Evaluation of Commercial Marine Fish Feeds for Production of Juvenile Cobia in Recirculating Aquaculture Systems

The effect of different commercially available marine fish diets on production characteristics and body composition of juvenile Cobia Rachycentron canadum reared in production‐scale recirculating aquaculture systems was evaluated in a 57‐d growth trial. Juvenile Cobia (mean weight ± SE, 26.7 ± 0.9 g) were stocked at an initial density of 1.2 kg/m3. After stocking, fish were fed one of three closed‐formula diets formulated for carnivorous marine finfish (coded diet A, 50% crude protein : 22% crude lipid; diet B, 49% crude protein : 17% crude lipid; and diet C, 48% crude protein : 17% crude lipid), all at a targeted feed rate of 3–5% body weight per day. At 2‐week intervals, 10% of the population of each tank was sampled to determine mean weight, weight gain, specific growth rate, feed conversion efficiency, and biomass. At the termination of the trial, the entire population of each tank was harvested to determine the same characteristics and survival. In addition, fish were sampled to determine relative changes in whole body composition, energy retention, protein efficiency ratio, and protein productive value. Final weight (203.3 g), specific growth rate (3.6%/d), feed conversion efficiency (92.2%), biomass (7.3 kg/m3), and protein productive value (25.2%) of fish fed the high‐lipid diet A were significantly higher than those of fish fed the other two diets. No differences in whole body composition were observed among fish fed the three diets with the exception of dry matter composition. Contrary to previous reports, the results of the current study indicate that juvenile Cobia reared in production‐scale recirculating aquaculture systems fed high‐lipid diets exhibit protein sparing and better growth.