A influência do manejo de lagos e de características ambientais sobre as assembleias de peixes de lagos de várzea do baixo rio Purus, na Reserva de Desenvolvimento Sustentável Piagaçu-Purus,Amazonas

Abstract

Floodplain lakes play an important function in the aquatic ecosystem productivity, contributing to high fish diversity and fishery productivity of the Amazon basin. The Purus river, due to its high productivity, has a major role on the fish landed in Manaus, although fishing effort has been concentrated in a few species with high commercial value, resulting in situations of overexploitation. In this sense, the management of fishing resources is necessary both for the conservation of aquatic environments and the maintenance of an activity of outstanding social and economic importance to the traditional Amazon population. Besides the use, many studies consider that communities organization is determined by abiotic factors and biological interactions. Therefore, the aim of this study was to evaluate the effect of lakes management and environmental characteristics on the attributes of fish assemblages of Purus river floodplain lakes. Samples were taken between October and November 2009 in 20 lakes included in lowland areas Caua-Cuiuanã and Itapuru, located at northern region of the Piagaçu-Purus Sustainable Development Reserve (RDS-PP), area influenced by the interfluve of Solimões-Purus rivers. For each lake we used a gill nets batteries with meshes of 30, 40, 60, 80, 100 and 120 mm (between opposite knots) and 10 meters long each, exposed for 4 hours and searched in periods of 1 hour at dusk. Also nine environmental parameters were sampled for each lake: surface area, perimeter, transparency, depth, euphotic zone, electrical conductivity, total nitrogen, total phosphorus and the relationship between nitrogen and phosphorus. Were sampled 2295 individuals belonging to 77 species, 21 families and six orders. Characiformes and Siluriformes were the most significant orders in richness and abundance, following the pattern found in similar studies in the Neotropics. It was found that fish assemblages are influenced by the kind of use (use or protection), and by the environmental characteristics conductivity and depth. Therefore, the management of the lake-sectors Caua Cuiuanã Itapuru at RDS-PP, is proving to be effective with respect to the resources conservation and sustainable use. The lakes chosen for protection were based on the traditional knowledge of the community in historical, logistic and cultural factors, and were shown to be the lakes with the more favorable environmental conditions for the fish fauna.