Habitat heterogeneity on feeding habit of two sympatric and congeneric characidae fishes in two tropical reservoirs

Jorge L. Nessimian,Ana Carolina I. M. Dias,José Henrique C. Gomes,Vanessa G. Lopes,Christina W.C. Branco,Elidiomar R. Da-Silva,Leonardo C. Souza

doi:10.1590/1678-4766e2016012

Abstract

Abstract Food flexibility and omnivory are important features pronounced in Neotropical freshwater fish species, particularly for Astyanax species. Traditionally most fish diet resources are known to be originated in the aquatic environment, however recent studies have pointed to the importance of allochthonous sources. Besides, the colonization of macrophytes, common at several tropical reservoirs, may enhance insectivory in fish diet expanding or concentrating the area of available resources for feeding. Here we employed stomach contents analysis of two sympatric Astyanax species to access the importance of habitat differentiations as spatial complexity in two tropical reservoirs with different environmental features. The NMDS analysis indicated separation in the diet of these species between reservoirs (Stress= 8.28%). Additionally, analysis of variance revealed a significative difference in the volume of food itens ingested between the reservoirs (Anova one-way F(1, 132)=4.4446; p= 0.037). This points out the importance of environmental conditions on the composition of the diet of fishes. This study highlighted the insectivorous feeding habit of Astyanax species and revealed different feeding strategies between sympatric fishes despite high niche overlap in both environments. Habitat heterogeneity increasing food resources availability plays an important role in the diet strategy of these Astyanax species and on their constant maintenance in the two different reservoirs.

Highlights

Trophic interactions and quantifying spatial and temporal variability in fish diet remains a challenge for ecologists (Scheffer & Carpenter, 2003; McCann et al, 2005)
Food flexibility and omnivory are important features pronounced in Neotropical freshwater fish species (Lowe-McConnell, 1999; González-Bergonzoni et al, 2012)
The food variety in the tropics can be associated with environmental conditions of the aquatic ecosystem

Summary

Introduction

Trophic interactions and quantifying spatial and temporal variability in fish diet remains a challenge for ecologists (Scheffer & Carpenter, 2003; McCann et al, 2005). Astyanax species have a great ecological importance in the trophic web of fish community in reservoirs (Loureiro-Crippa & Hahn, 2006; Wolff et al, 2009) linking nutrients and carbon sources available in marginal areas to the limnetic food chain. The colonization of macrophytes in many reservoirs may enhance aspects of invertivory in fish diet (Pelicice & Agostinho, 2006) expanding or concentrating the area of available resources for feeding. We employed stomach contents analysis to access the importance of habitat differences as spatial complexity for Astyanax feeding in two tropical reservoirs with different environmental features. Given the differences between these reservoirs, and based on aspects mentioned above we predicted that the environment where fishes inhabit will control the composition of the diet (niche width) influencing the trophic relation between the sympatric species (niche overlap) more than seasonality

Methods

Results

Conclusion