Aquatic insects selected as food for fishes of a tropical stream: Are there spatial and seasonal differences in their selectivity?

PINTO¹, T.L.F. & UIEDA^,2, V.S.

^1,2 Departamento de Zoologia, Instituto de Biociências, CP 510, Universidade Estadual Paulista- UNESP, 18618-000 Botucatu, São Paulo, Brazil.

1 tamaralfp@yahoo.com.br 2 vsuieda@ibb.unesp.br

ABSTRACT: The aim of this study was to examine the existence of feeding preference by insectivorous fish species through the analyses of benthic insects and fish diet. The influence of spatial factors (a "closed" area with riparian vegetation and an "open" area without riparian vegetation) and seasonal factors (dry and wet seasons) on food selectivity was also verified. Of the 14 fish species analyzed, most species were from Heptapteridae (five species) and Loricariidae (three species) families, and most individuals occurred in the dry season and in the open area. Although the insectivory was the predominant feeding habit in all analyzed situations (areas and seasons), the favorite insect groups eaten vary seasonal and spatially. In all cases of high selectivity, the selected insects were not sampled or were collected in a low density in the environment; what emphasizes the existence of a feeding preference. The fact that the majority of fish species ingested the most abundant insect group in a great amount, but with low selectivity, shows that these stream species are opportunistic.

Key-words: benthic macroinvertebrates, ichthyofauna, selectivity, diet, Brazil.