Effects of feeding levels of types of preys on growth and survival of "curimbatá” Prochilodus scrofa (Steindachner, 1881) larvae fed Brachionus plicatilis and natural zooplankton

Abstract

Growth and survival of curimbatá Prochilodus scrofa larvae were examined in the laboratory in relation to three feeding levels, during three experimental periods lasting 21 days each one. The initial daily rations consisted of 300 (R1 and PS1), 450 (R2 and PS2) and 600 (R3 and PS3) organisms.larva^-1.day^-1 of the rotifer (R) Brachionus plicatilis and wild zooplankton (PS). Mean survival rates of the R larvae were high (more than 60%) and not related to feeding levels, although these levels influenced the larval growth. This influence was more evident in the treatments with the lowest survival rates and the highest prey densities which correspond to R3 treatments of the 1^st and 3^rd periods. Among the larvae fed wild zooplankton, those of the 1^st period showed considerably lower mortality than those of the 2^nd and 3^rd ones and it seems to be related to the diversity of the zooplankton composition offered to the larvae in that period, which was constituted mainly of Brachionus sp. rotifers. This fact suggests that "curimbatá" larvae may be selective predators, at least for the first days of exogenous feeding.