years has been increasing in freshwater ecosystems, 10 caused by sewage disposal or leaching of agricultural inputs. However, this thesis addressed the toxicity of nitrate in concentrations acceptable by regulatory agencies in larvae of three species of fish, making the deleterious effects evident during the early stages of development. (4). Finally, the last chapter evaluates the effect of caffeine, an emerging contaminant that has been increasing its concentration in aquatic environments, in order to verify its effects on environmental dosages in larvae of a fish species endemic to the Neotropical region, with extensive discussion on the environmental risk of this compound in several countries, in order to compare the deleterious effects for other possible fish species. With these studies, it is clear the need to evaluate more carefully the different anthropic effects on Neotropical aquatic environments, thus helping mitigation forms to reduce the loss of ichthyofauna diversity, ecosystem services and public health issues