Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2009
Publication Date: 1/4/2010
Citation: Weirich, C.R., Wills, P.S., Baptiste, R.M., Riche, M.A. 2010. Production characteristics and body composition of juvenile cobia fed three different commercial diets in recirculating aquaculture systems. North American Journal of Aquaculture. 72:43-49. Interpretive Summary: Interest in the culture of cobia, a migratory marine pelagic finfish, has increased greatly in the U.S. over the course of the last decade. Although the vast majority of farmed cobia are currently produced by net pen rearing operations, establishment of land-based recirculating aquaculture system (RAS) technologies for cobia production could mitigate some of the issues associated with development of net pen culture in U.S. waters. Because feed expense generally accounts for > 50% of annual operational costs for marine finfish aquaculture operations, development of cost effective feeds and feeding strategies are of great importance to future development of cobia aquaculture, especially if practiced using RAS technologies. The present study was conducted to compare three commercial diets available in North America of different protein and lipid content on production characteristics and body composition of juvenile cobia reared in RAS. After a 56 d rearing trial juvenile cobia (initial weight = 29.2 g) fed Marine Grower (MG) reached a final weight of 311.0 g and outperformed fish fed Hybrid Striped Bass (HSB) and GOLD diets on the basis of weight, weight gain, specific growth rate, feed conversion efficiency, yield, and energy retention. No differences existed with respect to survival, gross energy, ash, or crude lipid content among fish fed the three diets. Although the cost of production per kg for rearing juvenile cobia on the high protein 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.
Technical Abstract: The effect of feeding three commercial diets on production characteristics and body composition of juvenile cobia Rachycentron canadum reared using recirculating aquaculture systems (RAS) was evaluated in a 56 d growth trial. Juvenile cobia (29.2 +/= 0.7 g, mean weight +/= SE) were stocked into three 8-m3 tanks of each of four RAS at an initial density of 1.2 kg/m3. Fish were fed one of three commercial diets: Hybrid Striped Bass (HSB; 44% protein, 12% lipid), Finfish Gold (GOLD; 42% protein, 16% lipid), or Marine Grower (MG; 50% protein, 15% lipid), at a targeted feed rate of 3-5% bw/d. At two week intervals, 10% of the fish population of each tank was sampled to determine mean weight, weight gain, specific growth rate (SGR), feed conversion efficiency (FCE), and biomass. At termination the entire population of each tank was harvested to determine production characteristics, survival, whole body composition, hepatosomatic index (HSI), intraperitoneal fat ratio (IPF), 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%/d), FCE (85.7%), biomass (11.20 kg/m3), 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 kg for rearing juvenile cobia on the high protein 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.