Insects in the diet of fish from Amazonian streams, in western Pará, Brazil

Abstract

In the present study we evaluated the contribution of insects, in particular aquatic forms, to the diet of Amazonian stream fish in western Pará, Brazil. The fish and insect fauna of 10 streams were sampled in the Tapajós National Forest. The fish consumed a diversity of nutrients of terrestrial and aquatic origin (algae, sediments, terrestrial and aquatic insects, fish), confirming that most are generalists. In the case of the species that fed exclusively on aquatic insects, a comparison of the diets with the availability of prey indicates that the fish do not forage selectively. Only 5 of the 21 species analysed fed exclusively on aquatic insects, and only 3 of these were taxon selective. Fifteen species consumed terrestrial insects, but did not feed exclusively on these organisms. This flexible feeding behaviour guarantees survival when preferred resources are scarce or absent. The results of the present study reinforce the importance of riparian forest in the feeding ecology of stream fish, because this habitat provides terrestrial insects and influences the occurrence of aquatic insects. The diversity of the Amazon region is reflected in that of local communities, and the present study provides important new data on the diet of the stream fish communities of western Pará.