The response of mature female captive milkfish to mammalian and salmon gonadotropin-releasing hormone analogues (mGnRH-A and sGnRH-A) was investigated. Prior to spawning, six groups of three females received (1) 10–16 μg mGnRH-A from an osmotic pump implanted intraperitoneally (IP); (2) 100 μg mGnRH-A from a cholesterol/cellulose pellet implanted IP; (3) 10 μg/kg mGnRH-A as an intramuscular (IM) injection; (4) 10–16 μg sGnRH-A from an osmotic pump implanted IP; (5) 100 μg sGnRH-A from a cholesterol/cellulose pellet implanted IP, and (6) a cholesterol/cellulose pellet without analogue implanted IP.