Full Length Research Paper

Study on sexual maturity and levels of gonad steroid hormones in female kutum Rutilus frisii kutum (Kamenskii, 1901) during spawning season from river Sefid-Rood of the southern Caspian sea

 Saeed Shafiei Sabet^1*, Imanpoor Mohammad, Reza¹, Aminian fatideh Bagher² and Gorgon Saeed¹

¹Guilan. Islamic Azad University, Lahijan Branch. Researcher of young researchers club.

²Guilan, Fishing Technology Department, Mirza Kochak Vocation and Higher Education Center for Fisheries Sciences and Technology.

*Corresponding author. E-mail: ahmedelsadig@yahoo.com.  Tel: 00249 912218596. Fax: 00249 183 769363.

Accepted 11 August, 2009

   Abstract

Sexual maturity and levels of two main steroid hormones in gonads, 17-β estradiol (E2) and testosterone (T) relations which occur in female kutum Rutilus frisii kutum during spawning season from the river Sefid-Rood of the southern Caspian sea were studied using histological and radioimmunoassay. The study was carried out from February to May, 2008 using 105 fish specimen. The results of present study revealed that changes in plasma levels of gonadal steroids, (E2) and (T) were closely correlated to ovarian development and increased in GSI (p < 0.05). Gonadosomatic index (GSI) was increased in March and reached the highest value (29.47 ± 4.2) in April then decreased sharply in early May. The highest peak of plasma level of (T) and (E2) showed during spawning season, associated with the highest values of GSI. The results showed that levels of (E2) and (T) in female kutum at the stage IV of sexual maturity was significantly highest compared to immature gonads (ovary in stages II and III) (p < 0.01). Plasma estradiol (E2) and (T) levels increased in February, highest levels was observed in March and early April (105.6 ± 75.3 and 29.2 ± 96.6 ng/ml, respectively), and decreased in late April and in early May during the spawning season (p < 0.05).
 
Key words: Kutum, Rutilus frisii kutum (Kamenskii, 1901), sex steroid hormones, spawning season, Caspian sea.