Advancing Captive Breeding Protocols for Bighead Carp (Hypophthalmichthys nobilis): Broodstock Conditioning, Spawning, and Larval Rearing Using Pond Water in Algeria

Reliable, locally adapted seed production of bighead carp (Hypophthalmichthys nobilis) is essential for expanding freshwater aquaculture in North Africa while reducing reliance on imported fry and associated biosecurity risks. This study optimized artificial reproduction through integrated refinement of broodstock conditioning, hormone induction, and pond-water hatchery management under local environmental conditions. Adult broodstock collected from Sidi Abdelli Dam (2020–2021) were acclimated and spawned at the Tabia hatchery using a semi-natural flow-through pond-water system with continuous monitoring of temperature, dissolved oxygen, and pH. Induction protocols (28 batches, 130 females) compared three standard hormonal approaches: (1) carp pituitary injections (0.5 and 4.5– 5mg kg⁻¹), (2) human chorionic gonadotropin (1,500–2,000IU kg⁻¹ for females; 200– 1,000IU for males), and (3) GnRH analogues (Ovopel/Ovaprim). Reproductive performance was evaluated using ovulation latency (degree-hours), egg yield, fertilization rate, hatch success, and larval survival till day 6. Successful inductions yielded fertilization rates of 87±6%, with optimal batches reaching ≥90%, and hatching occurring within 28– 32h at 23– 26°C. More than 2.5 million larvae were produced, supporting restocking of 21 water bodies across 12 Algerian regions and exceeding regional benchmarks while matching performance reported from intensive Chinese RAS operations. Between 2020 and 2021, fertilization, hatch success, and larval survival increased by 3, 7, and 12%, respectively, with all gains statistically significant. Temperature showed a strong positive correlation with reproductive success (r=0.72, P