Trace element accumulation in different edible fish species from the Bolivian Amazon and the risk for human consumption.

Artisanal mining and erosion of metalbearing soils can contaminate aquatic ecosystems and affect the health of riparian human populations, through metal bio-accumulation processes and fish consumption. Concentrations of eight trace metals (Cd, Cr, Co, Cu, Pb, Hg, Ni, Zn) and a metalloid (As) were measured in the muscle tissue of different edible fish species collected from markets of two cities along the Beni River banks, in the Bolivian Amazon. Relationships between the size of fish belonging to different trophic levels (carnivores, omnivores, detritivores and herbivorous) from four different fishing zones were analyzed. The most relevant results corresponded to the detritivore group, whose members exhibited significant positive correlations between the fish size and the concentration of three metals (cadmium, cobalt and nickel). Furthermore, a 3 × 3 scenario-risk analysis was performed to assess local risk for human health. This was done by relating three different scenarios of local fish consumption collected from literature (maximum, average and minimum) and three different levels of trace element concentrations (95th, 50th and 5th percentile) derived from the present study and the Minimal Risk Levels suggested by the Agency for Toxic Substances and Disease Registry. Results of these calculations determined the amount of fish muscle per contaminant that could be consumed per day without risking human's health. Finally, Target Hazard Quotients were calculated for each trace element, aiming to indicate the potential exposure to each one and the concentration at which no adverse effects are expected. The obtained results made clear that mercury is the only trace element that represents an important health risk to humans within the studied region, considering most of the combinations in the 3 × 3 analysis. Chronic mercury intoxication could occur when consumption of fish in Riberalta or Rurrenabaque exceeded 83 g/day in females and 110 g/day in males.

Assessing two hundred years of taxonomic doubt with the rediscovery and taxonomic establishment of the Amazonian armored catfish Hypostomus pantherinus Kner 1854 (Siluriformes: Loricariidae).

Hypostomus pantherinus was described by Kner in 1854 based on a single young specimen collected by Natterer with a type-locality just asserted as Guapor. No robust scientific paper focusing the distribution, taxonomy and ecology of this species has been published since the description. Here, based on the analysis of the holotype, recently collected material, and on an extensive searching on ichthyological fish collections, H. pantherinus Kner 1854 is redescribed and its geographical distribution is established to be in the rio Itez-Guapor and the mouth of its Bolivian and Brazilian tributaries. Hypostomus pantherinus is distinguished from congeners mainly by villiform teeth, conspicuous black, sharp and widely spaced spots on head, and dark blotches on trunk and fins, keels along lateral series of plates, sharp crests on supraoccipital and on compound pterotic-supracleithrum, less than 25 spots on compound pterotic-supracleithrum, one blotch per interradial membrane along each row on dorsal fin, and by usually attaining about 160 mm SL in size.

The combined effects of climate change and river fragmentation on the distribution of Andean Amazon fishes.

Upstream range shifts of freshwater fishes have been documented in recent years due to ongoing climate change. River fragmentation by dams, presenting physical barriers, can limit the climatically induced spatial redistribution of fishes. Andean freshwater ecosystems in the Neotropical region are expected to be highly affected by these future disturbances. However, proper evaluations are still missing. Combining species distribution models and functional traits of Andean Amazon fishes, coupled with dam locations and climatic projections (2070s), we (a) evaluated the potential impacts of future climate on species ranges, (b) investigated the combined impact of river fragmentation and climate change and (c) tested the relationships between these impacts and species functional traits. Results show that climate change will induce range contraction for most of the Andean Amazon fish species, particularly those inhabiting highlands. Dams are not predicted to greatly limit future range shifts for most species (i.e., the Barrier effect). However, some of these barriers should prevent upstream shifts for a considerable number of species, reducing future potential diversity in some basins. River fragmentation is predicted to act jointly with climate change in promoting a considerable decrease in the probability of species to persist in the long-term because of splitting species ranges in smaller fragments (i.e., the Isolation effect). Benthic and fast-flowing water adapted species with hydrodynamic bodies are significantly associated with severe range contractions from climate change.

A database of freshwater fish species of the Amazon Basin.

The Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation.

Fragmentation of Andes-to-Amazon connectivity by hydropower dams.

Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems-the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.

Age and growth of the Amazonian migratory catfish Brachyplatystoma rousseauxii in the Madeira River basin before the construction of dams

The goliath catfish Brachyplatystoma rousseauxii has crucial economical and ecological functions in the Amazon basin. Although its life history characteristics have been studied in the Amazon, there is little information in the Madeira River basin, which holds genetically distinct populations and where dams were recently built. Using fish collected in Bolivia, Brazil and Peru, this study provides a validation of growth rings deposition and details the growth patterns of B. rousseauxii in the Madeira before the dams' construction. Age structure and growth parameters were determined from 497 otolith readings. The species exhibits two growth rings per year and sampled fish were between 0 and 16 years old. In the Brazilian portion of the basin, mainly young individuals below 5 years old were found, whereas older fish (> 5 years) were caught only in the Bolivian and Peruvian stretches, indicating that after migrating upstream to reproduce, adults remain in the headwaters of the Madeira River. Comparing with previous publications, B. rousseauxii had a slower growth and 20 cm lower maximum standard length in the Madeira River than in the Amazon River. This study provides a baseline for future evaluation of changes in population dynamics of the species following dams closure.(AU)

Brachyplatystoma rousseauxii é um bagre de importante papel econômico e ecológico na bacia amazônica. Embora existam estudos acerca de sua história de vida na Amazônia, há pouca informação para a bacia do rio Madeira, onde existem populações geneticamente distintas e recentemente foram construídas duas usinas hidrelétricas. Este estudo validou a deposição das marcas de crescimento e detalhou os padrões de desenvolvimento dessa espécie no rio Madeira, antes da construção das barragens. As coletas abrangeram os territórios brasileiro, boliviano e peruano, com estrutura etária e parâmetros de crescimento determinados a partir de 497 otólitos. Foram observadas duas marcas de crescimento por ano e indivíduos entre 0 e 16 anos. Na porção brasileira foram encontrados principalmente jovens menores de 5 anos, enquanto que os peixes mais velhos (> 5 anos) foram capturados apenas na Bolívia e Peru, indicando que após a migração reprodutiva, os adultos permanecem nas cabeceiras do rio Madeira. Comparando com estudos prévios realizados na calha principal do rio Amazonas, B. rousseauxii apresentou crescimento mais lento e comprimento padrão máximo inferior de 20 cm no rio Madeira. Este estudo fornece uma base para a avaliação futura das mudanças na dinâmica populacional desse espécie após o implementação das barragens.(AU)