Population diversity and sexual dimorphism of Alburnus chalcoides Gueldenstaedt, 1772 in southern coast of the Caspian Sea

The aim of this study was the identification of morphometric and meristic characters and their diversity between males and females of Alburnus chalcoides in southern coast of the Caspian Sea in 2019. 160 specimens were caught randomly in 8 rivers leading to the Caspian Sea on the coast of Gilan (Anzali Wetland, Sefidrood River Basin, Allah Rud) and Mazandaran (Chalkroud, Cheshmeh Kileh, Mianroud, and Fereydoonkanaar River). All relative morphological and meristic characters were performed. The results of the t-test showed relative morphological and meristic characters between males and females, there was a significant difference in five morphological as well as in one meristic character. Examination of relative morphological and meristic characters between stations showed there was a significant difference in all indicators and this indicates the existence of different populations in different areas of the southern coast of the Caspian Sea. The coefficient of variation (C.V.) in morphometric characters is higher than meristic characters and shows the effect of environment on morphometric characters is more meristic characters. There was a significant relationship between logarithm weight and length. Irregular fishing of these fish in old age has caused the sampled age groups not to be more than three years old. And the highest frequency was related to the age group of two years. In the final conclusion, Morphometric characters have higher diversity than meristic characters and better performance in population separation, that indicates the high flexibility of this species for adaptation in different habitats.