Dissolved oxygen (DO) is one of the most important water quality variables associated with catfish culture. Understanding the oxygen dynamics in commercial catfish aquaculture ponds is important for understanding when oxygen problems could arise throughout the growing season. Oxygenation zones (OZ, here defined as the area with DO reaching 2.5 mg/L or greater) in both conventional (CP) and split (SP) earthen ponds were determined and compared in July and August, 2013. Hach Hydrolab data sondes were placed in the ponds, and DO concentrations were measured hourly from 9:00 P.M. to 9:00 A.M. for three consecutive nights. Variables including OZ volume, total DO mass in OZ, kg of DO/m(3), fish density in OZ, and kg of fish/m(3) in the OZ, and DO isopleths were determined using average DO concentrations. The smallest sizes or lowest volumes of the OZs occurred at 5:00 A.M. in both systems. The OZ volumes at 5:00 A.M. showed no significant difference between systems in both months. The entire fish zone was completely oxygenated in August in the SP ponds. The CP system was considered completely oxygenated at both 12:00 A.M. and 9:00 A.M. in both months, and the OZ volumes were significantly larger than those in the SP system at the same time slots. The fish density and kg of fish/m(3) in the OZ reached the highest at 5:00 A.M. in both systems in both months but without system difference. These results could help farmers evaluate the overall water quality performance of the two pond production systems. (C) 2016 Elsevier B.V. All rights reserved.