Growth and Feed Utilization of Hatchery-Reared Juvenile Nassau Grouper Fed Four Practical Diets

Abstract

Abstract The effects of four practical diets, formulated for carnivorous marine finfish, on growth, feed utilization, and body composition of hatchery-reared juvenile Nassau grouper Epinephelus striatus (mean weight ± SD = 2.37 ± 0.75 g) were compared for 56 d in 145-L flowthrough seawater (36–38 ‰) aquaria. Diets differed in crude protein (CP) and crude lipid (CL) content as follows: low CP (43.5%), low CL (5.91 %) trout grower (LP–LL); midlevel CP (52.7%), high CL (15.2%) salmon grower (MP–HL); midlevel CP (55.6%), low CL (7.79%) Japanese formulation for carnivorous fish (MP–LL); and a high CP (61.8%), high CL (14.2%) research diet for dolphin (mahimahi) Coryphaena hippurus (HP–HL). Energy : protein ratios (E:P) of these diets were 35.2, 32.0, 28.3 and 28.9 kJ/g, respectively. Relative growth rate (RGR, % increase in weight) and specific growth rate (SGR, % increase in body weight/day) were strongly correlated (P < 0.0005) to dietary CP and E:P ratio and were higher (P < 0.05) for fish fed the MP–LL and HP–HL diets (RGR = 454–502%; SGR = 3.05–3.19%/d) than in the LP–LL and MP–HL diets (RGR = 68.6–160%; SGR = 0.93–1.71%). Feed utilization, including conversion ratio (FCR), protein efficiency ratio (PER), apparent net protein retention (ANPR), and apparent net energy retention (ANER) were also highly correlated (P < 0.0005) to dietary CP and E:P ratio. These parameters were significantly (P < 0.05) higher in the MP–LL diet than in the other diets. No clear relationships between dietary nutrient levels and proximate body composition were observed. Results indicated that cultured juvenile Nassau grouper require a dietary protein level above 55% and an E:P ratio below 28.9 kJ/g for optimum growth.