Author(s): Brian L Brazil
Egg hatching success and fry and fingerling growth of channel catfish Ictalurus punctatus were examined to determine if ozonation of hatchery water would facilitate increased stocking densities without sacrificing growth characteristics. Egg masses reared in ozonated water hatched 18–24 h sooner than those in unozonated water, but hatching rates of 60.5 ± 3.6% and 56.7 ± 3.9% in ozonated and unozonated waters, respectively, were not significantly different. Sac fry weights, measured 24 h posthatch, were not significantly different (pooled average weight = 0.149 g). However, fingerlings reared for 85 d in ozonated water were significantly heavier than fish reared in unozonated waters, averaging 22.7 ± 0.4 g and 17.0 ± 0.4 g, respectively. Feed conversion rates (weight of feed fed divided by weight gained) of 1.06 and 1.15 under ozonated and unozonated conditions, respectively, were significantly different. Survival rates of fish reared in different environments were similar (pooled mean > 92%). Dissolved oxygen levels in ozonated water remained above 85% saturation during and immediately following feeding, while oxygen concentrations in unozonated waters routinely fell below 3.5 mg/L (40% of saturation). Water clarity improved and chemical oxygen demand was reduced after ozonation.