Interrelations of Oxygen Concentration, Fish Density, and Performance of Atlantic Salmon in an Ozonated Water Reuse System

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Abstract
In a 16-week study, we stocked duplicate groups of 3.3-g Atlantic salmon (Salmo salar) in 25-fish increments (25 to 100 fish/6.5-L jar) and in 250-fish increments (250 to 1,000 fish/144-L trough), in an ozonated, 100% closed water reuse system, to examine changes in fish performance in response to rearing at different densities and loadings within the system. Maximum rearing density (kg!m3) reached 219 in jars and 125 in troughs. Maximum loading (ratio of fish weight to water flow) reached 0.45 kg/(L/min) in jars, and 0.79 kg/(L/min) in troughs. A rise in water temperature from 18.9 to 21°C during weeks 11 and 12 was accompanied by a drop in effluent dissolved oxygen (DO), followed by an increase in mortality and a decline in biweekly weight gain. Later declines in water temperature to 18.4°C, and reductions in biomass, were followed by reduced mortality and increased weight gain. In both jars and troughs, mortality increased when dissolved oxygen dropped to 6.5 mg/L or lower, water temperature r...