Fish reared in captivity often fail to undergo final oocyte maturation, ovulation and spawning. This failure was shown to be due to lack of luteinizing hormone (LH) release from the pituitary. To ameliorate these problems, it is possible to use synthetic agonists of the gonadotropin-releasing hormone (GnRHa), in order to induce the release of LH and initiate the cascate of events leading to maturation and spawning. This approach will be employed to induce spawning of bluefin tuna (Thunnus thynnus) broodstock collected from the capture fisheries in the Mediterranean Sea and maintained in sea cages.