DIET COMPOSITION, CONDITION FACTOR AND INTESTINAL COEFFICIENT OF THE FISH Astyanax lineatus REFLECT THE ANTHROPOGENIC EFFECTS ON STREAMS IN CENTRAL BRAZIL

Abstract

Human activities, such as urbanization, can cause instability in the aquatic biota. This instability can modify aquatic food resource availability, consequently shifting the diet composition of fish. Because the diet consumed by fish closely affects the anatomy of their digestive tract, it can also alter their intestinal coefficient. In this study, we analyzed the diet composition, condition factor and intestinal coefficient of Astyanax lineatus (Perugia, 1891) from two distinct habitats: a “degraded habitat” (Cabaça stream) in a reserve inside the city perimeter and a “preserved habitat” (Salobra River) in Mato Grosso do Sul State, Central Brazil. We found a total of 15 food items, all of which were found in the urban stream, with a predominance of detritus and Chironomidae larvae, and six in the natural area, with a predominance of plant remains. There was a distinct difference in diet composition between fishes in the two areas ( p < 0.05, PERMANOVA); however, there was no significant difference in inter-individual variability. The most frequent food items were detritus in the “degraded habitat”, while in the “preserved habitat” plant and insect remains were most frequent. The relative condition factor measured by the fish's length-weight relationship was not significantly different between the two habitats. The intestinal coefficient was significantly different between the individuals from each habitat, and it was longer in fish from the natural habitat. Therefore, even though A. lineatus is known to be a generalist species, its feeding plasticity depends on the ecological integrity of the two types of habitats.