Assessment of natural feeding in larvae, free living fry and fingerlings of silver carp (Hypopthalmichthys molitrix Valenc. in Cuvier and Valenc., 1844) and grass carp (Ctenopharyngodon idella Valenc. in Cuvier and Valenc., 1844)

The diets of silver carp and grass carp have been studied in their early living stages. It resulted that these two species change their feeding habits with age growth. Larvae and free living fry are carnivores since their diet is dominated from animal living beings of plankton. The fingerlings had a mixed feeding regime, but in this stage appears the tendency to consume the vegetal components with prevalence. Relative average composition (μ+S²) % of algae in the diet of silver carp fingerlings was 70.600+5.631. In the diet of grass carp fingerlings this index had the value of 28.15+3.412 in algae and 23.82+2.325 in macrophytes. Larvae and free living fry for two cyprinidae studied, manifested positive selection ability for ciliata, rotifers, nauplii and cladocerans with small size. The dimension of living beings included in the diet go up with the increase of fish size.