Although the Aiuruoca River is recognized as a very important area for fish fauna, the species composition of this river remains unknown or restricted to technical reports of licensing projects. The aim of this study was to describe the composition and distribution of the ichthyofauna in the Aiuruoca River basin. Fifty-eight collection points were sampled along the Aiuruoca River basin during 2010 and 2011, including 38 streams, 11 lagoons and 9 points along the Aiuruoca River main channel. A total of 8562 specimens were collected belonging to 6 orders, 15 families, 33 genera and 47 species. The pirapetinga fish (Brycon nattereri) is listed on Brazil’s endangered species, and the rainbow trout (Oncorhynchus mykiss) was the only exotic species captured. Altitude is one of the main factors that influence fish community structure in the Aiuruoca River basin, confirming its importance for fish conservation

In dammed rivers, the conservation of free-flowing tributaries is considered an important strategy to mitigate the negative effects of the dam on fish communities. In this study, we evaluated the importance of a free-flowing tributary of a dammed river as a reproductive migration route. From August 2012 to July 2013, hydroacoustics data were collected alongside active fish sampling using cast nets and ichthyoplankton nets in the São Francisco and Abaeté rivers. Cast net sampling captured 738 individuals and hydroacoustics detected 42196 fishes. In almost all samples and sampling sites, preferential movements to the Abaeté River and the main São Francisco River were observed. The increase in the flow rate of the Abaeté coincided with a greater incidence of fish movements to upstream areas of the tributary. A higher density and proportion of larger fishes, as well as a higher density of ichthyoplankton, were observed in the Abaeté River compared with the main river. Because this tributary is an alternative route for migratory fishes, its protection is essential for fish conservation and therefore maintenance of local fisheries

The Formoso dam might also affect the Pirapora rapids (Figure 1), which are the most extensive rapids found in the main channel, and known to house many rheophilic fish species. Moreover, the alterations will impair the traditional fishing communities in the area both socially and economically. This will represent a clear violation of the national targets regarding the conservation of biodiversity and water bodies (Nos 6, 9, 12, 14 and 18) of the United Nations Convention on Biological Diversity, to which Brazil is a signatory. The stretch that will be affected by the Formoso dam is a cornerstone for both the conservation of fish biodiversity and the recently proposed Environmental Protection Area which, if created, will encompass the whole unfragmented segment to ensure that its natural resources are sustainably used (Coimbra et al., 2020). Therefore, the construction of the Formoso dam would be a critical setback for the world conservation initiative and a clear indication that unfortunately Brazil does not prioritize some of its most valuable natural resources.

The establishment of national parks are an important and often‐used tool to protect biodiversity. However, when considering freshwater ecosystems, many of these areas in Brazil are habitat mosaics in which a small part of the ecosystem is protected and strongly influenced by the surrounding environment. By assessing the fish fauna and their diversity patterns in five national parks (NPs) within the Brazilian savanna, we discuss whether the establishment of new NPs or the expansion of their current conservation limits would potentially conserve additional species. We selected all national parks within the third largest drainage area in Brazil. To sample fish communities, we explored 60 streams through a standardised field protocol. We also simulated the potential impact of the enlargement or implementation of a new national park. Our results reinforce the importance of national parks and their surrounding areas to preserve fish species. The enlargement of national parks would result in an increase of potentially protected species; however, the same achievement would be obtained if their buffer zones were effectively managed and protected. We recommend an alternative conservation approach to increase protection of tropical savanna fish biodiversity, especially in developing countries such as Brazil with scarce financial resources available for management, monitoring and creation of protected areas.

ABSTRACT Trophic structure of fish assemblages is one of the most sensitive indicators of changes in streams environments. Since it is crucial to understand the response of trophic groups to habitat alteration, our study aimed to address this research gap by assessing the influence of substrate composition, meso-habitat variability, and bank stability, on the richness, biomass, and number of individuals of carnivores, invertivores, omnivores, and herbivorous-detritivores. Using an electrofishing device, we sampled 13 Atlantic rainforest streams reaches in a degradation gradient, located in the upper Paranapanema river basin. Sample points were ranked using a physical habitat index. More pristine streams had high availability of twigs, trunks, rocks and boulders in the substrate, great meso-habitat variability, and the presence of roots, trunks, and rocks in the margins. Canonical correlations between habitat characteristics and trophic groups explained more than 90% of data variability. Richness and number of individuals of invertivores increased in more preserved stream reaches, while richness of carnivores and number of individuals of omnivores decreased. These results demonstrate that trophic structure varies according to level of degradation, and that invertivore richness represents the best indicator of fish trophic structure responses to physical habitat alterations in streams.