Some 1512 specimens of Siahmahi (Capoeta .) collected from 59 rivers in the country were studied.Five morphometric features, 14 meristic characteristic as well as geometric morphometric methods have been applied for accomplishing the biometric studies. Besides, some biometric features including length-weight relationship, condition factor and growth performance index have been evaluated.For statistical analysis, the nonparametric tests, analysis of canonical variables and the significantly analysis of form differences have been employed. The results of the analysis of canonical variables (CVA) for meristic characteristics of C . aculeata,C. barroisi,C. buhsei,C . damascina, C . fusca and C.gracilis showed that the populations of the rivers have differences and the overlap between these species is low and C . gracilis fish group isolated from other populations. Also,the analysis of canonical variables (CVA) of geometric morphometrics showed that the population of C. fusca from Lalbar river differ from other populations and showed that the overlap between these populations is high. The CVA of meristic characteristics of C . aculeata indicated that two groups of Ghalecheshmeh and Marbor have the highest distinctions with other populations of this species. The CVA geometric morphometric results of fish C . aculeata have separated the fish populations of Ghalecheshmeh, Qomrud and Lalbar rivers from other populations of this species. The results of CVA counting traits and as well as CVA of geometric morphometry of C. barroisi showed that the populations of the Kur, Sheldon and Qomrud rivers have significant differences and they are completely separated from each other. The CVA counting characteristics results of C. buhsei showed that the populations of Dizijan river have detached from populations of other two rivers (Qomrud and Dizijan dam). C. buhsei CVA geometric morphometric results showed that fish populations of Dizijan dam is different from otherQomrud and Dizijan populations. The results of CVA meristic traits for C. damascina demonstrated significant differences among the fish populations of Sivand, Khalij, Sirvan, Maroon, Aksrustam, Hasanabad, Khersan, Tangehbaragh, Tigris and Gharehaghaj rivers (p 0/05) and the Sirvan and Maroon fish groups have been isolated from other populations of this species. The CVA geometric morphometric results of C . damascina showed that the population of the Tigris, Khersan, Sirvan, Sivand and Maroon are separated from the rest of the populationof this species, respectively. The CVA meristic results of C . fusca indicated that three populations of Kalshur, Amirabad and Tabarak have meaningful differences and they are separated from each other (p 0/05). The CVA geometric morphometric outputs of C. fusca have isolated the population of Kalshur from the populations of Amirabad and Tabarak. The results of CVA meristic traits as well as the CVA of geometric morphometry of C.gracilis showed significant differences among populations of Caspian, Harirud and Orumiyeh and these three rivers have well been separated from each other. The morphometric and geometric method could separate many populations from each other to a great extent. However; for more details molecular studies are needed. Key words :Siahmahi, Meristic traits, Geometric morphometry, Biometry.