A macrófita aquática invasora Hydrilla verticillata como local de forrageamento para peixes de pequeno porte.

Abstract

Aquatic ecosystems have been colonized by many non-native species around the world and these issues are considered threats to several ecosystems. Hydrilla verticillata had recently invaded the upper Paraná River floodplain, and it was found co-occurring with the native Egeria najas in a secondary channel of the river. In this rare opportunity we assessed the invasive macrophyte (H. verticillata) as foraging habitat for small fish species. Fish were sampled in mono-specific patches of H. verticillata and of E. najas, using floating Plaxiglas traps (minnow traps type). The native species, whose life form is similar to H. verticillata, was used as control. Were assessed the feeding activity and the composition and overlap diet. Fish feeding activity, assessed by mean stomach fullness, did not differ significantly between H. verticillata and E. najas, showing that invasive macrophyte species did not affect the foraging efficiency. On the other hand, the PERMANOVA showed that the diet composition of five out of six fish species was significantly different between the patches of H. verticillata and E. najas, suggesting that the invasive and native macrophyte can provide different types of food resources for the fishes. The diet overlap values indicated food segregation among the fish species for both macrophytes. The results indicate that the foraging efficiency was not affected, but the diet composition was affected by the invasive macrophyte, probably as a result of the difference in the food availability provided by both macrophytes. Despite differences in diet composition, we infer that H. verticillata provides favorable feeding habitat for small fish species, because the feeding activity was similar in both macrophytes.