Mangrove red snapper (Lutjanus argentimaculatus) is a high demand in Southeast Asia for both consumption and aquaculture, yet over 90% of its fingerlings were sourced from the wild, putting pressure on natural populations. Moving towards hatchery-based production of fish is therefore critical to sustainability. This shift depended on developing high-quality, sustainable broodstock to ensure reliable and consistent fingerling output. This study aimed to the feasibility of using earthen pond-cultivated red snapper as broodstock to reduce dependence on wild populations. By investigating different spawning induction methods.
Researchers selected mature broodstock from grow-out ponds at Klongwan Fisheries Research Station, Kasetsart University, where they had been cultivated for 3.2 to 3.7 years. Males had a mean length of 58.3±1.2 cm and weight of 2.7±0.2 kg, while females had a mean length of 56.3±0.9 cm and weight of 3.1±0.2 kg. In 15-ton spawning tanks with a 2:3 male-to-female ratio, the brooders were divided into three groups to test different spawning induction methods. Each method had three replicates and was observed over a 30-day period.
Results indicated that (Figure 1) Method I, which involved environmental manipulation through a 70% water exchange per week, resulted in a mean of 1.3±0.5 spawning events but produced no fertilized eggs. Method II, which applied hormonal injections of 30 µg LHRHa + 10 µg Dom/kg for females and 15 µg LHRHa + 5 µg Dom/kg for males, led to a mean of 2.6±0.5 spawning events, with a mean fertilization rate of 70.1±8.8% and hatching rate of 69.8±7.8%. Method III, using a higher dose of hormonal injections (60 µg LHRHa + 20 µg Dom/kg for females and 30 µg LHRHa + 10 µg Dom/kg for males), resulted in a mean of 2.3±0.5 spawning events but produced a low mean fertilization rate of 3.8±5.2% and hatching rate of 0.9±1.5% due to the high proportion of defective eggs. Overall, Method II significantly outperformed Method III in both fertilization and hatching rates, while Method I was determined to be unsuitable for the broodstock used in this study.