Impacts of hydroelectric dams on fishes and fisheries in tropical rivers through the lens of functional traits

The Madeira River basin is one of the most important ecosystems for Amazonian fisheries (Doria, Ruffino, Hijazi & Cruz, 2012; Goulding, 1979). The high productivity of the Amazon basin generally is related not only to it being the world’s largest hydrographic basin but also the highly dynamic relationship between the terrestrial environment and the aquatic ecosystem, which is a characteristic of fluvial ecosystems located in tropical and equatorial regions (Junk, 2001). In this region, fishing patterns and the quantity and quality of the fish caught are determined primarily by the hydrological cycle, which regulates the formation of shoals and the timing of their migrations (Batista & Petrere, 2003; Junk, Bayley & Sparks, 1989). The equilibrium between terrestrial and aquatic environments in the Amazon basin is threatened by the construction of hydroelectric dams. The hydroelectric potential of the region’s rivers has led to major advance in this sector (Soito & Freitas, 2011), and 100 dams are already in operation within the whole Amazon region, while another 137 are planned or under construction in the countries that make up this region (Lees, Peres, Fearnside, Schneider & Zuanon, 2016; Tundisi, Goldemberg, MatsumuraTundisi & Saraiva, 2014). Plans for the Brazilian energy sector include the expansion of the hydroelectric potential by 6.8 GW, with 16 new dams, by 2026, with 57% of this potential being provided by dams located in the Amazon basin (MME/EPE, 2017). Despite being considered beneficial, by providing a clean and renewable source of energy, hydroelectric dams provoke major impacts on the hydrological cycle (Timpe & Kaplan, 2017), causing longitudinal disturbances throughout the course of the river, as predicted by the Ward and Stanford (1995) serial discontinuity concept. Received: 27 April 2018 | Revised: 16 June 2018 | Accepted: 20 July 2018 DOI: 10.1111/fme.12305

The decline of fisheries on the Madeira River, Brazil: The high cost of the hydroelectric dams in the Amazon Basin

Diversity and community structure of rapids-dwelling fishes of the Xingu River: Implications for conservation amid large-scale hydroelectric development

Baited remote underwater video (BRUV) systems are being used in marine ecosystems as a nonextractive, cost-effective method of assessing the fish fauna with minimal species bias. This technique has had limited applications in freshwater ecosystems. Rheophilic fish assemblages of the Xingu River, a clearwater Amazonian river in Northern Brazil, were sampled with BRUV systems. Two-hour video recordings were collected using five different bait treatments (sardine, croaker, cat food, sweet corn, and no bait) in two lotic habitat categories (rocky and sandy bottoms). A total of 2460 fish from 56 taxa and 13 families were recorded from the 80 BRUV deployments. Significantly different fish assemblages, species richness, and abundance were detected between habitat types and among treatments. Our results suggest that the use of crushed sardines as a standardized bait optimizes the sampling recording the highest species richness, relative abundance, and number of exclusive species of rheophilic fish in clearwater Amazonian rivers. The data also highlight the unique fish diversity of the Xingu River prior to the expected large-scale environmental degradation resulting from the forthcoming operation of the Belo Monte hydroelectric power plant.

Baited remote underwater video as a promising nondestructive tool to assess fish assemblages in clearwater Amazonian rivers: testing the effect of bait and habitat type

Rapidly escalating threats to the biodiversity and ethnocultural capital of Brazilian Indigenous Lands

The structure of fish assemblages in Neotropical rivers is influenced by a series of environmental, spatial and/or temporal factors, given that different species will occupy the habitats that present the most favourable conditions to their survival. The present study aims to identify the principal factors responsible for the structuring of the fish assemblages found in the middle Xingu River, examining the influence of environmental, spatial, and temporal factors, in addition to the presence of natural barriers (waterfalls). For this, data were collected every three months between July 2012 and April 2013, using gillnets of different sizes and meshes. In addition to biotic data, 17 environmental variables were measured. A total of 8,485 fish specimens were collected during the study, representing 188 species. Total dissolved solids, conductivity, total suspended matter, and dissolved oxygen concentrations were the variables that had the greatest influence on the characteristics of the fish fauna of the middle Xingu. Only the barriers and hydrological periods played a significant deterministic role, resulting in both longitudinal and lateral gradients. This emphasizes the role of the connectivity of the different habitats found within the study area in the structuring of its fish assemblages.

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Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin

The Xingu River has one of the most diverse fish faunas in the Amazon region. Loricariidae stands out as the most diverse family in the basin, comprising more than 60 species distributed over 26 genera. Species of Loricariidae are some of the most economically valued in the ornamental market worldwide. The loss of fishing environments in Altamira region due to dam impacts is driving a shift of ornamental fishing to areas upstream, among which are included the Xingu River and Iriri River Extractive Reserve Areas. Thus, the objective of this work was to inventory fish species with ornamental potential in these extractive reserves to serve as a baseline to help guide the future management of ornamental fishing in those areas. Thirty-two species of Loricariidae were collected in these reserves through either free diving or diving with compressed air. The composition of species varied according to the sampling method and area. The majority of species found in the reserves are also found in the impacted areas of Belo Monte near Altamira. The study areas showed high diversity of fish species in rapids environments, suggesting that this area could serve as an additional source of income for the residents of these reserves.

Diversity of Loricariidae (Actinopterygii: Siluriformes) assemblages in two Conservation Areas of the Middle Xingu River, Brazilian Amazon, and their suitability for sustainable ornamental fisheries

Alany Pedrosa Gonçalves

Papers

Diversity and community structure of rapids-dwelling fishes of the Xingu River: Implications for conservation amid large-scale hydroelectric development

Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin

Diversity of Loricariidae (Actinopterygii: Siluriformes) assemblages in two Conservation Areas of the Middle Xingu River, Brazilian Amazon, and their suitability for sustainable ornamental fisheries