Comparative Analysis of Stocking Density Effects on Growth Performance and Water Quality in Nile Tilapia (Oreochromis niloticus) and African Catfish (Clarias gariepinus) in Pond Culture Systems

Stocking density has a direct impact on fish survival, development, behavior, health, water quality, and feeding, playing a significant role in determining fish productivity and farm profitability. In this study, Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) reared in earthen ponds in Kisumu, Kenya, were examined for the effects of stocking density on growth performance, behavioral responses, water quality, and economic viability. In a completely randomized design, three stocking densities (low: 5 fish/m2, medium: 8 fish/m2, and high: 12 fish/ m2) were investigated for each species, with replicate ponds for each treatment. The results demonstrated significant species-specific reactions to crowding stress. High-density groups of tilapia showed 38% less weight gain (73.1 ± 4.3 g vs. 117 ± 6 g in low density), a lower feed conversion ratio (2.4 ± 0.3 vs. 1.6 ± 0.2), and a lower survival rate (74 ± 3% vs. 93 ± 1.9%), indicating density-dependent growth retardation. Catfish, on the other hand, showed steady growth up to medium density, with a weight gain drop of only 13% at high density as opposed to low density. High-density tilapia exhibited increased stress markers and aggression, as observed in behavioral assessments, whereas catfish demonstrated better adaptation to crowding. As density increased, water quality indicators drastically worsened, especially in tilapia ponds, where ammonia levels exceeded 0.6 mg/L and dissolved oxygen levels dropped to 3.2 mg/L. According to economic analysis, low-density tilapia produced the highest profitability (KSh 10,500/pond) because of premium market prices, while medium-density catfish achieved the ideal cost-benefit ratio (2.6). According to the study's findings, catfish can withstand higher densities (12 fish/m2) but require ammonia monitoring, whereas tilapia require conservative stocking (5-8 fish/m2) with rigorous oxygen management. These results provide valuable recommendations for enhancing stocking approaches to improve the sustainability and productivity of smallholder aquaculture systems.