Variações temporais e ontogenéticas na dieta de Piabina argentea (Characidae: Stevardiinae) em uma represa de pequeno porte

Abstract

Small impoundments in aquatic environments, such as streams, are commonly found in rural areas. The shift from a lotic to a lentic environment causes structural changes in the channels and substrates, changes in the availability of food resources and the fragmentation of habitats, inducing variations in the taxonomic and trophic structure of fish assemblages. In this context, the goal of the study was to characterize the diet of Piabina argentea in a small impoundment and assess possible temporal and ontogenetic differences in the diet of the species. The research was carried out in a small impoundment located on a first order stream at the Dourados River basin, Mato Grosso do Sul State, Brazil. Food items were analyzed according to volumetric and occurrence frequency methods, whereas the diet was characterized through the Alimentary Index (IAi%). To assess the temporal variation of the species’ diet, food items were divided into rainy (November 2020 and February 2021) and dry season (May and July 2021). To assess ontogenetic variations in the diet, fish individuals were divided into three size classes. PERMANOVA was performed to verify differences in the species’ diet between seasons and size classes. Piabina argentea presented a detritivore-insectivore diet, consuming mainly detritus and Chironomidae larvae. There was a significant difference in the diet of P. argentea between seasons. In the rainy season, the species fed on detritus, seeds, and fragments of aquatic insects, whilst in the dry season there was a predominance of detritus and Chironomidae larvae. The alimentary resources consumed in both seasons were predominantly of autochthonous and undetermined origin. There was a significant difference between size classes and in the interaction between seasons and size classes. In dammed environments, such as the one discussed in this study, it is important to assess fish diet and food resources availability because it helps to understand population dynamics, the interactions between fish community and environment, and their spatial and temporal relations, in addition to support future conservation efforts focused on P. argentea and/or aquatic ecosystems.