Effect of Seasonality on the Diet of Two Acaris of The Spectracanthicus Genus in the Xingu River, Altamira, Brazilian Amazon

Objective: The objective of this study was to study the effect of variations in the hydrological cycle on the feeding of Spectracanthicus zuanoni and Spectracanthicus punctatissimus. Theoretical Framework: Seasonal variations in water resources may result in changes in the food resources of ichthyofauna, determining the trophic profile of aquatic species dependent on these resources. Characterizing the trophic niche of the species studied may indicate whether the populations have any level of overlap and how this may affect their survival in an environment about to undergo major hydrological changes. Method: They were captured monthly from September 2012 to June 2013, by diving with a compressor, in a stretch of the Xingu River, Pará, near the city of Altamira. Biometrics were performed on the captured individuals, weighed and measured. Their stomachs were removed, weighed, fixed, and preserved in alcohol for later laboratory analysis. The indexes used in the analysis consisted of frequency of occurrence, volumetric and numerical, composing the index of relative importance. Results and Discussion: The analysis of the diet showed that the most consumed item was detritus/sediment, complemented by diatoms, chlorophytes, filamentous algae, invertebrates and sponges. A high degree of specialization in the capture of detritus was characterized. The niche overlap verified by the multivariate analysis did not observe evident niche overlap, being explained by the abundance of available resources. Research Implications: It was inferred that the detritivorous diet of the acaris was not significantly affected by seasonality, and the trophic behavior observed is in accordance with that expected in seasonal changes. Originality/Value: The specialized habit of scraping and sucking the benthic periphyton is what determines a trophic profile specialized in the capture of detritus. Chlorophytes, diatoms and filamentous algae are not very representative in the flood period, being very abundant in the dry season. The consistent use of a detritivorous diet is important information for the survival of the studied ichthyofauna, where the apparent overlap of trophic niche is attenuated by the sharing of abundant resources used by both species.