Effect of dissolved oxygen and aeration management on nitrification in catfish ponds

Abstract Dissolved oxygen management of ponds plays a critical role in ictalurid catfish aquaculture production. If the minimum dissolved oxygen concentration falls below 3.0 mg O 2 L −1 , appetite is reduced, and production ultimately decreases. Although the effect of dissolved oxygen management on catfish production has been well characterized, how dissolved oxygen and aeration impact other water quality parameters is less understood. Six 0.10‐ha earthen catfish ponds were stocked with 7500 (74,300 fish ha −1 ) hybrid catfish (male Ictalurus furcatus × female I . punctatus ) fingerlings averaging 39.5 g and were managed for either high (3.3 mg O 2 L −1 ; high dissolved oxygen [HDO]) or low (1.2 mg O 2 L −1 ; low dissolved oxygen [LDO]) minimum dissolved oxygen concentrations. Catfish in the HDO treatment grew 35% larger than their LDO counterparts, reached 456 ± 10 g after 189 days and had average net production of almost 30,000 kg ha −1 . Although HDO ponds ate 38% more feed on average, total (TAN) and un‐ionized (NH 3 ) ammonia concentrations were not different between treatments. However, nitrite (NO 2 − ) and nitrate (NO 3 − ) concentrations were both significantly higher in the HDO ponds, indicating a greater proportion of ammonia was oxidized through nitrification while maintaining similar concentrations of nitrogen assimilated by phytoplankton. Higher rates of nitrification in HDO ponds are supported through higher dissolved oxygen concentrations, increased water circulation from aeration and increased suspended solids that lead to ammonia oxidation in the water column.