Recent trends in research on induced spawning of fish in aquaculture

Since 1973, the treatment of sexually mature fish with brain hormones (i. e. neurohormones) in order to induce spawning activity has gradually been replacing the hypophysation, although the latter is still widely used. Some brain-hormone analogues have a hightened spawning-inducing effect. Since the discovery that dopamine inhibits gonadotropic hormone release, dopamine antagonists—pimozide or domperidone—are injected before or together with brain-hormone analogues. This double treatment, i. e. the suppression of dopamine inhibition followed by neurohormone stimulation, has become a current technique in aquaculture. The discovery of the pulsatile release of gonadotropic hormone from the pituitary hints at the possibility of using techniques in which exogenous hormones are injected in pulses. In the past few years, induction of spawning through the control of photoperiod and/or temperature has become increasingly important.