Effects of Stocking Density and Water Management on Stress Responses and Reproductive Performance of Bighead Catfish (Clarias macrocephalus) Female Broodstock after Hormone Injection

Stress responses and reproductive performance of female bighead catfish (Clarias macrocephalus Günther, 1864) broodfish in response to different stocking densities and water systems after hormone injection were investigated. The experiment followed a 4×2 factorial in a completely randomized design, wherein the female broodfish were injected with 30 mg LHRHa and 5 mg domperidone per kg of fish. They were then stocked at four different densities: 5 fish·m-2, 10 fish·m-2, 15 fish·m-2, or 20 fish·m-2. They were provided with either a water flow-through or stagnant water (without water exchange). The results revealed that neither the densities nor the water systems affected the stress response, as measured by blood plasma cortisol. Regarding reproduction-related traits, blood 17b estradiol concentration and the percentage of females spawned were not significantly influenced by these two factors (p>0.05). Interestingly, the water flow-through system tended to induce faster ovulation and spawning compared to the no water exchange system. Additionally, the water flow-through system also significantly (p<0.05) contributed to better reproductive outcomes, namely higher egg hatching rates and larval survival, compared to the no water exchange system. The loss of spawned female within 72 h after spawning was not affected by density or water system. In conclusion, this study suggests that female broodfish should be kept at a stocking density of 20 fish·m-2 in the water flow-through system following hormone injection for optimal reproductive performance.