As aquaculture has intensified during the last three decades, it has become increasingly obvious that commercial hatcheries must gain complete control over the reproductive cycle of the cultured fish and produce fertilized eggs on demand. The original spawning induction technologies used pituitary extracts or mammalian gonadotropins. With the determination that in many farmed fish the failure to spawn in captivity reflects a lack of luteinizing hormone (LH) release from the pituitary, research and development efforts focused on the use of gonadotropin-releasing hormones (GnRHs). Analogs of GnRH were designed which are resistant to enzymatic degradation, have a higher affinity to the GnRH receptor and are potent stimulators of LH release and ovulation. These analogs were incorporated into a range of sustained-release delivery systems that have been optimized for the induction and synchronization of final oocyte maturation (FOM), ovulation, spermiation and spawning in multiple farmed species. The discovery that the brains of many teleosts contain 3 forms of GnRH, and information about their relative roles in the regulation of reproduction, is now being used to tailor more physiologically-compatible GnRH spawning induction therapies. The cloning of the genes and cDNAs coding the multiple GnRH forms and their receptors, and our current understanding of the regulation of GnRH synthesis and release, is shedding new light on the nature of the hormonal failure responsible for the absence of FOM, ovulation and spawning in many farmed species, and will lead to the development of novel strategies for their induction.