Study on moving direction and survival index of Persian sturgeon (Acipenser persicus) fingerlings using mark-recapture method in Caspian Sea (Guilan province coasts)

To study moving direction and survival index of Persian sturgeon fingerlings, a total of 390200 individuals of the fish in three weight classes: less than 3g, 3 to 5g and 6 to10g were marked by coded wire tags (CWT) during 2003 to 2008. In 2003, 101500 of these individuals were marked in Shahid Beheshti, Shahid Rajaee and Shahid Marjani Sturgeon Rearing Centers, in north of Iran and then released in Sephidrud, Tajan and Gorganrud rivers. During 2004 to 2008, 288700 pieces were marked by Shahid Beheshti Rearing Centers and released in Sephidrud River. Catch and detection of fingerlings carried out by gill net prepared from nylon with mesh sizes 22, 26, 33 (2 filaments for each mesh) and one 40mm mesh size. Totally, 175 meters of net was used to study fishes in waters under 10m depth in Guilan province. In all, 2827 pieces of this fish were caught of which 40 had CWT and these belonged to weight classes 6-10g (22 pieces), 3-5g (17 pieces) and under 3g (one piece). Results on release and catch of the fingerlings for Sephirud River showed that more than 70% of fingerlings moved to eastern parts of the estuary and eastern coasts of Guilan province (stations like 12 Bahman, Dastak and Chaboksar). Of the fingerlings released in Gorganrud and Tajan rivers, only one piece was caught in Chaboksar and another in Lisar after 15 months. Hence, we postulated that the fingerlings released in Mazandaran and Golestan provices migrated to Guilan province coasts. Statistical analysis of the survival index in different weight classes indicated that the class 6-10g had higher survival rate, twice than class 3-5g and 20 times more than that of the class under 3g. Considering these results, probably the higher weight at release time can be effective in increasing the survival rate of the Persian sturgeon fingerlings.