Temporal and ontogenetic diet changes of omnivorous fish in an impacted (reservoir) and in a natural environment (lagoon) - DOI: 10.4025/actascibiolsci.v29i4.878

Abstract

Temporal and ontogenetic changes in the diet of Pimelodus maculatus were assessed in the Manso Reservoir and Sinhá Mariana lagoon, Mato Grosso State. Fishes were collected monthly from March/2000 to February/2001 by gillnets and seining. Stomach contents (N = 199) were analyzed by volumetric method. In the reservoir, P. maculatus consumed mainly insects, whereas in the Sinhá Mariana lagoon it was more generalist, feeding on similar proportions of higher plant, fish and scale. Terrestrial food was important in the reservoir, whereas aquatic food was more so in the bay. In the reservoir, the diet of P. maculatus was composed predominantly of insects in almost every period, and in all size classes, whereas in the lagoon seasonal and ontogenetic variations in the diet were observed. The results showed that P. maculatus has high trophic plasticity, and it was very opportunistic, consuming the abundant terrestrial food resources, mainly insects, when the reservoir started to flood the surrounding land.