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

GROWTH rates in fish and aquaculture systems are impacted by environmental parameters and contaminants. A complete growth model was constructed for Orange-spotted Grouper (Epinephelus coioides) by assimilating water quality and heavy metals toxicity effects in three production systems: recirculating aquaculture systems (RAS), earthen ponds, and natural habitats of the Red Sea. The model involved water quality features (temperature, dissolved oxygen, pH, electrical conductivity), soil (pH, EC, CEC, exchangeable cations), and heavy metals (Hg, Cd, Pb, Cr, Cu, Zn). With regard to validation, the model accuracy was remarkable across growth phases, R² > 0.999, with phase-wise precision highest with fingerlings (RMSE: 0.53g, MAPE: 1.28%), and juveniles (RMSE: 6.12g, MAPE: 1.41%). Environmental parameters have distinct bases: temperature optimal range 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 had the greatest toxicity (CT=0.14 mg/l 70% reduction), followed by cadmium (CT=0.17 mg/l) while zinc demonstrated the lowest (CT=0.80 mg/l 40% reduction). The comparison found that each system had its own particular advantages. Ponds scored lower on energy use and operational expenditures by 61.6% and 14.3% respectively, and also grew faster, achieving a 15-25% higher growth rate along with 16.7% improved FCR. RAS contrarily outperformed with its renewable natural resources. Natural areas gave optimization data for the environment. The model was able to predicted synergistic effects among environmental controls especially the interactions of dissolved metals and pH, temperature and oxygen, as well as soil and water in earthen ponds. These results have important implications for improving aquaculture management systems through system specific environmental regulation to achieve higher productivity levels while reducing the impact on the environment in marine aquaculture systems.