Densité de stockage et performances du tilapia du Nil en cages flottantes sur le lac Itasy (Madagascar).

Abstract

The effect of stocking density (20, 40, 60 fish/m³) on the growth and survival of Nile tilapia was evaluated in floating cages (2 m³) on Lake Itasy (Madagascar) over 120 days (September 2025 to January 2026). Nine triple cages, monosex male fry (5.2 g initial weight), weekly fertilization (cassava-poultry), and a feed of 3% biomass/day were used. Final weight (68.4 g T1; 54.2 g T2; 42.1 g T3), somatic cell count (2.1–1.42%/day), survival (96.3–79.4%), and yield (12.8 kg/m³ optimal T2) showed a negative dose-dependent effect (ANOVA p < 0.001; R² = 0.95). T2 maximizes productivity (25.6 kg/m³/year) with TCA=2.2. Hypoxia (OD 3.1 mg /l T3) and toxic NH₃ (0.45 mg /l ) explain 76% of the variance in TCS (r=-0.76). Critical threshold: 20 kg/m³ biomass. T2 generates 2.56 M MGA/cage (+52% vs. local), aligned with FAO 34,000 t/2030.