FOOD PARTITIONING AMONG SOME CHARACIDS OF A SMALL BRAZILIAN FLOODPLAIN LAKE FROM THE PARANA RIVER BASIN

Resource partitioning and the seasonal patterns of food intake of four characids (Astyanax fasciatus, A. bimaculatus, A. schubarti and Cheir odon stenodon) were studied during 1988 in a floodplain lake of Mogi-G uacu River, Sao Paulo State. For interspecific comparisons, data of th e previously studied Moenkhausia intermedia have also been used. A. fa sciatus and A. bimnculatus can be considered omnivorous species, while A. schubarti and C. stenodon are predominantly herbivorous. The river flood cycle (following the wet season October-March and dry season Ap ril-September) seems to influence both seasonal food intake and food o verlap between species. February-March and September-October are proba bly the months of highest food availability, and the months preceding these periods have the lowest resource amount. Our study shows that bo th omnivorous and herbivorous species modified the intensity of their interactions according to this cycle. Omnivorous species maintained fa irly segregated diets when resources were presumably limited, and show ed a rapid change from distinct food niches in the dry season to widel y overlapping ones when resources were presumably more abundant. Conve rsely, the herbivorous species showed higher overlap during the dry se ason. Acute cyclic changes in the environment, as observed in this stu dy, suggest the necessity of small interval sampling in food partition ing studies in tropical freshwater floodplains, in order to understand how species interact and cope with changes in food availability.