M. Tavakoli - International Sturgeon Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran
H. Fazli - Iranian Fisheries Science Research Institute, Caspian Sea Ecology Research Center, Agricultural Research, Education and Extension Organization, Sari, Iran
M. Moghim - Iranian Fisheries Science Research Institute, Caspian Sea Ecology Research Center, Agricultural Research, Education and Extension Organization, Sari, Iran
M.R. Behrooz Khoshghalb - International Sturgeon Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran

The objective of this study was to compare the biological parameters such as length, weight, age, caviar production indices, caviar/weight, condition factor and sex ratio of Persian sturgeon (Acipenser persicus Borodin, ۱۸۹۷) and Russian sturgeon (A. gueldenstaedtii Brandt & Ratzeburg, ۱۸۳۳) in the Caspian Sea during ۱۹۹۰-۲۰۱۴. All these characteristics (except condition factor) of Persian sturgeon were greater than the Russian sturgeon. In the long period, annually average (±SD) fork length ranged from ۱۲۹.۳ (±۱۱.۸۷) to ۱۴۰.۹ (±۱۵.۹۹) cm for Russian sturgeon and ۱۴۵.۷ (±۱۷.۶۱) to ۱۵۷.۴ (±۱۹.۳۱) cm for the Persian sturgeon. The annually caviar harvest for the Russian sturgeon ranged from ۳.۸۶ (±۱.۰۵) to ۵.۰۲ (±۱.۸۲) kg with a caviar/weight ratio were ranged from ۱۶.۹ (±۴.۱۲) to ۲۰.۱% (±۵.۱۲), while comparatively for the Persian sturgeon was greater and ranged from ۴.۸۴ (±۱.۶۲) and ۷.۰۴ (±۲.۵۸) kg with a caviar/weight ratio of ۱۶.۲ (±۳.۹۹) to ۲۱.۱% (±۵.۲۰). The age of both species ranged between ۶ to ۴۰ years but the modal age of Russian sturgeon was less than Persian sturgeon. The male:female sex ratio of Russian and Persian sturgeons were ۰.۲۳:۱ and ۰.۵۷:۱, respectively. The sex ratio of Russian sturgeon was significantly different from sex ratio of Persian sturgeon (p<۰.۰۰۱). The condition factor of Russian and Persian sturgeons were ۰.۹۲ (±۰.۱۶) and ۰.۷۴ (±۰.۱۳), respectively. Moreover, results of the MANOVA revealed significant differences in population structure of two species (p<۰.۰۰۱). Therefore, different conservation and management activities need for these two valuable sturgeons in the Caspian Sea.

Acipenser persicus, Acipenser gueldenstaedtii, Age, Length, Weight, Sex, Caspian Sea