Cuidado onde pisa: poças temporárias têm importante papel na ecologia de peixes em igarapés de terra firme na Amazônia

Abstract

Disturbances, either natural or anthropogenic, are common in nature and their effects on biological communities depend on disturbance characteristics, and on organisms’ and landscapes’ attributes. In this thesis, we evaluated the importance of seasonal variation in hydrodynamic characteristics and of temporary environments for the dynamics of fish communities in Amazonian terra-firme forest streams, regionally known as igarapés. Through field studies in Adolpho Ducke Forest Reserve (Manaus, Brazil), we obtained information on temporal variation of fish abundance in stream channel and temporary ponds, as well as details of life-history traits of species and movement patterns of individual fish. In addition, we measured environmental characteristics related to the hydrology of the stream-pond systems and evaluated the responses of the fish to temporal changes in the environment. Based on abundance data and using a community approach, we show that the seasonal use of temporary ponds minimizes the temporal variability of assemblage composition through its effect on the abundance of fish species. We also show that the hydrological fluctuations regulate the distribution of species between the two habitats (temporary ponds and stream channel) and that this abundance partition is strongly associated with the use of different reproductive strategies among fish species. Finally, based on a capture-marking-recapture experiment with a common and abundant species in the stream-pond system (Pyrrhulina brevis, Lebiasinidae), we show that decisions of fish regarding the timing of entry and exit of ponds are based on a refined perception of momentary hydrological conditions, integrating environmental information accumulated over time. The combination of these results indicate that the aquatic environment seasonally available in the riparian zone of terra-firme forest streams comprises an important habitat for several species of fish, with important role in population processes and organization of communities, as well as being a possible agent in the evolution of behavioral and life history traits of fish in this ecosystem.