Spatial and temporal patterns of diversity and distribution of the Upper Jurua River fish community (Brazilian Amazon)

We studied spatial and temporal patterns in fish species composition and di versity at the upper Jurua River located in the west Brazilian Amazon. We c ollected with gillnet 822 fishes belonging to 90 species in the main Jurua River, its tributaries and the floodplain lakes during wet and dry seasons. Fish abundance and species richness were greater in the dry season. During that season, fishes may be concentrated due to the low water level, being caught more easily by gillnets. There has been a trend towards a greater fi sh biomass caught in lakes. This might be associated with a greater environ mental stability as lakes may be less subject to large variations in water level. The fish communities differed between the two seasons and between la kes and the lotic environments (main river and tributaries). Fish species f rom the family Curimatidae were most abundant in the lakes, while Pimelodus spp. and Hypostomus spp. predominated in the main Jurua River. Seasonal va riations in fish communities may be related to differences in the migratory behavior among fish species. Such spatial and temporal patterns influencin g fish community structure at the Upper Jurua Extractive Reserve must be ac counted for in management and conservation strategies.