Genetic parameters of growth in rainbow trout, Oncorhynchus mykiss, at early rearing stage.

The heritability response for growth of rainbow trout during early developmental stages was detected on the basis of full-sib and half-sib cross between the selected lines. The experiment was done in Shahid Bahonar Salmon Propagation Center, Kelardasht, Iran. Breeders were taken from the stocks maintained in this station. A bifactorial cross was done between two line using four randomly sire and four randomly chosen dams form each line Analysis of variance revealed a significant difference at 300 days of age between half and full-sib (P 0.026). The effective difference in weight between half/full-sibs of juveniles was not statistically significant on 150 days (P 0.8 I7) and 225 days (P 0.081). No significant difference between mean body weight of male and female half-sib group was found (P 0.05); neither were there significant differences between sireline (P 0.324) and dam line (P 0.230) at age of 300 days. The heritability ranged from 0.093 to 0.223 in sire and 0.11 to 0.329 in dam groups. The average heritability in sire regardless of age was 0.16 and in dams 0.21. The heritability in total regardless of age and sex was estimated about 0.185. Genetic parameters (h^2) were different between dams (0.15-0.27) and sires (0.130.19) for all ages of samplings and for age of 150 day old, was significant (P 0.035).