In the frame of the SELFDOTT project (From capture based to SELF-sustained aquaculture and Domestication Of bluefin tuna, Thunnus thynnus) captive-reared Atlantic bluefin tuna (Thunnus thynnus) (n=15, estimated body weight=90 Kg) maintained for 3 years in captivity in El Gorguel (Cartagena, Spain) were administered a gonadotrophin releasing hormone agonist (GnRHa) implant underwater, during the natural spawning period for this species in the Mediterranean Sea (June). Beginning 48-72 h later, massive spawnings occurred everyday for 17 days, with a daily maximum fecundity of 34 million eggs. Egg collection was accomplished by placing a special curtain around the perimeter of the cage and at 6 m allowed the floating eggs to be maintained within the cage and be collected at night and sunrise with 500 ìm mesh size nets from the surface of the water.