We evaluated the factors that affect the food resource use by Plagioscion ternetzi using three approaches: spatial, seasonal, and ontogenetic changes. Fish were sampled between March 2000 and February 2001 and March 2003 and February 2004 in the Sinhá Mariana and Chacororé lagoons, wetlands of the Pantanal Matogrossense. Fish was the predominant food in the diet, but shrimps and insects have been also consumed. The diet of P. ternetzi was significantly different between lagoons, but no difference was detected between dry and flood periods. In Sinhá Mariana lagoon, the diet mainly consisted of Psectrogaster curviventris, in both periods. In the flood period in Chacororé lagoon, fish was the dominant food (especially Astyanax spp., Leporinus spp. and Schizodon borellii), and in dry, shrimp and Eigenmannia spp. The Spearman coefficient indicated no correlation between the abundance of caught fish species and their abundances in the diet of P. ternetzi in Sinhá Mariana lagoon, and a strong negative correlation at Chacororé lagoon, although some very consumed preys were numerically abundant in the environment. Despite the intake of insect and shrimp, P. ternetzi was piscivorous since immature stages. A correlation between each item and the size classes of P. ternetzi was tested by means of Pearson correlation that showed that the changes in the use of resources over ontogenetic development have been represented by increased intake of P. curviventris in Mariana lagoon, and S. borellii at Chacororé lagoon, accompanying the increase in the size of the predator. In this way, the results suggest that several factors can be involved in the use of food resources by P. ternezi, among them the abundance, the size and morphological characteristics of the prey.
Chacororé lagoon; Diet; Plagioscion ternetzi ; Sciaenidae; Sinhá Mariana lagoon