Comparative Analysis of Environmental Parameters and Growth Performance of Orange-spotted Grouper (Epinephelus coioides) in RAS, Earthen Ponds, and Natural Habitats: Integrating Water Quality, Soil Chemistry, and Heavy Metal Dynamics

Environmental parameters and contaminants significantly influence fish growth rates and aquaculture system performance. A comprehensive growth model was developed for Orange-spotted Grouper (Epinephelus coioides), integrating water quality parameters and heavy metal toxicity effects across three production systems: recirculating aquaculture systems (RAS), earthen ponds, and natural Red Sea habitats. The model incorporated water quality indicators (temperature, dissolved oxygen, pH, electrical conductivity), soil characteristics (pH, EC, CEC, exchangeable cations), and heavy metal concentrations (Hg, Cd, Pb, Cr, Cu, Zn).
Model validation demonstrated exceptional accuracy across growth phases (R² > 0.999), with phase-specific precision highest in fingerlings (RMSE: 0.53g, MAPE: 1.28%) and juveniles (RMSE: 6.12g, MAPE: 1.41%). Environmental parameters showed distinct thresholds: temperature optimal range at 27.5 ± 0.5°C with growth reductions of 45% and 52% at 22.3°C and 31.8°C respectively; dissolved oxygen optimal levels above 6.5 mg/L with growth cessation below 4.8 mg/L. Heavy metal toxicity exhibited element-specific patterns: mercury showed highest toxicity (CT=0.14 mg/L, 70% reduction), followed by cadmium (CT=0.17 mg/L, 65% reduction), while zinc demonstrated lowest toxicity (CT=0.80 mg/L, 40% reduction).
Comparative analysis revealed system-specific advantages: RAS outperformed with 15-25% higher growth rates and 16.7% better FCR, while earthen ponds demonstrated 61.6% lower energy requirements and 14.3% reduced operational costs. Natural habitats provided baseline data for environmental optimization. The model successfully captured synergistic effects between environmental parameters, particularly pH-metal bioavailability interactions, temperature-oxygen relationships, and soil-water dynamics in earthen ponds. These findings provide crucial insights for optimizing aquaculture management strategies through system-specific environmental control, contributing to enhanced production efficiency while maintaining environmental sustainability in marine aquaculture systems.