Effects of Dietary Lipid Levels and Energy: Protein Ratios on Growth and Feed Utilization of Juvenile Nassau Grouper Fed Isonitrogenous Diets at Two Temperatures

The growth and feed utilization of juvenile Nassau grouper Epinephelus striatus (mean weight = 2.12 g; N = 9) were compared for 75 d in laboratory aquaria supplied with flow-through seawater. Fish were fed four isonitrogenous (45% crude protein) diets differing in lipid content (6, 9, 12, or 15% dry weight) and energy: protein (E:P) ratio (28.4, 31.0, 33.5, or 36.0 kJ/g protein) at two temperatures (25°C and 30°C). Specific growth rates and final weights increased (P < 0.001) with decreasing dietary lipid and E:P ratios, from a minimum of 1.20% of body weight (bw) per day (5.21 g) for fish fed the 15% lipid diet to a maximum of 2.04% bw/d (9.31 g) for fish fed the 6% lipid diet. The specific growth rate was greater (P < 0.01) at 30°C (1.38–2.09%/d) than at 25°C (1.02–1.99%/d). Feed consumption (2.16–3.30% bw/d) was inversely correlated (P < 0.001) to dietary lipid content and E:P ratio and was greater (P < 0.005) at 30°C than at 25°C. Feed conversion ratio (1.91–2.74) was positively correlated and protein efficiency ratio (1.01–1.45) negatively correlated with dietary lipid content and E:P ratio (P < 0.01). Thus, for diets consisting of 45% protein, those with lipid contents of 6–9% produced greater feed consumption, efficiency, and growth of juvenile Nassau grouper than those with 12–15% lipids. Feed consumption and growth were greater at 30°C than at 25°C.