Morphological variation of shad fish Alosa brashnicowi (Teleostei, Clupeidae) populations along the southern Caspian Sea coasts, using a truss system

A 15-landmark morphometric truss network system was used to investigate the hypothesis of population fragmentation of Shad fish Alosa braschnicowi Borodin, 1904 along the southern Caspian Sea. A total of 181 A. braschnicowi specimens were caught from six localities, respectively from the west to the east including; Astara, Rezvanshahr, Anzali, Tonekabon, Sari and Miankale. Principal component analysis, canonical variates analysis and clustering analysis were used to examine morphological differences. Univariate analysis of variance showed significant differences between the means of the six groups for 72 standardized morphometric measurements out of 105 characters studied. In canonical variates analysis, the overall assignment of individuals into their original groups was 71.46% and scatter plot of individual component scores between CV1 and CV2 showed fish specimens grouped into six areas. Clustering analysis based on Euclidean square distances among groups of centroids using UPGMA resulted into six main clusters indicating morphologically distinction populations of A. braschnicowi in the region. These populations of A. braschnicowi are distinguished especially by head shape, eye diameter, and pre-dorsal, pre-pelvic and pre-anal distances. Therefore, it is suggested considering these morphologically different populations as distinct stock in the southern Caspian Sea coasts.