Feeding ecology of an Amazonian electric knifefish under altered flood-pulse dynamics caused by hydroelectric damming.

This study evaluated the effects of the controlled flood pulse on diet composition, trophic niche breadth and feeding intensity of Archolaemus janeae, an electric knifefish species with a restricted distribution in the Amazon Basin. Monthly samples were collected from December 2020 to November 2021 in the Volta Grande stretch of the Xingu River, and stomach contents of 134 specimens were analysed. The diet was predominantly composed of aquatic insect larvae, with a notable occurrence of terrestrial plant fragments. Hydrological variation affected diet composition, trophic niche breadth and feeding intensity, indicating temporal shifts in resource use associated with changes in river flow. Feeding intensity was higher during filling and flood periods than during the ebb phase, suggesting that the reduction and regulation of the flood pulse by the Belo Monte Hydropower Plant influenced the diet composition by A. janeae. This study provides the first data on the feeding ecology of this species, highlighting the role of habitat heterogeneity in sustaining fish populations and underscoring the potential impacts of hydropower development on the feeding ecology of Amazonian fishes. Such information is essential for the conservation of A. janeae populations in the Xingu River Basin.