Juvenile silversides (Odontesthes regia Humboldt, 1821) reared in a sea net pen system performed well and adapted rapidly to this type of confinement. Values obtained for growth and mortality parameters in a period of 12 months, are similar to those observed in other marine fish cultured at industrial levels. The value of SGR obtained for the whole period (0.57), was similar to the value obtained in trials with juvenile rainbow trout using 20% replacement of fishmeal with white lupin meal (Lupino albus), over a period of 6 months (SGR=0.58), but lower in relation to trials performed with red tilapia fry (Oreochromis aureus x Oreochromis niloticus) fed with coffee pulp diet (20% fishmeal replacement) where SGR was 1.51, or when compared with Japanese seabass (Lateolabrax japonicus) fed with rations based on 30% fishmeal replacement with soybean meal (SGR=2.98) over a 153 days trial. Mortality rate observed during the 12 months for the marine silverside reared in sea net pens, was in the range of typical values observed for rainbow trout reared in freshwater (17,9 % in 14 months), or for Atlantic salmon in freshwater (22 % from egg to smolt in 13 months); but lower in relation to mortality observed on Japanese seabass (50.7 %) and red tilapia (34,5 %), where the experimental period was about half of Odontesthes regia.