Production Characteristics and Body Composition of Juvenile Cobia Fed Three Different Commercial Diets in Recirculating Aquaculture Systems

—The effect of feeding three commercial diets on production characteristics and body composition of juvenile cobia Rachycentron canadum reared using recirculating aquaculture systems (RASs) was assessed in a 56-d growth trial. Juvenile cobia (mean weight 6 SE, 29.2 6 0.7 g) were stocked into three 8-m tanks in each of four RASs at an initial density of 1.2 kg/m. After stocking, fish were fed one of three commercial diets: Hybrid Striped Bass diet (HSB; 44% protein, 12% lipid), Finfish Gold diet (GOLD; 42% protein, 16% lipid), or Marine Grower diet (MG; 50% protein, 15% lipid), all at a targeted feed rate of 3–5% of body weight per day. At 2-week intervals, 10% of the population of each tank was collected to determine mean weight, weight gain, specific growth rate (SGR), feed conversion efficiency (FCE), and biomass. At the end of the rearing trial, the entire population of each tank was harvested to determine production characteristics and survival. In addition, fish were sampled to determine whole-body composition, hepatosomatic index, intraperitoneal fat ratio, energy retention (ER), protein efficiency ratio (PER), and protein productive value (PPV). Final weight (311.0 g), weight gain (281.8 g), SGR (4.23% per day), FCE (85.7%), biomass (11.20 kg/m), and ER (32.7%) of fish fed the MG diet were significantly greater than those of fish fed the HSB and GOLD diets. No differences in survival, gross energy, ash, or crude lipid content existed among fish fed the three diets. Lowest dry matter content, lowest PPV, and highest protein content were observed in fish fed the HSB diet. Highest PER was observed in fish fed the GOLD diet. Although the cost of production per kilogram for rearing juvenile cobia with the MG diet would be greater, this cost could be offset by the 15% reduction in rearing time required as compared with the HSB and GOLD diets. Interest in culture of the cobia Rachycentron canadum, a migratory marine pelagic finfish and lone member of the family Rachycentridae (Smith 1986), has increased greatly in the United States over the course of the last decade. Cobia possess a number of attributes desirable for a commercially cultured fish. They can be spawned in captivity with or without hormonal induction (Dodd 2001; Franks et al. 2001; Arnold et al. 2002; Kilduff et al. 2002; Weirich et al. 2006), and protocols for larval rearing have been developed for the mass production of weaned juveniles to ensure a consistent and reliable supply of seed stock for on-growing operations (Liao et al. 2001; Holt et al. 2007; Benetti et al. 2008). Under suitable conditions, cobia exhibit extremely rapid growth rates (Chou et al. 2001, 2004; Weirich et al. 2004; Lunger et al. 2006), attaining weights of 4–6 kg in less than 1 year (Chou et al. 2004; Liao et al. 2004); they adapt well to confinement and readily accept formulated feeds (Schwarz et al. 2004; Weirich et al. 2004), and they are of excellent food quality, with high consumer appeal (McClane 1974; Chen 2001; Oesterling 2001; Rickards 2001; Shiau 2007). These characteristics, coupled with the successful expansion and growth of cobia aquaculture in Taiwan, China, and southeast Asia (Liao et al. 2001, 2004; Liao 2003; De Silva and Phillips 2007), have served as stimulants for industry development elsewhere, including Central America and the Caribbean (Benetti et al. 2007, 2008). Although the vast majority of farmed cobia are currently produced by net-pen rearing operations, establishment of land-based recirculating aquaculture * Corresponding author: [email protected] Received March 3, 2009; accepted May 29, 2009 Published online October 22, 2009 43 North American Journal of Aquaculture 72:43–49, 2010 Copyright by the American Fisheries Society 2009 DOI: 10.1577/A09-015.1 [Article]