Comparing some biological characteristics of two sturgeons species, Persian sturgeon (Acipenser persicus Borodin, 1897) and Russian sturgeon (A. gueldenstaedtii Brandt & Ratzeburg, 1833) in the Caspian Sea

The objective of this study was to compare biological parameters such as length, weight, age, caviar production indices, caviar/weight, growth, condition factor and sex ratios of Persian sturgeon (Acipenser persicus Borodin, 1897) and Russian sturgeon (A. gueldenstaedti Brandt & Ratzeburg, 1833) in the Caspian Sea during 1990-2014. The results showed that a variety of differences between this two species. All these characteristics (except condition factor) of Persian sturgeon were greater than Russian sturgeon. In the long period, the average (±SD) fork length ranged from 129.3 (±11.87) to 140.9 (±15.99) cm and 145.7 (±17.61) to 157.4 (±19.31) cm for the Persian sturgeon. The caviar harvest for the Russian sturgeon ranged from 3.86 (±1.05) to 5.02 (±1.82) kg with a caviar/weight ratio were ranged from 16.9 (±4.12) to 20.1% (±5.12), while comparatively for the Persian sturgeon was greater and ranged from 4.84 (±1.62) and 7.04 (±2.58) kg with a caviar/weight ratio of 16.2 (±3.99) to 21.1 (±5.20) %. The age of both species ranged between 6 to 40 years but the modal age of Russian sturgeon was less than Persian sturgeon. The male:female sex ratio of Russian and Persian sturgeons were 0.23:1 and 0.57:1, respective. The sex ratio of Russian sturgeon was significantly different from sex ration of Persian sturgeon (P