Abstract:
This work was conducted to study the patterns of morphological differences in body shape in Squalius turcicus De Filippi, 1865
from the most east (Atrak River) to the most west (Aras River) populations of the southern Caspian Sea basin using landmarkbased
geometric morphometric method to understand how the body shape alters in relation to geographical alternations or
environmental characters of their habitats. A total of 102 specimens were collected from the Aras, Tajan, Atrak, Ghareh-Su,
Khyer and Sefid rivers and after anesthesia, their left faces were photographed. To extract shape data, 14 homologous landmarkpoints
were digitized and data after generalized procrustes analysis, analysed using principal component analysis, canonical
variate analysis, cluster analysis, and Mantel test. The results showed significant differences between the body shape of six
studied populations, mostly related to snout, base of the dorsal and anal-fins, body depth and pectoral fin position as result of
phenotypic plasticity to the environmental features of their habitats. The Tajan and Atrak populations have a higher and lower
body depth, and the Kheyr population a longer snout.