SEASONAL VARIATION IN THE DIET OF Astyanax aff. paranae EIGENMANN, 1914, IN A RIVER SOURCE IN THE RIVER IVAÍ BASIN

Abstract

Trophic ecology provides the specific ecological characteristics of each organism, such as foraging forms and interrelationships with other organisms. Several ecological factors must be analyzed so that the structure of an ecosystem could be understood. The study of food resources with regard to the origin of sources, relationships with adjacent areas and seasonal variation, may be one of these factors. Current paper quantifies and analyzes the diet of A. aff. paranae between seasonal periods to test the hypothesis that the species´s diet changes in different seasonal periods. The volumetric method was performed and the food index was calculated by comparing diet between the sampled periods. There were differences between periods, especially with regard to food resources in the diet of the species. Resources with the greatest representations during the dry period were those from an autochthonous origin, whilst during the rainy season, they were mainly from allochthonous origin. The formation of creeks during the dry period and the environmental un-forecasting in this type of ecosystem caused a change in the diet and selection of organisms in the environment.