Unravelling a specialised diet of an Amazonian catfish in a controlled flood-pulse area by combining stomach-content and stable-isotope analyses

Abstract

Context Hydrological dynamics are crucial in fish ecology. Aims To evaluate the effect of the flood pulse on the feeding ecology of Doras higuchii in the reduced-flow section of the Belo Monte dam, Xingu River, Brazil. Methods Collections were conducted between December 2020 and November 2021. The fish were measured and had their stomachs removed. Muscle tissue was also extracted for stable-isotope analysis. Stomach contents were inspected to assess diet, testing the influence of hydrological periods by using GLM. In addition, we evaluated the effect of the flood pulse on the δ13C and isotopic ratios of individuals Results In total, 362 specimens of D. higuchii were analysed, highlighting a diet mainly on the basis of sediment (74.9%) and aquatic insects (24.8%), not varying between periods characterising the species as a specialist for having detritivorous habit, as well as the extension of the trophic niche. There was variation in food intensity, with higher average food consumption in the flood period. The isotopic composition (δ13C and δ15N) also did not differ between periods. Finally, δ15N did not vary by length class. Conclusions This information helps understand the interface between environmental and biological factors in an environment affected by a hydroelectric dam. Implications Our results may help fill gaps in knowledge about the diet of doradid fishes.