ARS | Publication request: Stocking density effects on production characteristics and body composition of market size cobia, Rachycentron canadum, reared in recirculating aquaculture systems

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2012
Publication Date: April 4, 2013
Citation: Riche, M.A., Weirich, C.R., Wills, P.S., Baptiste, R.M. 2013. Stocking density effects on production characteristics and body composition of market size cobia, Rachycentron canadum, reared in recirculating aquaculture systems. Journal of the World Aquaculture Society. 44:259-266.

Interpretive Summary: The production of fish under conditions of over-crowding can reduce growth, alter composition and condition of fish fillets, and increase the time to harvest. This study was conducted to evaluate growth and production efficiency of juvenile cobia reared to market size in production-scale recirculating aquaculture systems at increasing numbers of animals per rearing unit. Cobia, (322 g initial weight) were reared for 119 days at densities to attain a final in-tank production of 10, 20, or 30 kg/m3. The specific objective was to determine the effects of in-tank crowding resulting from higher biomass per unit rearing volume independent of other potential constraints of the rearing system. Survival was >/= 96% among all treatments. Mean final weight ranged from 2.13 to 2.15 kg (approximately 4.7 pounds) with feed conversion efficiencies of 65 - 66% (approximately 1.5 pounds of feed/pound of growth). No significant differences were detected in growth rate, survival, feed efficiency or body composition. This study is the first to demonstrate that cobia can be reared to greater than 2 kg harvest weight at densities of at least 30 kg/m3 in recirculating aquaculture systems. The information generated provides needed criteria for development of production models that allow U.S. domestic aquaculture producers to competitively offset China's 80% market share of cobia production.

Technical Abstract: Production density in excess of a critical threshold can result in a negative relationship between stocking density and fish production. This study was conducted to evaluate production characteristics of juvenile cobia Rachycentron canadum, reared to market size in production-scale recirculating aquaculture systems at three different densities. Cobia, (322 g initial weight) were reared for 119 days at densities to attain a final in-tank biomass of 10, 20, or 30 kg/m3. The specific objective was to determine the effects of in-tank crowding resulting from higher biomass per unit rearing volume independent of system loading rates. Survival was >/= 96% among all treatments. Mean final weight ranged from 2.13 to 2.15 kg with feed conversion efficiencies of 65 - 66%. No significant differences were detected in growth rate, survival, feed efficiency or body composition. This study demonstrates that cobia can be reared to greater than 2 kg final weight at densities </= 30 kg/m3 under suitable environmental conditions without detrimental effects on production.