Morphological characteristics of the native brown trout (Salmo trutta fario) from five major rivers of the southern Caspian Sea basin were analyzed using 31 morphometric and 7 meristic characters in order to investigate the hypothesis differentiation and clarify its taxonomic status. Univariate analysis of variance of 162 adult specimens showed significant differences among the means of the five studied groups for 14 standardized morphometric measurements out of 31 characters. In morphometric traits linear discriminant function analysis (DFA), the overall assignments of individuals into their original groups were 60.0% and 55.1% in males and females, respectively. The principal component analysis (PCA), scatter plot of individual component score between PC1 and PC2 showed in male and female specimens grouped into 5 areas in morphometric. The present study indicated that brown trout populations surveyed had high morphologically in the rivers across of the southern Caspian Sea basin that can be considered in conservational policy and restocking programs.
