Ovulation experiments were carried out using mature female offspring of a cross between a female African catfish, Clarias gariepinus, from an established laboratory stock and a feral individual. Ovulation could successfully be induced in 67% of the females when they were held in the presence of a male and another ovulated female although visual and tactile stimuli could not be perceived due to compartmentalization in the aquaria by opaque perforated partitions. Successful ovulation (55%) was also obtained when ovarian fluid of an ovulated female was administered as a replacement of the ovulated female. However, experimental females with sectioned olfactory tracts did not respond. In addition, it was found that females exposed to ovarian fluid had increased plasma gonadotropin (GTH) levels. These ovulation responses were observed from March to May 1986, but not in December 1985 nor in June 1986. Experiments with the next generation of catfish led to a slight increase in plasma GTH levels, but not to ovulation induction. The importance of the nature of the offspring and the time of year for pheromonally induced GTH release and ovulation are discussed.