Impact of Ozonation on System Performance and Growth Characteristics of Hybrid Striped Bass (Morone chrysops (f) x Morone saxatilis (m)) Reared in Recirculating Aquaculture Systems
Brazil, Brian Ligar
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This study was conducted to evaluate the impact of sustained ozone dosages rates (0, 3, 13, 25, and 45 g O₃ per kg feed delivered per day)on water quality profile, fish physiology, and growth during a production cycle of hybrid striped bass reared in pilot scale recirculating systems. Nitrogenous wastes and dissolved organic compounds increased linearly (p < 0.01) throughout the trial under both ozonated and unozonated conditions. Ozone treatments 13 and 25 g O₃ / kg feed received 170 kg more feed than the control treatment (0 g O₃ / kg feed) by the end of trial. The ozonated system received an average 1 kg more feed per day than did the unozonated system, although the unozonated system received 25% more freshwater during the trial. Ozonation increased nitrification efficiency which resulted in a 25% reduction in residual ammonia measured per kilogram of feed delivered. Biologically degradable organics (CBOD5) were lowered 45% under ozonation when adjusted for daily feed input. Microbial activity as determined by the rate of degradation of DOC was 43% higher in the ozonated environments. Increased environmental quality provided through ozonation did not result in measurable physiological improvements (p 0.05). All parameters monitored except plasma protein and hematocrit values varied significantly (p>0.05) over time. Hemoglobin, plasma protein, and hematocrit values in fish under all rearing conditions were 10.2 ± 0.4 g/dL, 7.1± 0.6 g/dL, and 52.9 ± 1.9%, respectively. Final mean serum chloride level of 115.8 ± 3.4 mE/L and mean glucose level of 186.3 ± 2.1 mg/dL were measured in fish reared at treatments 0, 13, and 25 g O3. Fish reared under ozonated conditions possessed an overall mean growth rate of 2.3 g/day and FCR of 1.58:1. Simultaneously, fish in the unozonated environment gained 1.8 g/day at an FCR of 1.90:1. At the conclusion of the trial, the final mean weight (443 ± 11.6 g) of fish reared in the unozonated environment was significantly lower (p<0.01) than fish reared in the ozone treatments 13, and 25 g O3 (combined mean of 576.6 ±16.4 g).
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