Abstract
In this investigation, serum steroid hormones such as testosterone (T), 17β-estradiol (E2) and progesterone (P) in 12 female of the migratory population of Common carp (Cyprinus carpio) in southeast of Caspian Sea during a year from May 2011 to May 2012 were studied. The results of present study revealed that changes in levels of steroid hormones, (E2) and (T) were closely correlated to ovarian development. There was significant difference in level of 17 β- estradiol between autumn and winter seasons that the highest of 17-β estradiol level was observed in autumn season. In the case of progesterone hormone, higher levels was recorded in summer season and there was significant difference between summer and spring seasons and lower level of testosterone was observed in spring season.