Flood pulse influence on the feeding ecology of two Amazonian auchenipterid catfishes

Abstract

We assessed the flood pulse effect on the diet composition, trophic niche breadth, and the amount of food intake of two Amazonian auchenipterids with different feeding strategies. Sampling was carried out quarterly (from April/2012 to January/2014) on the middle Xingu River, using gillnets. We measured specimens for standard length and total weight. The specimens’ stomachs were removed, weighed, and had their contents identified. We analyzed 360 stomachs of Auchenipterus nuchalis and 584 of Tocantinsia piresi. The diet of A. nuchalis was mainly composed of aquatic insects and crustaceans, while T. piresi fed on fruits and seeds. The diet composition of both species varied seasonally, but only T. piresi changed its trophic niche breadth in response to hydrological changes, becoming more specialist during the higher water periods (filling and flood). Both species also showed differences in their amount of food intake between hydrological periods, with A. nuchalis feeding more intensely in lower water periods (ebb and dry), while T. piresi in the higher water periods. We evidenced different responses to the hydrological periods for the related species. We emphasize that studies considering the relationship between flood pulse and feeding ecology of the organisms are essential to understanding river floodplain systems’ dynamics.

First Record of Spinal Deformity in the South American Silver Croaker Plagioscion squamosissimus (Eupercaria: Sciaenidae) in the Xingu River, Brazil

“…Specimens were collected in the middle Xingu River region (Pará, Brazil) from December 2020 to November 2021, using gillnets with different mesh sizes. This section of the Xingu River Basin, commonly referred to as "Volta Grande do Xingu" (3 • 25 33.0 S, 51 • 57 03.3 W) (Figure 1), is of great ecological significance and recognized for its clear water and high flow, which runs over a bedrock, harboring a diverse flora and fauna [15]. However, this region is affected by the Belo Monte Dam, resulting in a 100 km stretch of reduced water flow and an 80% reduction in the overall flow.…”

Feeding ecology of Moenkhausia collettii (Steindachner, 1882) (Characiformes: Characidae) in streams in the eastern Amazon: Environmental factors and body size

“…Hydrological variation is considered the primary predictor of fish ecology in the tropics, including their feeding dynamics (Winemiller & Jepsen, 1998). In large Amazonian rivers, fish diet is strongly influenced by predictable and unimodal seasonal variations in water levels, known as flood pulses (Freitas et al, 2022; Junk et al, 1989). The periodic expansion of aquatic ecosystems results in floodplains rich in nutrients, exhibiting high availability and heterogeneity of food resources extensively utilized by fish species (Goulding, 1980; Lowe‐Mcconnell, 1999).…”

Effect of logged forests on diet of small characids from Neotropical streams

“…This is of great concern because Amazonian riparian cover has been modified by conversion of forest to pasture, agro‐industrial plantations and especially for timber harvesting (Marengo et al, 2018). In the Amazon, studies on fish trophic ecology have been conducted (Benone et al, 2020; Catarino & Zuanon, 2010; Freitas et al, 2022; Mendonça et al, 2005; Moraes et al, 2013; Sabino & Zuanon, 1998), but with a special focus on flood pulse effects or spatial–temporal variations. However, there is a lack of information linking fish diet with riparian cover in small streams.…”

“…This study aimed to compare the food items consumed by small characid species between streams with pristine and logged riparian cover. Small characids comprise the most representative group of fish in small Amazonian streams, occurring in a wide range of microhabitats and exhibiting a variety of feeding strategies (Freitas et al, 2022). Logging activities can be performed following two approaches (Calvão et al, 2016): In conventional logging, vegetation is removed without silviculture practices; on the other hand, selective logging maintains protected buffers along the streams.…”