Abstract
Electrophoretic variation of 12 enzyme systems, representing 26 loci in 4 strains of domesticated rainbow trout (S. gairdneri Richardson) were studied. The variances among and within strains, estimated from observed frequencies, were compared to data of other studies of biochemical polymorphism carried out in this species. A large proportion of the variability in rainbow trout is present in the French hatchery stocks studied; isolation of these groups for several generations has not caused a significant genetic differentiation as compared to all the domesticated strains studied.