Manejo alimentar e desempenho de juvenis de robalo-flecha, Centropomus undecimalis (Bloch, 1792) e de beijupirá, Rachycentron canadum (Linnaeus, 1766)

Abstract

The combined effects of feeding frequency and ration size on the growth of laboratory-reared common snook (Centropomus undecimalis) and cobia (Rachycentron canadum) juveniles were evaluated. For the first experiment (named "S") juveniles of snook with a mean weight of 2.55 g (± 0.48) and mean total length of 6.81 cm (± 0.48) were divided into groups of 20 fish and kept in 30 x 50 L experimental units for 60 days. For the cobia experiment ("C") juveniles with a weight of 2.47 g (± 0.12) and total length of 9.55 cm (± 0.18) were divided into groups of 12 fish and kept at 30 x 50 L experimental units for 28 days. In both studies the experimental design was factorial (3 x 3) with three feeding frequencies and three ration sizes, which differed between species. For the snook, 2, 4 and 6 daily meals and ration sizes of 1.0, 2.5 and 4.0% of fish biomass were tested, while for the cobia we tested 1, 3 and 6 daily meals and 3, 6 and 12% of fish biomass. An external control, using the mean food frequency of each experiment (S = 4 and C = 3) and feeding to apparent satiation, was added. There were thus ten treatments with three replicates each. The weight and length of all fish in both studies was measured to adjust the amount of feed to be administered every 15 (S) and 7 days (C). Water quality remained within acceptable levels for both species. For both species, the ration size had a larger effect on the results than feeding frequency. It is recommended to feed common snook juveniles weighing from 1 to 16 g with 4 to 6 meals a day with a ration size between 1.86 and 3.31%, while for juvenile cobia ranging from 1.6 to 38.6 g it is recommended 3 to 6 daily meals with a ration size between 6.16 and 10.51%. In both cases the ration size should decrease according to fish size.