A comparative study on the body shape of Alosa caspia (Teleostei, Clupeidae) populations in the southern Caspian Sea basin using geometric morphometric analysis

Geometric morphometric method was used to examine body shape variations among the three populations of the Caspian shad, Alosa caspia, in the southern Caspian Sea coasts of Iran. A total of 289 A. caspia specimens were caught from three localities, from the west to the east including Guilan (Anzali), Mazandaran (Sari) and Golestan (Miankale), respectively. Shape data was extracted using 15 landmark points on 2-D pictures of specimens. The PCA, DFA, CVA/MANOVA analyses and cluster analysis (CA) based on Euclidean square distances were used to examine shape differences among the three populations. Significant differences were found among the populations of A. caspia in terms of body shape. Cluster analysis showed separation of Mazandaran populations from the other provinces. Results revealed that the studied populations are divided into two categories; a group with large body and head depth and short and wide caudal peduncle and the other one with shallow body, small head and longer caudal peduncle. Observed differences in the head shape of Mazandaran population of A. caspia could be indirectly related to the feeding resources. Changes in head and mouth shapes can be considered as reflective of differences in selection of food items and direction of feeding. The obtained body shape properties can provide a shape-based identification key for Alosa caspia, which is useful for fisheries and stock management or conservation programs.