Convergent responses of fish belonging to different feeding guilds to sewage pollution

ABSTRACT

This study aimed to evaluate if the presence of pollutants promotes changes in feeding habits of fish species from different trophic guilds: the detritivorous species, Hypostomus francisci, and the piscivorous, Hoplias intermedius. Both species were sampled at 12 sites (with different degrees of pollution) in the Rio das Velhas basin, which is heavily polluted by domestic and industrial sewage from the Metropolitan Region of Belo Horizonte (MRBH). Stable isotope analyses of carbon (δ¹³C) and nitrogen (δ¹⁵N) of fish tissue and the main food resources were performed. Fishes from both trophic guilds altered their diets in degraded environments, but the detritivorous species showed greater trophic plasticity. The isotopic niche of both trophic guilds was broadest in unpolluted sites and more δ¹⁵N enriched in polluted regions. The detritivorous species presented high niche-breadth in unpolluted sites, probably due to the greater variety of resources consumed. In addition, the δ¹⁵N of the detritivorous was more enriched than the piscivorous species in polluted sites. In conclusion, fishes from both trophic guilds presented similar isotopic responses to environmental pollution. However, the detritivorous species was more sensitive to these alterations and therefore, is likely a better indicator of environmental condition than the piscivorous.

Keywords:
Detritivorous; Hoplias intermedius; Hypostomus francisci; Piscivorous; Stable isotopes