Trophic ecology of Loricariichthys anus (Valenciennes, 1835), (Loricariidae: Loricariinae) in a subtropical reservoir, Rio Grande do Sul, Brazil

Abstract

The paper describes the trophic ecology of the Loricariichthys anus in a subtropical reservoir. The specimens were collected in the reservoir of the Chasqueiro stream, in Rio Grande do Sul, Brazil. The digestive tract of each specimen was removed for the analysis of the contents and defi nition of the diet. The Index of Relative Importance (IRI) was used to estimate which types of prey were most important. The diet of the L. anus population was compared among different water levels, seasons, ontogenetic classes, feeding strategy and fractional trophic level. There was a signifi cant difference between hydrological levels, although no signifi cant variation was found in the composition of the L. anus diet between seasons or among ontogenetic classes. This is probably due to the fact that L. anus is a specialist species, with a diet composed predominantly of fi ne particulate material. At the trophic level, the diet of the species was based on detritus, which refl ects the morphology of its body and digestive tract. Considering these fi ndings, L. anus may be a keystone species in the Chasqueiro reservoir and its conservation, in both natural and artifi cial environments, is necessary for the bottom-up management of this and other Neotropical ecosystems.