Dynamics of ovarian steroids in female Nile catfish [clarias lazera] during the different seasons and ages

ABSTRACT

The present investigation was done on 84 female Nile catfish [Clarias lazera] during the different seasons all over the year. The age of the fish was determined after preparation and examination of the third detachable vertebrae. Serum estradiol and progesterone concentrations were determined by using radioimmunoassay technique. The results revealed that maximal estradiol concentration was reported during spring [prespawning phase], while minimal concentration was recorded during winter [preparatory phase]. Serum progesterone concentration showed no significant variations during the different seasons and reproductive phases in all ages of female catfish. The influence of age on serum estradiol concentration is a season-dependent. It was concluded that variations in the concentration of estradiol 17-B in the blood may play an important role in ovarian activity in Nile catfish