Effect of Total Water Hardness and Chloride on Survival, Growth, and Feed Conversion of Juvenile Red Drum Sciaenops ocellatus

Juvenile red drum Sciaenops ocellatus were tank-reared in two, separate 30-d trials to assess effects of total water hardness and chloride concentratlon on growth, survival, and feed conversion. Two levels of total hardness and chloride were used in 2 × 2 factorial designs to obtain total hardness and chloride levels in trial one of 100 and 200mg/L CaCO₃ and 125 and 250mg/L Cl⁻, and hardness and chloride levels of 100 and 400mg/L CaCO₃ and 150 and 500mg/L Cl⁻ in trial two. In trial one, average daily growth and feed conversion were significantly ( P ≤ 0.05) improved at 100mg/L hardness levels compared to 200mg/L at both chloride levels. Average daily growth was 0.11 ± 0.02g/d at 100mg/L hardness and 125mg/L Cl⁻ compared to 0.06 ± 0.01g/d at 200 mg/L hardness and 125mg/L chlorides. No significant ( P ≥ 0.05) difference in survival could be attributed to levels of total hardness or chloride. In trial two, 500 mg/L Cl⁻ treatments produced significantly ( P ≤ 0.01) better growth, survival and feed conversion than 150mg/L Cl⁻ at either level of total hardness (100 and 400mg/L). Survival at 150mg/L chloride and 100mg/L hardness was 48.8 ± 18.7%, while at 500mg/L chloride and 400mg/L hardness survival increased to 96.6 ± 2.1%. Growth also increased from 0.14 ± 0.03 to 0.27 ± 0.01g/d and feed conversion improved from 5.77 ± 1.56 to 1.87 ± 0.06 at the same levels. No interactions between levels of hardness or chlorides were shown to affect red drum growth, survival, or feed conversion in either trial.