Submitted to: Fish Farming News
Publication Type: Trade Journal
Publication Acceptance Date: 6/1/2008
Publication Date: 6/15/2008
Citation: Weirich, C.R., Wills, P.S. 2008. Production of cobia in recirculating systems. Fish Farming News. 13(2):28-30.
Technical Abstract: Only limited information exists with respect to rearing juvenile cobia Rachycentron canadum to stocker and marketable sizes using recirculating aquaculture systems (RAS). To investigate this topic, two rearing trials were conducted using commercial scale RAS. In Trial 1, juvenile cobia (29 g) were stocked into three tanks of each RAS at an initial density of 1.2 kg/m3. Fish in each of the three tanks in each RAS were fed one of three commercial diets: Zeigler Marine Grower (MG; 50% crude protein, 15 % crude lipid; slow sinking pellet), Zeigler Gold (42% CP, 16% CL, floating pellet), or Zeigler Hybrid Striped Bass (HSB; 44% CP, 12% CL; floating pellet). At two week intervals 10% of the population in each tank was sampled to determine mean weight, specific growth rate (SGR), feed conversion ratio (FCR), and survival. At 56 days after stocking, tanks were harvested to determine production characteristics body composition parameters (gross energy, % dry matter, % ash, % protein, and % lipid. On the basis of weight, weight gain, SGR, and FCR, cobia juveniles fed the MG diet outperformed fish fed the GOLD and HSB diets throughout and at the conclusion of the trial (Table 1). Regarding body composition, with the exception of % dry matter and % protein, no differences existed between dietary treatments. In Trial 2, juveniles (322 g) were stocked into three tanks of each RAS, each at a different density: low (1.4 kg/m3); medium (2.8 kg/m3); or high (4.2 kg/m3). Fish were fed a commercial slow sinking pelleted diet (Cargill/Burris; 45% CP, 15% CL) twice daily. At three week intervals 10% of the population in each tank was sampled to estimate production characteristics and at 119 days after stocking, tanks were harvested to determine production characteristics and samples were taken to determine selected body composition parameters and fillet yield. Although tissue samples have not yet been analyzed, results indicate that rearing density had no effect on production characteristics throughout and at the conclusion of the trial (Table 2). Final biomass of low, medium, and high density treatments was 9.0, 18.1, and 27.8 kg/m3, respectively. Across treatment fillet yield was 42.1 % and average total fillet weight of each harvested fish was 884 g.