Caractérisation et modélisation des paramètres physico-chimiques pour une gestion durable de l’aquaculturesur la côte est et hautes terres Malagasy

Abstract

This study analyzes 500 water samples taken from the East Coast and the Madagascar Highlands, two essential regions for the development of tropical aquaculture. The average temperature recorded is 26.01 ± 1.77 °C, compatible with the physiological needs of tilapia and carp, although values exceeding 30 °C can cause significant thermal stress. The pH varies between 6.15 and 8.82 (mean 7.52 ± 0.49), with a critical threshold around 8.5, where ammonia toxicity increases sharply. Dissolved oxygen has a wide amplitude (2.52–9.12 mg/L, average 6.13 ± 1.21 mg/L); values below 4 mg/L indicate potential hypoxia episodes. Conductivity (306.81 ± 143.18 μS/cm) and hardness (180.23 ± 39.66 mg/L CaCO3) suggest a mineralization generally favorable to the stability of the medium. The average turbidity (30.58 ± 6.7 NTU) reflects a moderate particle concentration, influencing the light available for photosynthesis. Ammonia contents (0.003–1.24 mg/L), nitrates (0.04–32.95 mg/L) and nitrites (0–0.75 mg/L) show nitrogen variability sometimes close to toxicity thresholds. The statistical analysis reveals an excellent predictive performance (AUC = 0.993, p = 0.000999), which confirms the reliability of the model to identify critical water quality thresholds. These results provide essential benchmarks for sustainably optimizing Malagasy aquaculture systems and better anticipating the effects of environmental variations.