Morphometric variation of the endangered Caspian lamprey, (Pisces: Petromyzontidae), from migrating stocks of two rivers along the southern Caspian Sea.

Background: Morphological studies on fishes are important from various viewpoints. Studies carried out on the Caspian Sea fishes show that many species possess speciation and population formation microprocess running. Morphologicalcharacteristics of the native endangered Caspian lamprey, Kessler1870, from migrating stocks of two major rivers in the southern Caspian Sea were analyzed to investigate the hypothesis population structure and morphologic sexual dimorphism.

Results: Univariate analysis of variance of 180 adult specimens showed significant differences between the means of the two studied groups for 15 standardized morphometric measurements out of 31 ( < 0.05). In morphometric trait linear discriminant function analysis, the overall assignments of individuals into their original groups in male and female specimens were 77.1 and 84.0 %, respectively. The discriminant analysis showed a morphological segregation of the studied populations based on the characters predorsal length, interdorsal, interorbital distance, tail length, and first dorsal fin length. The principal component analysis, scatter plot of individual component score between PC1 and PC2, showed the specimens grouped into two areas but with high and moderate overlap between two localities in males and females, respectively.

Conclusions: The present study indicated that there are at least two types of morphological forms of Caspian lamprey that had high morphometric differentiation in the rivers across the southern Caspian Sea, which can be considered in conservational policy of this valuable species.