Spatio temporal variations in <em>Pimelodus ortmanni</em> (Siluriformes, Pimelodidae) feeding in Segredo reservoir and contigous areas (PR)

Abstract

The aim of this paper is to investigate the diet of Pimelodus ortmanni in Segredo reservoir and contigous areas in three different periods after the reservoir formation (Iguaçu river, state of Paraná, Brazil). The samples were collected from March/93 to February/96 in the reservoir, tributaries and downstream. A total of 808 stomachs were analyzed by occurrence and volumetric methods combined in the food index. The species was characterized as omnivorous-carnivorous due to the ample food spectrum (41 items), though fishes and insects prevailed in the diet over the whole investigated time. In the first and second periods allocthonous food resources were more expressive than authoctonous resources in the reservoir and downstream, but decreased in the last period. The reverse was observed in the tributaries. The detrended correspondence analysis (DCA) discriminated two spatiotemporal groups in relation to diet: the lower scores grouped fishes coming from downstream (second period) and from the reservoir (second and third periods), while the higher scores grouped fishes from downstream (first period) and tributaries (second and third periods). This segregation may be due to the availability of food resources in the different stations and periods of sampling.