Padrões temporais na dieta do bagre Auchenipterichthys longimanus: efeito da regeneração de um igapó amazônico e especialização

Abstract

The trophic ecology of Auchenipterichthys longimanus (Günther, 1864) in Lake Batata was studied in annual campaigns in the flood period, in a long time series. The data base of this study consisted of the qualitative and quantitative analysis of the stomach contents of 303 fish specimens collected with standardized sets of nets in two areas: one impacted by bauxite tailings (area with tailings) and another a pristine area (natural area). We used comparisons between dietary habits, food intensity, richness and composition of food items, niche width and body condition of A. longimanus in order to discuss the patterns exhibited in the areas with reject and natural, as well as to evaluate the variations of these parameters along the regeneration of the igapó, under the influence of the interannual variation of the level of flood in the lake (Chapter I). The food habit of the populations in both areas was generalist with groups of specialists opportunistic individuals. The food intensity was smaller and heterogeneous in the area with tailings and did not present increase under the influence of the igapó regeneration. Richness was similar between areas and did not increase under the influence of igapó regeneration. The composition of food items between areas was similar, but items was consumed in different proportions. The consumption of autochthonous and allochthonous items between areas was different and the natural area varied under the influence of flood level. When evaluating the area with tailings, during the 24 years of igapó regeneration, the structure of items consumed became similar to the natural area. The niche amplitudes between areas were similar, but when we observed over the years in the area with tailings, there was increase under the influence of flood level. The body condition of the species was maintained without significant differences between the different areas, temporarily. We also present data analyzed with the objective of describing qualitatively the diet of the population collected in the natural area, over 15 years comparing the intrapopulational aspect individual specialization, through the diet of 113 specimens (Chapter II). We conclude that in terms of individual specialization the composition of the diet varied temporarily, but the individual specialization (SI) was consistently high in all the years. Regarding the variations associated with the recovery of the igapó, we concluded that the species presented food plasticity, which was reflected in the absence of variation in the body condition and showed to be indicative of the recovery of the igapó