Abstract: Hydroelectric power generated from man-made reservoirs is sometimes regarded as a ‘clean' or environmental friendly energetic source, due to the lack of pollution mainly from liquid and solid effluents. However, several researchers have been claiming that such form of energy production may sometimes generate intense and irreversible environmental impacts, especially when large reservoirs are built in natural tropical regions, which usually have a rich biodiversity of aquatic and terrestrial organisms. Our major goal is to provide a brief review of one dimension of such reservoirs' impacts in a large tropical region: the ecological effects of large dams and reservoirs to fish and fisheries in the Brazilian Amazon rainforest. We also analyzed in detail the ecological effect of Tucurui reservoir on fish and fisheries of the Lower Tocantins River, as a study case. Amazon people rely mostly and sometimes solely on fisheries as their main source of animal protein and cash income. Some of the large reservoirs may had potentially affected this economic activity mainly in the region downstream from the dam, due to changes in the flooding regime, retention of nutrients in the reservoir and blockage of reproductive migrations of economically important fishes. Such effects may generate or enhance poverty in short time, social conflicts and economic isolation of riverside fishing communities, but these problems are less understood than direct changes on fish communities. In a recent survey (2006-2008) in the Lower Tocantins River, interviewed fishers from eight communities mentioned impacts of the Tucurui reservoir, such as decrease in the abundance of fish. Nevertheless, these fishers still maintain a frequent fishing activity, which indicates that at least some commercial fishes have been able to cope with the reservoir effects, some may have even benefited from this, although the composition of fish catches changed compared to pre-impoundment period (before 1985). A possible factor allowing the persistence of fishes and fisheries in this region may be the floodplain with several lakes, which are important fish spawning sites, according to fishers and biological data. This survey also highlights that effects of a large dam may extend far beyond the reservoir itself, and that fishers have a good deal of knowledge about their aquatic environments and changes to it. Also, the potential effects of alleged ‘less impacting' energy production on people and fish should be better acknowledged in political and economic decisions regarding energy issues.

* Project supported and financed by P&D Eletronorte, N? Contract: 4500057477; Project (ANEEL): 018/2005.

Brief Biography of the Speaker:
I have been doing research dealing with artisanal fisheries, fish ecology and ethnobiology since 1994, participating in about 11 research projects conducted in marine, estuarine and freshwater environments in the southeast and northeast Brazilian coasts, as well as the Brazilian Amazon. Currently, I am a research and professor in the department of Ecology of the Federal University of Rio Grande do Sul in Porto Alegre, Brazil. I published about 16 peer-reviewed articles in journals such as Environmental Biology of Fishes, Fisheries Research, Ecological Economics, Hydrobiologia and Aquatic Conservation. I presented either orally or as poster more than 30 abstracts in Brazilian and international scientific meetings.
I have been also reviewing manuscripts to Brazilian and international scientific Journals, such as Environmental Biology of Fishes, Fisheries Research, Human Ecology, Environmental Management and Journal of Ethnobiology.
Since December 2007, I am an official advisor of the International Foundation for Science (IFS) (Sweden), evaluating research projects for funding.