In this study, three densities 1,000, 1,500 and 2,000 ind./m2 were experimented in order to identify a suitable density for rearing rainbow trout from the stages of larvae to fry. Results showed that rearing densities had strongly effects on growth and survival rates of rainbow trout. In which, the fish reared at the density of 1. 000 ind./m2 gave a higher absolute and relative growth rate (0.21 g/ind./day
85.5 percent) compared to the density of 1,500 ind./m2 (0.17 g/ind./day
75.9 percent) and 2,000 ind./m2 (0.16 g/ind./day
73.9 percent) (P 0.05). Similarly, the fish reared at the density of 1,000 ind./m2 attained the higher weight gain (4,62 +/- 0,19 g/ind.) compared to the density of 1,500 and 2,000 ind./m2. However, there was no significant difference in weight gain between the density of 1,500 (3.73 +/- 0.21 g/ind.) and 2,000 ind/m2 (3,39 +/- 0,22 g/ind.). The fish reared at the densities of 1,000 and 1,500 ind./m2 (95.5 and 93. 7 percent) obtained a higher survival rates compared to the density of 2,000 ind./m2 (89.0 percent) (P 0.05). From the results of this study, it can be suggested that the suitable density for rearing the rainbow trout at the stage of larvae to fry was 1,500 ind./m2 for optimizing the rearing efficiency.