Shape Analysis of Sagitta otolith a tool for Probable detection of the Caspian kutum Rutilus kutum Kamenskii, 1901 on the Southern Coast of the Caspian Sea

The Caspian kutum, Rutilus kutum Kamenskii, 1901 from Cyprinidae family is native in the Caspian Sea, with the highest distribution in the southern part and rarely seen in the northern and is an economically important species along the Caspian Sea. Despite this, knowledge about stock structure is scarce and there is no formal management strategy to ensure the long-term sustainability of this valuable resource. This study was carried out using Sagitta otolith as an effective tool for possible diagnosis of the Caspian kutum species population structure. A total 153 individuals fish were collected from the ten Cooperative bony fish beach sein in southern coasts the Caspian Sea (Astara, Bandar-e Anzali, Roudsar, Tonekabon, Nowshahr, Babolsar, Sari, Miyankaleh (Golestan Province),  Khajeh Nafas and Gomishan) from 2016 to 2017. Otolith shape indices were analyzed by uni- and multivariate statistics. Significant differences were observed in some regions in otolith shape analysis.The sampled fish had a reclassification rate of about 40 to 60% at sampling stations, indicating no single population. However, using differential analysis as well as MANOVA / CVA there were four distinct spatial groups including: the first group with samples of Gomishan, the second group Khajeh Nafas- Miyankaleh- Sari- Babolsar, the third, Nowshahr- Tonekabon- roodsar and the forth one, Bandar-e Anzali- Astara. Overall, the data showed the complex spatial dynamics of the Caspian kutum.