Spatial and temporal variation of the diet of the flag tetra Hyphessobrycon heterorhabdus (Characiformes: Characidae) in streams of the Eastern Amazon

ABSTRACT Spatial and temporal variations in streams promote large fluctuations of resource availability, thus affecting the diet of fishes. We evaluated the effects of hydrological periods and stream order within periods on the diet of the flag tetra Hyphessobrycon heterorhabdus. We analyzed 160 stomachs in eight streams ranging from 1st to 3rd order between dry and flood period. Sampled streams belonged to a well-preserved area in the Eastern Amazon. The flag tetra is omnivorous, with a tendency towards insectivory. During the dry period, the species exhibited a higher amount of autochthonous than allochthonous items. Fish consumed more allochthonous items in 1st and 2nd order streams in the dry period and in 1st and 3rd order streams in the flood period. These results reflect the interactions between temporal and longitudinal factors on resource availability and its influence on fish diet. This pattern is probably dependent on the extensive riparian vegetation as a direct and indirect source of food for stream fish.