Variação temporal da ictiofauna em igarapés de terra-firme, reserva ducke, Manaus, Amazonas.

Abstract

Temporal variability of fish assemblages between different season along one year and their relationship with environmental factors was investigated in 31 first and second order streams in terra-firme rainforest of Reserva Florestal Adolpho Ducke, in Central Amazonia. Fish were caught with hand and seine nets and stream volume and physical-chemical variables were estimated in 50m sections in each stream in each survey. The average richness and number of individuals captured per section were lower in the rainy season, contrasting with previous studies that detected no significant differences between seasons. Fish assemblage composition showed strong seasonal tendency, based mainly on seasonal variations in abundance of common species, possibly related to lateral moves of fish species to temporary ponds adjacent to streams in the rainy season. Water quality and substrate diversity showed seasonal tendencies, but these were not related to fish assemblage composition. Comparisons of assemblage composition between the years 2001 and 2006 revealed the maintenance of general assemblage structure based on common species, and large change in composition of less-abundant species. Common species were highly detectable in surveys and confer consistent spatial structure to the assemblage, which is predictable along environmental gradients and throughout the year. The assemblage structure based on abundances of common species should be the main focus of biodiversity monitoring programs on terra-firme streams, unless the focus of the study is on endemism, in which case special attention should be given to the spatial distribution of endemics species.