Feed-based production of ictalurid catfish in ponds is the largest aquaculture sector in the USA. Feed has an oxygen demand, and increases carbon dioxide, ammonia nitrogen, and phosphate inputs to ponds. Major sources of oxygen in ponds are phytoplankton photosynthesis and mechanical aeration; the major sink for oxygen is respiration by fish and by microorganisms in the water column and sediment. Dissolved oxygen concentrations decline when respiration exceeds photosynthesis, and the most crucial time for low dissolved oxygen concentration is at night. Mechanical aeration is applied to avoid nighttime dissolved oxygen concentrations from falling below the critical level for catfish of 3 mg/L. Electrically powered paddlewheel aerators are used by most catfish producers. The oxygen-transfer efficiency of these aerators is known, but calculations of aeration requirement from stocking and feeding rates are not reliable because of variation in phytoplankton abundance and in weather conditions. Dissolved oxygen concentrations must be monitored, and when measurements suggest that nighttime dissolved oxygen concentration will be unacceptably low, tractor-powered emergency aerators must be operated to supplement dedicated aeration. Dissolved oxygen concentration also is important in hatcheries, and small aeration systems have been developed for hatchery application.

Aeration allows for higher feeding rates and increased production of channel catfish Ictalurus punctatus in intensive and semi-intensive aquaculture systems. However, the effect of specific dissolved oxygen (DO) concentrations on various production parameters remains unknown. The purpose of this 2-year study was to determine the effect of daily minimum DO concentration on channel catfish production. Six 0.1-ha ponds were each equipped with three 0.37-kW (0.5-hp) aerators and one 0.37-kW circulator. Dissolved oxygen concentrations were monitored and recorded with a commercial oxygen monitor that also controlled aeration. During both years, aeration in the high-oxygen treatment was initiated when the DO concentration dropped below 5.0 mg/L (mean, 64% saturation from May to September); aeration in the low-oxygen treatment was initiated when the DO concentration dropped below 2.5 mg/L (32% saturation; 2001) or 1.5 mg/L (19% saturation; 2002). The minimum DO concentrations resulting from this aeration protocol differed somewhat from aerator set points. In the low-oxygen treatment, delaying aeration until the DO concentration dropped below 2.5 mg/L reduced feed consumption by 6% relative to the highoxygen treatment. Other production parameters were not significantly different. In 2002, when aeration was delayed until the DO concentration dropped below 1.5 mg/L, the low-oxygen treatment group exhibited reductions in food consumption (45% less than consumption by the high-oxygen treatment), average fish weight (31% less), and net production (54% less). Even at the high feeding rates of 2002 (maximum of 680 kg · ha Ϫ1 · d Ϫ1 ; 44,066 kg/ha total in one pond), other water quality variables were acceptable. Net production in the high-oxygen treatment in 2002 averaged 23,547 kg/ha, a potential record for channel catfish in earthen ponds. Neither the feed conversion ratio nor survival was significantly different between treatments in either year. While these results cannot be directly extrapolated to large commercial ponds, it appears that increased aeration may increase production well above current commercial levels.

Effects of high summer temperatures on Channel Catfish Ictalurus punctatus are poorly understood, particularly for thermal regimes that mimic pond aquaculture conditions. Therefore, this study examined the effects of three cycling upper‐range temperature regimes (23–27°C, 27–31°C, and 31–35°C) characteristic of aquaculture environments in the Mississippi Delta. Feed conversion ratio, feed consumption, specific growth rate, activity levels, survival, and overall growth in terms of wet weight and TL were measured in fingerling channel catfish over an 8‐week period in a flow‐through, multiple‐tank system. Specific growth rate, feed consumption, TL, and wet weight of fish increased significantly in the 27–31°C treatment in contrast to the 23–27°C and 31–35°C treatments. Feed conversion ratio was lowest in the 27–31°C treatment, whereas activity levels were highest in the 31–35°C treatment. Survival significantly decreased for catfish in the warmest treatment compared with catfish in the coolest treatment. These results indicate that high temperatures decrease growth in Channel Catfish, largely due to reduced food consumption and feed conversion and increased levels of activity. Therefore, increases in temperatures, such as from climate change, present challenges to the culture and management of Channel Catfish.

This study determined the effects of the minimum daily dissolved oxygen (DO) concentration on the production parameters of channel catfish Ictalurus punctatus in earthen ponds. Fifteen 1-acre ponds (five ponds per treatment) were managed as high-oxygen (minimum DO concentrations averaging 4.37 ppm or 54% air saturation from June through September), medium-oxygen (minimum DO concentrations averaging 2.68 ppm or 33.2% air saturation), or low-oxygen treatments (minimum DO concentrations averaging 2.32 ppm or 28.7% air saturation) using one 5-hp electric paddlewheel aerator per pond. Fish in the high-, medium-, and low-oxygen treatment ponds were fed a mean total of 14,008, 13,212, and 12,607 lb/acre of 28%-protein floating feed, respectively. Net production paralleled the total amount of feed fed, averaging 5,772, 5,278, and 5,113 lb/acre in the high-, medium-, and low-oxygen treatments, respectively. Individual fish weight at harvest also showed a similar trend, averaging 1.37, 1.33, and 1.30 lb in the high-, medium-, and low-oxygen treatments, respectively. No visible stress responses were observed in any ponds during this study. Total aeration averaged 5,245, 2,518, and 1,337 hp-h/acre in the high-, medium-, and low-oxygen treatments, respectively. Treatments with higher minimum DO concentrations had significantly higher nitritenitrogen, suspended solids, chlorophyll a, and pH and lower Secchi disk visibility, alkalinity, and hardness; however, no water quality parameters exceeded the normal acceptable range for channel catfish. While the cost of electricity must be considered, maintaining a minimum daily DO concentration of 2.3-2.5 ppm is suggested as a compromise between maximizing both the amount of feed fed and fish production while minimizing aeration costs.