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 the biological parameters such as length, weight, age, caviar production indices, caviar/weight, condition factor and sex ratio of persian sturgeon (acipenser persicus borodin, 1897) and russian sturgeon (a. gueldenstaedtii brandt & ratzeburg, 1833) in the caspian sea during 1990-2014. 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 129.3 (±11.87) to 140.9 (±15.99) cm for russian sturgeon and 145.7 (±17.61) to 157.4 (±19.31) cm for the persian sturgeon. the annually 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, respectively. the sex ratio of russian sturgeon was significantly different from sex ratio of persian sturgeon (p<0.001). the condition factor of russian and persian sturgeons were 0.92 (±0.16) and 0.74 (±0.13), respectively. moreover, results of the manova revealed significant differences in population structure of two species (p<0.001). therefore, different conservation and management activities need for these two valuable sturgeons in the caspian sea.