Ovulation chemicals like Ovulin, Ovaprim, or catfish pituitary, which is the catfish brain, can be used to cause "egg release" ovulation in catfish females.
The chemical is injected into the body of the fish using needles and syringes, at the dose of 0.5mills to 1 kg body weight.
The infected female fish is kept alone with enough water for 8 to 10 hours of ovulation period.
After ovulation, you will notice drops of eggs in the place where the female is kept.
You can also bring it out and apply a slight force on the under belly and the eggs will come out easily.