Landmark based geometric morphometrics and comparison of meristic characters was used to understand potential differences between populations of Waspi in Mashkil and Mokran Basins. 97 specimens of Waspies were caught (64 from Mashkil River and 33 from Sarbaz River). 14 landmarks were digitized on pictures taken from left side of specimens and meristic characters were counted. Data were analyzed using PCA and DFA after procrustes superimposition and data standardization. There are some meaningful shape differences between populations (P<0.001). The body and caudal peduncle in Sarbaz fishes where higher than that of Mashkil fishes, but the peduncle in Mashkil River was longer than Sarbaz fishes. Considering to no meaningful differences between the two populations in meristic characteristics and Due to different conditions in the rivers (vegetation density, water depth, water flow and food availably), the observed differences in shape of fishes could be considered as phenotype plasticity to the conditions of the rivers
