Dams change the hydrological dynamics, patterns of biological production and distribution of organisms in space and time. In contrast, tributary rivers can function as source areas in reservoirs, since they harbor spawning and early development grounds for native fish species. Here, we analyze a time series of the first 14 years after the impoundment of the Porto Primavera Reservoir, a large reservoir with free tributaries in southeastern Brazil. To evaluate the impact of damming on the fish assemblage, we evaluated the abundance (catch per unit effort, CPUE) and α (species richness and Shannon-Wiener index) and β (Sørensen dissimilarity and turnover) diversity of four sites distributed along the reservoir. Overall, there was no decreasing trend in the α diversity and no increasing trend in the β diversity relative to the initial year or among the sites over time. Despite the expected disturbance in the fish assemblage at the lacustrine site, the sites located near the tributary mouths presented resistant fish assemblages, compensating the results of the overall assessment. We attribute this unusual variation in the ecological attributes to source-sink demographic dynamics, with the undammed tributaries as the source and the reservoir as the sink for native species. We highlight that the presence of these rivers minimized the expected trend towards biotic homogenization, and the preservation of the tributaries is imperative since they contribute to diversity maintenance in areas that are already impacted by damming. The inclusion of this agenda in environmental management programs and new impoundment plans will allow a balance between the demand for electricity production and the conservation of fish diversity.

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AIM: The aim of the present study was to evaluate the diet and biological attributes of the population of Apareiodon affinis residing near net-cage fish farming activities in the Chavantes reservoir. METHODS: Samples were collected from two populations: one near the net cages (NC) and one from an area not influenced by these cages denominated the "reference site" (RS). Monthly sampling was carried out from Mar/2008 to Feb/2009. Fish were caught with a standardized effort using gill nets deployed for 14 hours. After all individuals were measured (standard length) and weighed (total weight, carcass weight , body weight without gonads). To determine the composition of the diet, the alimentary index was calculated (AI). We also calculated the length-weight relationship, condition factor, gonad-somatic index (GSI ) and reproductive potential. RESULTS: A total of 3050 individuals were caught. The results of the (AI) revealed that the item detritus was the main food used for populations of A. affinis studied in two areas (NC = 73.1% and RS = 95.7%). The use of feed on diet A. affinis was recorded for the populations of NC adding (20.5%) of the total items consumed by the population. The resident populations residing near net-cage showed higher condition factor and more reproductive period. CONCLUSIONS: The results show the ability of the species to benefit from the input of organic matter from fish farming activities, inserting a new item in their diet (ration). This work indicates that the species A. affinis managed to establish near net-cage, allocating enough energy to increase their reproductive period and maintain viable populations close to net-cage, evidenced by the high abundance. This study suggests that systems of fish farming in net-cage influence diet and biological attributes of the species A. affinis residents Chavantes reservoir, Brazil.

Brazil is a megadiverse country and is participant of fundamental environmental agreements for biodiversity conservation. However, the internal politics and the cultures that affect negatively the ecological integrity in Brazilian freshwater need to be improved on the condition of sustainable management. Scientific community, the government and stakeholders are in constant conflicts of goals. Meanwhile, the current model for Brazilian aquaculture shows problems of ecological impact due to the lack of appropriated planning and legislation to the aquatic biota. The non‐recognition of sustainable census incorporated in its environmental politics reflects in an archaic and unsustainable management, with the following characters: a non‐specific approach for technical management, the indiscriminate use of interspecific hybrids and non‐native species and the lack of skilled labour. The potential impact on native species and the introduction of pathogens are the main negative effects on aquatic biota. This way, the aim of this article is to elucidate the conflicts of interests and ecological effects of fish aquaculture in Brazil, besides providing good practices and sustainable alternatives for management.

This study reports the infection of fishes by Austrodiplostomum compactum metacercariae in the Chavantes reservoir, medium Paranapanema River, municipality of Ipaussu, São Paulo State, Brazil. Twenty-three fish species were analysed, and 13 were infected with A. compactum metacercariae (56.5%) in their eyes. The following six fish species are new hosts for this metacercaria: Crenicichla haroldoi (1/1), Eigenmannia trilineata (11/6), Hoplosternum littorale (11/1), Iheringichthys labrosus (17/2), Leporinus amblyrhynchus (11/1), and Piaractus mesopotamicus (3/1). These new species increase the number of Brazilian fish species infected with this parasite to 36. Based on these findings, we hypothesise that the metacercariae larval stage of the parasite has a low specificity for the second intermediate host (fish). The majority of fish species infected in Brazil belong to the Loricariidae and Cichlidae families. For the fish species with higher mean abundances in Brazil, six are non-native species, and currently, Plagioscion squamosissimus has the highest mean abundance. The majority of fish species infected with A. compactum in Brazil are concentrated in the Paraná basin, although this may be related to the distribution of researchers.Keywords: Freshwater fishes, parasite, Trematoda, metacercariae, infection, Paraná basin. ResumoEste estudo relata a infecção por metacercárias de Austrodiplostomum compactum em peixes do reservatório de Chavantes, médio Paranapanema, Ipaussu, São Paulo, Brasil. Vinte e três espécies de peixes foram analisadas, e 13 estavam infectadas com metacercárias (56,5%) em seus olhos. Seis espécies de peixes foram registradas como novos hospedeiros: Crenicichla haroldoi (1/1), Eigenmannia trilineata (11/6), Hoplosternum littorale (11/1), Iheringichthys labrosus (17/2), Leporinus amblyrhynchus (11/1), and Piaractus mesopotamicus (3/1), aumentando para 36 o número de peixes brasileiros infectados por este parasita. Assim, inferimos que este estágio larval do parasita possui baixa especificidade parasitária em relação ao seu segundo hospedeiro intermediário (peixes). No Brasil, a maioria das espécies de peixes infectadas pertence às famílias Loricariidae e Cichlidae. Quanto às espécies de peixes com as maiores abundâncias médias no Brasil, seis são espécies não-nativas, sendo Plagioscion squamosissimus a espécie com a maior abundância média. Ainda, a maioria das espécies de peixes infectadas por A. compactum no Brasil, estão concentradas na bacia do Paraná, sendo este fato possivelmente relacionado com a distribuição de pesquisadores.Palavras-chave: Peixes de água doce, parasita, Trematoda, metacercária, infecção, bacia do Paraná.