Composição e estabilidade temporal de assembleias de peixes em igarapés de cabeceira na bacia do rio Xingu

Abstract

The Amazon basin harbor to a complex system of small watercourses, known regionally as igarapés. These small streams are highly dependent on the availability of rain in their drainage areas, which makes them sensitive to the environmental changes taking place on the planet. Recent studies indicate that ichthyofauna amazonian presents a low resistance and resilience to climate change, being sensitive to abrupt climate changes, such as extreme and gradual droughts, such as increased precipitation and frequency of stormy. Faced with the fragility of this ichthyofauna and the climatic models that predict the increase in the frequency and intensity of extreme events, it is essential to identify the effects of these events on these assemblies in order to develop efficient conservation strategies. In this study, we verified whether there are differences in the composition of the fish assemblages of terra-firme perennial streams between periods of drought and rain, and we assessed the effects of the flow interruption caused by a severe drought on the ichthyofauna of 12 streams of terra-firme in the Xingu river basin, in the Brazilian East Amazon, between 2012 and 2014. At the end of the dry period of the first year of sampling, six streams dried up completely or were reduced to disconnected puddles of water. It was found that the fish assemblages of the perennial streams present stability in their structure over time, not differing between periods. On the other hand, the fish assemblages of the streams that dried up took on a new configuration after the temporary interruption of the flow. Most of the changes detected were transient, however, some persisted after the flow resumed. Together, these results indicate that severe drought events can change the composition of fish species in headwater streams and that such changes may persist in the medium term (years).