Spawning Induction in Carp (PG Extract)

Spawning induction in carp with pituitary gland (PG) extract is the classic hypophysation technique that made carp aquaculture industrial: a broodfish is injected with acetone-dried, powdered carp pituitary, whose gonadotropins drive final oocyte maturation and ovulation on demand. The standard protocol is a two-injection schedule, a low priming dose of roughly 1 to 2 mg/kg followed 12 to 24 hours later by a resolving dose of 3 to 5 mg/kg, with water temperature between 20 and 26°C critical for success; ovulation follows in 8 to 16 hours at the resolving dose. Females ready to spawn show swollen, soft abdomens and red genital papillae, and are hand-stripped into dry bowls for fertilization with milt from hormone-primed males, then eggs are adhesiveness-removed or transferred to hatching jars or hapas. Modern alternatives such as GnRHa analogues are replacing crude PG extract in many hatcheries because they are more standardized and avoid the biosecurity and supply risks of donor pituitaries, but PG extract remains widespread in small-scale carp culture across Asia and Eastern Europe. Success is measured by ovulation rate, fertilization above 80%, and hatching rate above 70%. The technique anchors induced ovulation practice in cyprinid hatcheries and connects to photothermal broodstock conditioning and egg quality assessment.