The effect of individual selection on improving feed conversion ratio of rainbow trout (Oncorhynchus mykiss) F1 progenies

The purpose of breeding is to improve the quantity and quality of the desired characteristics in cultured species in the next generations. Individual selection is a simple and practical way to provide a quick response in improving high heritability traits for breeding most species in aquaculture. At first step, in Yasouj cold water fishes breeding research Center, in order to conducting selection program in rainbow trout brood stock as base population and improving food conversion ratio (FCR) in  their offsprings, 150 female and male broods with higher mean weight were  selected, striped in 6 stage and eggs were incubated. One-year produced Fish (45000 pcs.) of the six groups with higher mean weight  in 5 stage were selected (438 pcs.) and remainder was discarded. Before selection, a few fish of six aged-groups as control group were cultured apart. Significant difference (p<0.05) induced between final mean weight of some groups (the selected groups and control group) and significant difference (p<0.05) between mean weight of the control group (717±96 g.) and the selected groups (1007±136 g.) can be a result of genetic improvement of growth rate trait induced of selection process in one generation and most likely because of age difference in them and because of no selection and deletion in control group (don’t throw out small individuals). There were no  significant difference (p>0.05) between FCR of six aged-groups (1.56±  0.16) and control group (1.53±  0.07). The lack of disclosure or promotion of FCR of most of the groups under selection program compared to the control group indicates that the effect of this selection method on the genetic improvement of FCR in one generation is indiscernible and to reveal the improvement of this trait, continuing the selection program to promote growth rate over several generations and, consequently, improve FCR is necessary.