Review of fisheries resource use and status in the Madeira River Basin (Brazil, Bolivia, and Peru) before hydroelectric dam completion

The Madeira River, which drains one of the major tributary river basins of the upper Amazon, contributes to small-scale fisheries in Peru, Bolivia, and Brazil. This paper provides a base-line of fisheries resources and their status in six sub-basins of the Madeira River: upper Madre de Dios River basin (Peru), Beni and Mamore River basins (Bolivia), Itenez or Guapore River basin (Bolivia and Brazil), middle Madeira, and (two sections of the) lower Madeira River (Brazil). Data were collected between 2009 and 2011, before the completion of two hydroelectric dams in the Brazilian portion of the basin. Biophysical, social, and biological indicators were used to characterize the fisheries. The results show an overall small-scale multispecies fisheries pattern but with notorious differences between the Madeira sub-basins. The Beni and Mamore sub-basin shows the largest flooded area, with associated higher total fisheries yields. Trophic level of the catch, diversity, and mean weight of fish caught were shown to be very sensitive to exploitation level, river water type (white or clear water), flooded area, and the introduction of Arapaima gigas in Bolivia. The Bolivian fisheries are characterized by less exploited stocks, whereas stocks in Peru and Brazil show signs of intensive exploitation, resulting in fisheries of smaller bodied, lower trophic-level species. Landing data in the upper basin show a predominant reliance on migrating fish resources, which might be vulnerable to the construction of dams. These data serve as a baseline to evaluate anthropogenic impacts on the Madeira River basin fisheries in the future

Delimiting species by reproductive isolation : the genetic structure of epigean and hypogean Trichomycterus spp. (Teleostei, Siluriformes) in the restricted area of Torotoro (Upper Amazon, Bolivia)

Genetic variability of Trichomycterus from the region of Torotoro (Bolivia, Upper Amazon), distributed in the same watershed where the habitat is structured by waterfalls, canyons and a cave, was studied by allozyme (twelve putative loci) and RFLP-mtDNA (DLoop and cytochrome b) analyses. Alloenzymatic variation studied by Correspondence Analysis and Maximum Likelihood Analysis revealed a four-group structure, which was largely congruent with the distribution of the 14 mtDNA haplotypes. Two of these four clusters (I and II) were differentiated by two diagnostic loci (IDH and G3PDH), two semi-diagnostic loci (PGM and 6PGDH) and consequently a very high F-st value (estimator theta = 0.77). Therefore, clusters I and II are reproductively isolated. The distribution limit of these two (sibling) species does not correspond to those of the morphological species of Trichomycterus identified in this region: the epigean T. cf. barbouri and the hypogean T. chaberti. However, hypogean fish exhibited two mtDNA haplotypes, a private one and another shared with the epigean Trichomycterus from upstream reaches

Hydropower and the future of Amazonian biodiversity

In an effort to ensure energy independence and exploit mineral resources, the governments of Amazonian countries are embarking on a major dam building drive on the basin’s rivers, with 191 dams finished and a further 246 planned or under construction. This rush to harvest the basin’s vast renewable energy capacity has come without proper consideration of the likely negative environmental externalities on the world’s most speciose freshwater and terrestrial biotas. Here we highlight the economic drivers for hydropower development and review the literature to summarise the impacts of dam building on Amazonian biodiversity. We identify both direct and indirect impacts through the anticipated loss, fragmentation and degradation of riparian habitats. We then propose a series of measures to assess, curb and mitigate the impacts of destructive dams on Amazonian biodiversity

The Silent Threat of Non-native Fish in the Amazon: ANNF Database and Review

Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limited information is available for the Amazon Region. In this study we review NNF data in the Amazonian macroregion using spatiotemporal records on the occurrence and the richness of NNF from a collaborative network of 35 regional experts, establishing the Amazon NNF database (ANNF). The NNF species richness was analyzed by river basin and by country, as well as the policies for each geopolitical division for the Amazon. The analysis included six countries (Brazil, Peru, Bolivia, Ecuador, Venezuela, and Colombia), together comprising more than 80% of the Amazon Region. A total of 1314 NNF occurrence records were gathered. The first record of NNF in this region was in 1939 and there has been a marked increase in the last 20 years (2000–2020), during which 75% of the records were observed. The highest number of localities with NNF occurrence records was observed for Colombia, followed by Brazil and Bolivia. The NNF records include 9 orders, 17 families and 41 species. Most of the NNF species are also used in aquaculture (12 species) and in the aquarium trade (12 species). The most frequent NNF detected were Arapaima gigas, Poecilia reticulata and Oreochromis niloticus. The current data highlight that there are few documented cases on NNF in the Amazon, their negative impacts and management strategies adopted. The occurrence of NNF in the Amazon Region represents a threat to native biodiversity that has been increasing “silently” due to the difficulties of large-scale sampling and low number of NNF species reported when compared to other South American regions. The adoption of effective management measures by decision-makers is urgently needed and their enforcement needed to change this alarming trend and help protect the Amazon’s native fish diversity.