Effects of Timing and Duration of Aeration on Water Quality and Production of Channel Catfish

Sccond-year (660 g) channel catfish, Ictalurus punctatus, were stocked in ponds at a density of 1,931 kg/ha and fed a floating, commercial diet at 74 kg/ha/day for 10 weeks. The effect of five aeration treatments on fish growth, survival, and pond water quality was evaluated. The aeration treatments were: no aeration (0 hours), aeration from 0400-0700 (3 hours), aeration from 0400-0600 and again from 1600-1800 (4 hours), aeration from 0100-0700 (6 hours), and continual aeration (24 hours). Dissolved oxygen, temperature, turbidity, Secchi disk visibility, alkalinity, hardness, pH, total and un-ionized ammonia, nitrite, chlorophyll a, and chemical oxygen demand were measured at 5 intervals during the three-month study. Average final weight of fish was significantly affected by aeration. Relative to initial body weight, fish growth in unaerated ponds was lower (- 54%) than that in ponds aerated for 3, 4, or 6 hours (+32, +32, and +23%) or in continually-aerated ponds (+97%) (P < 0.05). Survival was lowest (67%) in unaerated ponds and highest (95%) in continually-aerated ponds. The proportion of stocked biomass recovered from ponds ranged from 40% (0 hours) to 174% (24 hours). Fish production in continually aerated ponds was significantly higher than 0, 3, 4, and 6 hours aeration, but no difference was found between ponds aerated for 3, 4, or 6 hours. Early morning dissolved oxygen concentration was the only water-quality parameter significantly affected by aeration treatment and was always less than 1 mg/L in unaerated ponds, between 2-4 mg/L in partially aerated ponds, and more than 4 mg/L in continually-aerated ponds. Average un-ionized ammonia-nitrogen concentration was between 0.22-0.45 mg/L. Early morning low dissolved oxygen, high temperature, and high concentrations of un-ionized ammonia affected growth, survival, and production of channel catfish.