Fontes autotróficas de energia e dieta de Characiformes Juvenis em herbáceas aquáticas do Rio Solimões/Amazonas

Abstract

Aquatic macrophyte communities are important environments in aquatic ecosystems in that they produce a great quantity of organic material and are also indispensable for the initial development of many fish species particularly the migrating Characiforms. In order to evaluate this a total of 1181 Triportheus angulatus, Brycon amazonicus, Semaprochilodus insignis and Mylossoma duriventre specimens captured among the macrophyte stands were examined. They varied from 15 to 60mm standard length. Stomach contents and carbon and nitrogen isotopes of these specimens were analysed in order to determine their principle prey, their energy sources and their position in the food chain. In the smaller fish links between the producers were principally insects and zooplankton. As they grew the four species incorporated different items in their diet in different manners. Based on the carbon isotope analyses it was possible to confirm that the C3 plants are the most important plant group for these young fish. It was observed that in this development stage the Characiforms alternate their energy sources between more and less negative as they grow. The greatest difference in trophic position was observed in the juveniles of S. insignis whose diet consisted principally of detritus. The other species occupied positions between the first and second trophic level. A combination of the results obtained here shows that herbaceous aquatic macrophytes in the floodplain of the Solimões/Amazon River are essential for the development of fish species in the first stages of their lives.