This paper deals with the diet and feeding habitats os three species of "sardinha": Triportheus angulatus, Triportheus elongatus and Triportheus culter, collected at lago do Castanho, a varzea lake in the Central Amazon in an attempt to determine the feeding behavioux of these three species relative to: the regional hydrological and ecological variations, and individual development. A study was also made of the various monphoanatomical structures more closely associated with the particular diet of each species. Based on the food types consumed and field observations ore determined the probable biotopes occupied by the species.