Annual correlative changes in gonads and pituitary gonadotropes of feral African catfish, Clarias gariepinus

The reproductive cycle of male and female African catfish (Clarias gariepinus) can be divided into a breeding period (May–August), a resting period (September–February) and a period of full gametogenesis (March–April). The pituitary gonadotropin (GTH) content and the ultrastructure of the gonadotropes largely parallel the cyclical changes in the gonads. The main characteristics of the pituitary GTH cycle are a prespawning GTH surge and a postspawning regression of the gonadotropes. These phenomena are suppressed when African catfish are kept under favourable husbandry conditions. Under such circumstances the pituitary stores large amounts of GTH and shows a limited, continuous secretion of the hormone, sufficient for a sustained gametogenesis and gonadal steroid production, but not for spontaneous spawning. Under such adequate fish culture conditions, ovulation can be induced and healthy larvae obtained at any time of year